ALBERT

Description: This paper reports a new balance for the measurement of three components of force - lift, drag and pitching moment - in impulsively starting flows which have a duration of about one millisecond. The basics of the design of the balance are presented and results of tests on a 15 deg semi-angle cone set at incidence in the T4 shock tunnel are compared with predictions. These results indicate that the prototype balance performs well for a 1.9 kg, 220 mm long model. Also presented are results from initial bench tests of another application of the deconvolution force balance to the measurement of thrust produced by a 2D scramjet nozzle.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

Description: The concept of the well-known Langley plot technique, used for the calibration of ground-based instruments, has been generalized for application to satellite instruments. In polar regions, near summer solstice, the solar backscattered ultraviolet (SBUV) instrument on the Nimbus 7 satellite samples the same ozone field at widely different solar zenith angles. These measurements are compared to assess the long-term drift in the instrument calibration. Although the technique provides only a relative wavelength-to-wavelength calibration, it can be combined with existing techniques to determine the drift of the instrument at any wavelength. Using this technique, we have generated a 12-year data set of ozone vertical profiles from SBUV with an estimated accuracy of +/- 5% at 1 mbar and +/- 2% at 10 mbar (95% confidence) over 12 years. Since the method is insensitive to true changes in the atmospheric ozone profile, it can also be used to compare the calibrations of similar SBUV instruments launched without temporal overlap.

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.

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.

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.

Description: We have studied the implications of recent trends in the annual mean and the amplitude of the annual harmonic of ozone in the upper stratosphere from the 15 years of the combined data from the Nimbus-7 SBUV and the NOAA-11 SBUV/2 instruments. This was done in the context of the GSFC 2D model predictions of these trends which are based on plausible scenarios of anthropogenic Cly increase in the atmosphere. The comparison of the observed and model-estimated annual mean ozone trends show some similarity in their latitude and altitude characteristics. Both the model and data show a maximum ozone decrease of -6 to -10 % per decade at high latitudes in the upper stratosphere. However, there are also significant differences between the observed and computed trends which may be related to both the model uncertainty and the uncertainty in correcting for the long term instrument drift. The observations also suggest a decrease of 10-25 % per decade in the annual amplitude of ozone at 2 mb between 40 deg - 60 deg in both hemispheres, with a relatively larger interannual variability in the northern hemisphere. These values are in general agreement with the model predictions and thus provide additional support in favor of the chlorine induced changes in ozone in the upper stratosphere.

Description: BrO measured from the NASA ER-2 during Airborne Arctic Stratospheric Expedition (AASE) II exhibited a mean value (for 20-minute averages) of 5.4 +/- 0.3 pptv, with a standard deviation of 3.1 pptv. Ratios of BrO to available inorganic bromine (Br(sub y)) show only slight increases in polar regions relative to midlatitudes. A comparison between observed latitudinal and diurnal variations of this same ratio and that calculated by photochemical models shows reasonable agreement in behavior, but significant discrepancies in magnitude. It is unclear whether this difference is due to errors in measurements, models or both.

Description: Measurements of stratospheric hydrofluoric acid (HF) have been made by the JPL MkIV interferometer during high-altitude balloon flights. Infrared solar absorption spectra were acquired near 35 deg N at altitudes between local tropopause and 38 km. Volume mixing ratio profiles of HF derived from 4 flights (1990-93), in conjunction with simultaneously observed N2O profiles, indicate an average rate of HF increase of (5.5 +/- 0.3)% per year, in agreement with time-dependent, two-dimensional model simulations (6% per year) and ATMOS measurements.

Description: Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) measurements of lower stratospheric ClO during 1992-93 and 1993-94 Arctic winters are presented. Enhanced ClO in the 1992-93 winter was first observed in early December, and extensively during February when temperatures were continually low enough for polar stratospheric cloud (PSCs). Sporadic episodes of enhanced ClO were observed for most of the 1993-94 winter as minimum temperatures hovered near the PSC threshold, with largest ClO amounts occurring in early March after a sudden deep cooling in late February.

Description: The thermal-infrared (longwave) emission from a vegetated terrain is generally anisotropic, i.e., the emission temperature varies with the view direction. If a directional measurement of temperature is considered to be equal to the effective temperature of the hemispheric emission, then the estimate of the latter can be significantly in error. The view-direction (zenith angle theta(sub eq) at which the emission equivalence does hold is determined in our modeling study. In a two-temperature field-of-view (soil and plants), theta(sub eq) falls in a narrow range depending on plant density and canopy architecture. Theta(sub eq) does not depend on soil and (uniform) plant temperatures nor on their ratio, even though the pattern of emission vs. the view direction depends crucially on this ratio. For a sparse canopy represented as thin, vertical cylindrical stalks (or vertical blades uniformly distributed in azimuth) with horizontal facets, theta(sub eq) ranges from 48 to 53 deg depending on the optical density of the vertical elements alone. When plant elements are modeled as small spheres, theta(sub eq) lies between 53 to 57 deg (for the same values of the canopy optical density). Only for horizontal leaves (a truly planophile canopy) is the temperature measured from any direction equal to the temperature of the hemispheric emission. When the emission temperature changes with optical depth within the canopy at a specified rate, theta(sub eq) depends to some extent on that rate. For practically any sparsely vegetated surface, a directional measurement at the zenith angle of 50 deg offers an appropriate evaluation of the hemispheric emission, since the error in the estimate will, at most, only slightly exceed 1% (around 4 W/sq m). Estimates of the hemispheric emission through a nadir measurement, on the other hand, can be in error in some cases by about 10%, i.e., on the order of 40 W/sq m.

Description: Numerical simulation experiments were conducted to delineate the influence of in situ deforestation data on episodic rainfall by comparing two ensembles of five 5-day integrations performed with a recent version of the Goddard Laboratory for Atmospheres General Circulation Model (GCM) that has a simple biosphere model (SiB). The first set, called control cases, used the standard SiB vegetation cover (comprising 12 biomes) and assumed a fully forested Amazonia, while the second set, called deforestation cases, distinguished the partially deforested regions of Amazonia as savanna. Except for this difference, all other initial and prescribed boundary conditions were kept identical in both sets of integrations. The differential analyses of these five cases show the following local effects of deforestation. (1) A discernible decrease in evapotranspiration of about 0.80 mm/d (roughly 18%) that is quite robust in the averages for 1-, 2-, and 5-day forecasts. (2) A decrease in precipitation of about 1.18 mm/d (roughly 8%) that begins to emerge even in 1-2 day averages and exhibits complex evolution that extends downstream with the winds. (3) A significant decrease in the surface drag force (as a consequence of reduced surface roughness of deforested regions) that, in turn, affects the dynamical structure of moisture convergence and circulation. The surface winds increase significantly during the first day, and thereafter the increase is well maintained even in the 2- and 5-day averages.

Description: A steady-state scheme for data assimilation in the context of a single, short period (relative to a day), sun-synchronous, polar-orbiting satellite is examined. If the satellite takes observations continuously, the gains, which are the weights for blending observations and predictions together, are steady in time. For a linear system forced by random noise, the optimal steady-state gains (Wiener gains) are equivalent to those of a Kalman filter. Computing the Kalman gains increases the computational cost of the model by a large factor, but computing the Wiener gains does not. The latter are computed by iteration using prior estimates of the gains to assimilate simulated observations of one run of the model, termed 'truth' into another run termed 'prediction'. At each stage, the prediction errors form the basis for the next estimate of the gains. Steady state is achieved after three or four iterations. Further simplification is achieved by making the gains depend on longitudinal distance from the observation point, not on absolute longitude. For a single-layer primitive equation model, the scheme works well even if only the mass field is observed but not the velocity field. Although the scheme was developed for Mars Observer, it should be applicable to data retrieved from Earth atmosphere satellites, for example, UARS.

Description: Brightness temperature difference (BTD) values are calculated for selected Geostationary Operational Environmental Satellite (GOES-6) channels (3.9, 12.7 micrometer) and Advanced Very High Resolution Radiometer channels (3.7, 12.0 micrometer). Daytime and nighttime discrimination of particle size information is possible given the infrared cloud extinction optical depth and the BTD value. BTD values are presented and compared for cirrus clouds composed of equivalent ice spheres (volume, surface area) versus randomly oriented hexagonal ice crystals. The effect of the hexagonal ice crystals is to increase the magnitude of the BTD values calculated relative to equivalent ice sphere (volume, surface area) BTDs. Equivalent spheres (volume or surface area) do not do a very good job of modeling hexagonal ice crystal effects on BTDs; however, the use of composite spheres improves the simulation and offers interesting prospects. Careful consideration of the number of Legendre polynomial coefficients used to fit the scattering phase functions is crucial to realistic modeling of cirrus BTDs. Surface and view-angle effects are incorporated to provide more realistic simulation.

Description: An examination and analysis of video images of lightning, captured by the payload bay TV cameras of the space shuttle, provided a variety of examples of lightning in the stratosphere above thunderstorms. These images were obtained on several recent shuttle flights while conducting the Mesoscale Lightning Experiment (MLE). The images of stratospheric lightning illustrate the variety of filamentary and broad vertical discharges in the stratosphere that may accompany a lightning flash. A typical event is imaged as a single or multiple filament extending 30 to 40 km above a thunderstorm that is illuminated by a series of lightning strokes. Examples are found in temperate and tropical areas, over the oceans, and over the land.

Description: A prototype of the Josephson-effect spectrum analyzer developed for the millimeter wave band is described. The measurement results for spectra obtained in the frequency band from 50 to 250 GHz are presented.

Description: This summary describes the spatial, spectral, and radiometric calibration of Thermal Infrared Multispectral Scanner (TIMS) performed at the Jet Propulsion Laboratory (JPL) Thermal Infrared Calibration Facility (TIRCAL) between May and August, 1994. The 1994 calibration of TIMS was the first to make use of the new EXABYTE (8mm helical-scan tape) recording system. With the new recorder, the TIMS data tapes may be read directly on any computer system that has an EXABYTE tape drive. We analyzed the calibration data sets using image processing procedures written in Interactive Data Language.

Description: This summary describes the 9 March 1994 Thermal Infrared Multispectral Scanner (TIMS) airborne calibration experiment conducted at Castaic Lake, California. This experiment was a collaborative effort between the TIMS and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) science teams at the Jet Propulsion Laboratory (JPL). TIMS was flown on the NASA/Ames Research Center C130 with the new retractable air fence installed in the TIMS instrument bay. The purpose of this experiment was to determine if the fence would reduce the air turbulence in the TIMS instrument bay, thereby reducing the errors in calibration caused by wind-blast cooling of the blackbody reference sources internal to TIMS. Previous experiments have indicated that the wind blast effect could cause TIMS to over-estimate surface temperatures by more than 10 C. We have examined the TIMS data from twelve lines flown over Castaic Lake. Four of the lines were flown at an altitude of approximately 2.5 km (MSL), four at an altitude of approximately 6.7 km, and four at approximately 8.3 km. At each altitude there were flights with northern and southern headings, with the aircraft level and at a positive pitch (nose-up attitude). The suite of twelve flights was designed to subject the TIMS/air fence system to different wind conditions and air temperatures. The TIMS flights were supported by a ground-truth team, who measured lake surface temperatures from a boat, and an atmosphere characterization team, who launched an airsonde and measured solar irradiance with a Reagan Sun Photometer. The Reagan measurements were used to construct a time-series of estimates of the total abundance of water vapor in the atmospheric column. These estimates were used to constrain modifications of the airsonde water vapor profile measurements made when processing the TIMS data with a customized version of the MODTRAN radiative transfer code.

Description: The sedimentary geology of the western Grand Canyon consists of gently northeast dipping sandstones, shales, and carbonates. However, due to facies changes within the units, the geomorphology varies from that seen by visitors at the National Park Headquarters. There, the cliff and slope expression of the rocks is replaced in the west by a series of mesas, ridges, and horizontal platforms. The largest of these occurs on the Esplanade Sandstone within the Supai Formation. The Esplanade is formed by slope retreat of the overlying units and resistance to erosion by the underlying limestones. It is onto this platform that the lavas of the Uinkaret Plateau were emplaced. The Uinkaret lava field lies 120 km south of St. George, Utah and is tectonically defined by two major normal faults -- the Hurricane to the west and the Toroweap to the east. The purpose of this investigation was to collect visible, near and thermal infrared data at different periods of the day and year. It is expected that these data will provide the ability to retrieve water temperatures; monitor sediment loads; map and examine any changes in the near shore vegetation communities and understand some of the intricacies of the geology. This paper will serve, to some degree, as a progress report on the Grand Canyon study, since only a fraction of the data has been received and processed thus far. Data from the Thermal Infrared Multispectral Scanner (TIMS) and the Landsat Thematic Mapper simulator (NS001) were acquired simultaneously on April 4, 1994. A second data acquisition occurred on August 27, 1994. Initial analysis of the TIMS data indicates a remarkably noise-free data set with minimal atmospheric attenuation. environments is evident.

Description: The Jet Propulsion Laboratory (JPL) Field Emission Spectrometer (FES) was built by Designs and Prototypes based on a set of functional requirements supplied by JPL. The instrument has a spectral resolution of 6 wavenumbers (wn) and can acquire spectra from either the Mid Infrared (3-5 mu m) or the Thermal Infrared (8-12 pm) depending on whether the InSb or HgCdTe detector is installed respectively. The instrument consists of an optical head system unit and battery. The optical head which is tripod mounted includes the interferometer and detector dewar assembly. Wavelength calibration of the interferometer is achieved using a Helium-Neon laser diode. The dewar needs replenishing with liquid Nitrogen approximately every four hours. The system unit includes the controls for operation and the computer used for acquiring viewing and processing spectra. Radiometric calibration is achieved with an external temperature-controlled blackbody that mounts on the fore-optics of the instrument. The blackbody can be set at 5 C increments between 10 and 55 C. The instrument is compact and weighs about 33 kg. Both the wavelength calibration and radiometric calibration of the instrument have been evaluated. The wavelength calibration was checked by comparison of the position of water features in a spectrum of the sky with their position in the output from a high resolution atmospheric model. The results indicatethat the features in the sky spectrum are within 6-8 wn of their position ill the model spectrum. The radiometric calibration was checked by first calibrating the instrument using the external blackbody supplied with the instrument and then measuring the radiance from another external blackbody at a series of temperatures. The temperatures of these radiance spectra were then recovered by inventing Planck's law and the recovered temperatures compared lo the measured blackbody temperature. These results indicate that radiometric calibration is good to 0.5 C over the range of temperatures 10 to 55 C. The results also indicate that the instrument drifts slowly over time and should be recalibrated every 20 to 30 minutes in the field to ensure good radiometric fidelity. The instrument has now been extensively tested in the field in the United States and Australia. These in situ field measurements are being used to validate emissivity spectra recovered from the Thermal Infrared Multispectral Scanner (TIMS) and also the Australian CO2 Laser. The availability of in situ measurements is proving crucial to validation of the spectra derived from the airborne instruments since many natural surfaces cannot be easily transported back to the laboratory.

Description: AVIRIS is a NASA-sponsored Earth-remote-sensing imaging spectrometer designed, built and operated by the Jet Propulsion Laboratory (JPL). While AVIRIS has been operational since 1989, major improvements have been completed in most of the sensor subsystems during the winter maintenance cycles. As a consequence of these efforts, the capabilities of AVIRIS to reliably acquire and deliver consistently high quality, calibrated imaging spectrometer data continue to improve annually, significantly over those in 1989. Improvements to AVIRIS prior to 1994 have been described previously. This paper details recent and planned improvements to AVIRIS in the sensor task.

Description: This paper serves as a brief overview of the AVIRIS instrument (Airborne Visible/Infrared Imaging Spectrometer). The AVIRIS sensor collects data that will be used for quantitative characterization of the Earth's surface and atmosphere from geometrically coherent spectroradiometric measurements. This data can be applied to studies in the fields of oceanography, environmental science, snow hydrology, geology, volcanology, soil and land management, atmospheric and aerosol studies, agriculture, and limnology. Applications under development include the assessment and monitoring of environmental hazards such as toxic waste, oil spills, and land/air/water pollution. Mission planning and flight operations are discussed, and recommendations are given regarding the deployment of ground truth experiments.

Description: The AVIRIS sensor must be calibrated at the time it measures spectra from the ER-2 airborne platform in order to achieve research and application objectives that are both quantitative and physically based. However, the operational environment inside the Q-bay of the ER-2 at 20 km altitude differs from that in the AVIRIS laboratory with respect to temperature, pressure, vibration, and high-frequency electromagnetic fields. Experiments at surface calibration targets are used in each flight season to confirm the accuracy of AVIRIS in-flight radiometric calibrations. For these experiments, the MODTRAN radiative transfer code is constrained by using in situ measurements to independently predict the upwelling spectral radiance arriving at AVIRIS for a specific calibration target. AVIRIS calibration is validated in flight by comparing the MODTRAN-predicted radiance to the laboratory-calibrated radiance measured by the AVIRIS sensor for the same time over the calibration target. We present radiometric calibration results for the AVIRIS in-flight calibration experiment held at the beginning of the 1994 flight season.

Description: The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) measures spectra from 400 to 2500 nm through 224 contiguous spectral channels. These spectra are used to identify and determine the abundances of constituents of the earth's surface and atmosphere through the analysis of spectral molecular absorptions and scattering properties of materials. Spectral calibration of the AVIRIS is required to pursue these determinations, which are based on these fundamental spectral characteristics. The spectral calibration of AVIRIS consists of a description of the spectral response function for each of the 224 spectral channels. The spectral response function of AVIRIS channels was measured in the laboratory and shown to be Gaussian in shape. A subset of nine AVIRIS spectral channels is shown with channel centers at 10 nm intervals and channel shapes of Gaussian form with 10 nm full width and half maximum (FWHM). For AVIRIS the spectral calibration is described by the spectral center and FWHM of a Gaussian function for each channel. Uncertainty in the determination of the spectral center and FWHM for each channel are also reported. This paper presents results from an investigation of the sensitivity of AVIRIS-measured upwelling radiance to errors in spectral calibration. Based on this sensitivity analysis in conjunction with earlier work, an improved spectral calibration requirement for AVIRIS is proposed.

Description: Spectral calibration of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) as data are acquired in flight is essential to quantitative analysis of the measured upwelling spectral radiance. In each spectrum measured by AVIRIS in flight, there are numerous atmospheric gas absorption bands that drive this requirement for accurate spectral calibration. If the surface and atmospheric properties are measured independently, these atmospheric absorption bands may be used to deduce the in-flight spectral calibration of an imaging spectrometer. Both the surface and atmospheric characteristics were measured for a calibration target during an in-flight calibration experiment held at Lunar Lake, Nevada on April 5, 1994. This paper uses upwelling spectral radiance predicted for the calibration target with the MODTRAN radiative transfer code to validate the spectral calibration of AVIRIS in flight.

Description: Since initial contact between Earth Search Sciences, Inc. (ESSI) and the Idaho National Engineering Laboratory (INEL) in February, 1994, at least seven proposals have been submitted in response to a variety of solicitations to commercialize and improve the AVIRIS instrument. These proposals, matching ESSI's unique position with respect to agreements with the National Aeronautics and Space Administration (NASA) and the Jet Propulsion Laboratory (JPL) to utilize, miniaturize, and commercialize the AVIRIS instrument and platform, are combined with the applied engineering of the INEL. Teaming ESSI, NASA/JPL, and INEL with diverse industrial partners has strengthened the respective proposals. These efforts carefully structure the overall project plans to ensure the development, demonstration, and deployment of this concept to the national and international arenas. The objectives of these efforts include: (1) developing a miniaturized commercial, real-time, cost effective version of the AVIRIS instrument; (2) identifying multiple users for AVIRIS; (3) integrating the AVIRIS technology with other technologies; (4) gaining the confidence/acceptance of other government agencies and private industry in AVIRIS; and (5) increasing the technology base of U.S. industry.

Description: Recent laboratory calibrations of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) include new methods for the characterization of the geometric, spectral, temporal and radiometric properties of the sensor. New techniques are desired in order to: (1) increase measurement accuracy and precision, (2) minimize measurement time and expense, (3) prototype new field and inflight calibration systems, (4) resolve measurement ambiguities, and (5) add new measurement dimensions. One of the common features of these new methods is the use of the full data collection and processing power of the AVIRIS instrument and data facility. This allows the collection of large amounts of calibration data in a short period of time and is well suited to modular data analysis routines.

Description: The AVIRIS instrument uses an onboard calibration system to provide auxiliary calibration data. The system consist of a tungsten halogen cycle lamp imaged onto a fiber bundle through an eight position filter wheel. The fiber bundle illuminates the back side of the foreoptics shutter during a pre-run and post-run calibration sequence. The filter wheel contains two neutral density filters, five spectral filters and one blocked position. This paper reviews the general workings of the onboard calibrator system and discusses recent modifications.

Description: The JPL DSN Microwave Antenna Holography System (MAHST) was applied to the newly constructed DSS-24 34-m beam-waveguide antenna at Goldstone, California. The application of MAHST measurements and corrections at DSS 24 provided the critical RF performance necessary to not only meet the project requirements and goals, but to surpass them. A performance increase of 0.35 dB at X-band (8.45 GHz) and 4.9 dB at Ka-band (32 GHz) was provided by MAHST, resulting in peak efficiencies of 75.25 percent at X-band and 60.6 percent at Ka-band (measured from the Cassegrain focus at f1). The MAHST enabled setting the main reflector panels of DSS 24 to 0.25-mm rms, making DSS 24 the highest precision antenna in the NASA/JPL DSN. The precision of the DSS-24 antenna (diameter/rms) is 1.36 x 10(exp 5), and its gain limit is at 95 GHz.

Description: Frequency measurements of electromagnetic oscillations of millimeter and submillimeter wavebands with frequency growth due to a number of reasons become more and more difficult. First, these frequencies are considered to be cutoffs for semiconductor converting devices and one has to use optical measurement methods instead of traditional ones with frequency transfer. Second, resonance measurement methods are characterized by using relatively narrow bands and optical ones are limited in frequency and time resolution due to the limited range and velocity of movement of their mechanical elements as well as the efficiency of these optical techniques decrease with the increase of wavelength due to diffraction losses. That requires a priori information on the radiation frequency band of the source involved. Method of measuring frequency of harmonic microwave signals in millimeter and submillimeter wavebands based on the ac Josephson effect in superconducting contacts is devoid of all the above drawbacks. This approach offers a number of major advantages over the more traditional measurement methods, that is one based on frequency conversion, resonance and interferometric techniques. It can be characterized by high potential accuracy, wide range of frequencies measured, prompt measurement and the opportunity to obtain a panoramic display of the results as well as full automation of the measuring process.

Description: As data communications rates climb toward 10 Gbits/s, clock recovery and synchronization become more difficult, if not impossible, using conventional electronic circuits. The high-speed photonic clock regenerator described in this article may be more suitable for such use. This photonic regenerator is based on a previously reported photonic oscillator capable of fast acquisition and synchronization. With both electrical and optical clock inputs and outputs, the device is easily interfaced with fiber-optic systems. The recovered electrical clock can be used locally and the optical clock can be used anywhere within a several kilometer radius of the clock/carrier regenerator.

Description: Industry and university participants have joined together to form the IMPA:Ct consortium (In-situ Monitors of the Particulate Ambient: Circumterrestrial) which offers a broad range of flight qualified instruments for monitoring the small particle (0.1 micron to 10 cm) environment in space. Instruments are available in 12 months or less at costs ranging from 0.5 to 1.5 million dollars (US) for the total program. Detector technologies represented by these groups are: impact-induced capacitor-discharge (MOS, metal-oxide-silicon), cratering or penetration of electroactive thin film (polyvinylidene fluoride (PVDF)), impact-plasma detection, acoustic detection, CCD tracking of optical scatter of sunlight, and photodiode detection of optical scatter of laser light. The operational characteristics, general spacecraft interface and resource requirements (mass/power/telemetry), cost and delivery schedules, and points of contact for seven different instruments are presented.

Description: The Tropical Rainfall Measuring Mission (TRMM) is an earth observing satellite that will be in a low earth orbit (350 kilometers) during the next period of maximum solar activity. The TRMM observatory is expected to experience an atomic oxygen fluence of 8.9 x 10(exp 22) atoms per square centimeter. This fluence is ten times higher than the atomic oxygen impingement incident to the Long Duration Exposure Facility (LDEF). Other environmental concerns on TRMM include: spacecraft glow, silicon oxide contaminant build-up, severe spacecraft material degradation, and contamination deposition resulting from molecular interactions with the dense ambient atmosphere. Because of TRMM's predicted harsh environment, TRMM faces many unique material concerns and subsystem design issues. The LDEF data has influenced the design of TRMM and the TRMM material selection process.

Description: This paper describes the requirements, design, assembly and testing of the linear Scan Mechanism (SM) of the Composite Infrared Spectrometer (CIRS) Instrument. The mechanism consists of an over constrained flexible structure, an innovative moving magnet actuator, passive eddy current dampers, a Differential Eddy Current (DEC) sensor, Optical Limit Sensors (OLS), and a launch lock. Although all the components of the mechanism are discussed, the flexible structure and the magnetic components are the primary focus. Several problems encountered and solutions implemented during the development of the scan mechanism are also described.

Description: The University of California at Santa Cruz and the NASA Ames Research Center have developed a mid-infrared Si:Ga 128 x 128 array camera. The camera has been used on several flights on the KAO to obtain data in the mid-infrared wavelength (4-8 micron) range. At the f/17 bent Cassegrain focus, the pixel spacing is 1.6 arcsec, resulting in a FOV of 3.4 arcmin. The bandpass of the camera is determined by a set of 4 fixed filters and a 4-8 micron CVF. Camera performance of 92mJy/square arcsec/minute has been achieved, but is far from optimal. Realistic improvements to the camera and pointing stability on the KAO in the near future should increase the camera's sensitivity on future flights by 5-10x.

Description: We describe a focal plane guider for the Kuiper Airborne Observatory which consists of a CCD camera interfaced to an AMIGA personal computer. The camera is made by Photometrics Ltd. and utilizes a Thomson 576 x 384 pixel CCD chip operated in Frame Transfer mode. Custom optics produce a scale of 2.4 arc-sec/pixel, yielding an approx. 12 ft. diameter field of view. Chopped images of stars with HST Guide Star Catalog magnitudes fainter than 14 have been used for guiding at readout rates greater than or equal to 0.5 Hz. The software includes automatic map generation, subframing and zooming, and correction for field rotation when two stars are in the field of view.

Description: The High-efficiency, Infrared Faint Object Grating Spectrometer (HIFOGS) provides spectral coverage of selectable portions of the 3 to 18 micron range at resolving powers from 00 to 1000 using 120 Si/Bi detectors. Additional coverage to 30 microns is provided by a bank of 32 Si:P detectors. Selectable apertures, gratings and band-pass filters provide flexibility to this system. Software for operation of HIFOGS and reduction of the data runs on a MacIntosh computer. HIFOGS has been used to establish celestial flux standards using 3 independent approaches: comparison to star models, comparisons to asteroid models and comparisons to laboratory blackbodies. These standards are expected to have wide application in astronomical thermal-infrared spectroscopy.

Description: Spectroscopic studies in the 'fingerprint' region of the thermal IR from 3 to 14 microns of celestial dust components and the overall energy distribution of the sources are best served by moderate spectral resolution (R = lambda/Delta lambda approximately 30 to 200), high sensitivity observations. Spectral purity and the reproducibility of the spectral shape are critical as well, when using the spectral shape to assign temperatures to dust grains or to gas clouds based on the wavelength and shape of molecular bands. These sensor attributes are also important to the use of wavelengths and ratios of solid state features to derive compositions of dust grains in celestial sources. The advent of high quality linear arrays of blocked impurity band (BIB) detectors of Si:As permitted the development of a state-of-the-art, patented, cooled prism spectrograph. Developed at The Aerospace Corporation largely with in-house funds, the Broadband Array Spectrograph System (BASS) has been used for a variety of remote sensing applications, but especially for IR astronomical studies on the Kuiper Airborne Observatory and at the NASA Infrared Telescope Facility (IRTF). The attributes of the spectrograph, specifically having the pupil imaged onto the 2 linear 58 element detector arrays so that the effects of guiding errors are minimized, being able to maximally exploit the limited observing time by acquiring all 116 spectral channels simultaneously, and having all spectral channels imaged through the same aperture so that spectral mapping is readily and reliably accomplished, afford the scientist with a unique opportunity to conduct both surveys of examples of many different types of sources as well as in-depth studies of a given class of object by thoroughly sampling the class members. This duality was demonstrated with the BASS through a combination of KAO flights where spectral maps were obtained as part of in-depth studies of specific source regions (such as Orion and W3) and flights where up to 21 legs/flight were used to survey many different sources of different types.

Description: The Yerkes Observatory Far Infrared Camera employs a two-dimensional, 60-detector array of (3)He-cooled silicon bolometers for broadband imaging in the spectral range of 40 to 240 microns. Four interchangeable filters have effective wavelengths of 60, 100, 160, and 200 microns. Three interchangeable lens sets give pixel sizes of 17, 27, and 45 in. Signals are processed through nitrogen-temperature JFET source-follower amplifiers, warm preamplifiers, and digital signal processors, and the system is controlled through a graphical user interface on a Macintosh computer. The camera has been used to image a wide variety of galactic and extragalactic far infrared sources.

Description: In 1992, in an effort to significantly improve knowledge in the field of hyperspectral imagery, the Naval Research Laboratories defined a set of requirements for a new generation sensor. Construction of this instrument, designated HYDICE, has recently been completed at Hughes Danbury Optical Systems. It is currently being flight tested on a Convair 580 operated by ERIM. This paper reports on some of the performance parameters measured to date. The majority of these are derived from laboratory test data. Optomechanical parameters include MTF, spatial co-registration, 'smile', spectral profile and spectral calibration. Detector-related parameters include system responsivity, signal to noise ratio, radiometric stability and gain linearity. The results are compared with the original system performance predictions.

Description: A near infrared differential absorption lidar technique is developed using atmospheric oxygen as a tracer for high resolution vertical profiles of pressure and temperature with high accuracy. Solid-state tunable lasers and high-resolution spectrum analyzers are developed to carry out ground-based and airborne measurement demonstrations and results of the measurements presented. Numerical error analysis of high-altitude airborne and spaceborne experiments is carried out, and system concepts developed for their implementation.

Description: A facility that allows interrogation of combusting flows by advanced diagnostic methods and instrumentation has been developed at the NASA Lewis Research Center. An optically accessible flame tube combustor is described which has high temperature, pressure, and air flow capabilities. The windows in the combustor measure 3.8 cm axially by 5.1 cm radially, providing 67% optical access to the 7.6 cm x 7.6 cm cross section flow chamber. Advanced gas analysis instrumentation is available through a gas chromatography/mass spectrometer system (GC/MS), which has on-line capability for heavy hydrocarbon measurement with resolution to the parts per billion level. The instrumentation allows one to study combusting flows and combustor subcomponents, such as fuel injectors and air swirlers. Planar Laser Induced Fluorescence (PLIF) can measure unstable combustion species, which cannot be obtained with traditional gas sampling. This type of data is especially useful to combustion modellers. The optical access allows measurements to have high spatial and temporal resolution. GC/MS data and PLIF images of OH- are presented from experiments using a lean direct injection (LDI) combustor burning Jet-A fuel at inlet temperatures ranging from 810 K to 866 K, combustor pressures up to 1380 kPa, and equivalence ratios from 0.41 to 0.59.

Description: The Radar Wind Sensor (RAWS) was proposed as a complement to laser wind sensors, allowing coverage in cloudy regions excluded from laser coverage. Previous University of Kansas studies showed the feasibility of the wind measurement at various levels in the atmosphere and indicated that RAWS can also measure rain rates and ocean-surface winds. Here we discuss measurement of the wind vector in terms of the scan patterns for a conically scanned antenna. By using many measurements from cells about 66 km square and 132 km square, a least-squares algorithm gives results that are reasonable for insertion into global atmospheric models. For RAWS to be used successfully as a complement to a laser wind sensor, the design of the two sensors should be integrated and radial velocity measurements in a given atmospheric cell should be combined to get the most accurate results.

Description: The third ATmospheric Laboratory for Applications and Science (ATLAS-3) mission was flown aboard the Space Shuttle launched on November 3, 1994. The mission length was approximately 10 days and 22 hours. The ATLAS-3 Earth-viewing instruments provided a large number of measurements which were nearly coincident with observations from experiments on the Upper Atmosphere Research Satellite (UARS). Based on ATLAS-3 instrument operating schedules, simulations were performed to determine when and where correlative measurements occurred between ATLAS and UARS instruments, and between ATLAS and surface observations. Results of these orbital and instrument simulations provide valuable information for scientists to compare measurements between various instruments on the two satellites and at selected surface sites.

Description: The last version of Edwin Land's retinex model for human vision's lightness and color constancy has been implemented. Previous research has established the mathematical foundations of Land's retinex but has not examined specific design issues and their effects on the properties of the retinex operation. We have sought to define a practical implementation of the retinex without particular concern for its validity as a model for human lightness and color perception. Here we describe issues involved in designing the surround function. We find that there is a trade-off between rendition and dynamic range compression that is governed by the surround space constant. Various functional forms for the retinex surround are evaluated and a Gaussian form is found to perform better than the inverse square suggested by Land. Preliminary testing led to the design of a Gaussian surround with a space constant of 80 pixels as a reasonable compromise between dynamic range compression and rendition.

Description: The purpose of the CS/LAB project was to obtain images of cloud to stratosphere lightning discharges from aboard NASA's DC-8 Airborne Laboratory while flying in the vicinity of thunderstorms over the Amazon Basin. We devised a low light level imaging package as an add-on experiment to an airborne Laboratory deployment to South America during May-June, 1993. We were not successful in obtaining the desired images during the South American deployment. However, in a follow up flight over the American Midwest during the night of July 8-9, 1993 we recorded nineteen examples of the events over intense thunderstorms. From the observations were estimated absolute brightness, terminal altitudes, flash duration, horizontal extents, emission volumes, and frequencies relative to negative and positive ground strokes.

Description: This plan describes the Structural Mathematical Model of the METSAT AMSU-A2 instrument. The model is used to verify the structural adequacy of the AMSU-A2 instrument for the specified loading environments.

Description: This paper describes the results from a collaborative study between the European Space Operations Center, the European Organization for the Exploitation of Meteorological Satellites, the National Oceanic and Atmospheric Administration, and the Cooperative Institute for Meteorological Satellite Studies investigating the relationship between satellite-derived monthly mean fields of wind and humidity in the upper troposphere for March 1994. Three geostationary meteorological satellites GOES-7, Meteosat-3, and Meteosat-5 are used to cover an area from roughly 160 deg W to 50 deg E. The wind fields are derived from tracking features in successive images of upper-tropospheric water vapor (WV) as depicted in the 6.5-micron absorption band. The upper-tropospheric relative humidity (UTH) is inferred from measured water vapor radiances with a physical retrieval scheme based on radiative forward calculations. Quantitative information on large-scale circulation patterns in the upper-troposphere is possible with the dense spatial coverage of the WV wind vectors. The monthly mean wind field is used to estimate the large-scale divergence; values range between about-5 x 10(exp -6) and 5 x 10(exp 6)/s when averaged over a scale length of about 1000-2000 km. The spatial patterns of the UTH field and the divergence of the wind field closely resemble one another, suggesting that UTH patterns are principally determined by the large-scale circulation. Since the upper-tropospheric humidity absorbs upwelling radiation from lower-tropospheric levels and therefore contributes significantly to the atmospheric greenhouse effect, this work implies that studies on the climate relevance of water vapor should include three-dimensional modeling of the atmospheric dynamics. The fields of UTH and WV winds are useful parameters for a climate-monitoring system based on satellite data. The results from this 1-month analysis suggest the desirability of further GOES and Meteosat studies to characterize the changes in the upper-tropospheric moisture sources and sinks over the past decade.

Description: The purpose of this task was to begin development of a unified approach to the sensing, analysis, and modeling of the wind environments in which launch systems operate. The initial activity was to examine the current usage and requirements for wind modeling for the Titan 4 vehicle. This was to be followed by joint technical efforts with NASA Langley Research Center to develop applicable analysis methods. This work was to be performed in and demonstrate the use of prototype tools implementing an environment in which to realize a unified system. At the convenience of the customer, due to resource limitations, the task was descoped. The survey of Titan 4 processes was accomplished and is reported in this document. A summary of general requirements is provided . Current versions of prototype Process Management Environment tools are being provided to the customer.

Description: The Shuttle and its cargo are occasionally exposed to an amount of radiation large enough to create non-image forming exposures (fog) on photographic flight film. The television/photography working group proposed a test plan to quantify the sensitivity of photographic films to space radiation. This plan was flown on STS-37 and was later incorporated into a detailed supplementary objective (DSO) which was flown on STS48. This DSO addressed the effects of significant space radiation on representative samples of six highly sensitive flight films. In addition, a lead-lined bag was evaluated as a potential shield for flight film against space radiation.

Description: This document presents results of a field study of the effect of sheltering of wind sensors by nearby foliage on the validity of wind measurements at the Space Shuttle Landing Facility (SLF). Standard measurements are made at one second intervals from 30-feet (9.1-m) towers located 500 feet (152 m) from the SLF centerline. The centerline winds are not exactly the same as those measured by the towers. A companion study, Merceret (1995), quantifies the differences as a function of statistics of the observed winds and distance between the measurements and points of interest. This work examines the effect of nearby foliage on the accuracy of the measurements made by any one sensor, and the effects of averaging on interpretation of the measurements. The field program used logarithmically spaced portable wind towers to measure wind speed and direction over a range of conditions as a function of distance from the obstructing foliage. Appropriate statistics were computed. The results suggest that accurate measurements require foliage be cut back to OFCM standards. Analysis of averaging techniques showed that there is no significant difference between vector and scalar averages. Longer averaging periods reduce measurement error but do not otherwise change the measurement in reasonably steady flow regimes. In rapidly changing conditions, shorter averaging periods may be required to capture trends.

Description: This paper outlines the lessons learned implementing Get Away Specials (GAS) payloads G-399 and G-178 with regard to power systems, computer/data logger, structure and working with undergraduates.

Description: The Sierra College Space Technology Program is currently building their third GAS payload in addition to a small satellite. The project is supported by an ARPA/TRP grant. One aspect of the grant is the design of standard hardware for Get Away Specials (GAS) payloads. A standard structure has been designed and work is progressing on a standard battery box and computer.

Description: We have constructed a sensitive submillimeter receiver for the NASA Kuiper Airborne Observatory (KAO) which at present operates in the 500-750 GHz band. The DSB receiver noise temperature is about 5 h nu/k(sub B) over the 500-700 GHz range. This receiver has been used to detect H2O(18)O, HCl, and CH in interstellar molecular clouds, and also to search for C(+) emission from the highly redshifted galaxy (z = 2.3) IRAS 10214.

Description: The Kuiper Widefield Infrared Camera (KWIC) is a wide-field (5.8 arcmin x 5.8 arcmin) imaging spectrometer for use on the KAO in the wavelength range of 18 to 44 micron. Two resolution modes, R = 35 to 200 and R = 2000 to 10,000 are available. Diffraction limited and near background limited images were obtained on the first flights.

Description: In active cooling of a structure it is beneficial to use a plurality of passages for conducting coolant to various portions of the structure. Since most structures do not undergo isotropic thermal loads it is desirable to allow for variation in coolant flow to each area of the structure. The present invention allows for variable flow by a variation of the area of a portion of each of the coolant passages. Shape memory alloys and bi-material springs are used to produce passages that change flow area as a function of temperature.

Description: Use of a spaceborne scatterometer to determine the ocean-surface wind vector requires accurate measurement of radar backscatter from ocean. Such measurements are hindered by the effect of attenuation in the precipitating regions over sea. The attenuation can be estimated reasonably well with the knowledge of brightness temperatures observed by a microwave radiometer. The NASA SeaWinds scatterometer is to be flown on the Japanese ADEOS2. The AMSR multi-frequency radiometer on ADEOS2 will be used to correct errors due to attenuation in the SeaWinds scatterometer measurements. Here we investigate the errors in the attenuation corrections. Errors would be quite small if the radiometer and scatterometer footprints were identical and filled with uniform rain. However, the footprints are not identical, and because of their size one cannot expect uniform rain across each cell. Simulations were performed with the SeaWinds scatterometer (13.4 GHz) and AMSR (18.7 GHz) footprints with gradients of attenuation. The study shows that the resulting wind speed errors after correction (using the radiometer) are small for most cases. However, variations in the degree of overlap between the radiometer and scatterometer footprints affect the accuracy of the wind speed measurements.

Description: The Hubble Space Telescope (HST) was launched into near-earth orbit by the Space Shuttle Discovery on April 24, 1990. The payload of two cameras, two spectrographs, and a high-speed photometer is supplemented by three fine-guidance sensors that can be used for astronomy as well as for star tracking. A widely reported spherical aberration in the primary mirror causes HST to produce images of much lower quality than intended. A Space Shuttle repair mission in January 1994 installed small corrective mirrors that restored the full intended optical capability of the HST. A Second Servicing Mission (SM2) scheduled in 1997 will involve considerable Extra Vehicular Activity (EVA). To reduce EVA time, the addition of robotic capability in the remaining servicing missions has been proposed. Toward that end, two concept designs for a general purpose end effector for robots are presented in this report.

Description: The last version of Edwin Land's retinex model for human vision's lightness and color constancy has been implemented. Previous research has established the mathematical foundations of Land's retinex but has not examined specific design issues and their effects on the properties of the retinex operation. Here we describe the signal processing design of the retinex. We find that the placement of the logarithmic function is important and produces best results when placed after the surround formation. We also find that best rendition is obtained for a 'canonical' gain-offset applied after the retinex operation.

Description: An improved accelerometer is introduced. It comprises a transducer responsive to vibration in machinery which produces an electrical signal related to the magnitude and frequency of the vibration; and a decoding circuit responsive to the transducer signal which produces a first fault signal to produce a second fault signal in which ground shift effects are nullified.

Description: Method and apparatus for making measurements on fluids are disclosed, including the use of a capacitive probe for measuring the flow volume of a material within a flow stream. The capacitance probe has at least two elongate electrodes and, in a specific embodiment of the invention, has three parallel elongate electrodes with the center electrode being an extension of the center conductor of a co-axial cable. A conductance probe is also provided to provide more accurate flow volume data in response to conductivity of the material within the flow stream. A preferred embodiment of the present invention provides for a gas flow stream through a microgravity environment that allows for monitoring a flow volume of a fluid sample, such as a urine sample, that is entrained within the gas flow stream.

Description: This paper describes testing that was conducted using a mass gauge in a liquid hydrogen environment. The mass gauge, herein referred to as the 'compressibility gauge,' is being developed as a means to accurately determine the mass of liquid contained in a tank in a low-gravity environment. The concept is based on the thermodynamic principle that the pressure of gas or vapor changes when its volume changes. Previous work has been conducted by Southwest Research Institute in collaboration with NASA Lewis Research Center. This consisted of testing the concept with water and other cryogenic simulant fluids. The purpose of conducting liquid hydrogen tests is to test the concept in actual cryogenic conditions, and address hardware issues that arise in fabricating a test article for use in liquid hydrogen.

Description: Wind data measured during a field experiment were used to verify the analytical model of wind gusts. Good coincidence was observed; the only discrepancy occurred for the azimuth error in the front and back winds, where the simulated errors were smaller than the measured ones. This happened because of the assumption of the spatial coherence of the wind gust model, which generated a symmetric antenna load and, in consequence, a low azimuth servo error. This result indicates a need for upgrading the wind gust model to a spatially incoherent one that will reflect the real gusts in a more accurate manner. In order to design a controller with wind disturbance rejection properties, the wind disturbance should be known at the input to the antenna rate loop model. The second task, therefore, consists of developing a digital filter that simulates the wind gusts at the antenna rate input. This filter matches the spectrum of the measured servo errors. In this scenario, the wind gusts are generated by introducing white noise to the filter input.

Description: The Space Shuttle Thermal Protection System (TPS) tiles and blankets are waterproofed using DimethylEthoxySilane (DMEX) in the Orbiter Processing Facilities (OPF). DMES has a Threshold Limit Value (TLV) for exposure of personnel to vapor concentration in air of 0.5 ppm. The OPF high bay cannot be opened for normal work after a waterproofing operation until the DMES concentration is verified by measurement to be below the TLV. On several occasions the high bay has been kept closed for up to 8 hours following waterproofing operations due to high DMES measurements. In addition, the Miran 203 and Miran 1 BX infrared analyzers calibrated at different wavelengths gave different readings under the same conditions. There was reason to believe that some of the high DMES concentration readings were caused by interference form water and ethanol vapors. The Toxic Vapor Detection Laboratory (TVDL) was asked to test the existing DMES instruments and identify the best qualified instrument. In addition the TVDL was requested to develop instrumentation to ensure the OPF high bay could be opened safely as soon as possible after a waterproofing operation. A Fourier Transform Infrared (FTIR) spectrophotometer instrument developed for an earlier project was reprogrammed to measure DMES vapor along with ethanol, water, and several common solvent vapors. The FTIR was then used to perform a series of laboratory and field tests to evaluate the performance of the single wavelength IR instruments in use. The results demonstrated that the single wavelength IR instruments did respond to ethanol and water vapors, more or less depending on the analytical IR wavelength selected. The FTIR was able to separate the responses to DMES, water and ethanol, and give consistent readings for the DMES vapor concentration. The FTIR was then deployed to the OPF to monitor real waterproofing operations. The FTIR was also used to measure the time for DMES to evaporate from TPS tile under a range of humidity conditions in controlled laboratory tests. The combination of laboratory and field tests with the FTIR instrument demonstrated superior sensitivity, ability to reject interference from water and ethanol vapors, ruggedness to be transported from the lab to the OPF and set up without special procedures or degradation of performance. The multiple component vapor analysis algorithm was developed at KSC and incorporates automatic baseline correction and shape fitting of the spectra. The analysis for DMES, TetraMethylDiSiloxane (TMDS), ethanol, methanol, isopropanol, and baseline parameters uses 161 points per sample at 4 cm(exp -1) resolution, and processes an eight scan sample every ten seconds. The standard deviation of the measurements is 0.013 ppm and the upper linear limit is 125 ppm DMES. Based on successful demonstration of capabilities we produced three mobile instrument carts to be used in each OPF to support future waterproofing operations. The design and building of the 'DMES Carts' were accomplished in Fiscal year 1995.

Description: A noncontact pyroelectric infrared detector is described. A pyroelectric film that also has piezoelectric properties is held in place so that it is free to vibrate. It is electrically stimulated to vibrate at a resonance frequency. The vibrating film forms part of a balanced bridge circuit. As thermal radiation impinges on the film the pyroelectric effect causes the resonance frequency to change, thereby unbalancing the bridge circuit. A differential amplifier tracks the change in voltage across the bridge. The resulting voltage signal is further processed by a bandpass filter and a precision rectifier. The device allows for DC or static temperature measurements without the use of a mechanical chopping device.

Description: A system for automatically calibrating force balances is provided. The invention uses a reference balance aligned with the balance being calibrated to provide superior accuracy while minimizing the time required to complete the calibration. The reference balance and the test balance are rigidly attached together with closely aligned moment centers. Loads placed on the system equally effect each balance, and the differences in the readings of the two balances can be used to generate the calibration matrix for the test balance. Since the accuracy of the test calibration is determined by the accuracy of the reference balance and current technology allows for reference balances to be calibrated to within +/-0.05% the entire system has an accuracy of +/-0.2%. The entire apparatus is relatively small and can be mounted on a movable base for easy transport between test locations. The system can also accept a wide variety of reference balances, thus allowing calibration under diverse load and size requirements.

Description: A Hydrazine Vapor Area Monitor (HVAM) system is currently being field tested as a detector for the presence of hydrazine in ambient air. The MDA/Polymetron Hydrazine Analyzer has been incorporated within the HVAM system as the core detector. This analyzer is a three-electrode liquid analyzer typically used in boiler feed water applications. The HVAM system incorporates a dual-phase sample collection/transport method which simultaneously pulls ambient air samples containing hydrazine and a very dilute sulfuric acid solution (0.0001 M) down a length of 1/4 inch outside diameter (OD) tubing from a remote site to the analyzer. The hydrazine-laden dilute acid stream is separated from the air and the pH is adjusted by addition of a dilute caustic solution to a pH greater than 10.2 prior to analysis. Both the dilute acid and caustic used by the HVAM are continuously generated during system operation on an "as needed" basis by mixing a metered amount of concentrated acid/base with dilution water. All of the waste water generated by the analyzer is purified for reuse by Barnstead ion-exchange cartridges so that the entire system minimizes the generation of waste materials. The pumping of all liquid streams and mixing of the caustic solution and dilution water with the incoming sample are done by a single pump motor fitted with the appropriate mix of peristaltic pump heads. The signal to noise (S/N) ratio of the analyzer has been enhanced by adding a stirrer in the MDA liquid cell to provide mixing normally generated by the high liquid flow rate designed by the manufacturer. An onboard microprocessor continuously monitors liquid levels, sample vacuum, and liquid leak sensors, as well as handles communications and other system functions (such as shut down should system malfunctions or errors occur). The overall system response of the HVAM can be automatically checked at regular intervals by measuring the analyzer response to a metered amount of calibration standard injected into the dilute acid stream. The HVAM system provides two measurement ranges (threshold limit value (TLV): 10 to 1000 parts per billion (ppb)/LEAK: 100 ppb to 10 parts per million (ppm)). The LEAK range is created by dilution of the sulfuric acid/hydrazine liquid sample with pure water. This dual range capability permits the analyzer to quantify ambient air samples whose hydrazine concentrations range from 10 ppb to as high as 10 ppm. The laboratory and field prototypes have demonstrated total system response times on the order of 10 to 12 minutes for samples ranging from 10 to 900 ppb in the lLV mode and is greater than 2 minutes for samples ranging from 100 to 1300 ppb in the LEAK mode. Service intervals of over 3 months have been demonstrated for continuous 24 hour/day, 7 day/week usage. The HVAM is made up of a purged cabinet that contains power supplies, RS422 signal transmission capabilities, a UPS, an on-site warning system, and a Line Replaceable Unit (LRU). The LRU includes all of the liquid flow system, the analyzer, the control/data system microprocessor and assorted flow and liquid-level sensors. The LRU is mounted on a track slide system so it can be serviced inplace or totally removed and quickly exchanged with another calibrated unit, thus minimizing analyzer downtime. Once an LRU is removed from an analyzer enclosure, it can be brought to a laboratory facility for complete calibration and periodic maintenance.

Description: A temperature sensor uses a type R thermocouple wire element in a ceramic sheath to sense temperatures up to 3,200 deg F., and is particularly suitable for flexible insulations. The sensor includes a thermocouple wire embedded in a sheath having two sections disposed at right angles to each other. The junction of the thermocouple is located at one end of one of the sections and the lead wires extend from the other section. The section which includes the junction is secured to a flexible surface with ceramic cement.

Description: Precision analog signal conditioning electronics have been developed for wind tunnel model attitude inertial sensors. This application requires low-noise, stable, microvolt-level DC performance and a high-precision buffered output. Capacitive loading of the operational amplifier output stages due to the wind tunnel analog signal distribution facilities caused regenerative oscillation and consequent rectification bias errors. Oscillation suppression techniques commonly used in audio applications were inadequate to maintain the performance requirements for the measurement of attitude for wind tunnel models. Feedback control theory is applied to develop a suppression technique based on a known compensation (snubber) circuit, which provides superior oscillation suppression with high output isolation and preserves the low-noise low-offset performance of the signal conditioning electronics. A practical design technique is developed to select the parameters for the compensation circuit to suppress regenerative oscillation occurring when typical shielded cable loads are driven.

Description: A system and method are provided for recording density changes in a flow field surrounding a moving object. A mask having an aperture for regulating the passage of images is placed in front of an image recording medium. An optical system is placed in front of the mask. A transition having a light field-of-view and a dark field-of-view is located beyond the test object. The optical system focuses an image of the transition at the mask such that the aperture causes a band of light to be defined on the image recording medium. The optical system further focuses an image of the object through the aperture of the mask so that the image of the object appears on the image recording medium. Relative motion is minimized between the mask and the transition. Relative motion is also minimized between the image recording medium and the image of the object. In this way, the image of the object and density changes in a flow field surrounding the object are recorded on the image recording medium when the object crosses the transition in front of the optical system.

Description: The environment above earth's atmosphere offers significant advantages in sensitivity and wavelength coverage in infrared astronomy over ground-based observatories. In support of future infrared space missions, technology development efforts were undertaken to develop detectors sensitive to radiation between 2.5 micron and 200 micron. Additionally, work was undertaken to develop mechanisms supporting the imaging and spectroscopy requirements of infrared space missions. Arsenic-doped-Silicon and Antimony-doped-Silicon Blocked Impurity Band detectors, responsive to radiation between 4 micron and 45 micron, were produced in 128x128 picture element arrays with the low noise, high sensitivity performance needed for space environments. Technology development continued on Gallium-doped-Germanium detectors (for use between 80 micron and 200 micron), but were hampered by contamination during manufacture. Antimony-doped-Indium detectors (for use between 2.5 micron and 5 micron) were developed in a 256x256 pixel format with high responsive quantum efficiency and low dark current. Work began on adapting an existing cryogenic mechanism design for space-based missions; then was redirected towards an all-fixed optical design to improve reliability and lower projected mission costs.

Description: This reference publication presents selected results from space-time spectral analyses of 13 years of version 6 daily global ozone fields from the Total Ozone Mapping Spectrometer (TOMS). One purpose is to illustrate more quantitatively the well-known richness of structure and variation in total ozone. A second purpose is to provide, for use by modelers and for comparison with other analysts' work, quantitative measures of zonal waves 1, 2, 3, and medium-scale waves 4-7 in total ozone. Their variations throughout the year and at a variety of latitudes are presented, from equatorial to polar regions. The 13-year averages are given, along with selected individual years which illustrate year-to-year variability. The largest long wave amplitudes occur in the polar winters and early springs of each hemisphere, and are related to strong wave amplification during major warning events. In low attitudes total ozone wave amplitudes are an order of magnitude smaller than at high latitudes. However, TOMS fields contain a number of equatorial dynamical features, including Rossby-gravity and Kelvin waves.

Description: A method for producing a phase hologram using e-beam lithography provides n-ary levels of phase and amplitude by first producing an amplitude hologram on a transparent substrate by e-beam exposure of a resist over a film of metal by exposing n is less than or equal to m x m spots of an array of spots for each pixel, where the spots are randomly selected in proportion to the amplitude assigned to each pixel, and then after developing and etching the metal film producing a phase hologram by e-beam lithography using a low contrast resist, such as PMMA, and n-ary levels of low doses less than approximately 200 micro-C/sq cm and preferably in the range of 20-200 micro-C/sq cm, and aggressive development using pure acetone for an empirically determined time (about 6 s) controlled to within 1/10 s to produce partial development of each pixel in proportion to the n-ary level of dose assigned to it.

Description: A new instrument, the liquid crystal point diffraction-interferometer (LCPDI), has been developed for the measurement of phase objects. This instrument maintains the compact, robust design of Linnik's point diffraction interferometer (PDI) and adds to it phase stepping capability for quantitative interferogram analysis. The result is a compact, simple to align, environmentally insensitive interferometer capable of accurately measuring optical wavefronts with very high data density and with automated data reduction. This dissertation describes the theory of both the PDI and liquid crystal phase control. The design considerations for the LCPDI are presented, including manufacturing considerations. The operation and performance of the LCPDI are discussed, including sections regarding alignment, calibration, and amplitude modulation effects. The LCPDI is then demonstrated using two phase objects: defocus difference wavefront, and a temperature distribution across a heated chamber filled with silicone oil. The measured results are compared to theoretical or independently measured results and show excellent agreement. A computer simulation of the LCPDI was performed to verify the source of observed periodic phase measurement error. The error stems from intensity variations caused by dye molecules rotating within the liquid crystal layer. Methods are discussed for reducing this error. Algorithms are presented which reduce this error; they are also useful for any phase-stepping interferometer that has unwanted intensity fluctuations, such as those caused by unregulated lasers.

Description: A single-pass method for accurate and precise temperature control in the -160 to +90 C range is discussed. The method exhibited minimal set-point overshoot during temperature transitions. Control to +/-2 C with transitions between set-points of 7 C per minute were achieved. The method uses commercially available temperature controllers and a gaseous nitrogen/liquid nitrogen mixer to dampen the amplitude of cold temperature spikes caused by liquid nitrogen pulsing.

Description: The demands of accurate predictions of radiative transfer for climate applications are well-documented. While much effort is being devoted to evaluating the accuracy of the GCM radiative transfer schemes, the problem of developing accurate, computationally efficient schemes for climate models still remains. This paper discusses our efforts in developing accurate and fast computational methods for global and regional climate models.

Description: A device has been developed at the Jet Propulsion Laboratory, California Institute of Technology, for the adsorption of contaminants inside a space instrument during flight. The molecular adsorber was developed for use on the Wide Field Planetary Camera 2, and it has been shown to perform at its design specifications in the WFPC-2. The basic principle of the molecular adsorber is a zeolite-coated ceramic honeycomb. The arrangement is efficient for adsorption and also provides the needed rigidity to retain the special zeolite coating during the launch vibrational environment. The adsorber, on other forms, is expected to be useful for all flight instruments sensitive to internal sources of contamination. Typically, some internal contamination is unavoidable. A common design solution is to increase the venting to the exterior. However, for truly sensitive instruments, the external contamination environment is more severe. The molecular adsorber acts as a one-way vent to solve this problem. Continued development is planned for this device.

Description: This was a Tropical Rainfall Measurement Mission (TRMM) modeling, analysis and applications research project. Our broad scientific goals addressed three of the seven TRMM Priority Science Questions, specifically: What is the monthly average rainfall over the tropical ocean areas of about 10(exp 5) sq km, and how does this rain and its variability affect the structure and circulation of the tropical oceans? What is the relationship between precipitation and changes in the boundary conditions at the Earth's surface (e.g., sea surface temperature, soil properties, vegetation)? How can improved documentation of rainfall improve understanding of the hydrological cycle in the tropics?

Description: A formvar replicator for installation in an aircraft pod has been designed, built, and flight tested on the NASA DC-8. The system incorporates a deicing capability (which can be pressure activated) to enable climb out through icing situations prior to deployment. The system can be operated at preselected speeds such that data can be recorded over a period of one to ten hours on 200 ft of 16mm film. A x2 speed control can be used during flight. Capability exists for detection of chemical constituents by appropriate doping of the formvar solution. An article entitled 'Measurements of ice particles in tropical cirrus anvils: importance in radiation balance' is attached as appendix A.

Description: The following monthly mean global distributions for 1993 are presented with a common color scale and geographical map: 10-m height wind speed estimated from the Special Sensor Microwave Imager (SSMI) on a United States (U.S.) Air Force Defense Meteorological Satellite Program (DMSP) spacecraft; sea surface temperature estimated from the Advanced Very High Resolution Radiometer (AVHRR/2) on a U.S. National Oceanic and Atmospheric Administration (NOAA) satellite; 10-m height wind speed and direction estimated from the Active Microwave Instrument (AMI) on the European Space Agency (ESA) European Remote Sensing (ERS-1) satellite; sea surface height estimated from the joint U.S.-France Topography Experiment (TOPEX)/POSEIDON spacecraft; and 10-m height wind speed and direction produced by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of annual mean, monthly mean, and sampling distributions are displayed.

Description: Pressure is one of the most important parameters measured when testing models in wind tunnels. For models tested in the cryogenic environment of the National Transonic Facility at NASA Langley Research Center, the technique of utilizing commercially available multichannel pressure modules inside the models is difficult due to the small internal volume of the models and the requirement of keeping the pressure transducer modules within an acceptable temperature range well above the -173 degrees C tunnel temperature. A prototype multichannel pressure transducer module has been designed and fabricated with stable, repeatable sensors and materials optimized for reliable performance in the cryogenic environment. The module has 16 single crystal silicon piezoresistive pressure sensors electrostatically bonded to a metalized Pyrex substrate for sensing the wind tunnel model pressures. An integral temperature sensor mounted on each silicon micromachined pressure sensor senses real-time temperature fluctuations to within 0.1 degrees C to correct for thermally induced non-random sensor drift. The data presented here are from a prototype sensor module tested in the 0.3 M cryogenic tunnel and thermal equilibrium conditions in an environmental chamber which approximates the thermal environment (-173 degrees C to +60 degrees C) of the National Transonic Facility.

Description: The concept of rotationally sampled wind speed is described. The unusual wind characteristics that result from rotationally sampling the wind are shown first for early measurements made using an 8-point ring of anemometers on a vertical plane array of meteorological towers. Quantitative characterization of the rotationally sampled wind is made in terms of the power spectral density function of the wind speed. Verification of the importance of the new concept is demonstrated with spectral analyses of the response of the MOD-OA blade flapwise root bending moment and the corresponding rotational analysis of the wind measured immediately upwind of the MOD-OA using a 12-point ring of anemometers on a 7-tower vertical plane array. The Pacific Northwest Laboratory (PNL) theory of the rotationally sampled wind speed power spectral density function is tested successfully against the wind spectrum measured at the MOD-OA vertical plane array. A single-tower empirical model of the rotationally sampled wind speed is also successfully tested against the measurements from the full vertical plane array. Rotational measurements of the wind velocity with hotfilm anemometers attached to rotating blades are shown to be accurate and practical for research on winds at the blades of wind turbines. Some measurements at the rotor blade of a MOD-2 turbine using the hotfilm technique in a pilot research program are shown. They are compared and contrasted to the expectations based upon application of the PNL theory of rotationally sampled wind to the MOD-2 size and rotation rate but without teeter, blade bending, or rotor induction accounted for. Finally, the importance of temperature layering and of wind modifications due to flow over complex terrain is demonstrated by the use of hotfilm anemometer data, and meteorological tower and acoustic doppler sounder data from the MOD-2 site at Goodnoe Hills, Washington.

Description: A particle fallout/activity sensor measures relative amounts of dust or other particles which collect on a mirror in an area to be monitored. The sensor includes a sensor module and a data acquisition module, both of which can be operated independently of one another or in combination with one another. The sensor module includes a housing containing the mirror, an LED assembly for illuminating the mirror and an optical detector assembly for detecting light scattered off of the mirror by dust or other particles collected thereon. A microprocessor controls operation of the sensor module's components and displays results of a measurement on an LCD display mounted on the housing. A push button switch is also mounted on the housing which permits manual initiation of a measurement. The housing is constructed of light absorbing material, such as black delrin, which minimizes detection of light by the optical detector assembly other than that scattered by dust or particles on the mirror. The data acquisition module can be connected to the sensor module and includes its own microprocessor, a timekeeper and other digital circuitry for causing the sensor module to make a measurement periodically and send the measurement data to the data acquisition module for display and storage in memory for later retrieval and transfer to a separate computer. The time tagged measurement data can also be used to determine the relative level of activity in the monitored area since this level is directly related to the amount of dust or particle fallout in the area.

Description: A laser-based profilometer was developed to measure the thickness and shape of ice accretions on the leading edge of airfoils and other models in icing wind tunnels. The instrument is a hand held device that is connected to a desk top computer with a 10 meter cable. It projects a laser line onto an ice shape and used solid state cameras to detect the light scattered by the ice. The instrument corrects the image for camera angle distortions, displays an outline of the ice shape on the computer screen, saves the data on a disk, and can print a full scale drawing of the ice shape. The profilometer has undergone extensive testing in the laboratory and in the NASA Lewis Icing Research Tunnel. Results of the tests show very good agreement between profilometer measurements and known simulated ice shapes and fair agreement between profilometer measurements and hand tracing techniques.

Description: The stated goals of the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE) are 'to promote the development of improved cloud and radiation parameterization for use in climate models, and to provide for assessment and improvement of ISCCP projects'. FIRE Phase 2 has focused on the formation, maintenance and dissipation of cirrus and marine stratocumulus cloud systems. These objectives have been approached through a combination of modeling, extended-time observations and intensive field observation (IFO) periods. The work under this grant was associated with the FIRE Cirrus IFO 2. This field measurement program was conducted to obtain observations of cirrus cloud systems on a range of scales from the synoptic to the microscale, utilizing simultaneous measurements from a variety of ground-based, satellite and airborne platforms. By combining these remote and in situ measurements a more complete picture of cirrus systems can be obtained. The role of the University of North Dakota in Phase 2 was three-fold: to collect in situ microphysical data during the Cirrus IFO 2; to process and archive these data; and to collaborate in analyses of IFO data. This report will summarize the activities and findings of the work performed under this grant; detailed description of the data sets available and of the analyses are contained in the Semi-annual Status Reports submitted to NASA.

Description: Under this program, Dimension Technologies Inc. (DTI) developed a prototype display that uses a proprietary illumination technique to create autostereoscopic hologram-like full resolution images on an LCD operating at 180 fps. The resulting 3D image possesses a resolution equal to that of the LCD along with properties normally associated with holograms, including change of perspective with observer position and lack of viewing position restrictions. Furthermore, this autostereoscopic technique eliminates the need to wear special glasses to achieve the parallax effect. Under the program a prototype display was developed which demonstrates the hologram-like full resolution concept. To implement such a system, DTI explored various concept designs and enabling technologies required to support those designs. Specifically required were: a parallax illumination system with sufficient brightness and control; an LCD with rapid address and pixel response; and an interface to an image generation system for creation of computer graphics. Of the possible parallax illumination system designs, we chose a design which utilizes an array of fluorescent lamps. This system creates six sets of illumination areas to be imaged behind an LCD. This controlled illumination array is interfaced to a lenticular lens assembly which images the light segments into thin vertical light lines to achieve the parallax effect. This light line formation is the foundation of DTI's autostereoscopic technique. The David Sarnoff Research Center (Sarnoff) was subcontracted to develop an LCD that would operate with a fast scan rate and pixel response. Sarnoff chose a surface mode cell technique and produced the world's first large area pi-cell active matrix TFT LCD. The device provided adequate performance to evaluate five different perspective stereo viewing zones. A Silicon Graphics' Iris Indigo system was used for image generation which allowed for static and dynamic multiple perspective image rendering. During the development of the prototype display, we identified many critical issues associated with implementing such a technology. Testing and evaluation enabled us to prove that this illumination technique provides autostereoscopic 3D multi perspective images with a wide range of view, smooth transition, and flickerless operation given suitable enabling technologies.

Description: Use of luminescent paints for the measurement of global pressures on wind tunnel model surfaces requires a full understanding of the inherent accuracy of the technique. Theoretical emission of the paint luminophor follows the well known Stern-Volmer relation. Inherent in this relation are fundamental limits to achievable sensitivity and accuracy. Equations for relative error in pressure as a function of relative signal intensity (emittance), relative error in pressure as a function of pressure, and the relationship between sensitivity and pressure are derived and represented graphically.

Description: As the current fleet of meteorological satellites age, the accuracy of the imagery sensed on a spectral channel of the image scanning system is continually and progressively degraded by noise. In time, that data may even become unusable. We describe a novel approach to the reconstruction of the noisy satellite imagery according to empirical functional relationships that tie the spectral channels together. Abductive networks are applied to automatically learn the empirical functional relationships between the data sensed on the other spectral channels to calculate the data that should have been sensed on the corrupted channel. Using imagery unaffected by noise, it is demonstrated that abductive networks correctly predict the noise-free observed data.