ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Other Sources  (5,987)
  • NASA Technical Reports  (5,978)
  • Bibliography on Seismology  (9)
  • Earth Resources and Remote Sensing  (2,254)
  • METEOROLOGY AND CLIMATOLOGY  (1,902)
  • Communications and Radar  (1,822)
  • Physics
  • 2000-2004  (2,289)
  • 1995-1999  (1,906)
  • 1980-1984  (1,787)
  • 1945-1949  (5)
  • 1925-1929
Collection
  • Other Sources  (5,987)
Source
  • NASA Technical Reports  (5,978)
  • Bibliography on Seismology  (9)
Keywords
Years
Year
  • 1
    facet.materialart.
    Unknown
    Starch columns: Analog model for basalt columns (1998)
    In:  J. Geophys. Res., Warszawa, American Geophysical Union, vol. 103, no. B7, pp. 15,239-15,253, pp. L08304, (ISSN: 1340-4202)
    Details
    Publication Date: 1998
    Keywords: Stress ; Rock mechanics ; Fracture ; Physical properties of rocks ; Laboratory measurements ; 5104 ; Fracture ; and ; flow ; 8010 ; Structural ; geology ; Fractures ; and ; faults ; 8168 ; Tectonophysics ; Stresses--general ; 8439 ; Volcanology ; Physics ; and ; chemistry ; of ; magma ; bodies ; Muller ; JGR
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    BIBLIOGRAPHY SEISMOLOGY
  • 2
    facet.materialart.
    Unknown
    Dike propagation through an elastic plate (1998)
    In:  J. Geophys. Res., Kalamazoo, Michigan 49001, The Upjohn Company, vol. 103, no. B8, pp. 18,295-18,324, pp. L09603, (ISSN: 1340-4202)
    Details
    Publication Date: 1998
    Keywords: Elasticity ; Volcanology ; 8434 ; Volcanology ; Magma ; migration ; 8145 ; Tectonophysics ; JGR ; Physics ; of ; magma ; and ; magma ; bodies ; 8414 ; Eruption ; mechanisms
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    BIBLIOGRAPHY SEISMOLOGY
  • 3
    facet.materialart.
    Unknown
    Focusing of magma in the upper mantle through dike interaction (2002)
    In:  J. Geophys. Res., Amsterdam, Schweizerbart'sche Verlagsbuchhandlung, vol. 107, no. B10, pp. ECV 6-1-ECV 6-17, pp. 2223, (ISSN 0016-8548, ISBN 3-510-50045-8)
    Details
    Publication Date: 2002
    Description: We use laboratory experiments and numerical models to quantify the effects of dike interaction on the focusing of magma as it ascends in the upper mantle. Laboratory experiments involve injecting buoyant fluid into the base of a tank filled with solidified gelatin. When we initiate two dikes parallel to each other, but separated by a horizontal distance x, they tend to merge as they ascend. This behavior is also predicted by numerical models of two-dimensional dikes. The key parameters that control the maximum horizontal separation x c over which dikes will intersect are dike driving pressures, dike head lengths L (i.e., the length over which driving pressure is large), and the difference between the principal stresses of the remote stress field. When the remote differential stress is small compared to the dike driving pressure, two dikes of equal driving pressure and length will intersect over distances of x c ? L. This distance decreases with increasing remote differential stress. We quantify the effects on magma transport from a broad lateral distribution of magma using numerical simulations of multiple-dike interaction. When the average dike spacing prior to interaction is within ?3 L and remote differential stresses are insignificant, dike interaction can focus magma over horizontal distances many times L but at least ?6 L. Dike interaction can focus magma in the asthenosphere beneath mid-ocean ridges for low mantle viscosities (?10 19 Pa s) and if dikes initiate with average separations of a few hundred meters, or less. Such focusing is predicted to grow dikes of increasing magma flux approaching lateral separations of a kilometer.
    Keywords: Fluids ; Plate tectonics ; ascent ; sheeted ; dykes ; Modelling ; JGR ; 8434 ; Volcanology: ; Magma ; migration ; 8145 ; Tectonophysics: ; Physics ; of ; magma ; and ; magma ; bodies ; 8120 ; Dynamics ; of ; lithosphere ; and ; mantle--general ; 3035 ; Marine ; Geology ; and ; Geophysics: ; Midocean ; ridge ; processes
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    BIBLIOGRAPHY SEISMOLOGY
  • 4
    facet.materialart.
    Unknown
    Volcanic gas concentration and aquifer permeability estimated from tidal fluctuations in groundwater level: Case of Koshimizu Well in Izu-Oshima, Japan (1998)
    In:  Geophys. Res. Lett., New York, Conseil de l'Europe, vol. 25, no. 12, pp. 2237-2240, pp. B06307, (ISSN: 1340-4202)
    Details
    Publication Date: 1998
    Keywords: Volcanology ; Earthquake precursor: chemical (Rn, water(-level,...) ; TIDES ; Earth tides ; Physical properties of rocks ; 8135 ; Tectonophysics ; GRL ; Hydrothermal ; systems ; (8424) ; 8439 ; Volcanology ; Physics ; and ; chemistry ; of ; magma ; bodies ; 7223 ; Seismology ; Seismic ; hazard ; assessment ; and ; prediction ; 1832 ; Hydrology ; Groundwater ; transport
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    BIBLIOGRAPHY SEISMOLOGY
  • 5
    facet.materialart.
    Unknown
    An accurate and efficient method for including the effects of topography in three-dimensional elastic models of ground deformation with applications to radar interferometry (2000)
    In:  J. Geophys. Res., Hannover, Dt. Geophys. Ges. e. V., vol. 105, no. B4, pp. 8103-8120, pp. 1058, (ISSN: 1340-4202)
    Details
    Publication Date: 2000
    Keywords: Crustal deformation (cf. Earthquake precursor: deformation or strain) ; InSAR ; Geodesy ; Modelling ; JGR ; 1243 ; Geodesy ; and ; gravity ; Space ; geodetic ; surveys ; 3210 ; Mathematical ; geophysics ; (new ; field) ; Modeling ; 8145 ; Tectonophysics ; Physics ; of ; magma ; and ; magma ; bodies ; 8499 ; Volcanology
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    BIBLIOGRAPHY SEISMOLOGY
  • 6
    facet.materialart.
    Unknown
    In situ ground deformation measurements from the summit of Axial Volcano during the 1998 volcanic episode (1999)
    In:  Geophys. Res. Lett., Kobe, 1, vol. 26, no. 23, pp. 3437-3440, pp. 8010, (ISBN: 0534351875, 2nd edition)
    Details
    Publication Date: 1999
    Description: The formation of ocean crust along the midocean ridge system is volumetrically one of the most important geological processes on the surface of the earth. Volcanic eruptions along the ridge can be catastrophic events during which magma rises to the surface of the sea floor to release heat and gases into turbulent megaplumes that disrupt the overlying water column, initiate and rejuvenate hydrothermal circulation, and trigger an outpouring of microbial debris. Though these events may persist only a few weeks or months at one site, taken together, they may play a major role in the oceanic biogeochemical cycle. Axial Volcano on the Juan de Fuca Ridge has become a laboratory for the study of ephemeral aspects of sea floor volcanism, including results from expeditionary, rapid response, and permanent instrument installations. The geological context and description of the most significant magmatic event on the Juan de Fuca Ridge in the past decade is provided by Embley et al. [3425]. Dziak and Fox [3429], describe a rapid increase in the seismicity remotely monitored by the U.S. Navy hydrophone array. The increase in seismic swarms is the earliest indicator that an eruption has begun. Within hours, volcanic deflation is observed in concert with increases in the bottom water temperature due to venting. Instruments in place for the first time during such a midocean ridge volcanic event measured ground deformation and caldera subsidence resulting from the extraction of magma as described by Fox [3437] and Chadwick et al. [3441], while a coincident outpouring of hot water recorded on moored temperature sensors is described in Baker et al. [3445]. A rapid response cruise in February brought researchers to the site only 14 days after the eruption began and in the midst of winter storms. Sohn et al. [3433] describe local seismicity derived from a network of sea floor hydrophones deployed during the February cruise. Repeated measurements of helium anomalies in the water column before and after the eruption are used by Lupton et al. [3449] to fingerprint the hydrothermal plume associated with the eruption, extending a considerable distance off-axis. Water samples collected during the February 1998 cruise were analyzed for hydrothermal methane and hydrogen by McLaughlin-West et al. [3453]. They find both species to be significantly elevated near the vents and invoke microbial processes to explain the observations.
    Keywords: Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Volcanology ; 3035 ; Marine ; geology ; and ; geophysics ; Midocean ; ridge ; processes ; 8145 ; Tectonophysics ; Physics ; of ; magma ; and ; magma ; bodies ; 8419 ; Volcanology ; Eruption ; monitoring ; (7280) ; 8434 ; Magma ; migration ; GRL
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    BIBLIOGRAPHY SEISMOLOGY
  • 7
    facet.materialart.
    Unknown
    Stress fields generating ring faults in volcanoes (1997)
    In:  Geophys. Res. Lett., London, Pergamon, vol. 24, no. 13, pp. 1559-1562, pp. B05401, (ISBN: 0534351875, 2nd edition)
    Details
    Publication Date: 1997
    Keywords: Volcanology ; Stress ; Iceland ; 8145 ; Tectonophysics ; Physics ; of ; magma ; and ; magma ; bodies ; 8414 ; Volcanology ; Eruption ; mechanisms ; GRL
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    BIBLIOGRAPHY SEISMOLOGY
  • 8
    facet.materialart.
    Unknown
    Readjustment of the Krafla spreading segment to crustal rifting measured by satellite radar interferometry (1997)
    In:  Geophys. Res. Lett., Dordrecht, National Academy of Sciences of the USA, vol. 24, no. 15, pp. 1843-1846, pp. TC5003, (ISSN: 1340-4202)
    Details
    Publication Date: 1997
    Keywords: Iceland ; SAR ; InSAR ; Plate tectonics ; Crustal deformation (cf. Earthquake precursor: deformation or strain) ; 1209 ; Geodesy ; Gravimetry, Gravitation ; 8145 ; Tectonophysics ; Physics ; of ; magma ; and ; magma ; bodies ; 8150 ; Plate ; boundary ; general ; Massonet ; (3040) ; 3035 ; Marine ; geology ; and ; geophysics ; Midocean ; ridge ; processes ; Volcanology ; GRL
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    BIBLIOGRAPHY SEISMOLOGY
  • 9
    facet.materialart.
    Unknown
    The effects of topography on magma chamber deformation models: Application to Mt. Etna and radar interferometry (1998)
    In:  Geophys. Res. Lett., Hannover, Dt. Geophys. Ges. e. V., vol. 25, no. 10, pp. 1549-1552, pp. 1058, (ISSN: 1340-4202)
    Details
    Publication Date: 1998
    Keywords: Volcanology ; Modelling ; InSAR ; Crustal deformation (cf. Earthquake precursor: deformation or strain) ; 1243 ; Geodesy ; and ; gravity ; Space ; geodetic ; surveys ; 3210 ; Mathematical ; geophysics ; (new ; field) ; Modeling ; 8145 ; Tectonophysics ; Physics ; of ; magma ; and ; magma ; bodies ; 8499 ; Volcanology ; General ; or ; miscellaneous ; GRL
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    BIBLIOGRAPHY SEISMOLOGY
  • 10
    facet.materialart.
    Unknown
    Phoning Home from Mars in 2025 (2000)
    In:  CASI
    Details
    Publication Date: 2009-11-17
    Description: It's spring at Martian Outpost 3, the year 2025. The Universe Cup's on later today, and next week little Suzie celebrates her fourth birthday. Fortunately, this football fan and parent will be able to participate in both of these activities, albeit at a slight time delay, due completely to the sophisticated, high-speed quasi-real-time multimedia/navigation MarsNet surrounding Mars and tying it to Earth. Capable of moving gigabits a second in either direction, the network supports not only the multiple manned and robotic science needs of teams and devices encircling Mars, but also the very real human need for communication.
    Keywords: Communications and Radar
    Type: Concepts and Approaches for Mars Exploration; Part 1; 1; LPI-Contrib-1062
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 11
    facet.materialart.
    Unknown
    Hyperspectral Image Classification using a Self-Organizing Map (2001)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The use of hyperspectral data to determine the abundance of constituents in a certain portion of the Earth's surface relies on the capability of imaging spectrometers to provide a large amount of information at each pixel of a certain scene. Today, hyperspectral imaging sensors are capable of generating unprecedented volumes of radiometric data. The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), for example, routinely produces image cubes with 224 spectral bands. This undoubtedly opens a wide range of new possibilities, but the analysis of such a massive amount of information is not an easy task. In fact, most of the existing algorithms devoted to analyzing multispectral images are not applicable in the hyperspectral domain, because of the size and high dimensionality of the images. The application of neural networks to perform unsupervised classification of hyperspectral data has been tested by several authors and also by us in some previous work. We have also focused on analyzing the intrinsic capability of neural networks to parallelize the whole hyperspectral unmixing process. The results shown in this work indicate that neural network models are able to find clusters of closely related hyperspectral signatures, and thus can be used as a powerful tool to achieve the desired classification. The present work discusses the possibility of using a Self Organizing neural network to perform unsupervised classification of hyperspectral images. In sections 3 and 4, the topology of the proposed neural network and the training algorithm are respectively described. Section 5 provides the results we have obtained after applying the proposed methodology to real hyperspectral data, described in section 2. Different parameters in the learning stage have been modified in order to obtain a detailed description of their influence on the final results. Finally, in section 6 we provide the conclusions at which we have arrived.
    Keywords: Earth Resources and Remote Sensing
    Type: Proceedings of the Tenth JPL Airborne Earth Science Workshop; 267-274
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 12
    facet.materialart.
    Unknown
    Spatial/Spectral Identification of Endmembers from AVIRIS Data using Mathematical Morphology (2001)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: During the last several years, a number of airborne and satellite hyperspectral sensors have been developed or improved for remote sensing applications. Imaging spectrometry allows the detection of materials, objects and regions in a particular scene with a high degree of accuracy. Hyperspectral data typically consist of hundreds of thousands of spectra, so the analysis of this information is a key issue. Mathematical morphology theory is a widely used nonlinear technique for image analysis and pattern recognition. Although it is especially well suited to segment binary or grayscale images with irregular and complex shapes, its application in the classification/segmentation of multispectral or hyperspectral images has been quite rare. In this paper, we discuss a new completely automated methodology to find endmembers in the hyperspectral data cube using mathematical morphology. The extension of classic morphology to the hyperspectral domain allows us to integrate spectral and spatial information in the analysis process. In Section 3, some basic concepts about mathematical morphology and the technical details of our algorithm are provided. In Section 4, the accuracy of the proposed method is tested by its application to real hyperspectral data obtained from the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) imaging spectrometer. Some details about these data and reference results, obtained by well-known endmember extraction techniques, are provided in Section 2. Finally, in Section 5 we expose the main conclusions at which we have arrived.
    Keywords: Earth Resources and Remote Sensing
    Type: Proceedings of the Tenth JPL Airborne Earth Science Workshop; 309-319
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 13
    facet.materialart.
    Unknown
    JPL VLBI Group Report for 1998-1999 (1999)
    In:  CASI
    Details
    Publication Date: 2011-09-13
    Description: This report describes the transitional activities of the JPL Analysis Center.
    Keywords: Earth Resources and Remote Sensing
    Type: International VLBI Service for Geodesy and Astrometry: 1999 Annual Report; 215-216; NASA/TP-1999-209243
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 14
    facet.materialart.
    Unknown
    The Advanced Communication Technology Satellite and ISDN (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: This paper depicts the Advanced Communication Technology Satellite (ACTS) system as a global central office switch. The ground portion of the system is the collection of earth stations or T1-VSAT's (T1 very small aperture terminals). The control software for the T1-VSAT's resides in a single CPU. The software consists of two modules, the modem manager and the call manager. The modem manager (MM) controls the RF modem portion of the T1-VSAT. It processes the orderwires from the satellite or from signaling generated by the call manager (CM). The CM controls the Recom Laboratories MSPs by receiving signaling messages from the stacked MSP shelves ro units and sending appropriate setup commands to them. There are two methods used to setup and process calls in the CM; first by dialing up a circuit using a standard telephone handset or, secondly by using an external processor connected to the CPU's second COM port, by sending and receiving signaling orderwires. It is the use of the external processor which permits the ISDN (Integrated Services Digital Network) Signaling Processor to implement ISDN calls. In August 1993, the initial testing of the ISDN Signaling Processor was carried out at ACTS System Test at Lockheed Marietta, Princeton, NJ using the spacecraft in its test configuration on the ground.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 2; NASA-CP-10183
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 15
    facet.materialart.
    Unknown
    Compilation and Analysis of 20 and 30 GHz Rain Fade Events at the ACTS NASA Ground Station: Statistics and Model Assessment (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The purpose of the propagation studies within the ACTS Project Office is to acquire 20 and 30 GHz rain fade statistics using the ACTS beacon links received at the NGS (NASA Ground Station) in Cleveland. Other than the raw, statistically unprocessed rain fade events that occur in real time, relevant rain fade statistics derived from such events are the cumulative rain fade statistics as well as fade duration statistics (beyond given fade thresholds) over monthly and yearly time intervals. Concurrent with the data logging exercise, monthly maximum rainfall levels recorded at the US Weather Service at Hopkins Airport are appended to the database to facilitate comparison of observed fade statistics with those predicted by the ACTS Rain Attenuation Model. Also, the raw fade data will be in a format, complete with documentation, for use by other investigators who require realistic fade event evolution in time for simulation purposes or further analysis for comparisons with other rain fade prediction models, etc. The raw time series data from the 20 and 30 GHz beacon signals is purged of non relevant data intervals where no rain fading has occurred. All other data intervals which contain rain fade events are archived with the accompanying time stamps. The definition of just what constitutes a rain fade event will be discussed later. The archived data serves two purposes. First, all rain fade event data is recombined into a contiguous data series every month and every year; this will represent an uninterrupted record of the actual (i.e., not statistically processed) temporal evolution of rain fade at 20 and 30 GHz at the location of the NGS. The second purpose of the data in such a format is to enable a statistical analysis of prevailing propagation parameters such as cumulative distributions of attenuation on a monthly and yearly basis as well as fade duration probabilities below given fade thresholds, also on a monthly and yearly basis. In addition, various subsidiary statistics such as attenuation rate probabilities are derived. The purged raw rain fade data as well as the results of the analyzed data will be made available for use by parties in the private sector upon their request. The process which will be followed in this dissemination is outlined in this paper.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 2; NASA-CP-10183
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 16
    facet.materialart.
    Unknown
    Use of CCSDS and OSI Protocols on the Advanced Communications Technology Satellite (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Although ACTS (Advanced Communications Technology Satellite) provides an almost error-free channel during much of the day and under most conditions, there are times when it is not suitable for reliably error-free data communications when operating in the uncoded mode. Because coded operation is not always available to every earth station, measures must be taken in the end system to maintain adequate throughput when transferring data under adverse conditions. The most effective approach that we tested to improve performance was the addition of an 'outer' Reed-Solomon code through use of CCSDS (Consultative Committee for Space Data Systems) GOS 2 (a forward error correcting code). This addition can benefit all users of an ACTS channel including those applications that do not require totally reliable transport, but it is somewhat expensive because additional hardware is needed. Although we could not characterize the link noise statistically (it appeared to resemble uncorrelated white noise, the type that block codes are least effective in correcting), we did find that CCSDS GOS 2 gave an essentially error-free link at BER's (bit error rate) as high as 6x10(exp -4). For users that demand reliable transport, an ARQ (Automatic Repeat Queuing) protocol such as TCP (Transmission Control Protocol) or TP4 (Transport Protocol, Class 4) will probably be used. In this category, it comes as no surprise that the best choice of the protocol suites tested over ACTS was TP4 using CCSDS GOS 2. TP4 behaves very well over an error-free link which GOS 2 provides up to a point. Without forward error correction, however, TP4 service begins to degrade in the 10(exp -7)-10(exp -6) range and by 4x10(exp -6), it barely gives any throughput at all. If Congestion Avoidance is used in TP4, the degradation is even more pronounced. Fortunately, as demonstrated here, this effect can be more than compensated for by choosing the Selective Acknowledgment option. In fact, this option can enable TP4 to deliver some throughput at error rates as high as 10(exp -5).
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 2; NASA-CP-10183
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 17
    facet.materialart.
    Unknown
    Vertical transport by convective clouds: Comparisons of three modeling approaches (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A preliminary comparison of the GEOS-1 (Goddard Earth Observing System) data assimilation system convective cloud mass fluxes with fluxes from a cloud-resolving model (the Goddard Cumulus Ensemble Model, GCE) is reported. A squall line case study (10-11 June 1985 Oklahoma PRESTORM episode) is the basis of the comparison. Regional (central U. S.) monthly total convective mass flux for June 1985 from GEOS-1 compares favorably with estimates from a statistical/dynamical approach using GCE simulations and satellite-derived cloud observations. The GEOS-1 convective mass fluxes produce reasonable estimates of monthly-averaged regional convective venting of CO from the boundary layer at least in an urban-influenced continental region, suggesting that they can be used in tracer transport simulations.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 9; p. 1089-1092
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 18
    facet.materialart.
    Unknown
    Remote sensing of flooding in the U.S. upper Midwest during the summer of 1993 (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The U.S. upper Midwest was subjected to severe flooding during the summer of 1993. Heavy rainfall in the Mississippi River basin from April through July caused flooding on many Midwest rivers, including the Mississippi, Illinois, Missouri, and Kansas Rivers. The flood crest of 15.1 m at St. Louis, Missouri, on 1 August 1993 was the highest ever measured, surpassing the previous record of 13.2 m set on 28 April 1973. Damage estimates include at least 47 flood-related deaths and a total damage cost of $12 billion. Remotely sensed imagery of severe flooding in the U.S. Midwest was obtained under cloud-free skies on 29 July 1993 by the MODIS (Moderate Resolution Imaging Spectroradiometer) Airborne Simulator (MAS). The MAS is a newly developed scanning spectrometer with 50 spectral bands in the wavelength range 0.55-14.3 micrometers. Estimation of the total flooded area in the MAS scene acquired near St. Louis was accomplished by comparing the MAS scene to a Landsat-5 thematic mapper (TM) scene of the same area acquired on 14 April 1984 in nonflood conditions. For comparison, the MAS band centered at 0.94 micrometers and the TM band centered at 1.65 micrometers were selected because of the high contrast seen in these bands between land and water-covered surfaces. An estimate of the area covered by water in the MAS and TM scenes was obtained by developing land/water brightness thresholds from histograms of the MAS and TM digital image data. Afetr applying the thresholds, the difference between the area covered by water in the MAS and TM scenes, and hence the flooded area in the MAS scene, was found to be about 396 sq km, or about 153 square miles.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: American Meteorological Society, Bulletin (ISSN 0003-0007); 76; 6; p. 933-943
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 19
    facet.materialart.
    Unknown
    First global WCRP shortwave surface radiation budget dataset (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Shortwave radiative fluxes that reach the earth's surface are key factors that influence atmospheric and oceanic circulations as well as surface climate. Yet, information on these fluxes is meager. Surface site data are generally available from only a limited number of observing stations over land. Much less is known about the large-scale variability of the shortwave radiative fluxes over the oceans, which cover most of the globe. Recognizing the need to produce global-scale fields of such fluxes for use in climate research, the World Climate Research Program has initiated activities that led to the establishment of the Surface Radiation Budget Climatology Project with the ultimate goal to determine various components of the surface radiation budget from satellite data. In this paper, the first global products that resulted from this activity are described. Monthly and daily data on a 280-km grid scale are available. Samples of climate parameters obtainable from the dataset are presented. Emphasis is given to validation and limitations of the results. For most of the globe, satellite estimates have bias values between +/- 20 W/sq m and root mean square (rms) values are around 25 W/sq m. There are specific regions with much larger uncertainties however.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: American Meteorological Society, Bulletin (ISSN 0003-0007); 76; 6; p. 905-922
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 20
    facet.materialart.
    Unknown
    Lidar-measured winds from space: A key component for weather and climate prediction (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The deployment of a space-based Doppler lidar would provide information that is fundamental to advancing the understanding and prediction of weather and climate. This paper reviews the concepts of wind measurement by Doppler lidar, highlights the results of some observing system simulation experiments with lidar winds, and discusses the important advances in earth system science anticipated with lidar winds. Observing system simulation experiments, conducted using two different general circulation models, have shown (1) that there is a significant improvement in the forecast accuracy over the Southern Hemisphere and tropical oceans resulting from the assimilation of simulated satellite wind data, and (2) that wind data are significantly more effective than temperature or moisture data in controlling analysis error. Because accurate wind observations are currently almost entirely unavailable for the vast majority of tropical cyclones worldwide, lidar winds have the potential to substan- tially improve tropical cyclone forecasts. Similarly, to improve water vapor flux divergence calculations, a direct measure of the ageostrophic wind is needed since the present level of uncer- tainty cannot be reduced with better temperature and moisture soundings alone.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: American Meteorological Society, Bulletin (ISSN 0003-0007); 76; 6; p. 869-888
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 21
    facet.materialart.
    Unknown
    Global precipitation estimates based on a technique for combining satellite-based estimates, rain gauge analysis, and NWP model precipitation information (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The 'satellite-gauge model' (SGM) technique is described for combining precipitation estimates from microwave satellite data, infrared satellite data, rain gauge analyses, and numerical weather prediction models into improved estimates of global precipitation. Throughout, monthly estimates on a 2.5 degrees x 2.5 degrees lat-long grid are employed. First, a multisatellite product is developed using a combination of low-orbit microwave and geosynchronous-orbit infrared data in the latitude range 40 degrees N - 40 degrees S (the adjusted geosynchronous precipitation index) and low-orbit microwave data alone at higher latitudes. Then the rain gauge analysis is brougth in, weighting each field by its inverse relative error variance to produce a nearly global, observationally based precipitation estimate. To produce a complete global estimate, the numerical model results are used to fill data voids in the combined satellite-gauge estimate. Our sequential approach to combining estimates allows a user to select the multisatellite estimate, the satellite-gauge estimate, or the full SGM estimate (observationally based estimates plus the model information). The primary limitation in the method is imperfections in the estimation of relative error for the individual fields. The SGM results for one year of data (July 1987 to June 1988) show important differences from the individual estimates, including model estimates as well as climatological estimates. In general, the SGM results are drier in the subtropics than the model and climatological results, reflecting the relatively dry microwave estimates that dominate the SGM in oceanic regions.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Climate (ISSN 0894-8755); 8; 5, pt; p. 1284-1295
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 22
    facet.materialart.
    Unknown
    Tropical stratospheric water vapor measured by the microwave limb sounder (MLS) (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The lower stratospheric variability of equatorial water vapor, measured by the Microwave Limb Sounder (MLS), follows an annual cycle modulated by the quasi-biennial oscillation. At levels higher in the stratosphere, water vapor measurements exhibit a semi-annual oscillatory signal with the largest amplitudes at 2.2 and 1hPa. Zonal-mean cross sections of MLS water vapor are consistent with previous satellite measurements from the limb infrared monitor of the stratosphere (LIMS) and the stratospheric Aerosol and Gas Experiment 2 (SAGE 2) instruments in that they show water vapor increasing upwards and the polewards from a well defined minimum in the tropics. The minimum values vary in height between the retrieved 46 and 22hPa pressure levels.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 6; p. 691-694
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 23
    facet.materialart.
    Unknown
    SPACEWAY(TM) Providing Afordable and Versatile Telecommunication Solutions (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: This paper presents a summary description of SPACEWAY(TM), a network of Ka band geostationary satellites being developed by Hughes Communications, Inc. to provide worldwide interactive telecommunications services to small, low cost user terminals. By the end of this decade SPACEWAY(TM), using relatively few satellites and tightly focused spot beams, will provide affordable interactive 'bandwidth on demand' communication services on a global basis to consumer and commercial end users. This paper describes the system concept, details the space and ground segment characteristics, and discusses communication links.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 2; NASA-CP-10183
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 24
    facet.materialart.
    Unknown
    The reaction O((3)P) + HOBr: Temperature dependence of the rate constant and importance of the reaction as an HOBr stratospheric loss process (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The absolute rate constant for the reaction O((3)P) + HOBr has been measured between T = 233K and 423K using the discharge-flow kinetic technique coupled to mass spectrometric detection. The value of the rate coefficient at room temperature is (2.5 +/- 0.6) x 10(exp -11)cu cm/molecule/s and the derived Arrhenius expression is (1.4 +/- 0.5) x 10(exp -10) exp((-430 +/- 260)/T)cu cm/molecule/s. From these rate data the atmospheric lifetime of HOBr with respect to reaction with O((3)P) is about 0.6h at z = 25 km which is comparable to the photolysis lifetime based on recent measurements of the UV cross section for HOBr. Implications for HOBr loss in the stratosphere have been tested using a 1D photochemical box model. With the inclusion of the rate parameters and products for the O + HOBr reaction, calculated concentration profiles of BrO increase by up to 33% around z = 35 km. This result indicates that the inclusion of the O + HOBr reaction in global atmospheric chemistry models may have an impact on bromine partitioning in the middle atmosphere.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 7; p. 827-830
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 25
    facet.materialart.
    Unknown
    A diagnostic analysis of the VVP single-doppler retrieval technique (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A diagnostic analysis of the VVP (volume velocity processing) retrieval method is presented, with emphasis on understanding the technique as a linear, multivariate regression. Similarities and differences to the velocity-azimuth display and extended velocity-azimuth display retrieval techniques are discussed, using this framework. Conventional regression diagnostics are then employed to quantitatively determine situations in which the VVP technique is likely to fail. An algorithm for preparation and analysis of a robust VVP retrieval is developed and applied to synthetic and actual datasets with high temporal and spatial resolution. A fundamental (but quantifiable) limitation to some forms of VVP analysis is inadequate sampling dispersion in the n space of the multivariate regression, manifest as a collinearity between the basis functions of some fitted parameters. Such collinearity may be present either in the definition of these basis functions or in their realization in a given sampling configuration. This nonorthogonality may cause numerical instability, variance inflation (decrease in robustness), and increased sensitivity to bias from neglected wind components. It is shown that these effects prevent the application of VVP to small azimuthal sectors of data. The behavior of the VVP regression is further diagnosed over a wide range of sampling constraints, and reasonable sector limits are established.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Atmospheric and Oceanic Technology (ISSN 0739-0572); 12; 2; p. 230-248
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 26
    facet.materialart.
    Unknown
    An analysis of the Antarctic Halogen Occultation Experiment trace gas observations (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Analysis of the version 16 Halogen Occultation Experiment (HALOE) CH4 data shows that this long-lived trace gas is well correlated with potential vorticity (PV) computed from National Meteorological Center balanced winds. Analyzing late September and October 1992 data, we show that very low CH4 values are confined to the interior of a vortex edge defined by the maximum gradient in PV. The CH4 and HF time tendency is used to estimate the descent rate in the Antarctic vortex. After removing a component of the trend correlated with the HALOE sampling pattern, we compute the lower stratosphere vertical descent rates and net heaing rates in the spring Antarctic vortex. Our computations of the spring Antarctic vortex heating rates give -0.5 to -0.1 K/day. Over the winter season, the overall lower stratospheric descent rate averages about 1.8-1.5 km/month. These computations are in line with radiative transfer estimates of the heating and descent rate. The HALOE data thus appear to be consistent with the picture of an isolated lower stratospheric Antarctic vortex.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; D3; p. 5159-5172
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 27
    facet.materialart.
    Unknown
    Partitioning of ocean and land uptake of CO2 as inferred by delta C-13 measurements from the NOAA Climate Monitoring and Diagnostics Laboratory Global Air Sampling Network (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Using delta C-13 measurements in atmospheric CO2 from a cooperative global air sampling network, we determined the partitioning of the net uptake of CO2 between ocean and land as a function of latitude and time. The majority of delta C-13 measurements were made at the Institute of Arctic and Alpine Research (INSTAAR) of the University of Colorado. We perform an inverse deconvolution of both CO2 and delta C-13 observations, using a two-dimensional model of atmospheric transport. Also, the discrimination against C-13 by plant photosynthesis, as a function of latitude and time, is calculated from global runs of the simple biosphere (SiB) model. Uncertainty due to the longitudinal structure of the data, which is not represented by the model, is studied through a bootstrap analysis by adding and omitting measurement sites. The resulting error estimates for our inferred sources and sinks are of the order of 1 GTC (1 GTC = 10(exp 15) gC). Such error bars do not reflect potential systematic errors arising from our estimates of the isotopic disequilibria between the atmosphere and the oceans and biosphere, which are estimated in a separate sensitivity analysis. With respect to global totals for 1992 we found that 3.2 GTC of carbon dissolved into the ocean and that 1.5 GTC were sequestered by land ecosystems. Northern hemisphere ocean gyres north of 15 deg N absorbed 2.7 GTC. The equatorial oceans between 10 deg S and 10 deg N were a net source to the atmosphere of 0.9 GTC. We obtained a sink of 1.6 GTC in southern ocean gyres south of 20 deg S, although the deconvolution is poorly constrained by sparse data coverage at high southern latitudes. The seasonal uptake of CO2 in the northern gyres appears to be correlated with a bloom of phytoplankton in surface waters. On land, northern temperate and boreal ecosystems between 35 deg N and 65 deg N were found to be a major sink of CO2 in 1992, as large as 3.5 GTC. Northern tropical ecosystems (equator-30 deg N) appear to be a net source to the source to the atmosphere of 2 GTC which could reflect biomass burning. A small sink, 0.3 GTC, was inferred for southern tropical ecosystems (30 deg S-equator).
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; D3; p. 5051-5070
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 28
    facet.materialart.
    Unknown
    Assessment of the global monthly mean surface insolation estimated from satellite measurements using global energy balance archive data (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Global sets of surface radiation budget (SRB) have been obtained from satellite programs. These satellite-based estimates need validation with ground-truth observations. This study validates the estimates of monthly mean surface insolation contained in two satellite-based SRB datasets with the surface measurements made at worldwide radiation stations from the Global Energy Balance Archive (GEBA). One dataset was developed from the Earth Radiation Budget Experiment (ERBE) using the algorithm of Li et al. (ERBE/SRB), and the other from the International Satellite Cloud Climatology Project (ISCCP) using the algorithm of Pinker and Laszlo and that of Staylor (GEWEX/SRB). Since the ERBE/SRB data contain the surface net solar radiation only, the values of surface insolation were derived by making use of the surface albedo data contained GEWEX/SRB product. The resulting surface insolation has a bias error near zero and a root-mean-square error (RMSE) between 8 and 28 W/sq m. The RMSE is mainly associated with poor representation of surface observations within a grid cell. When the number of surface observations are sufficient, the random error is estimated to be about 5 W/sq m with present satellite-based estimates. In addition to demonstrating the strength of the retrieving method, the small random error demonstrates how well the ERBE derives from the monthly mean fluxes at the top of the atmosphere (TOA). A larger scatter is found for the comparison of transmissivity than for that of insolation. Month to month comparison of insolation reveals a weak seasonal trend in bias error with an amplitude of about 3 W/sq m. As for the insolation data from the GEWEX/SRB, larger bias errors of 5-10 W/sq m are evident with stronger seasonal trends and almost identical RMSEs.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Climate (ISSN 0894-8755); 8; 2; p.315-328
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 29
    facet.materialart.
    Unknown
    Workshop on Satellite and In situ Observations for Climate Prediction (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Participants in this workshop, which convened in Venice, Italy, 6-8 May 1993, met to consider the current state of climate monitoring programs and instrumentation for the purpose of climatological prediction on short-term (seasonal to interannual) timescales. Data quality and coverage requirements for definition of oceanographic heat and momentum fluxes, scales of inter- and intra-annual variability, and land-ocean-atmosphere exchange processes were examined. Advantages and disadvantages of earth-based and spaceborne monitoring systems were considered, as were the structures for future monitoring networks, research programs, and modeling studies.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: American Meteorological Society, Bulletin (ISSN 0003-0007); 76; 2; p. 241-249
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 30
    facet.materialart.
    Unknown
    Anomalous meridional thermospheric neutral winds in the AE-E NATE data: Effects of the equatorial nighttime pressure bulge (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The work described here makes it possible to identify anomalous wind behavior such as the nighttime meridional wind abatements that occur at F-region heights. A new analysis technique uses a simple empirical wind model to simulate measurements of 'normal' winds (as measured by the Neutral Atmosphere and Temperature Experiment (NATE) that flew on the Atmosphere Explorer-E (AE-E)) to highlight anomalous wind measurements made by the satellite while in circular orbits at 270-290 km altitude. Our approach is based on the recognition that the 'in orbit' wind variation must show the combined effects of the diurnal wind variation as seen from the ground with the latitude variation of the satellite orbit. For the data period 77250-78035 examined thus far, the wind abatement always occurred with a corresponding pressure or temperature maximum, and was detected on 12 out of the 36 nights with data. This study has revealed that the wind abatement occur only during or shortly after increases in solar extreme ultraviolet (EUV) flux, as indicated by daily radio flux measurements. In the past, nighttime wind reversals at mid-latitudes have been associated with increased geomagnetic activity. This study indicates that intensified solar EUV heating may be responsible for anomalous thermospheric nighttime winds at mid-latitudes.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Geopysical Research Letters (ISSN 0094-8276); 22; 3; p. 271-274
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 31
    facet.materialart.
    Unknown
    Classification of rain regimes by the three-dimensional properties of reflectivity fields (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: An automated scheme to characterize precipitation echoes within small windows in the radar field is presented and applied to previously subjectively classified tropical rain cloud systems near Darwin, Australia. The classification parameters are (a) E(sub e), effective efficiency, as determined by cloud-top and cloud-base water vapor saturation mixing ratios; (b) BBF, brightband fraction, as determined by the fraction of the radar echo area in which the maximal reflectivity occurs within +/- 1.5 km of the 0 C isotherm level; and (c) del(sub r) Z, radial reflectivity gradients (dB/km). These classification criteria were applied to tropical rain cloud systems near Darwin, Australia, and to winter convective rain cloud systems in Israel. Both sets of measurements were made with nearly identical networks of C-band radars and rain gauge networks. The results of the application of these objective classification criteria to several independently predetermined rain regimes in Darwin have shown that better organized rain systems have smaller del(sub r) Z and larger BBF. Similarly, smaller del(sub r)Z and larger BBF were also observed from maritime rain cloud systems, as compared to continental rain cloud systems with the same degree of organization. Continental rain cloud system, regardless of their degree of organization, have larger depths, as expressed by E(sub e). The rainfall analyses presented in this study are based exclusively on rain gauge measurements, while radar information was used only to classify the individual gauge measurements.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Applied Meteorology (ISSN 0894-8763); 34; 1; p. 198-211
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 32
    facet.materialart.
    Unknown
    Marine ecosystem appropriation in the Indo-Pacific: a case study of the live reef fish food trade (2003)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Our ecological footprint analyses of coral reef fish fisheries and, in particular, the live reef fish food trade (FT), indicate many countries' current consumption exceeds estimated sustainable per capita global, regional and local coral reef production levels. Hong Kong appropriates 25% of SE Asia's annual reef fish production of 135 260-286 560 tonnes (t) through its FT demand, exceeding regional biocapacity by 8.3 times; reef fish fisheries demand out-paces sustainable production in the Indo-Pacific and SE Asia by 2.5 and 6 times. In contrast, most Pacific islands live within their own reef fisheries means with local demand at 〈 20% of total capacity in Oceania. The FT annually requisitions up to 40% of SE Asia's estimated reef fish and virtually all of its estimated grouper yields. Our results underscore the unsustainable nature of the FT and the urgent need for regional management and conservation of coral reef fisheries in the Indo-Pacific.
    Keywords: Earth Resources and Remote Sensing
    Type: Ambio (ISSN 0044-7447); Volume 32; 7; 481-8
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 33
    facet.materialart.
    Unknown
    ACTS Aeronautical Terminal Experiment System Description and Link Analysis (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: During the summer of 1994, the performance of an experimental mobile satellite communication system was demonstrated to industry and government representatives by the NASA Lewis Research Center (LeRC) and the Jet Propulsion Laboratory (JPL). The system was based on the advanced communications technology satellite (ACTS) and consisted of a K-/Ka-band active monolithic microwave integrated circuit (MMIC) phased array antenna system, ACTS mobile terminal (AMT) and link evaluation terminal (LET). A LeRC research aircraft, Learjet model 25, was outfitted with the active MMIC phased array antenna system and AMT and served as the experimental 20/30 Ghz aeronautical terminal. The LET at LeRC in Cleveland, OH, was interfaced with portions of fixed-AMT equipment and together provided the gateway station functions including ACTS interface and public service telephone network (PSTN) interface. The ACTS was operated in its microwave switch matrix (MSM) mode with a spot beam for the Learjet and another spot beam dedicated to the LET. The Learjet was flown over several major cities across the US and demonstrated the feasibility of a full-duplex compressed voice links for an aeronautical terminal through the 20/30 Ghz ACTS channel. This paper presents a technical description of the system including the MMIC phased array antenna system, AMT, Learjet, LET, and ACTS. The array antenna system consists of a 30 Ghz transmit array (LeRc/Texas Instruments) and two 20 Ghz receive arrays (USAF Rome Lab., Boeing, and Martin Marietta), each one very small with sufficient performance for a satellite voice link. The AMT consists of 2.4/4.8/9.6 Kbps voice coder/decoder, modem, PSTN interface and RF/IF converters. Link analysis is presented and compared to the actual performance data collected during the demonstration flights.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 1; NASA-CP-10183-Pt-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 34
    facet.materialart.
    Unknown
    MMIC Phased Array Demonstrations with ACTS (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Over a one year period from May 1994 to May 1995, a number of demonstrations were conducted by the NASA Lewis Research Center (LeRC) in which voice, data, and/or video links were established via NASA's advanced communications technology satellite (ACTS) between the ACTS link evaluation terminal (LET) in Cleveland, OH, and aeronautical and mobile or fixed Earth terminals having monolithic microwave integrated circuit (MMIC) phased array antenna systems. This paper describes four of these. In one, a duplex voice link between an aeronautical terminal on the LeRC Learjet and the ACTS was achieved. Two others demonstrated duplex voice (and in one case video as well) links between the ACTS and an Army vehicle. The fourth demonstrated a high data rate downlink from ACTS to a fixed terminal. Array antenna systems used in these demonstrations were developed by LeRC and featured LeRC and Air Force experimental arrays using gallium arsenide MMIC devices at each radiating element for electronic beam steering and distributed power amplification. The single 30 GHz transmit array was developed by NASA/LeRC and Texas Instruments. The three 20 GHz receive arrays were developed in a cooperative effort with the Air Force Rome Laboratory, taking advantage of existing Air Force array development contracts with Boeing and Lockheed Martin. The paper describes the four proof-of-concept arrays and the array control system. The system configured for each of the demonstrations is described, and results are discussed.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 1; NASA-CP-10183-Pt-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 35
    facet.materialart.
    Unknown
    Test Results of a 200 GHz, Low Noise Downconverter for USAT Applications (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A key component in the development of the advanced communication technology satellite (ACTS) ultra small aperture terminal (USAT) earth station is the low noise down converter (LND). NASA Lewis Research Center has tested a version of an LND designed by Electrodyne Systems Corporation. A number of tests were conducted to characterize the radio frequency performance of the LND over temperature. The test results presented in this paper are frequency response, noise figure, gain, group delay, power transfer characteristics, image rejection, and spurious product suppression. The LND was one of several critical microwave subsystems developed and tested for the ACTS USAT Earth stations.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 1; NASA-CP-10183-Pt-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 36
    facet.materialart.
    Unknown
    ACTS Mobile Terminal (AMT) Baseline Terminal and On-Board Satellite Results (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The advanced communications technology satellite (ACTS) mobile terminal (AMT) experiments have provided an excellent terminal technology testbed for the evaluation of K- and Ka-band mobile satellite communications (SATCOM). Such a system has proven to be highly beneficial for many different commercial and government mobile SATCOM users and applications. Combining newly developed SATCOM technology such as ACTS' highly concentrated spot beams with the smaller, higher gain K- and Ka-bands antenna technology, results in a system design that can support significantly higher throughput capacity than current commercial systems. This paper provides an overview of the architecture and design of each of these two terminals. Baseline terminal performance, satellite transponder characteristics, and an introduction to K- and Ka-band mobile SATCOM propagation are also provided.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 1; NASA-CP-10183-Pt-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 37
    facet.materialart.
    Unknown
    The Army's Use of the Advanced Communications Technology Satellite (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Tactical operations require military commanders to be mobile and have a high level of independence in their actions. Communications capabilities providing intelligence and command orders in these tactical situations have been limited to simple voice communications or low-rate narrow bandwidth communications because of the need for immediate reliable connectivity. The Advanced Communications Technology Satellite (ACTS) has brought an improved communications tool to the tactical commander giving the ability to gain access to a global communications system using high data rates and wide bandwidths. The Army has successfully tested this new capability of bandwidth-on-demand and high data rates for commanders in real-world conditions during Operation UPHOLD DEMOCRACY in Haiti during the fall and winter of 1994. This paper examines ACTS use by field commanders and details the success of the ACTS system in support of a wide variety of field condition command functions.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 1; NASA-CP-10183-Pt-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 38
    facet.materialart.
    Unknown
    Data Transfer Efficiency Over Satellite Circuits Using a Multi-Socket Extension to the File Transfer Protocol (FTP) (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: In several experiments using NASA's Advanced Communications Technology Satellite (ACTS), investigators have reported disappointing throughput using the transmission control protocol/Internet protocol (TCP/IP) protocol suite over 1.536Mbit/sec (T1) satellite circuits. A detailed analysis of file transfer protocol (FTP) file transfers reveals that both the TCP window size and the TCP 'slow starter' algorithm contribute to the observed limits in throughput. In this paper we summarize the experimental and and theoretical analysis of the throughput limit imposed by TCP on the satellite circuit. We then discuss in detail the implementation of a multi-socket FTP, XFTP client and server. XFTP has been tested using the ACTS system. Finally, we discuss a preliminary set of tests on a link with non-zero bit error rates. XFTP shows promising performance under these conditions, suggesting the possibility that a multi-socket application may be less effected by bit errors than a single, large-window TCP connection.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 1; NASA-CP-10183-Pt-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 39
    facet.materialart.
    Unknown
    Design Consideration on the ACTS T1-VSAT (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Advanced Communications Technology Satellite (ACTS) was developed by NASA as an experimental platform to demonstrate to industry the high risk technologies need for the next generation of communication satellites. The ACTS contains many state-of-the-art technologies including time division multiple accessing, adaptive error correction coding, multiple electronically steerable hopping beam antennas, spectrally efficient SMSK modulation, demand assignment multiple access protocol and on-board baseband circuit switching. An integral part of this testbed is the ACTS T1-very small aperture terminal (VSAT). The requirements imposed on the T1-VSAT demanded numerous design tradeoffs; balancing risk, cost, and implementation. Some of these considerations include: the method used for determining link quality, the development of a low cost and reliable Ka-band high power amplifier, the integration and testing environment for use in development and production and the low cost signal processing solution to high rate burst data. This paper discusses the tradeoffs considered in the selected implementation and the results obtained over the past two years of operation. Recommendations for improvements are also included.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 1; NASA-CP-10183-Pt-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 40
    facet.materialart.
    Unknown
    ACTS Multibeam Antenna On-Orbit Performance (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Advanced Communications Technology Satellite (ACTS) launched in September 1993 introduces several new technologies including a multibeam antenna (MBA) operating at Ka-band. The MBA with fixed and rapidly reconfigurable spot beams serves users equipped with small aperture terminals within the coverage area. The antenna produces spot beams with approximately 0.3 degrees beamwidth and gains of approximately 50 dBi. A number of MBA performance evaluations have been performed since the ACTS launch. These evaluations were designed to assess MBA performance (e.g., beam pointing stability, beam shape, gain, etc.) in the space environment. The on-orbit measurements found systematic environmental perturbation to the MBA beam pointing. These perturbations were found to be imposed by satellite attitude control system, antenna and spacecraft mechanical alignments, on-orbit thermal effects, etc. As a result, the footprint coverage of the MBA may not exactly cover the intended service area at all times. This report describes the space environment effects on the ACTS MBA performance as a function of time of the day and time of the year and compensation approaches for these effects.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 1; NASA-CP-10183-Pt-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 41
    facet.materialart.
    Unknown
    ACTS Operational Performance Review: September 1995 (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Advanced Communications Technology Satellite (ACTS) utilized a proven spacecraft bus with a payload that qualified new technologies to provide a wide range of on-orbit demonstrations. A comprehensive development, qualification and ground test program was implemented to reduce technology risks. Since launch in September, 1993, and insertion into its geostationary slot ACTS has accumulated over 16,000 hours of successful operation. This paper briefly reviews the technology development background then provides a summary of the operational performance observed for the spacecraft bus and communication payload subsystems and units.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 1; NASA-CP-10183-Pt-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 42
    facet.materialart.
    Unknown
    Results from ACTS Development and On-Orbit Operations (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Advanced Communications Technology Satellite (ACTS) was sponsored by NASA to develop the technology for 30/20 Ghz, spot beam communications satellites with on-board baseband and microwave matrix switching. The spot beams allow the use of very small aperture, low cost terminals as well as provide a large degree of frequency reuse. These technologies also significantly reduce the on-orbit weight per unit communication capacity. The ACTS system provides, for the most part, on-demand, integrated digital satellite /terrestrial networks with service data rates from 64 Kbps to 622 Mbps. This paper discusses the results obtained from the ACTS development and its first two years of on-orbit operations for fixed and mobile services.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 1; NASA-CP-10183-Pt-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 43
    facet.materialart.
    Unknown
    A Well Connected Future: Networking Trends (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: It is clear networks of various types are beginning to have a substantial impact on every aspect of our lives, our jobs, society and the way we perceive and use information. Commerce is moving onto the Internet; doctors are performing surgery and diagnosis with the aid of high performance networks and satellites; and political revolutions and coups are reported through the use of networks. This is only the first glimpse of what is yet to come. This paper is a brief survey of technology research in networking, with emphasis on the use of satellites present and future as a component of a global information mesh.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 2; NASA-CP-10183
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 44
    facet.materialart.
    Unknown
    Use of the Advanced Communications Technology Satellite to Promote International Distance Education Programs for Georgetown University (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Georgetown's distance education program is designed to demonstrate to faculty and administrators the feasibility and desirability of using two-way video transmission for international education. These programs will extend the reach of Georgetown's educational offerings; enrich the curriculum and content of Georgetown's offerings by interaction with institutions in other nations; enhance the world view of the School of Business Administration; enable Georgetown to share its resources with other institutions outside of the United States; and promote Commerce within the Americas. The primary reason for this pilot program is to evaluate the effectiveness and economic viability of offering academic courses and Small Business Development training.
    Keywords: Communications and Radar
    Type: Advanced Communication Technology Satellite Results Conference; Part 2; NASA-CP-10183
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 45
    facet.materialart.
    Unknown
    Accuracy of wet troposphere radio path delay estimated from infrared emission (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Several radio science applications require determination of the excess radio-propagation path delay caused by the Earth's atmosphere. These include very long baseline interferometry, spacecraft tracking, and potentially, detection of gravitational waves utilizing a link to a distant interplanetary spacecraft. At Ka band, the major source of variability of path delay is the fluctuations in the moisture content of the troposphere. The path delay characterization requirements for a planned gravitational wave experiment are novel and challenging. the error contribution to the phase observations due to path delay variation must be reduced by nearly two orders of magnitude over that occurring naturally on time scales of 100 to 10,000 seconds. Current approaches relying on microwave water vapor radiometry with ancillary data can deliver one order of magnitude calibration of these fluctuations, and more advanced systems are under development within the 2001-2002 time frame of the Cassini Mission to Saturn. The current work evaluates the potential for an alternative observational approach, using a ground-based Fourier transform spectrometer.
    Keywords: Communications and Radar
    Type: ; 33-35
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 46
    facet.materialart.
    Unknown
    Effect of stratospheric aerosol on ozone profile from BUV measurements (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Results of a simulation study on the effects of optically thick stratospheric sulfate aerosol layers on the backscattered ultraviolet radiation (buv) in the range 256-340 nm are presented. In general, the increased Mie scattering produced by the aerosols results in an enhancement of the buv radiation. The increase is approximately linear with optical depth and strongly depends on solar zenith angle and aerosol layer altitude in relation to the ozone maximum. The effect is greatest at those wavelenghts whose contribution functions peak in the vicinity of the densest part of the aerosol layer. The aerosol induced perturbation of the buv field affects the ozone profile retrieval from space measurements by the Solar Backscatter Ultraviolet Experiment (SBUV) experiment. In the tropical stratosphere, the retrieved ozone between 25 and 45 km is underestimated as a result of increased Mie scattering. On the other hand, an algorithm related effect causes the retrieved ozone below 25 km to be overestimated by an amount similar to the stratospheric deficit.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Geopysical Research Letters (ISSN 0094-8276); 22; 3; p. 235-238
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 47
    facet.materialart.
    Unknown
    Improved accuracy of radar WPMM estimated rainfall upon application of objective classification criteria (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Application of the window probability matching method to radar and rain gauge data that have been objectively classified into different rain types resulted in distinctly different Z(sub e)-R relationships for the various classifications. These classification parameters, in addition to the range from the radar, are (a) the horizontal radial reflectivity gradients (dB/km); (b) the cloud depth, as scaled by the effective efficiency; (c) the brightband fraction within the radar field window; and (d) the height of the freezing level. Combining physical parameters to identify the type of precipitation and statistical relations most appropriate to the precipitation types results in considerable improvement of both point and areal rainfall measurements. A limiting factor in the assessment of the improved accuracy is the inherent variance between the true rain intensity at the radar measured volume and the rain intensity at the mouth of the rain guage. Therefore, a very dense rain gauge network is required to validate most of the suggested realized improvement. A rather small sample size is required to achieve a stable Z(sub e)-R relationship (standard deviation of 15% of R for a given Z(sub e)) -- about 200 mm of rainfall accumulated in all guages combined for each classification.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Applied Meteorology (ISSN 0894-8763); 34; 1; p. 212-223
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 48
    facet.materialart.
    Unknown
    Remote sensing and human health: new sensors and new opportunities (2000)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Since the launch of Landsat-1 28 years ago, remotely sensed data have been used to map features on the earth's surface. An increasing number of health studies have used remotely sensed data for monitoring, surveillance, or risk mapping, particularly of vector-borne diseases. Nearly all studies used data from Landsat, the French Systeme Pour l'Observation de la Terre, and the National Oceanic and Atmospheric Administration's Advanced Very High Resolution Radiometer. New sensor systems are in orbit, or soon to be launched, whose data may prove useful for characterizing and monitoring the spatial and temporal patterns of infectious diseases. Increased computing power and spatial modeling capabilities of geographic information systems could extend the use of remote sensing beyond the research community into operational disease surveillance and control. This article illustrates how remotely sensed data have been used in health applications and assesses earth-observing satellites that could detect and map environmental variables related to the distribution of vector-borne and other diseases.
    Keywords: Earth Resources and Remote Sensing
    Type: Emerging infectious diseases (ISSN 1080-6040); Volume 6; 3; 217-27
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 49
    facet.materialart.
    Unknown
    Mars Communication Protocols (2000)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Over the next decade, international plans and commitments are underway to develop an infrastructure at Mars to support future exploration of the red planet. The purpose of this infrastructure is to provide reliable global communication and navigation coverage for on-approach, landed, roving, and in-flight assets at Mars. The claim is that this infrastructure will: 1) eliminate the need of these assets to carry Direct to Earth (DTE) communications equipment, 2) significantly increase data return and connectivity, 3) enable small mission exploration of Mars without DTE equipment, 4) provide precision navigation i.e., 10 to 100m position resolution, 5) supply timing reference accurate to 10ms. This paper in particular focuses on two CCSDS recommendations for that infrastructure: CCSDS Proximity-1 Space Link Protocol and CCSDS File Delivery Protocol (CFDP). A key aspect of Mars exploration will be the ability of future missions to interoperate. These protocols establish a framework for interoperability by providing standard communication, navigation, and timing services. In addition, these services include strategies to recover gracefully from communication interruptions and interference while ensuring backward compatibility with previous missions from previous phases of exploration.
    Keywords: Communications and Radar
    Type: Concepts and Approaches for Mars Exploration; Part 1; 172-173; LPI-Contrib-1062-Pt-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 50
    facet.materialart.
    Unknown
    Minimum High Fire Temperatures Detected in AVIRIS Spectral Measurements from Brazil in 1995 (1998)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: In August and September of 1995 the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) was deployed to Brazil as part of the NASA Smoke Cloud Aerosol and Radiation experiment in Brazil (SCAR-B). AVIRIS measures spectra from 400 to 2500 nm at 10-nm intervals. These spectra are acquired as images with dimensions of 11 by up to 800 km with 20-m spatial resolution. Spectral images measured by AVIRIS are spectrally, radiometrically, and spatially calibrated. During the SCAR-B deployment, AVIRIS measured more than 300 million spectra of regions of Brazil. A portion of these spectra were acquired over areas of actively burning fires. Actively burning fires emit radiance in the AVIRIS spectral range as a function of temperature. This emitted radiance is expressed from the 2500-nm end of the AVIRIS spectrum to shorter wavelengths as a function of intensity and modeled by the Planck function.. The objective of this research and analysis was to use spectroscopic methods to determine the minimum high temperature of the most intense fires measured in the SCAR-B AVIRIS data set. Spectra measured by AVIRIS with hot sources have been previously examined for volcanic lava and fires in Brazil.
    Keywords: Earth Resources and Remote Sensing
    Type: Summaries of the Seventh JPL Airborne Earth Science Workshop January 12-16, 1998; Volume 1; 185-192A; JPL-Publ-97-21-Vol-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 51
    facet.materialart.
    Unknown
    Calibration Targets of the Southwest: Albedo and Homogeneity Comparisons Using AVIRIS Data (1998)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Various locations in the southwestern U.S. are used to calibrate remote sensing instruments. This study shows how some of these targets compare in terms of albedo and homogeneity, and records the variation of these factors for a single location (Ivanpah Playa) over a period of one year. Results indicate that there is a great deal of variation among these targets in albedo, spectral flatness, and surface uniformity, and that these factors can change throughout the year.
    Keywords: Earth Resources and Remote Sensing
    Type: Summaries of the Seventh JPL Airborne Earth Science Workshop January 12-16, 1998; Volume 1; 319-323; JPL-Publ-97-21-Vol-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 52
    facet.materialart.
    Unknown
    Communications Between Crews on Mars and Scientists on Earth (1998)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: For the purpose of the following discussion, we assume that of the six crew members sent to Mars, at least three will be scientists. We further assume that geological and biological investigations will proceed together (although investigative techniques may vary), both for vestiges of ancient life, and for evidence of living organisms. Finally, unexpected discoveries may cause sudden changes in exploration strategies, and mission planning should be flexible enough to accommodate such shifts.
    Keywords: Communications and Radar
    Type: Mars Field Geology, Biology. and Paleontology Workshop: Summary and Recommendations; 31-37; LPI-Contrib-968
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 53
    facet.materialart.
    Unknown
    Mars Global Surveyor Ka-Band Link Experiment Results (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: This paper presents The Mars Global Surveyor Ka-Band Link Experimental Results in viewgraph form. Topics include: 1) Deep Space Ka-band Link Advantage; 2) Deep Space Ka-band Telecommunications; 3) Mars Global Surveyor (MGS) Signal Levels and Ka-band Top for Clear Weather Pass; 4) MGS Signal Levels and Ka-band Top for Rainy Weather Pass; 5) MGS Ka-band to X-band Link Advantage; and 6) Conclusion. A 6 to 8 dB link advantage can be realized by using Ka band (32 GHz) as a telecommunications link frequency in place of X-band (8.4 GHz). This link advantage was demonstrated using two years worth of Mars Global Surveyor simultaneous Ka/X data after correcting for known equipment deficiencies.
    Keywords: Communications and Radar
    Type: Proceedings of the Twenty-Third NASA Propagation Experimenters Meeting (NAPEX XXIII) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Workshop; 295-301; JPL-Publ-99-16
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 54
    facet.materialart.
    Unknown
    Ice Flow in the North East Greenland Ice Stream (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Early observations with ERS-1 SAR image data revealed a large ice stream in North East Greenland (Fahnestock 1993). The ice stream has a number of the characteristics of the more closely studied ice streams in Antarctica, including its large size and gross geometry. The onset of rapid flow close to the ice divide and the evolution of its flow pattern, however, make this ice stream unique. These features can be seen in the balance velocities for the ice stream (Joughin 1997) and its outlets. The ice stream is identifiable for more than 700 km, making it much longer than any other flow feature in Greenland. Our research goals are to gain a greater understanding of the ice flow in the northeast Greenland ice stream and its outlet glaciers in order to assess their impact on the past, present, and future mass balance of the ice sheet. We will accomplish these goals using a combination of remotely sensed data and ice sheet models. We are using satellite radar interferometry data to produce a complete maps of velocity and topography over the entire ice stream. We are in the process of developing methods to use these data in conjunction with existing ice sheet models similar to those that have been used to improve understanding of the mechanics of flow in Antarctic ice streams.
    Keywords: Earth Resources and Remote Sensing
    Type: Program for Arctic Regional Climate Assessment (PARCA); 16-19; NASA/TM-1999-209205
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 55
    facet.materialart.
    Unknown
    Interdisciplinary Determination of Ice Sheet Accumulation Patterns: Combined Atmospheric Modeling and Field and Remote Sensing Studies (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: This research is focusing on two related areas that are fundamental to the NASA PARCA (Program for Arctic Regional Climate Assessment) program. The primary research area is the determination of the amount, rate, and timing of accumulation at distributed sites in the dry snow zone of Greenland and evaluation of these results in light of accumulation modeling results. The secondary research area is the calibration of the isotope "thermometer" at these ice sheet sites as well as the determination of long-term temperature trends in Greenland.
    Keywords: Earth Resources and Remote Sensing
    Type: Program for Arctic Regional Climate Assessment (PARCA); 60-62; NASA/TM-1999-209205
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 56
    facet.materialart.
    Unknown
    Mapping Volcanic Gas Emissions in the Mammoth Mountain Area Using AVIRIS (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The Long Valley Caldera located in the eastern Sierra Nevada (California) shows new signs of volcanic activity. This renewed activity is expressed by gas emissions, hydrothermal activity and frequent earthquakes. Analysis of the gas composition regarding the percentage biogenic carbon and the He-3/He-4 ratio revealed that the gas source is the magma body approximately 7 km beneath the Long Valley Caldera. The gas from the magma body surfaces not only via the fumaroles but also emerges along geological faults. Some of the spots where gas surfaces are marked by dead or stressed trees. Other spots may not yet be identified. It is only recently known, from research at 'Vulcano Island' in southern Italy, that volcanoes release abundant carbon dioxide from their flanks as diffuse soil emanations. Mammoth Mountain seems to behave in a similar manner. The research described in this paper is designed to determine whether AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) can be used to identify areas of volcanic gas emissions.
    Keywords: Earth Resources and Remote Sensing
    Type: Summaries of the Sixth Annual JPL Airborne Earth Science Workshop; Volume 1; 75-81; NASA/CR/96-113073
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 57
    facet.materialart.
    Unknown
    Repeat Pass Aircraft Interferometry Results at Portage Lake, Maine and Innisfail, Australia (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The NASA/JPL AIRSAR/TOPSAR instruments have the capability of collecting fully polarimetric radar data at three wavelengths (C, L and P-Bands) and dual antenna interferometry at C-Band, and more recently L-Band. In order to understand frequency and baseline dependent scattering effects in vegetated regions repeat pass interferometry data was collected for two vegetated regions in 1993. Portage Lake, Maine is a primarily coniferous forested region with some clear cutting from logging activities in the region. The second site at Innisfail, Australia borders a tropical rain forest and is situated adjacent to some major clear cut regions and banana plantations. Preliminary analysis of repeat pass data collected in these areas shows that the smaller the wavelength the greater the temporal decorrelation between passes, the longer the wavelength the greater the penetration depth for some types of vegetation canopy, yet for some vegetation canopy types, in particular for a banana plantation there appears to be no frequency dependent penetration into the canopy.
    Keywords: Earth Resources and Remote Sensing
    Type: Summaries of the Sixth Annual JPL Airborne Earth Science Workshop; Volume 2; 9-33; NASA/CR-96-112598
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 58
    facet.materialart.
    Unknown
    Fade Dynamics and its Evolution: The Other Part of the ACTS Rain Prediction Model (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The inception of the Advanced Communication Technology Satellite (ACTS) Project has required a similarly advanced statistical mathematical modeling formalism to describe the behavior of the 30/20 GHz links emanating to and from the earth terminals through the deleterious effects of the earth's atmosphere. The resulting ACTS Rain Attenuation Prediction Model has been thoroughly described in (Manning). In the present paper, the basic rudiments of this model will be reviewed; Section 1 covers the static or time-independent portion of the model and Section 2 covers the dynamic or time-dependent portion. The results of Section 2 are then applied to a new approximate solution of the famous problem of the time duration tau of a fade of a random process below some threshold. This is known as the fade duration. The new approximate solution was published in Russian (Denisenko) and, unfortunately, was never published into English. Hence, this work is restated following (Denisenko) in Section 3 which is immediately applied to the random rain fade process. The results for all five ACTS propagation sites as well as Tampa, FL are then given.
    Keywords: Communications and Radar
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 59
    facet.materialart.
    Unknown
    A Database for Propagation Models (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The Propagation Models Database is designed to allow the scientists and experimenters in the propagation field to process their data through many known and accepted propagation models. The database is an Excel 5.0 based software that houses user-callable propagation models of propagation phenomena. It does not contain a database of propagation data generated out of the experiments. The database not only provides a powerful software tool to process the data generated by the experiments, but is also a time- and energy-saving tool for plotting results, generating tables and producing impressive and crisp hard copy for presentation and filing.
    Keywords: Communications and Radar
    Type: Proceedings of the Twenty-First NASA Propagation Experimenters Meeting (NAPEX XXI) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop; NASA-CR-205595
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 60
    facet.materialart.
    Unknown
    CERES and the S'COOL Project (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The first Clouds and the Earth's Radiant Energy System (CERES) instrument will be launched on the Tropical Rainfall Measuring Mission (TRMM) spacecraft from a Japanese launch site in November 1997. This instrument is a follow-on to the Earth Radiation Budget Experiment (ERBE) begun in the 1980's. The instrument will measure the radiation budget - incoming and outgoing radiant energy - of the Earth. It will establish a baseline and look for climatic trends. The major feature of interest is clouds, which play a very strong role in regulating our climate. CERES will identify clear and cloudy regions and determine cloud physical and microphysical properties using imager data from a companion instrument. Validation efforts for the remote sensing algorithms will be intensive. As one component of the validation, the S'COOL (Students' Cloud Observations On-Line) project will involve school children from around the globe in making ground truth measurements at the time of a CERES overpass. Their observations will be collected at the NASA Langley Distributed Active Archive Center (DAAC) and made available over the Internet for educational purposes as well as for use by the CERES Science Team in validation efforts. Pilot testing of the S'COOL project began in January 1997 with two local schools in Southeastern Virginia and one remote site in Montana. This experience is helping guide the development of the S'COOL project. National testing is planned for April 1997, international testing for July 1997, and global testing for October 1997. In 1998, when the CERES instrument is operational, a global observer network should be in place providing useful information to the scientists and learning opportunities to the students.
    Keywords: Earth Resources and Remote Sensing
    Type: The Sixth Alumni Conference of the International Space University; 150-157; NASA-CP-3355
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 61
    facet.materialart.
    Unknown
    SIR-C Measurements of Soil Moisture, Vegetation and Surface Roughness and their Hydrological Application (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The objectives of the study are: (1) Analysis of SIR-C/X-SAR response to soil moisture, vegetation and surface roughness and development of an algorithm to retrieve these parameters; (2) Combination of the visible and near-infrared data and the SIR-C/X-SAR data to improve the range and accuracy of vegetation classification; (3) Testing of theoretical models for microwave propagation with SIR-C/X-SAR and microwave radiometric measurements over rough surfaces; and (4) Evaluation of a water balance model using SIR-C/X-SAR derived soil moisture values and other ancillary data. Progress, significant results and future plans are presented.
    Keywords: Earth Resources and Remote Sensing
    Type: Science Results from the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR): Progress Report; 215-217; NASA/CR-97-206707
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 62
    facet.materialart.
    Unknown
    Radar Interferometric and Penetration Investigations using SIR-C Data (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Progress, significant results, publications and future plans are discussed in relation to the following objectives: (1) To model, experimentally characterize, and verify penetration phenomena in hyperarid and vegetated regions using the SIR-C/X-SAR multiparameter radar system and groundbased receivers; (2) To invert measured radar backscatter as a function of frequency and polarization in terms of geophysical parameters of the surface, subsurface and vegetation canopy such as surface roughness, subsurface geomorphology, or tree height and density; and (3) To display subsurface and within-canopy features in an image format, thus easing the interpretability of the results.
    Keywords: Earth Resources and Remote Sensing
    Type: Science Results from the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR): Progress Report; 228-230; NASA/CR-97-206707
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 63
    facet.materialart.
    Unknown
    SIR-C/X-SAR: Imaging Radar Analyses for Forest Ecosystem Modeling (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Progress, significant results and future plans are discussed relating to the following objectives: (1) Ecosystem characterization using SIR-C/X-SAR and AirSAR data; (2) Improving radar backscatter models for forest canopies; and (3) Using SAR measurements and models with forest ecosystem models to improve inferences of ecosystem attributes and processes.
    Keywords: Earth Resources and Remote Sensing
    Type: Science Results from the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR): Progress Report; 153-158; NASA/CR-97-206707
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 64
    facet.materialart.
    Unknown
    Differential Radar Interferometry (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Progress and future plans regarding the following objectives are presented: (1) Test differential radar interferometry as a new monitoring technique for remote sensing of a forest site, a farm site, and a desert site; and (2) Generate topographic maps of test sites from radar data.
    Keywords: Earth Resources and Remote Sensing
    Type: Science Results from the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR): Progress Report; 66-67; NASA/CR-97-206707
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 65
    facet.materialart.
    Unknown
    Multifrequency, Multipolarization External Calibration of the SIR-C/X-SAR Radars (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Progress and the future plans for the following objectives are discussed: (1) Assess the accuracy at which the SIR-C/X-SAR standard data products can be calibrated through the use of ground calibrators to estimate the end-to-end system polarization calibration constants (or distortion parameters) and incorporate the constants into the data processing; (2) Study the cross-calibration between three multipolarization systems: SIR-C, the National Aeronautics and Space Administration/Jet Propulsion Laboratory (NASA/JPL) DC-8 SAR, and the University of Michigan ground-based polarimetric scatterometer; (3) Evaluate the calibration "stability" of SIR-C/X-SAR (measured by variations in the calibration constants) over the range swath width and over a specified distance in azimuth. Variations over a 12-hour period (between ascending and descending passes) will also be studied; and (4) Develop a cost-effective calibration plan including development of inexpensive polarimetric active calibrators.
    Keywords: Communications and Radar
    Type: Science Results from the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR): Progress Report; 55-57; NASA/CR-97-206707
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 66
    facet.materialart.
    Unknown
    Application of SIR-C SAR to Hydrology (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The progress, results and future plans regarding the following objectives are presented: (1) Determine and compare soil moisture patterns within one or more humid watersheds using SAR data, ground-based measurements, and hydrologic modeling; (2) Use radar data to characterize the hydrologic regime within a catchment and to identify the runoff producing characteristics of humid zone watersheds; and (3) Use radar data as the basis for scaling up from small scale, near-point process models to larger scale water balance models necessary to define and quantify the land phase of GCM's (Global Circulation Models).
    Keywords: Earth Resources and Remote Sensing
    Type: Science Results from the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR): Progress Report; 43-47; NASA/CR-97-206707
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 67
    facet.materialart.
    Unknown
    Culture and Workplace Communications: A Comparison of the Technical Communications Practices of Japanese and U.S. Aerospace Engineers and Scientists (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The advent of global markets elevates the role and importance of culture as a mitigating factor in the diffusion of knowledge and technology and in product and process innovation. This is especially true in the large commercial aircraft (LCA) sector where the production and market aspects are becoming increasingly international. As firms expand beyond their national borders, using such methods as risk-sharing partnerships, joint ventures, outsourcing, and alliances, they have to contend with national and corporate cultures. Our focus is on Japan, a program participant in the production of the Boeing Company's 777. The aspects of Japanese culture and workplace communications will be examined: (1) the influence of Japanese culture on the diffusion of knowledge and technology in aerospace at the national and international levels; (2) those cultural determinants-the propensity to work together, a willingness to subsume individual interests to a greater good, and an emphasis on consensual decision making-that have a direct bearing on the ability of Japanese firms to form alliances and compete in international markets; (3) and those cultural determinants thought to influence the information-seeking behaviors and workplace communication practices of Japanese aerospace engineers and scientists. In this article, we report selective results from a survey of Japanese and U.S. aerospace engineers and scientists that focused on workplace communications. Data are presented for the following topics: importance of and time spent communicating information, collaborative writing, need for an undergraduate course in technical communication, use of libraries, use and importance of electronic (computer) networks, and the use and importance of foreign and domestically produced technical reports.
    Keywords: Communications and Radar
    Type: Journal of Air Transportation World Wide; Volume 2; No. 1; 1-21; NASA/TM-97-112609
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 68
    facet.materialart.
    Unknown
    Repeat Pass Aircraft Interferometry Results at Portage Lake, Maine and Innisfail, Australia (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The NASA/JPL AIRSAR/TOPSAR instruments have the capability of collecting fully polarimetric radar data at three wavelengths (C, L, and P-bands) and dual antenna interferometry at C-band, and more recently, L-band. In order to understand frequency and baseline dependent scattering effects in vegetated regions, repeat pass interferometry data was collected for two vegetated regions in 1993. Portage Lake, Maine is a primarily coniferous forested region with some clear cutting from logging activities in the region. The second site at Innisfail, Australia borders a tropical rain forest and is situated adjacent to some major clear cut regions and banana plantations. Preliminary analysis of repeat pass data collected in these areas shows that the smaller the wavelength the greater the temporal decorrelation between passes, the longer the wavelength the greater the penetration depth for some types of vegetation canopy, yet for some vegetation canopy types, in particular for a banana plantation, there appears to be no frequency dependent penetration into the canopy.
    Keywords: Earth Resources and Remote Sensing
    Type: Summaries of the Sixth Annual JPL Airborne Earth Science Workshop, March 4-8, 1996; Volume 2; 9-33; NASA-CR-203428
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 69
    facet.materialart.
    Unknown
    System and antenna design considerations for highly elliptical orbits as applied to the proposed Archimedes Constellation (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The paper discusses various aspects of the system design for a satellite in a highly elliptical inclined orbit, and presents a number of antenna design options for the proposed Archimedes mission. A satellite constellation was studied for the provision of multi media communication services in the L and S Band for northern latitudes. The inclined elliptical orbit would allow coverage of Europe, America, and East Asia. Using Canada and North America as the baseline coverage area, this paper addresses system considerations such as the satellite configuration and pointing, beam configuration, and requirements for antennas. A trade-off is performed among several antenna candidates including a direct radiating array, a focal-fed reflector, and a single reflector imaging system. Antenna geometry, performance, and beam forming methods are described. The impact of the designs on the antenna deployment is discussed.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 236-241; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 70
    facet.materialart.
    Unknown
    Architecture of the TELEDESIC satellite system (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: There is a significant worldwide demand for broadband communications capacity. Teledesic plans to meet this demand using a constellation of 924 low-Earth orbit (LEO) satellites operating in Ka-band (30/20 GHz). The Teledesic network will provide 'fiber-like' service quality, including low transmission delay, high data rates, and low bit error rates, to fixed and mobile users around the world starting in 2001.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 212-218; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 71
    facet.materialart.
    Unknown
    Alternative beam configuration for a Canadian Ka-band satellite system (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Satellite systems operating in the Ka-band have been proposed to offer wide band personal communications services to fixed earth terminals employing small aperture antennas as well as to mobile terminals. This requirement to service a small aperture antenna leads to a satellite system utilizing small spot beams. The traditional approach is to cover the service area with uniform spot beams which have been sized to provide a given grade of service at the worst location over the service area and to place them in a honeycomb pattern. In the lower frequency bands this approach leads to a fairly uniform grade of service over the service area due to the minimal effects of rain on the signals. At Ka-band, however, the effects of rain are quite significant. Using this approach over a large service area (e.g. Canada) where the geographic distribution of rain impairment varies significantly yields an inefficient use of satellite resources to provide a uniform grade of service. An alternative approach is to cover the service area using more than one spot beam size in effect linking the spot beam size to the severity of the rain effects in a region. This paper demonstrates how for a Canadian Ka-band satellite system, that the use of two spot beam sizes can provide a more uniform grade of service across the country as well as reduce the satellite payload complexity over a design utilizing a single spot beam size.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 231-235; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 72
    facet.materialart.
    Unknown
    The NUONCE engine for LEO networks (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Typical LEO networks use constellations which provide a uniform coverage. However, the demand for telecom service is dynamic and unevenly distributed around the world. We examine a more efficient and cost effective design by matching the satellite coverage with the cyclical demand for service around the world. Our approach is to use a non-uniform satellite distribution for the network. We have named this constellation design NUONCE for Non Uniform Optimal Network Communications Engine.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 193-197; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 73
    facet.materialart.
    Unknown
    Air traffic management system design using satellite based geo-positioning and communications assets (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The current FAA and ICAO FANS vision of Air Traffic Management will transition the functions of Communications, Navigation, and Surveillance to satellite based assets in the 21st century. Fundamental to widespread acceptance of this vision is a geo-positioning system that can provide worldwide access with best case differential GPS performance, but without the associated problems. A robust communications capability linking-up aircraft and towers to meet the voice and data requirements is also essential. The current GPS constellation does not provide continuous global coverage with a sufficient number of satellites to meet the precision landing requirements as set by the world community. Periodic loss of the minimum number of satellites in view creates an integrity problem, which prevents GPS from becoming the primary system for navigation. Furthermore, there is reluctance on the part of many countries to depend on assets like GPS and GLONASS which are controlled by military communities. This paper addresses these concerns and provides a system solving the key issues associated with navigation, automatic dependent surveillance, and flexible communications. It contains an independent GPS-like navigation system with 27 satellites providing global coverage with a minimum of six in view at all times. Robust communications is provided by a network of TDMA/FDMA communications payloads contained on these satellites. This network can support simultaneous communications for up to 30,000 links, nearly enough to simultaneously support three times the current global fleet of jumbo air passenger aircraft. All of the required hardware is directly traceable to existing designs.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 198-203; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 74
    facet.materialart.
    Unknown
    Description of AMSC's North American Private Voice Network (PVN) service (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: This paper provides both a technical description of the American Mobile Satellite Corporation (AMSC) Point-to-Multipoint Voice service and initial service offering descriptions. AMSC has selected the term Private Voice Network (PVN) for this service. The PVN service has been designed to take advantage of AMSC's continent-wide coverage. Thus PVN provides a service not currently found in the mobile communications marketplace, seamless 2-way point-multipoint voice communications across North America. This paper describes the PVN system within terms of physical components and configurations overall PVN system capabilities and initial PVN product offerings.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 535; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 75
    facet.materialart.
    Unknown
    European Mobile Satellite Services (EMSS): A regional system for Europe (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The European Space Agency is presently procuring two L-band payloads in order to promote a regional system for the provision of European Mobile Satellite Services (EMSS). These are the EMS payload on the Italsat I-F2 satellite and the LLM payload on the ARTEMIS satellite. Telecommunication system studies have been concentrating on mobile applications where full European geographical coverage is required. Potential applications include high priority Private Mobile Radio networks requiring national or European coverage, such as civil security, fire brigades, police and health services, as well as a dedicated system for provision of Air Traffic Services to the civil aviation community. A typical application is an intelligent road traffic management system combining a geographically selective traffic data collection service based on probe vehicles with a geographically selective traffic information broadcast service. Network architectures and bearer services have been developed both for data only and voice/data services. Vehicle mounted mobile transceivers using CDMA access techniques have been developed. The EMSS operational phase will start with the EMS payload in orbit in 1996 and continue with the LLM payload in 1997.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 545-550; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 76
    facet.materialart.
    Unknown
    The Telestation: A product for distributed data gathering and operations (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Advances in computer, navigation and wireless telecommunication technologies are enabling better electronic devices at reduced costs. Individually, these devices have been applied to increase the performance of many common systems, such as desktop computers, surveying equipment, and modems. However, we believe the convergence of these three technologies will create a product that simultaneously lowers life cycle costs while increasing operational effectiveness. Space Systems/Loral (SS/L) is developing portions of this product, known as the Telestation, for both terrestrial and orbital applications. The Telestation consists of an advanced microprocessor for command and data handling; a GPS receiver for position, time, and attitude information; and a Globalstar Transceiver for two-way digital communications. The Telestation provides the user with real-time command and control of globally distributed hardware elements. This capability can be applied terrestrially for gathering information (e.g., science, environmental, etc.) in remote or inhospitable locations, or where logistical support is inadequate. An in-orbit version can be used for spacecraft or payload operations, allowing principal investigators instant access to their payloads during all phases of a mission. This paper describes some cost effectiveness metrics of the Telestation, its development status, and its utility in both terrestrial and orbital applications.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 539-544; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 77
    facet.materialart.
    Unknown
    Using ATM over SATCOM links (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The Asynchronous Transfer Mode (ATM) protocol is studied from the standpoint of determining what limitations, if any, exist in using it over satellite links. It is concluded that, while there is nothing intrinsic about ATM that would generally preclude its use over satellite links, there are, however, several intrinsic characteristics of satellite links, as well as some satellite system configuration-specific issues, that must be taken into account.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 525-532; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 78
    facet.materialart.
    Unknown
    Satellite-enhanced personal communications experiments (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: As an initial step in exploring the opportunities afforded by the merging of satellite and terrestrial networks, Bellcore and JPL conducted several experiments utilizing Bellcore's experimental Personal Communications System, NASA's Advanced Communications Technology Satellite (ACTS) and JPL's ACTS Mobile Terminal. These experiments provided valuable information on the applications, interfaces, and protocols needed for seamless integration of satellite and terrestrial networks.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 518-524; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 79
    facet.materialart.
    Unknown
    IRIDIUM (R): A Lockheed transition to commercial space (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: At Lockheed Missiles & Space Company, the IRIDIUM commercial space program is dramatically revolutionizing spacecraft development and manufacturing processes to reduce cost while maintaining quality and reliability. This report includes the following sections: an overview of the IRIDIUM system, the Lockheed IRIDIUM project and challenges; cycle-time reduction through production reorganization; and design for manufacturing and quality.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 90-95; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 80
    facet.materialart.
    Unknown
    David Florida Laboratory: Support for mobile satellite communications (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The comprehensive integration and environmental (including RF) test facilities of the Canadian Space Agency's David Florida Laboratory (CSA)(DFL) were used extensively for the MSAT Program. Following a description of the facilities, the paper outlines their application to the qualification of the two MSAT satellites following an overview of the test plan. Particular emphasis is given to passive intermodulation measurement (PIM) demands, which for the MSAT satellites, contributed to the need to extend the anechoic chamber. The extended chamber was also used for an EMC test and SAR signature test of the RADARSAT satellite. The DFL's facilities are being used for additional aspects of mobile satellite communications. One shielded anechoic Extra High Frequency (EHF) chamber and associated test equipment are employed predominantly for measuring the performance of the IRIDIUM satellites' Engineering Model Gateway Moveable Antennas (EM)(GMA). Other chambers are used for testing aeronautical antennas on behalf of Inmarsat. Still others combine thermal and PIM testing. The paper concludes with a review of the test requirements of evolving satcom missions such as Inmarsat Aero-1.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 86-89; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 81
    facet.materialart.
    Unknown
    DS-CDMA satellite diversity reception for personal satellite communication: Downlink performance analysis (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The downlink of a satellite-mobile personal communication system employing power-controlled Direct Sequence Code Division Multiple Access (DS-CDMA) and exploiting satellite-diversity is analyzed and its performance compared with a more traditional communication system utilizing single satellite reception. The analytical model developed has been thoroughly validated by means of extensive Monte Carlo computer simulations. It is shown how the capacity gain provided by diversity reception shrinks considerably in the presence of increasing traffic or in the case of light shadowing conditions. Moreover, the quantitative results tend to indicate that to combat system capacity reduction due to intra-system interference, no more than two satellites shall be active over the same region. To achieve higher system capacity, differently from terrestrial cellular systems, Multi-User Detection (MUD) techniques are likely to be required in the mobile user terminal, thus considerably increasing its complexity.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 463-468; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 82
    facet.materialart.
    Unknown
    Boeing Satellite Television Airplane Receiving System (STARS) performance (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Boeing Defense and Space Group is developing a Satellite Television Airplane Receiving System (STARS) capable of delivering Direct Broadcast Satellite (DBS) television to an aircraft in-flight. This enables a new service for commercial airplanes that will make use of existing and future DBS systems. The home entertainment satellites, along with STARS, provide a new mobile satellite communication application. This paper will provide a brief background of the antenna issues associated with STARS for commercial airplanes and then describe the innovative Boeing phased-array solution to these problems. The paper then provides a link budget of the STARS using the Hughes DBS as an example, but the system will work with all of the proposed DBS satellites in the 12.2-12.7 GHz band. It concludes with operational performance calculations of the STARS system, supported by measured test data of an operational 16-element subarray. Although this system is being developed for commercial airplanes, it is well suited for a wide variety of mobile military and other commercial communications systems in air, on land and at sea. The applications include sending high quality video for the digital battlefield and large volumes of data on the information superhighway at rates in excess of 350 Mbps.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 301-305; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 83
    facet.materialart.
    Unknown
    Mobile satellite business networks: A part of the European mobile system (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The European Space Agency (ESA) is presently procuring an L-band payload EMS, to be embarked on the ITALSAT-2 satellite due for launch in early 1996, in order to promote a regional European mobile system. One of the Land Mobile Communication systems supported by EMS is the MSBN (Mobile Satellite Business Network) voice and data system which will offer the services of a business network on a seamless European coverage. This paper will first recall the characteristics of the MSBN system, which is based on quasi-synchronized CDMA (Code Division Multiple Access) techniques in both directions, and then describe the CDMA receivers implementation. Main validation test results will also be reported confirming predicted performances.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 219-224; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 84
    facet.materialart.
    Unknown
    Global tracking and inventory of military hardware via LEO satellite: A system approach and likely scenario (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: A system for global inventory control of electronically tagged military hardware is achievable using a LEO satellite constellation. An equipment Tag can communicate directly to the satellite with a power of 5 watts or less at a data rate of 2400 to 50,000 bps. As examples, two proposed commercial LEO systems, IRIDIUM and ORBCOMM, are both capable of providing global coverage but with dramatically different telecom capacities. Investigation of these two LEO systems as applied to the Tag scenario provides insight into satellite design trade-offs, constellation trade-offs and signal dynamics that effect the performance of a satellite-based global inventory control system.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 204-211; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 85
    facet.materialart.
    Unknown
    The GEMnet (TM) global data communication (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The GEMnet(TM) (Global Electronics Message network) will provide global digital data communications anywhere in the world at any time for minimum cost. GEMnet(TM) is an end-to-end Non-Voice Non-Geostationary Mobile Satellite (NVNG) (sometimes dubbed 'Little LEO') System which consists of a constellation of 38 low Earth orbiting small satellites and a ground segment. The GEMnet(TM) ground segment will consist of subscriber user terminals, gateway stations, a Network Operational Center(NOC), and a backbone network interconnecting the NOC and gateways. This paper will describe the GEMnet(TM) system concept including ground and space segments, system heritage, data communication services, and protocols.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 179-184; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 86
    facet.materialart.
    Unknown
    A LEO concept for millimeter wave satellite communication (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: A conceptual 60 satellite LEO constellation for millimeter wave communication is discussed. It could be launched in segments, with the first 30 satellites providing high elevation angles for all time in the Northern latitudes between Miami and Thule. The second set of 30 satellites would complete the worldwide coverage with emphasis on high ground elevation angles in the densely populated temperate zones. Full earth searches for all time are used to generate probability density functions for elevation angle. The density functions are used to derive optimum frequencies for random elevation systems. The 55 degree average elevation angle and 14 degree standard deviation are seen to be acceptable for 0.997 rain availability in Washington, DC for the 40 to 47 GHz region. The 40 to 47 GHz region is nearly optimum, if 0.99 rain availability is acceptable.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 185-192; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 87
    facet.materialart.
    Unknown
    Land mobile satellite narrowband propagation campaign at Ka-band (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: This paper gives a short description of the equipment used, lists the activities of the experimental campaign and presents the first statistical evaluation of the recorded data. Due to the restricted size of the document only few results are reported.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 134-138; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 88
    facet.materialart.
    Unknown
    AMT experiment results (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The Advanced Communications Technology Satellite (ACTS) Mobile Terminal (AMT) experiments have provided a terminal technology testbed for the evaluation of K- and Ka-band mobile satellite communications (satcom). Such a system could prove to be highly beneficial for many different commercial and government mobile satcom users. Combining ACTS' highly concentrated spotbeams with the smaller, higher-gain Ka-band antenna technology, results in a system design that can support a much higher throughput capacity than today's commercial configurations. To date, experiments in such diverse areas as emergency medical applications, enhanced Personal Communication Services (PCS), disaster recovery assistance, military applications, and general voice and data services have already been evaluated. Other applications that will be evaluated over the next year include telemedicine, ISDN, and television network return feed. Baseline AMT performance results will be presented, including Bit Error Rate (BER) curves and mobile propagation data characterizing the K- and Ka-band mobile satcom channel. In addition, observations from many of the application-specific experiments will also be provided.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 147-157; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 89
    facet.materialart.
    Unknown
    A wideband channel model for land mobile satellite systems (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: A wideband channel model for Land Mobile Satellite (LMS) services is presented which characterizes the time-varying transmission channel between a satellite and a mobile user terminal. The channel model statistic parameters are the results of fitting procedures to measured data. The data used for fitting have a time resolution of 33 ns corresponding to a bandwidth of 30 MHz. Thus, the model is capable to characterize the channel behaviour for a wide range of services e.g., voice transmission, digital audio broadcasting (DAB), and spread spectrum modulation schemes. The model is presented for different environments and scenarios. The model is derived for a quasi-mobile user with hand-held terminal being in two different environments: rural and urban. The parameters needed for the description are (a) the number of echoes, (b) the distribution of the echo power, and (c) the distribution of the echo delay. It is shown that the direct path follows a Rician distribution whereas the reflected paths are Rayleigh/lognormal distributed. The parameters are given for an elevation angle of 25 deg.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 122-127; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 90
    facet.materialart.
    Unknown
    Narrow- and wide-band channel characterization for land mobile satellite systems: Experimental results at L-band (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The results of an airborne measurement campaign aimed at the characterization of the mobile satellite link are presented in this paper. The experimental tests were carried out at 1.8 GHz. The objective of the campaign was to obtain results applicable to all proposed satellite constellations: LEO, HEO, and GEO. Therefore, the measurements were performed for elevation angles from 10 deg...80 deg using a light aircraft. A set of different environments and operational scenarios have been investigated, typically for hand-held and car-mounted applications. We present a survey of wide- and narrowband results for a wide range of elevation angles and environments. For the wideband characterization, the power delay profiles of the channel impulse response are presented and discussed. Figures for the delay spread versus elevation and for the carrier-to-multipath ratio versus time are also given. The narrowband behaviour of the channel is described by power series.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 115-121; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 91
    facet.materialart.
    Unknown
    An efficient software implementation of a variable rate modem (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: This paper describes the software implementation of the baseband portion of a variable rate modem. The modem can handle arbitrary symbol rates with a fixed input/output sample rate. This approach reduces hardware complexity related to external clock generation circuitry, offers complete flexibility in the selection of symbol rates, and conveniently accommodates symbol timing and symbol rate corrections.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 8-12; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 92
    facet.materialart.
    Unknown
    Low bitrate system design in the presence of phase noise (1995)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: There are a number of interesting mobile satellite applications that require the transmission of short packets of data. In the design of such systems one of the challenges is often to minimize the transmitted power to reduce cost, which implies using power efficient low bit-rate modulation and coding methods. PSK systems can be very power efficient, but at low bit-rates the carrier recovery circuits can be sensitive to oscillator phase noise. In this paper we address the problem of determining the lowest bit-rate that can be supported using PSK for a given level of system phase noise. The classical formulas are reviewed, and a method is derived to calculate the minimum C/N(sub 0) required to recover the carrier for CW, BPSK and QPSK signals for a given phase noise level.
    Keywords: Communications and Radar
    Type: Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995); 3-7; NASA-CR-199955
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 93
    facet.materialart.
    Unknown
    Diurnal Reflectance Changes in Vegetation Observed with AVIRIS (1998)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Among the most important short-term dynamic biological processes are diurnal changes in canopy water relations. Plant regulation of water transport through stomatal openings affects other gaseous transport processes, often dramatically decreasing photosynthetic fixation of carbon dioxide during periods of water stress. Water stress reduces stomatal conductance of water vapor through the leaf surface and alters the diurnal timing of stomatal opening. Under non-water stressed conditions, stomates typically open soon after dawn and transpire water vapor throughout the daylight period. During stress periods, stomates may close for part of the day, generally near mid-day. Under prolonged stress conditions, stomatal closure shifts to earlier times during the day; stomates may close by mid-morning and remain closed until the following morning - or remain closed entirely. Under these conditions the relationship between canopy greenness (e.g., measured with a vegetation index or by spectral mixture analysis) and photosynthetic fixation of carbon is lost and the remotely sensed vegetation metric is a poor predictor of gas exchange. Prediction of stomatal regulation and exchange of water and trace gases is critical for ecosystem and climate models to correctly estimate budgets of these gases and understand or predict other processes like gross and net ecosystem primary production. Plant gas exchange has been extensively studied by physiologists at the leaf and whole plant level and by biometeorologists at somewhat larger scales. While these energy driven processes follow a predictable if somewhat asymmetric diurnal cycle dependent on soil water availability and the constraints imposed by the solar energy budget, they are nonetheless difficult to measure at the tree and stand levels using conventional methods. Ecologists have long been interested in the potential of remote sensing for monitoring physiological changes using multi-temporal images. Much of this research has focused on day-to-day changes in water use, especially for agricultural applications. Ustin et al. showed seasonal changes in canopy water content in chaparral shrub could be estimated using optical methods. Vanderbilt et al. followed asymmetric diurnal changes in the reflectance of a walnut orchard, but could not attribute specific reflectance changes to specific changes in canopy architecture or physiology. Forests and shrub lands in California experience prolonged periods of drought, sometimes extending six months without precipitation. The conifer and evergreen chaparral communities common to the foothill region around the central valley of California retain their foliage throughout the summer and have low transpiration rates despite high net radiation and temperature conditions. In contrast, grasslands and drought resistant deciduous species in the same habitat are seasonally dormant in summer. Because of differences in the mechanisms of drought tolerance, rooting depth and physiology between different plant communities in the region, it is likely that they display differences in diurnal water relations. The presence of diverse plant communities provides an opportunity to investigate possible diurnal landscape patterns in water relations that could be observed by an airborne hyperspectral scanner. This investigation of AVIRIS data collected over forest and shrub land represents the continuation of a prior investigation involving spectral mixture analysis of diurnal effects in the same AVIRIS data set.
    Keywords: Earth Resources and Remote Sensing
    Type: Summaries of the Seventh JPL Airborne Earth Science Workshop January 12-16, 1998; Volume 1; 399-408; JPL-Publ-97-21-Vol-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 94
    facet.materialart.
    Unknown
    Mapping Agricultural Crops with AVIRIS Spectra in Washington State (1998)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Spectroscopy is used in the laboratory to measure the molecular components and concentrations of plant constituents to answer questions about the plant type, status, and health. Imaging spectrometers measure the upwelling spectral radiance above the Earth's surface as images. Ideally, imaging spectrometer data sets should be used to understand plant type, plant status, and health of plants in an agricultural setting. An Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data set was acquired over agricultural fields near Wallula, Washington on July 23rd, 1997. AVIRIS measures upwelling radiance spectra through 224 spectral channels with contiguous 10-nm sampling from 400 to 2500 nm in the solar-reflected spectrum. The spectra are measured as images of 11 by up to 800 km with 20-m spatial resolution. The spectral images measured by AVIRIS represent the integrated signal resulting from: the solar irradiance; two way transmittance and scattering of the atmosphere; the absorptions and scattering of surface materials; as well as the spectral, radiometric and spatial response functions of AVIRIS. This paper presents initial research to derive properties of the agricultural fields near Wallula from the calibrated spectral images measured by AVIRIS near the top of the atmosphere.
    Keywords: Earth Resources and Remote Sensing
    Type: Summaries of the Seventh JPL Airborne Earth Science Workshop January 12-16, 1998; Volume 1; 213-220B; JPL-Publ-97-21-Vol-1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 95
    facet.materialart.
    Unknown
    Interference of Backscatter from Two Droplets in a Focused Continuous Wave CO2 Doppler Lidar Beam (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Interference due to the superposition of backscatter, beta, from two micron-sized droplets using a NASA/MSFC cw (continuous wave) CO2 Doppler lidar at 9.1 micrometer wavelength was detected for the first time. The resultant single beta signal from both droplets contained an interference structure with a well-defined periodicity which was accurately measured and compared with cw lidar theory. The agreement between measurements and theory is excellent, indicating that the interference arises because the droplets are moving at different speeds and, therefore, the relative droplet separation is not constant. This gives the superimposed beta signal from both droplets in the lidar beam moving in and out of constructive and destructive interference with a well-defined periodic structure. A measurement of a time-resolved signal pulse with an oscilloscope of the combined from two approx. 14.12 micrometers in diameter silicone oil droplets responding to the Gaussian lidar beam intensity at the lidar beam focus is shown. Full details of this laboratory experimental setup, particle generation method, measurement technique, and the cw lidar can be found elsewhere. The stream of silicone oil droplets resided at a Doppler-shift center frequency of f (sub D) approx. (3.4 plus or minus 0.2) MHz, giving droplet speed v approx.(21.9 plus or minus 1.3) ms (exp. -1). Also shown on a separate channel is the corresponding signature using an amplitude demodulator circuit designed to detect the amplitude envelope of f(sub D) within the pulse profile. beta from simultaneous droplet events show a complete cyclic interference structure of maximum and minimum. The average period T of the complete cycle of interference is 13.02 plus or minus.39 microseconds. Toward the right edge of the profile, the interference disappears because one of the droplets is leaving the lidar beam while the other one remains in the beam, thus, giving beta for a single droplet.
    Keywords: Communications and Radar
    Type: Tenth Biennial Coherent Laser Radar Technology and Applications Conference; 264-266; NASA/CP-1999-209758
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 96
    facet.materialart.
    Unknown
    CDDIS Data Center Summary (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: This report summarizes the current and future plans of the Crustal Dynamics Data Information System (CDDIS) with respect to the International VLBI Service for Geodesy and Astrometry (IVS). Included are background information about the CDDIS, the computer architecture, staffing supporting the system, archive contents, and future plans for the CDDIS within the IVS.
    Keywords: Earth Resources and Remote Sensing
    Type: International VLBI Service for Geodesy and Astrometry: 1999 Annual Report; 173-176; NASA/TP-1999-209243
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 97
    facet.materialart.
    Unknown
    Propagation Effects of Importance to the NASA/JPL Deep Space Network (DSN) (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: This paper presents Propagation Effects of Importance To The NASA/JPL Deep Space Network (DSN). The topics include: 1) DSN Antennas; 2) Deep Space Telecom Link Basics; 3) DSN Propagation Region of Interest; 4) Ka-Band Weather Effects Models and Examples; 5) Existing Goldstone Ka-Band Atmosphere Attenuation Model; 6) Existing Goldstone Atmosphere Noise Temperature Model; and 7) Ka-Band delta (G/T) Relative to Vacuum Condition. This paper summarizes the topics above.
    Keywords: Communications and Radar
    Type: Proceedings of the Twenty-Third NASA Propagation Experimenters Meeting (NAPEX XXIII) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Workshop; 303-310; JPL-Publ-99-16
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 98
    facet.materialart.
    Unknown
    LASE measurements of convective boundary layer development during SGP97 (1998)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The Southern Great Plains 1997 (SGP97) field experiment was conducted in Oklahoma during June-July 1997 to validate the models used for computing remote soil moisture using measurements by microwave radiometers. One of the objectives of SGP97 was to examine the effect of soil moisture on the evolution of the Atmospheric Boundary Layer (ABL) and clouds over the Southern Great Plains (SGP) during the warm season. The LASE (Lidar Atmospheric Sensing Experiment) airborne DIAL (Differential Absorption Lidar) system, which was flown autonomously on the NASA ER-2 aircraft during previous missions, was reconfigured to fly on the NASA P3 research aircraft. During SGP97 LASE was used to study the morning evolution of the ABL, particularly as manifested in the development of the convective boundary layer, and to study the influence of soil moisture variations on the development of ABL. The ABL development is strongly influenced by the surface energy budget, which is in turn influenced by soil moisture, mesoscale meteorology, clouds, and solar insolation. LASE data acquired during this mission are being used to study the ABL water vapor budget, the development of the ABL, spatial and temporal variabilities in the ABL, and the meteorological factors that influence the ABL development. This field experiment also permitted comparisons of LASE water vapor measurements with water vapor profiles acquired by radiosondes launched at the DOE (Department of Energy) Atmospheric Radiation Measurement (ARM) Southern Great Plain (SGP) site and at NASA/Wallops Flight Facility, as well as with measurements from other SGP97 aircraft.
    Keywords: Earth Resources and Remote Sensing
    Type: Nineteenth International Laser Radar Conference; 261-264; NASA/CP-1998-207671/PT1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 99
    facet.materialart.
    Unknown
    Examination of Biomass Fire Temperature and Areal Extent from Calibrated AVIRIS Spectra (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Biomass burning is an important process on the Earth at the local, regional and global scales. To investigate issues related to biomass burning, a range of remotely acquired data were measured as part of the NASA Smoke Cloud Aerosol and Radiation experiment in Brazil, 1995. As part of this experiment, images of calibrated spectral radiance from 400 to 2500 nm at 10 nm intervals were acquired by AVIRIS. To investigate the expression of biomass fires in AVIRIS spectra, a model of the upwelling radiance from a burning fire was developed. This spectral model accounts for four components in the 20 by 20 m AVIRIS spatial resolution element. These are: (1) the atmospheric path radiance, (2) the solar reflected radiance from unburnt vegetation and soil, (3) the apparent temperature and area of a primary fire, and (4) the apparent temperature and area of a secondary fire. A nonlinear least squares spectral fitting algorithm was developed to invert this model for the AVIRIS spectra. The derived biomass burning parameters from this algorithm are presented for AVIRIS spectral images acquired over Cuiaba, Brazil on 25 August 1995.
    Keywords: Earth Resources and Remote Sensing
    Type: Summaries of the Sixth Annual JPL Airborne Earth Science Workshop; Volume 1; 105-113; NASA/CR/96-113073
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 100
    facet.materialart.
    Unknown
    Surveying Dead Trees and CO2-Induced Stressed Trees Using AVIRIS in the Long Valley Caldera (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Since 1980 the Long Valley Caldera in the eastern Sierra Nevada (California) has shown signs of renewed volcanic activity. Frequent earthquakes, a re-inflation of the caldera, hydrothermal activity and gas emissions are the outer symptoms of this renewed activity. In 1990 and 1991 several areas of dying trees were found around Mammoth Mountain. The cause of the die off of the trees was first sought in the persistent drought in the preceding years. However, the trees died regardless of age and species. Farrar et al. (1995) started a soil-gas survey in 1994 in the dead-tree areas and found carbon dioxide concentrations ranging from 30 to 96% at soil depths between 30 and 60 cm. CO2 concentrations in the atmosphere are usually around 0.03% and in the soil profile CO2 levels do commonly not exceed 4 to 5%. Although not much is known about the effect of high levels of carbon dioxide in the soil profile on roots, it is most likely that the trees are dying due to oxygen deprivation: the CO2 drives the oxygen out of the soil. So far, four sites of dead trees have been mapped around Mammoth Mountain. The two largest dying trees sites are located near Horseshoe Lake and near Mammoth Mountain Main Lodge covering approximately an area of 10 and 8 ha respectively. Analysis of the gas composition regarding the He-3/He-4 ratio and the percentage biogenic carbon reveals the source of the gas: the magma body beneath the Long Valley Caldera. Until recently it was not known that volcanoes release abundant carbon dioxide from their flanks as diffuse soil emanations. As a result of the magma gas emission around Mammoth Mountain there is an excellent sequence of dead trees, stressed trees, healthy trees and bare soil surfaces. This research site provides excellent opportunities to: (1) Study the capabilities of imaging spectrometry to map stressed (and dead) pine and fir species; (2) Study methods to separate the vivid vegetation, stressed vegetation and dead vegetation from the soil background of glacial deposits and crystalline rocks. The dead tree areas are located on the flanks of Mammoth Mountain (N:37 deg 37' 45" and W:119 deg 02' 05") at an elevation between 2600 and 3000 meters. The area is covered by an open type of Montane Forest. The dominant tree species are Lodgepole Pine (Pinus contorta), the Red Fir (Abies magnifica) and the Jeffrey Pine (Pinus jeffreyi). The soil surface near Horseshoe Lake is generally fairly bright. The surface is covered by glacial deposits (till) consisting mainly of weathered granitic rocks.
    Keywords: Earth Resources and Remote Sensing
    Type: Summaries of the Sixth Annual JPL Airborne Earth Science Workshop; Volume 1; 67-73; NASA/CR/96-113073
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...