ALBERT

Description: The development of an integrated approach to the modeling of forest dynamics encompassing submodels of forest growth and succession, soil processes and radiation interactions, is reported. Remote sensing technology is a key element of this study in that it provides data for developing, initializing, updating, and validating the models. The objectives are reviewed, the data collected and models in use are discussed, and a framework for studying interactions between the forest growth, soil process and energy interaction components, is described. Remote sensing technology used in the study includes optical and microwave field, aircraft and satellite borne instruments. The types of data collected during intensive field and aircraft campaigns included bidirectional reflectance, thermal emittance and multifrequency, multipolarization synthetic aperture radar backscatter. Synthetic imagery of derived products such as forest biomass and NDVI (Normalized Difference Vegetative Index), and collections of ground data are being assembled in a georeferenced data base. These data are used to drive or test multidiscipline simulations of forested ecosystems. Enhancements to the modeling environment permit considerable flexibility in configuring simulations and selecting results for reporting and graphical display.

Description: The quantitative interpretation of satellite observations requires the use of mathematical tools to extract the desired information on terrestrial environments from the radiation data collected in space. A whole range of approaches can be pursued, from the development of models capable of explaining the nature of the physical signal being measured and of characterizing the state of the system under observation, to the empirical correlations between the variables of interest and the space measurements. The premises and implications of these approaches are outlined, paying special attention to the mathematical and numerical requirements. The role and specific applications of empirical bidirectional reflectance models is also discussed, even though these models do not contribute to the understanding of the theory of radiation transfer or to the assessment of the variables of interest. The advantages and drawbacks of these various approaches and the research priorities for the next few years are discussed in the context of the planned availability of new sensors.

Description: Management of crop residues, the portion of a crop left in the field after harvest, is an important conservation practice for minimizing soil erosion and for improving water quality. Quantification of crop residue cover is required to evaluate the effectiveness of conservation tillage practices. Methods are needed to quantify residue cover that are rapid, accurate, and objective. The fluorescence of crop residue was found to be a broadband phenomenon with emission maxima at 420 to 495 nm for excitations of 350 to 420 nm. Soils had low intensity broadband emissions over the 400 to 690 nm region for excitations of 300 to 600 nm. The range of relative fluorescence intensities for the crop residues was much greater than the fluorescence observed of the soils. As the crop residues decompose their blue fluorescence values approach the fluorescence of the soil. Fluorescence techniques are concluded to be less ambiguous and better suited for discriminating crop residues and soils than reflectance methods. If properly implemented, fluorescence techniques can be used to quantify, not only crop residue cover, but also photosynthetic efficiency in the field.

Description: The importance of the measurement of wind fields is discussed. Wind regime data can be used to infer the amount and type of wind induced (aerolian) transport of sand and dust, or to establish global circulation models, for example on other planets. Since local measurements are costly and often impossible, it is desired to infer such data from remotely sensed information. A potential mechanism for remotely inferring the wind regime by using synthetic aperture radar data to describe the roughness of the surface is described. A project to estimate the practicality of using such a mechanism is described. An experiment that extends the mechanism to vegetated sites, where the goal is to measure potential for erosion, is reported.

Description: Surface reflectance is required to quantitatively investigate molecular absorption and particle scattering properties of materials on the Earth's surface. Atmospheric aerosol optical depth, surface pressure and water vapor are required to constrain a radiative transfer code for the inversion of measured spectral radiance to apparent surface reflectance. A suite of algorithms using nonlinear least squares fitting techniques are described that directly estimate these atmospheric parameters from spectral radiance measured by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). The derived atmospheric parameters are used to constrain a radiative transfer code for the inversion of the imaging spectrometer radiance to apparent reflectance. The derived apparent reflectance is validated with respect to in situ measurement on the same target.

Description: Investigations designed to study land surface hydrologic-atmospheric interactions, showing the potential of L band passive microwave radiometry for measuring surface soil moisture over large areas, are discussed. Satisfying the data needs of these investigations requires the ability to map large areas rapidly. With aircraft systems this means a need for more beam positions over a wider swath on each flightline. For satellite systems the essential problem is resolution. Both of these needs are currently being addressed through the development and verification of Electronically Scanned Thinned Array Radiometer (ESTAR) technology. The ESTAR L band radiometer was evaluated for soil moisture mapping applications in two studies. The first was conducted over the semiarid rangeland Walnut Gulch watershed located in south eastern Arizona (U.S.). The second was performed in the subhumid Little Washita watershed in south west Oklahoma (U.S.). Both tests showed that the ESTAR is capable of providing soil moisture with the same level of accuracy as existing systems.

Description: A weather resistant automatic scanning Sun photometer system is assessed and demonstrated as practical for measurements of aerosol concentrations and properties at remote sites. Interfaced with a transmitter using the Geostationary Data Collection System (GDCS), the data are processed in near real time. The processing allows a time dependence of the aerosols and water vapor and an ongoing assessment of the health and calibration of the instruments. The system's automatic data acquisition, transmission, and processing offer immediate application to atmospheric monitoring and modeling on a regional to global scale and validation of satellite retrievals. It is estimated that under normal circumstances the retrieved aerosol optical thickness has a network wide accuracy of +/- 0.02 from 340 nm to 1020 nm, water vapor +/- 0.2 cm and size distribution from 0.1 to 3 micrometers.

Description: As part of a global program to validate the ocean surface sensors on board ERS-1, a joint experiment on the Grand Banks of Newfoundland was carried out in Nov. 1991. The principal objective was to provide a field validation of ERS-1 Synthetic Aperture Radar (SAR) measurement of ocean surface structure. The NASA-P3 aircraft measurements made during this experiment provide independent measurements of the ocean surface along the validation swath. The Radar Ocean Wave Spectrometer (ROWS) is a radar sensor designed to measure direction of the long wave components using spectral analysis of the tilt induced radar backscatter modulation. This technique greatly differs from SAR and thus, provides a unique set of measurements for use in evaluating SAR performance. Also, an altimeter channel in the ROWS gives simultaneous information on the surface wave height and radar mean square slope parameter. The sets of geophysical parameters (wind speed, significant wave height, directional spectrum) are used to study the SAR's ability to accurately measure ocean gravity waves. The known distortion imposed on the true directional spectrum by the SAR imaging mechanism is discussed in light of the direct comparisons between ERS-1 SAR, airborne Canadian Center for Remote Sensing (CCRS) SAR, and ROWS spectra and the use of the nonlinear ocean SAR transform.

Description: Terrain slopes, which can be measured with Synthetic Aperture Radar (SAR) interferometry either from a height map or from the interferometric phase gradient, were used to calculate the local incidence angle and the correct pixel area. Both are required for correct thematic interpretation of SAR data. The interferometric correlation depends on the pixel area projected on a plane perpendicular to the look vector and requires correction for slope effects. Methods for normalization of the backscatter and interferometric correlation for ERS-1 SAR are presented.

Description: The relationship between the gradient of the interferometric phase and the terrain slope, which, it is thought, would allow a derivation of the terrain slopes without phase unwrapping, is presented. A linear relationship between the interferometric phase gradient and the terrain slopes was found. A quantitative error analysis showed that only very small errors are introduced by these approximations for orbital Synthetic Aperture Radar (SAR) geometries. An example of a slope map for repeat pass interferometry from ERS-1 SAR data is given. A number of direct and indirect applications of the terrain slope are indicated: erosion and avalanche hazard studies, radiometric calibration of SAR data, and normalization of the interferometric correlation coefficient.

Description: Research on the use of active microwaves in remote sensing, presented during plenary and poster sessions, is summarized. The main highlights are: calibration techniques are well understood; innovative modeling approaches have been developed which increase active microwave applications (segmentation prior to model inversion, use of ERS-1 scatterometer, simulations); polarization angle and frequency diversity improves characterization of ice sheets, vegetation, and determination of soil moisture (X band sensor study); SAR (Synthetic Aperture Radar) interferometry potential is emerging; use of multiple sensors/extended spectral signatures is important (increase emphasis).

Description: Crop residues, the portion of the crop left in the field after harvest, can be an important management factor in controlling soil erosion. Methods to quantify residue cover are needed that are rapid, accurate, and objective. Scenes with known amounts of crop residue were illuminated with long wave ultraviolet (UV) radiation and fluorescence images were recorded with an intensified video camera fitted with a 453 to 488 nm band pass filter. A light colored soil and a dark colored soil were used as background for the weathered soybean stems. Residue cover was determined by counting the proportion of the pixels in the image with fluorescence values greater than a threshold. Soil pixels had the lowest gray levels in the images. The values of the soybean residue pixels spanned nearly the full range of the 8-bit video data. Classification accuracies typically were within 3(absolute units) of measured cover values. Video imaging can provide an intuitive understanding of the fraction of the soil covered by residue.

Description: Global study of land surface properties uses AVHRR channels 1 and 2, but channel 3 may be of interest, although its use requires preprocessing. It consists of both a reflective part and an emissive part, the former can be derived from T3, T4 and T5. Since the water vapor affects channel 3, its content is retrieved from the channel 4 and 5 using the split window technique. A formula of reflective part retrieval at 3.75 micrometers is tested in the case of sunglint observations where the emissivities of channels 4 and 5 can be set to the unity. The formula is adapted and validated to land surface using the FIFE-87 data set. Preliminary applications of the reflectance at 3.75 micrometers to the studies of surface properties retrieval, aerosol retrieval over land, and desertic aerosol retrieval, are addressed.

Description: The polarization of the sunlight scattered by atmospheric aerosols or cloud droplets and reflected from ground surfaces or plant canopies may convey much information when used for remote sensing purposes. The typical polarization features of aerosols, cloud droplets, and plant canopies, as observed by ground based and airborne sensors, are investigated, looking especially for those invariant properties amenable to description by simple models when possible. The question of polarization measurements from space is addressed. The interest of such measurements for remote sensing purposes is investigated, and their feasibility is tested by using results obtained during field campaigns of the airborne POLDER instrument, a radiometer designed to measure the directionality and polarization of the sunlight scattered by the ground atmosphere system.

Description: Papers focused on land surface, atmospheric, and ocean properties are reported. Specific comments pertaining to polarization, models and inversion, and measurements, are given. Recommendations are: continued research into the application potential of the BRDF (Bidirectional Reflectance Distribution Function) and polarization properties of ground surface and atmospheric targets; three dimensional models, which account for the statistical behavior of remotely sensed data, should be extended and inverted in order to support analysis of data potentially covering rolling terrain such that pixels represent heterogeneous mixtures of surface cover types and project ground footprints with sizes between 10 to 6 km, the ground pixel sizes of planned future sensors; available reflectance models should be further validated by means of multi dimensional (directional, spectral, temporal) field data and existing models should be intercompared in more depth to evaluate their performance and limitations; existing methods for model inversion should be validated in more depth in order to quantify the practical limitations and the expected accuracy of the parameters retrieved and new approaches should be developed based upon apriori knowledge of plant canopy development and spectral BRDF properties; there is a need to establish a protocol of validation and intercomparison of the indices and compositing techniques which have been proposed during these last years.

Description: Traditionally, the remote sensing community has relied totally on spectral knowledge to extract vegetation characteristics. However, there are other knowledge bases (KB's) that can be used to significantly improve the accuracy and robustness of inference techniques. Using AI (artificial intelligence) techniques a KB system (VEG) was developed that integrates input spectral measurements with diverse KB's. These KB's consist of data sets of directional reflectance measurements, knowledge from literature, and knowledge from experts which are combined into an intelligent and efficient system for making vegetation inferences. VEG accepts spectral data of an unknown target as input, determines the best techniques for inferring the desired vegetation characteristic(s), applies the techniques to the target data, and provides a rigorous estimate of the accuracy of the inference. VEG was developed to: infer spectral hemispherical reflectance from any combination of nadir and/or off-nadir view angles; infer percent ground cover from any combination of nadir and/or off-nadir view angles; infer unknown view angle(s) from known view angle(s) (known as view angle extension); and discriminate between user defined vegetation classes using spectral and directional reflectance relationships developed from an automated learning algorithm. The errors for these techniques were generally very good ranging between 2 to 15% (proportional root mean square). The system is designed to aid scientists in developing, testing, and applying new inference techniques using directional reflectance data.

Description: Most earth surfaces, particularly those supporting natural vegetation ecosystems, constitute structurally and spectrally complex surfaces that are distinctly non-Lambertian reflectors. Obtaining meaningful measurements of the directional radiances of landscapes and obtaining estimates of the complete bidirectional reflectance distribution functions of ground targets with complex and variable landscape and radiometric features are challenging tasks. Reasons for the increased interest in directional radiance measurements are presented, and the issues that must be addressed when trying to acquire directional radiances for vegetated land surfaces from different types of remote sensing platforms are discussed. Priority research emphases are suggested, concerning field measurements of directional surface radiances and reflectances for future research. Primarily, emphasis must be given to the acquisition of more complete and directly associated radiometric and biometric parameter data sets that will empower the exploitation of the 'angular dimension' in remote sensing of vegetation through enabling the further development and rigorous validation of state of the art plant canopy models.

Description: Synthetic aperture radar (SAR) images of the Greenland ice sheet collected by an airborne system clearly reveal the four melting facies of this sheet defined 30 years ago from snow stratigraphy studies by glaciologists. In particular, the radar echoes from the percolation facies have radiometric and polarimetric characteristics that are unique among terrestrial surfaces, but that resemble the exotic radar echoes recorded from the icy Galilean satellites. There, the radar signals interact with subsurface, massive ice features created in the cold, dry snow by seasonal melting and refreezing events. The subsurface features act as efficient reflectors of the incident radiation most likely via internal reflections. In the soaked-snow facies, the radar reflectivity is much lower because radar signals are attenuated by the wetter snow before they can interact with subsurface structures. Inversion algorithms to derive geophysical information from the SAR data are developed in both cases to estimate snow wetness in the soaked-snow facies and the mass of ice water retained in the percolation facies.

Description: An operational stratospheric correction scheme used after the Mount Pinatubo (Phillipines) eruption (Jun. 1991) is presented. The stratospheric aerosol distribution is assumed to be only variable with latitude. Each 9 days the latitudinal distribution of the optical thickness is computed by inverting radiances observed in the NOAA AVHRR channel 1 (0.63 micrometers) and channel 2 (0.83 micrometers) over the Pacific Ocean. This radiance data set is used to check the validity of model used for inversion by checking consistency of the optical thickness deduced from each channel as well as optical thickness deduced from different scattering angles. Using the optical thickness profile previously computed and radiative transfer code assuming Lambertian boundary condition, each pixel of channel 1 and 2 are corrected prior to computation of NDVI (Normalized Difference Vegetation Index). Comparison between corrected, non corrected, and years prior to Pinatubo eruption (1989 to 1990) NDVI composite, shows the necessity and the accuracy of the operational correction scheme.

Description: Aspects of aerosol studies and remote sensing are reviewed. Aerosol scatters solar radiation before it reaches the surface and scatters and absorbs it again after it is reflected from the surface and before it reaches the satellite sensor. The effect is spectrally and spatially dependent. Therefore atmospheric aerosol (dust, smoke and air pollution particles) has a significant effect on remote sensing. Correction for the aerosol effect was never achieved on an operational basis though several case studies were demonstrated. Correction can be done in a direct way by deriving the aerosol loading from the image itself and correcting for it using the appropriate radiative transfer model or by an indirect way, by defining remote sensing functions that are less dependent on the aerosol loading. To some degree this was already achieved in global remote sensing of vegetation where a composite of several days of NDVI (Normalized Difference Vegetation Index) measurements, choosing the maximal value, was used instead of a single cloud screened value. The Atmospheric Resistant Vegetation Index (ARVI) introduced recently for the NASA Earth Observing System EOS-MODIS is the most appropriate example of indirect correction, where the index is defined in such a way that the atmospheric effect in the blue spectral channel cancels to a large degree the atmospheric in the red channel in computations of a vegetation index. Atmospheric corrections can also use aerosol climatology and ground based instrumentation.

Description: A session dedicated to high spectral resolution in the solar spectrum, covering topics of calibration, atmospheric correction, geology/pedology, inland water, and vegetation, is reported. The session showed a high degree of diversity in the topics and the approaches used. It was highlighted that high spectral resolution data could provide atmospherically corrected ground level calibrated reflectance values. Important advances were shown in the use of radiative transfer models applied either on water bodies or vegetation. Several studies highlighted the high degree of redundancy contained in high spectral resolution data.

Description: Spectral absorption-coefficients (cross-sections) kappa(sub nu) (/cm/atm) have been measured in the 7.62, 8.97, and 12.3 micrometer bands of HCFC-22 (CHClF2) and the 10.6 micrometer bands of SF6 employing a high-resolution Fourier-transform spectrometer. Temperature and total pressure have been varied to simulate conditions corresponding to tropospheric and stratospheric layers in the atmosphere. The kappa(sub nu) are compared with values measured by us previously using a tunable diode laser spectrometer and with the appropriate entries in HITRAN and GEISA, two of the databases known to the atmospheric scientist. The measured absolute intensities of the bands are compared with previously published values.

Description: Microwave radar and radiometer measurements of grasslands indicate a substantial reduction in sensor sensitivity to soil moisture in the presence of a thatch layer. When this layer is wet it masks changes in the underlying soil, making the canopy appear warm in the case of passive sensors (radiometer) and decreasing backscatter in the active case (scatterometer). A model for a grass canopy with thatch will be presented in this paper to explain this behavior and to compare with observations. The canopy model consists of three layers: grass, thatch, and the underlying soil. The grass blades are modeled by elongated elliptical discs and the thatch is modeled as a collection of disk shaped water droplets (i.e., the dry matter is neglected). The ground is homogeneous and flat. The distorted Born approximation is used to compute the radar cross section of this three layer canopy and the emissivity is computed from the radar cross section using the Peake formulation for the passive problem. Results are computed at L-band (1.4 GHz) and C-band (4.75 GHz) using canopy parameters (i.e., plant geometry, soil moisture, plant moisture, etc.) representative of Konza Prairie grasslands. The results are compared to C-band scatterometer measurements and L-band radiometer measurements at these grasslands.

Description: There have been many significant improvements in the public access to the Space Shuttle Earth Observations Photography Database. New information is provided for the user community on the recently released videodisc of this database. Topics covered included the following: earlier attempts; our first laser videodisc in 1992; the new laser videodisc in 1994; and electronic database access.

Description: The Challenge Awards are designed to provide a unique perspective to students gifted in the arts and humanities from which to understand scientific endeavor by giving students an opportunity to participate in an ongoing research project. In the graduate program, seven students who had participated in previous Challenge Awards programs were selected to help develop the tools for Earth observations for the astronauts on the Space Radar Laboratory (SRL) missions. The goal of the Challenge Awards program was to prepare a training manual for the astronauts on the SRL missions. This paper describes the observations to be made by the astronauts on the SRL missions. The emphasis is on the dynamic seasonal features of the Earth's surface and atmosphere which justify the need for more than one flight of the SRL. Complete notebooks of the sites, global seasonal patterns, examples of radar and the Measurement of Air Pollution from Satellites data, and shuttle photographs have been given to each of the SRL crews.

Description: MacSigma0 is an interactive tool for the Macintosh which allows you to display and make computations from radar data collected by the following sensors: the JPL AIRSAR, ERS-1, JERS-1, and Magellan. The JPL AIRSAR system is a multi-polarimetric airborne synthetic aperture radar developed and operated by the Jet Propulsion Laboratory. It includes the single-frequency L-band sensor mounted on the NASA CV990 aircraft and its replacement, the multi-frequency P-, L-, and C-band sensors mounted on the NASA DC-8. MacSigma0 works with data in the standard JPL AIRSAR output product format, the compressed Stokes matrix format. ERS-1 and JERS-1 are single-frequency, single-polarization spaceborne synthetic aperture radars launched by the European Space Agency and NASDA respectively. To be usable by MacSigma0, The data must have been processed at the Alaska SAR Facility and must be in the "low-resolution" format. Magellan is a spacecraft mission to map the surface of Venus with imaging radar. The project is managed by the Jet Propulsion Laboratory. The spacecraft carries a single-frequency, single-polarization synthetic aperture radar. MacSigma0 works with framelets of the standard MIDR CD-ROM data products. MacSigma0 provides four basic functions: synthesis of images (if necessary), statistical analysis of selected areas, analysis of corner reflectors as a calibration measure (if appropriate and possible), and informative mouse tracking. For instance, the JPL AIRSAR data can be used to synthesize a variety of images such as a total power image. The total power image displays the sum of the polarized and unpolarized components of the backscatter for each pixel. Other images which can be synthesized are HH, HV, VV, RL, RR, HHVV*, HHHV*, HVVV*, HHVV* phase and correlation coefficient images. For the complex and phase images, phase is displayed using color and magnitude is displayed using intensity. MacSigma0 can also be used to compute statistics from within a selected area. The statistics computed depend on the image type. For JPL AIRSAR data, the HH, HV, VV, HHVV* phase, and correlation coefficient means and standard deviation measures are calculated. The mean, relative standard deviation, minimum, and maximum values are calculated for all other data types. A histogram of the selected area is also calculated and displayed. The selected area can be rectangular, linear, or polygonal in shape. The user is allowed to select multiple rectangular areas, but not multiple linear or polygonal areas. The statistics and histogram are displayed to the user and can either be printed or saved as a text file. MacSigma0 can also be used to analyze corner reflectors as a measure of the calibration for JPL AIRSAR, ERS-1, and JERS-1 data types. It computes a theoretical radar cross section and the actual radar cross section for a selected trihedral corner reflector. The theoretical cross section, measured cross section, their ratio in dBs, and other information are displayed to the user and can be saved into a text file. For ERS-1, JERS-1, and Magellan data, MacSigma0 simultaneously displays pixel location in data coordinates and in latitude, longitude coordinates. It also displays sigma0, the incidence angle (for Magellan data), the original pixel value (for Magellan data), and the noise power value (for ERS-1 and JERS-1 data). Grey scale computed images can be saved in a byte format (a headerless format which saves the image as a string of byte values) or a PICT format (a standard format readable by other image processing programs for the Macintosh). Images can also be printed. MacSigma0 is written in C-language for use on Macintosh series computers. The minimum configuration requirements for MacSigma0 are System 6.0, Finder 6.1, 1Mb of RAM, and at least a 4-bit color or grey-scale graphics display. MacSigma0 is also System 7 compatible. To compile the source code, Apple's Macintosh Programmers Workbench (MPW) 3.2 and the MPW C language compiler version 3.2 are required. The source code will not compile with a later version of the compiler; however, the compiled application which will run under the minimum hardware configuration is provided on the distribution medium. In addition, the distribution media includes an executable which runs significantly faster but requires a 68881 compatible math coprocessor and a 68020 compatible CPU. Since JPL AIRSAR data files can be very large, it is often desirable to reduce the size of a data file before transferring it to the Macintosh for use in MacSigma0. A small FORTRAN program which can be used for this purpose is included on the distribution media. MacSigma0 will print statistics on any output device which supports QuickDraw, and it will print images on any device which supports QuickDraw or PostScript. The standard distribution medium for MacSigma0 is a set of five 1.4Mb Macintosh format diskettes. This program was developed in 1992 and is a copyrighted work with all copyright vested in NASA. Version 4.2 of MacSigma0 was released in 1993.

Description: VICAR (Video Image Communication and Retrieval) is a general purpose image processing software system that has been under continuous development since the late 1960's. Originally intended for data from the NASA Jet Propulsion Laboratory's unmanned planetary spacecraft, VICAR is now used for a variety of other applications including biomedical image processing, cartography, earth resources, and geological exploration. The development of this newest version of VICAR emphasized a standardized, easily-understood user interface, a shield between the user and the host operating system, and a comprehensive array of image processing capabilities. Structurally, VICAR can be divided into roughly two parts; a suite of applications programs and an executive which serves as the interfaces between the applications, the operating system, and the user. There are several hundred applications programs ranging in function from interactive image editing, data compression/decompression, and map projection, to blemish, noise, and artifact removal, mosaic generation, and pattern recognition and location. An information management system designed specifically for handling image related data can merge image data with other types of data files. The user accesses these programs through the VICAR executive, which consists of a supervisor and a run-time library. From the viewpoint of the user and the applications programs, the executive is an environment that is independent of the operating system. VICAR does not replace the host computer's operating system; instead, it overlays the host resources. The core of the executive is the VICAR Supervisor, which is based on NASA Goddard Space Flight Center's Transportable Applications Executive (TAE). Various modifications and extensions have been made to optimize TAE for image processing applications, resulting in a user friendly environment. The rest of the executive consists of the VICAR Run-Time Library, which provides a set of subroutines (image I/O, label I/O, parameter I/O, etc.) to facilitate image processing and provide the fastest I/O possible while maintaining a wide variety of capabilities. The run-time library also includes the Virtual Raster Display Interface (VRDI) which allows display oriented applications programs to be written for a variety of display devices using a set of common routines. (A display device can be any frame-buffer type device which is attached to the host computer and has memory planes for the display and manipulation of images. A display device may have any number of separate 8-bit image memory planes (IMPs), a graphics overlay plane, pseudo-color capabilities, hardware zoom and pan, and other features). The VRDI supports the following display devices: VICOM (Gould/Deanza) IP8500, RAMTEK RM-9465, ADAGE (Ikonas) IK3000 and the International Imaging Systems IVAS. VRDI's purpose is to provide a uniform operating environment not only for an application programmer, but for the user as well. The programmer is able to write programs without being concerned with the specifics of the device for which the application is intended. The VICAR Interactive Display Subsystem (VIDS) is a collection of utilities for easy interactive display and manipulation of images on a display device. VIDS has characteristics of both the executive and an application program, and offers a wide menu of image manipulation options. VIDS uses the VRDI to communicate with display devices. The first step in using VIDS to analyze and enhance an image (one simple example of VICAR's numerous capabilities) is to examine the histogram of the image. The histogram is a plot of frequency of occurrence for each pixel value (0 - 255) loaded in the image plane. If, for example, the histogram shows that there are no pixel values below 64 or above 192, the histogram can be "stretched" so that the value of 64 is mapped to zero and 192 is mapped to 255. Now the user can use the full dynamic range of the display device to display the data and better see its contents. Another example of a VIDS procedure is the JMOVIE command, which allows the user to run animations interactively on the display device. JMOVIE uses the concept of "frames", which are the individual frames which comprise the animation to be viewed. The user loads images into the frames after the size and number of frames has been selected. VICAR's source languages are primarily FORTRAN and C, with some VAX Assembler and array processor code. The VICAR run-time library is designed to work equally easily from either FORTRAN or C. The program was implemented on a DEC VAX series computer operating under VMS 4.7. The virtual memory required is 1.5MB. Approximately 180,000 blocks of storage are needed for the saveset. VICAR (version 2.3A/3G/13H) is a copyrighted work with all copyright vested in NASA and is available by license for a period of ten (10) years to approved licensees. This program was developed in 1989.

Description: The Interactive Image Display Program (IMDISP) is an interactive image display utility for the IBM Personal Computer (PC, XT and AT) and compatibles. Until recently, efforts to utilize small computer systems for display and analysis of scientific data have been hampered by the lack of sufficient data storage capacity to accomodate large image arrays. Most planetary images, for example, require nearly a megabyte of storage. The recent development of the "CDROM" (Compact Disk Read-Only Memory) storage technology makes possible the storage of up to 680 megabytes of data on a single 4.72-inch disk. IMDISP was developed for use with the CDROM storage system which is currently being evaluated by the Planetary Data System. The latest disks to be produced by the Planetary Data System are a set of three disks containing all of the images of Uranus acquired by the Voyager spacecraft. The images are in both compressed and uncompressed format. IMDISP can read the uncompressed images directly, but special software is provided to decompress the compressed images, which can not be processed directly. IMDISP can also display images stored on floppy or hard disks. A digital image is a picture converted to numerical form so that it can be stored and used in a computer. The image is divided into a matrix of small regions called picture elements, or pixels. The rows and columns of pixels are called "lines" and "samples", respectively. Each pixel has a numerical value, or DN (data number) value, quantifying the darkness or brightness of the image at that spot. In total, each pixel has an address (line number, sample number) and a DN value, which is all that the computer needs for processing. DISPLAY commands allow the IMDISP user to display all or part of an image at various positions on the display screen. The user may also zoom in and out from a point on the image defined by the cursor, and may pan around the image. To enable more or all of the original image to be displayed on the screen at once, the image can be "subsampled." For example, if the image were subsampled by a factor of 2, every other pixel from every other line would be displayed, starting from the upper left corner of the image. Any positive integer may be used for subsampling. The user may produce a histogram of an image file, which is a graph showing the number of pixels per DN value, or per range of DN values, for the entire image. IMDISP can also plot the DN value versus pixels along a line between two points on the image. The user can "stretch" or increase the contrast of an image by specifying low and high DN values; all pixels with values lower than the specified "low" will then become black, and all pixels higher than the specified "high" value will become white. Pixels between the low and high values will be evenly shaded between black and white. IMDISP is written in a modular form to make it easy to change it to work with different display devices or on other computers. The code can also be adapted for use in other application programs. There are device dependent image display modules, general image display subroutines, image I/O routines, and image label and command line parsing routines. The IMDISP system is written in C-language (94%) and Assembler (6%). It was implemented on an IBM PC with the MS DOS 3.21 operating system. IMDISP has a memory requirement of about 142k bytes. IMDISP was developed in 1989 and is a copyrighted work with all copyright vested in NASA. Additional planetary images can be obtained from the National Space Science Data Center at (301) 286-6695.

Description: PC-SEAPAK is a user-interactive satellite data analysis software package specifically developed for oceanographic research. The program is used to process and interpret data obtained from the Nimbus-7/Coastal Zone Color Scanner (CZCS), and the NOAA Advanced Very High Resolution Radiometer (AVHRR). PC-SEAPAK is a set of independent microcomputer-based image analysis programs that provide the user with a flexible, user-friendly, standardized interface, and facilitates relatively low-cost analysis of oceanographic satellite data. Version 4.0 includes 114 programs. PC-SEAPAK programs are organized into categories which include CZCS and AVHRR level-1 ingest, level-2 analyses, statistical analyses, data extraction, remapping to standard projections, graphics manipulation, image board memory manipulation, hardcopy output support and general utilities. Most programs allow user interaction through menu and command modes and also by the use of a mouse. Most programs also provide for ASCII file generation for further analysis in spreadsheets, graphics packages, etc. The CZCS scanning radiometer aboard the NIMBUS-7 satellite was designed to measure the concentration of photosynthetic pigments and their degradation products in the ocean. AVHRR data is used to compute sea surface temperatures and is supported for the NOAA 6, 7, 8, 9, 10, 11, and 12 satellites. The CZCS operated from November 1978 to June 1986. CZCS data may be obtained free of charge from the CZCS archive at NASA/Goddard Space Flight Center. AVHRR data may be purchased through NOAA's Satellite Data Service Division. Ordering information is included in the PC-SEAPAK documentation. Although PC-SEAPAK was developed on a COMPAQ Deskpro 386/20, it can be run on most 386-compatible computers with an AT bus, EGA controller, Intel 80387 coprocessor, and MS-DOS 3.3 or higher. A Matrox MVP-AT image board with appropriate monitor and cables is also required. Note that the authors have received some reports of incompatibilities between the MVP-AT image board and ZENITH computers. Also, the MVP-AT image board is not necessarily compatible with 486-based systems; users of 486-based systems should consult with Matrox about compatibility concerns. Other PC-SEAPAK requirements include a Microsoft mouse (serial version), 2Mb RAM, and 100Mb hard disk space. For data ingest and backup, 9-track tape, 8mm tape and optical disks are supported and recommended. PC-SEAPAK has been under development since 1988. Version 4.0 was updated in 1992, and is distributed without source code. It is available only as a set of 36 1.2Mb 5.25 inch IBM MS-DOS format diskettes. PC-SEAPAK is a copyrighted product with all copyright vested in the National Aeronautics and Space Administration. Phar Lap's DOS_Extender run-time version is integrated into several of the programs; therefore, the PC-SEAPAK programs may not be duplicated. Three of the distribution diskettes contain DOS_Extender files. One of the distribution diskettes contains Media Cybernetics' HALO88 font files, also licensed by NASA for dissemination but not duplication. IBM is a registered trademark of International Business Machines. MS-DOS is a registered trademark of Microsoft Corporation. HALO88 is a registered trademark of Media Cybernetics, but the product was discontinued in 1991.

Description: The Land Analysis System (LAS) is an image analysis system designed to manipulate and analyze digital data in raster format and provide the user with a wide spectrum of functions and statistical tools for analysis. LAS offers these features under VMS with optional image display capabilities for IVAS and other display devices as well as the X-Windows environment. LAS provides a flexible framework for algorithm development as well as for the processing and analysis of image data. Users may choose between mouse-driven commands or the traditional command line input mode. LAS functions include supervised and unsupervised image classification, film product generation, geometric registration, image repair, radiometric correction and image statistical analysis. Data files accepted by LAS include formats such as Multi-Spectral Scanner (MSS), Thematic Mapper (TM) and Advanced Very High Resolution Radiometer (AVHRR). The enhanced geometric registration package now includes both image to image and map to map transformations. The over 200 LAS functions fall into image processing scenario categories which include: arithmetic and logical functions, data transformations, fourier transforms, geometric registration, hard copy output, image restoration, intensity transformation, multispectral and statistical analysis, file transfer, tape profiling and file management among others. Internal improvements to the LAS code have eliminated the VAX VMS dependencies and improved overall system performance. The maximum LAS image size has been increased to 20,000 lines by 20,000 samples with a maximum of 256 bands per image. The catalog management system used in earlier versions of LAS has been replaced by a more streamlined and maintenance-free method of file management. This system is not dependent on VAX/VMS and relies on file naming conventions alone to allow the use of identical LAS file names on different operating systems. While the LAS code has been improved, the original capabilities of the system have been preserved. These include maintaining associated image history, session logging, and batch, asynchronous and interactive mode of operation. The LAS application programs are integrated under version 4.1 of an interface called the Transportable Applications Executive (TAE). TAE 4.1 has four modes of user interaction: menu, direct command, tutor (or help), and dynamic tutor. In addition TAE 4.1 allows the operation of LAS functions using mouse-driven commands under the TAE-Facelift environment provided with TAE 4.1. These modes of operation allow users, from the beginner to the expert, to exercise specific application options. LAS is written in C-language and FORTRAN 77 for use with DEC VAX computers running VMS with approximately 16Mb of physical memory. This program runs under TAE 4.1. Since TAE 4.1 is not a current version of TAE, TAE 4.1 is included within the LAS distribution. Approximately 130,000 blocks (65Mb) of disk storage space are necessary to store the source code and files generated by the installation procedure for LAS and 44,000 blocks (22Mb) of disk storage space are necessary for TAE 4.1 installation. The only other dependencies for LAS are the subroutine libraries for the specific display device(s) that will be used with LAS/DMS (e.g. X-Windows and/or IVAS). The standard distribution medium for LAS is a set of two 9~track 6250 BPI magnetic tapes in DEC VAX BACKUP format. It is also available on a set of two TK50 tape cartridges in DEC VAX BACKUP format. This program was developed in 1986 and last updated in 1992.

Description: Spaceborne Synthetic Aperture Radar (SAR) images are useful for planetary mapping and Earth sciences investigations. However, swath widths rarely exceed 100 Kilometers, and images must be patched together to create a mosaic in order to analyze larger areas. The primary function of this program is to generate large digital mosaics of SAR imagery without manually marked tiepoints. MOSK can produce multiframe mosaics by combining images in the along-track, adjacent cross-track swaths, or ascending and descending passes. Geocoded map registered images, such as the ones produced by MAPJTC (NPO-17718), are required as input. The output is a geocoded mosaic on a standard map grid which permits easy registration with other geocoded data sets. Mosaicking of geocoded SAR imagery involves three steps. First, a match point is selected at the center of the overlapping area, then an image patch around the match point is extracted from both images and cross-correlation is done on this area. Then, images with their refined match points are merged together to form a mosaic. To handle the large data volume of overlapping intermediate stages, large mosaics are divided into equal size quadrants with each quadrant cut from an intermediate mosaic. The full mosaic can then be assembled from the individual quadrants. Finally, radiometric disparities at the image seams are smoothed by a "feathering" technique. The automatic mosaic system generates output with minimal operator interaction. However, manual tiepointing is required in cases of a large registration error or two images with smooth surfaces such as ocean images. MOSK is implemented on a DEC VAX 11/785 running VMS 4.5. Most subroutines are in FORTRAN, but three are in MAXL and one is in APAL. The program requires 1 Mb of memory and a Floating Point Systems AP-5210 array processor. The system memory usage is approximately 1000 pages and the requirement of page file size is 2000 blocks. MOSK was developed in 1988.

Description: MAPJTC was designed to rectify and transform the standard image output of the digital Synthetic Aperture Radar (SAR) correlator into a geocoded map registered image without operator interaction or manual tiepointing. This is accomplished by modeling the distortions and predicting the pixel displacements based on platform and radar parameters. The map projection implemented in MAPJTC is the Universal Transverse Mercator. Since the re-sampling operation is independent of the transformation data generation, other cartographic projections can be implemented with few software modifications. MAPJTC makes a precise determination of the geodetic location of an arbitrary pixel within the image frame based on the simultaneous solution of a set of earth model equations, SAR Doppler equations, and SAR range equations that identify the slant range from the sensor to the target at a specific image pixel. Based on a table of geodetic coordinates of the image pixels, the image is then mapped onto the desired cartographic projection by applying the appropriate transformation equations. Typically, mapping involves a two-dimensional re-sampling and is very computationally intensive. MAPJTC reduces the procedure to two one-dimensional passes, which saves computer time. Geocoding transforms the rectified image into a grid defined by a specific map projection. (The image is rotated and rectified to match the map projection.) Again, the two dimensional re-sampling process can be separated into two one-dimensional re-sampling processes. Optionally, MAPJTC can correct terrain-induced distortions in SAR imagery when a digital elevation map is available. MAPJTC was developed on a DEC VAX 11/785 under VMS 4.5. The program is written in FORTRAN (84%), APAL (2%), and MAXL (14%). It requires 6Mb of memory and a Floating Point Systems AP-5210 Array Processor equipped with 1Mb of memory. MAPJTC can run interactively or as a batch job. MAPJTC was developed in 1987.

Description: The Spectral Analysis Manager (SPAM) was developed to allow easy qualitative analysis of multi-dimensional imaging spectrometer data. Imaging spectrometers provide sufficient spectral sampling to define unique spectral signatures on a per pixel basis. Thus direct material identification becomes possible for geologic studies. SPAM provides a variety of capabilities for carrying out interactive analysis of the massive and complex datasets associated with multispectral remote sensing observations. In addition to normal image processing functions, SPAM provides multiple levels of on-line help, a flexible command interpretation, graceful error recovery, and a program structure which can be implemented in a variety of environments. SPAM was designed to be visually oriented and user friendly with the liberal employment of graphics for rapid and efficient exploratory analysis of imaging spectrometry data. SPAM provides functions to enable arithmetic manipulations of the data, such as normalization, linear mixing, band ratio discrimination, and low-pass filtering. SPAM can be used to examine the spectra of an individual pixel or the average spectra over a number of pixels. SPAM also supports image segmentation, fast spectral signature matching, spectral library usage, mixture analysis, and feature extraction. High speed spectral signature matching is performed by using a binary spectral encoding algorithm to separate and identify mineral components present in the scene. The same binary encoding allows automatic spectral clustering. Spectral data may be entered from a digitizing tablet, stored in a user library, compared to the master library containing mineral standards, and then displayed as a timesequence spectral movie. The output plots, histograms, and stretched histograms produced by SPAM can be sent to a lineprinter, stored as separate RGB disk files, or sent to a Quick Color Recorder. SPAM is written in C for interactive execution and is available for two different machine environments. There is a DEC VAX/VMS version with a central memory requirement of approximately 242K of 8 bit bytes and a machine independent UNIX 4.2 version. The display device currently supported is the Raster Technologies display processor. Other 512 x 512 resolution color display devices, such as De Anza, may be added with minor code modifications. This program was developed in 1986.

Description: The Spectral Analysis Manager (SPAM) was developed to allow easy qualitative analysis of multi-dimensional imaging spectrometer data. Imaging spectrometers provide sufficient spectral sampling to define unique spectral signatures on a per pixel basis. Thus direct material identification becomes possible for geologic studies. SPAM provides a variety of capabilities for carrying out interactive analysis of the massive and complex datasets associated with multispectral remote sensing observations. In addition to normal image processing functions, SPAM provides multiple levels of on-line help, a flexible command interpretation, graceful error recovery, and a program structure which can be implemented in a variety of environments. SPAM was designed to be visually oriented and user friendly with the liberal employment of graphics for rapid and efficient exploratory analysis of imaging spectrometry data. SPAM provides functions to enable arithmetic manipulations of the data, such as normalization, linear mixing, band ratio discrimination, and low-pass filtering. SPAM can be used to examine the spectra of an individual pixel or the average spectra over a number of pixels. SPAM also supports image segmentation, fast spectral signature matching, spectral library usage, mixture analysis, and feature extraction. High speed spectral signature matching is performed by using a binary spectral encoding algorithm to separate and identify mineral components present in the scene. The same binary encoding allows automatic spectral clustering. Spectral data may be entered from a digitizing tablet, stored in a user library, compared to the master library containing mineral standards, and then displayed as a timesequence spectral movie. The output plots, histograms, and stretched histograms produced by SPAM can be sent to a lineprinter, stored as separate RGB disk files, or sent to a Quick Color Recorder. SPAM is written in C for interactive execution and is available for two different machine environments. There is a DEC VAX/VMS version with a central memory requirement of approximately 242K of 8 bit bytes and a machine independent UNIX 4.2 version. The display device currently supported is the Raster Technologies display processor. Other 512 x 512 resolution color display devices, such as De Anza, may be added with minor code modifications. This program was developed in 1986.

Description: The Science and Technology Laboratory Applications Software (ELAS) was originally designed to analyze and process digital imagery data, specifically remotely-sensed scanner data. This capability includes the processing of Landsat multispectral data; aircraft-acquired scanner data; digitized topographic data; and numerous other ancillary data, such as soil types and rainfall information, that can be stored in digitized form. ELAS has the subsequent capability to geographically reference this data to dozens of standard, as well as user created projections. As an integrated image processing system, ELAS offers the user of remotely-sensed data a wide range of capabilities in the areas of land cover analysis and general purpose image analysis. ELAS is designed for flexible use and operation and includes its own FORTRAN operating subsystem and an expandable set of FORTRAN application modules. Because all of ELAS resides in one "logical" FORTRAN program, data inputs and outputs, directives, and module switching are convenient for the user. There are over 230 modules presently available to aid the user in performing a wide range of land cover analyses and manipulation. The file management modules enable the user to allocate, define, access, and specify usage for all types of files (ELAS files, subfiles, external files etc.). Various other modules convert specific types of satellite, aircraft, and vector-polygon data into files that can be used by other ELAS modules. The user also has many module options which aid in displaying image data, such as magnification/reduction of the display; true color display; and several memory functions. Additional modules allow for the building and manipulation of polygonal areas of the image data. Finally, there are modules which allow the user to select and classify the image data. An important feature of the ELAS subsystem is that its structure allows new applications modules to be easily integrated in the future. ELAS has as a standard the flexibility to process data elements exceeding 8 bits in length, including floating point (noninteger) elements and 16 or 32 bit integers. Thus it is able to analyze and process "non-standard" nonimage data. The VAX (ERL-10017) and Concurrent (ERL-10013) versions of ELAS 9.0 are written in FORTRAN and ASSEMBLER for DEC VAX series computers running VMS and Concurrent computers running MTM. The Sun (SSC-00019), Masscomp (SSC-00020), and Silicon Graphics (SSC-00021) versions of ELAS 9.0 are written in FORTRAN 77 and C-LANGUAGE for Sun4 series computers running SunOS, Masscomp computers running UNIX, and Silicon Graphics IRIS computers running IRIX. The Concurrent version requires at least 15 bit addressing and a direct memory access channel. The VAX and Concurrent versions of ELAS both require floating-point hardware, at least 1Mb of RAM, and approximately 70Mb of disk space. Both versions also require a COMTAL display device in order to display images. For the Sun, Masscomp, and Silicon Graphics versions of ELAS, the disk storage required is approximately 115Mb, and a minimum of 8Mb of RAM is required for execution. The Sun version of ELAS requires either the X-Window System Version 11 Revision 4 or Sun OpenWindows Version 2. The Masscomp version requires a GA1000 display device and the associated "gp" library. The Silicon Graphics version requires Silicon Graphics' GL library. ELAS display functions will not work with a monochrome monitor. The standard distribution medium for the VAX version (ERL~10017) is a set of two 9-track 1600 BPI magnetic tapes in DEC VAX BACKUP format. This version is also available on a TK50 tape cartridge in DEC VAX BACKUP format. The standard distribution medium for the Concurrent version (ERL-10013) is a set of two 9-track 1600 BPI magnetic tapes in Concurrent BACKUP format. The standard distribution medium for the Sun version (SSC-00019) is a .25 inch streaming magnetic tape cartridge in UNIX tar format. The standard distribution medium for the Masscomp version, (SSC-00020) is a .25 inch streaming magnetic tape cartridge in UNIX tar format. The standard distribution medium for the Silicon Graphics version (SSC-00021) is a .25 inch streaming magnetic IRIS tape cartridge in UNIX tar format. Version 9.0 was released in 1991. Sun4, SunOS, and Open Windows are trademarks of Sun Microsystems, Inc. MIT X Window System is licensed by Massachusetts Institute of Technology.

Description: The Science and Technology Laboratory Applications Software (ELAS) was originally designed to analyze and process digital imagery data, specifically remotely-sensed scanner data. This capability includes the processing of Landsat multispectral data; aircraft-acquired scanner data; digitized topographic data; and numerous other ancillary data, such as soil types and rainfall information, that can be stored in digitized form. ELAS has the subsequent capability to geographically reference this data to dozens of standard, as well as user created projections. As an integrated image processing system, ELAS offers the user of remotely-sensed data a wide range of capabilities in the areas of land cover analysis and general purpose image analysis. ELAS is designed for flexible use and operation and includes its own FORTRAN operating subsystem and an expandable set of FORTRAN application modules. Because all of ELAS resides in one "logical" FORTRAN program, data inputs and outputs, directives, and module switching are convenient for the user. There are over 230 modules presently available to aid the user in performing a wide range of land cover analyses and manipulation. The file management modules enable the user to allocate, define, access, and specify usage for all types of files (ELAS files, subfiles, external files etc.). Various other modules convert specific types of satellite, aircraft, and vector-polygon data into files that can be used by other ELAS modules. The user also has many module options which aid in displaying image data, such as magnification/reduction of the display; true color display; and several memory functions. Additional modules allow for the building and manipulation of polygonal areas of the image data. Finally, there are modules which allow the user to select and classify the image data. An important feature of the ELAS subsystem is that its structure allows new applications modules to be easily integrated in the future. ELAS has as a standard the flexibility to process data elements exceeding 8 bits in length, including floating point (noninteger) elements and 16 or 32 bit integers. Thus it is able to analyze and process "non-standard" nonimage data. The VAX (ERL-10017) and Concurrent (ERL-10013) versions of ELAS 9.0 are written in FORTRAN and ASSEMBLER for DEC VAX series computers running VMS and Concurrent computers running MTM. The Sun (SSC-00019), Masscomp (SSC-00020), and Silicon Graphics (SSC-00021) versions of ELAS 9.0 are written in FORTRAN 77 and C-LANGUAGE for Sun4 series computers running SunOS, Masscomp computers running UNIX, and Silicon Graphics IRIS computers running IRIX. The Concurrent version requires at least 15 bit addressing and a direct memory access channel. The VAX and Concurrent versions of ELAS both require floating-point hardware, at least 1Mb of RAM, and approximately 70Mb of disk space. Both versions also require a COMTAL display device in order to display images. For the Sun, Masscomp, and Silicon Graphics versions of ELAS, the disk storage required is approximately 115Mb, and a minimum of 8Mb of RAM is required for execution. The Sun version of ELAS requires either the X-Window System Version 11 Revision 4 or Sun OpenWindows Version 2. The Masscomp version requires a GA1000 display device and the associated "gp" library. The Silicon Graphics version requires Silicon Graphics' GL library. ELAS display functions will not work with a monochrome monitor. The standard distribution medium for the VAX version (ERL~10017) is a set of two 9-track 1600 BPI magnetic tapes in DEC VAX BACKUP format. This version is also available on a TK50 tape cartridge in DEC VAX BACKUP format. The standard distribution medium for the Concurrent version (ERL-10013) is a set of two 9-track 1600 BPI magnetic tapes in Concurrent BACKUP format. The standard distribution medium for the Sun version (SSC-00019) is a .25 inch streaming magnetic tape cartridge in UNIX tar format. The standard distribution medium for the Masscomp version, (SSC-00020) is a .25 inch streaming magnetic tape cartridge in UNIX tar format. The standard distribution medium for the Silicon Graphics version (SSC-00021) is a .25 inch streaming magnetic IRIS tape cartridge in UNIX tar format. Version 9.0 was released in 1991. Sun4, SunOS, and Open Windows are trademarks of Sun Microsystems, Inc. MIT X Window System is licensed by Massachusetts Institute of Technology.

Description: IMAGEP is a FORTRAN computer algorithm containing various image processing, analysis, and enhancement functions. It is a keyboard-driven program organized into nine subroutines. Within the subroutines are other routines, also, selected via keyboard. Some of the functions performed by IMAGEP include digitization, storage and retrieval of images; image enhancement by contrast expansion, addition and subtraction, magnification, inversion, and bit shifting; display and movement of cursor; display of grey level histogram of image; and display of the variation of grey level intensity as a function of image position. This algorithm has possible scientific, industrial, and biomedical applications in material flaw studies, steel and ore analysis, and pathology, respectively. IMAGEP is written in VAX FORTRAN for DEC VAX series computers running VMS. The program requires the use of a Grinnell 274 image processor which can be obtained from Mark McCloud Associates, Campbell, CA. An object library of the required GMR series software is included on the distribution media. IMAGEP requires 1Mb of RAM for execution. The standard distribution medium for this program is a 1600 BPI 9~track magnetic tape in VAX FILES-11 format. It is also available on a TK50 tape cartridge in VAX FILES-11 format. This program was developed in 1991. DEC, VAX, VMS, and TK50 are trademarks of Digital Equipment Corporation.

Description: A brief mission overview of STS-49 is given, and some of the pictorially outstanding and scientifically interesting photographs obtained during the mission are presented. The Earth observations are described and include the following: the Southwestern Pacific Ocean -- wind and water; the Southwestern Pacific Ocean -- coasts and volcanoes; the US; Cuba and the Bahamas; South America; Africa; the Red Sea and Western Indian Ocean; and the Indian Subcontinent.

Description: The Science and Technology Laboratory Applications Software (ELAS) was originally designed to analyze and process digital imagery data, specifically remotely-sensed scanner data. This capability includes the processing of Landsat multispectral data; aircraft-acquired scanner data; digitized topographic data; and numerous other ancillary data, such as soil types and rainfall information, that can be stored in digitized form. ELAS has the subsequent capability to geographically reference this data to dozens of standard, as well as user created projections. As an integrated image processing system, ELAS offers the user of remotely-sensed data a wide range of capabilities in the areas of land cover analysis and general purpose image analysis. ELAS is designed for flexible use and operation and includes its own FORTRAN operating subsystem and an expandable set of FORTRAN application modules. Because all of ELAS resides in one "logical" FORTRAN program, data inputs and outputs, directives, and module switching are convenient for the user. There are over 230 modules presently available to aid the user in performing a wide range of land cover analyses and manipulation. The file management modules enable the user to allocate, define, access, and specify usage for all types of files (ELAS files, subfiles, external files etc.). Various other modules convert specific types of satellite, aircraft, and vector-polygon data into files that can be used by other ELAS modules. The user also has many module options which aid in displaying image data, such as magnification/reduction of the display; true color display; and several memory functions. Additional modules allow for the building and manipulation of polygonal areas of the image data. Finally, there are modules which allow the user to select and classify the image data. An important feature of the ELAS subsystem is that its structure allows new applications modules to be easily integrated in the future. ELAS has as a standard the flexibility to process data elements exceeding 8 bits in length, including floating point (noninteger) elements and 16 or 32 bit integers. Thus it is able to analyze and process "non-standard" nonimage data. The VAX (ERL-10017) and Concurrent (ERL-10013) versions of ELAS 9.0 are written in FORTRAN and ASSEMBLER for DEC VAX series computers running VMS and Concurrent computers running MTM. The Sun (SSC-00019), Masscomp (SSC-00020), and Silicon Graphics (SSC-00021) versions of ELAS 9.0 are written in FORTRAN 77 and C-LANGUAGE for Sun4 series computers running SunOS, Masscomp computers running UNIX, and Silicon Graphics IRIS computers running IRIX. The Concurrent version requires at least 15 bit addressing and a direct memory access channel. The VAX and Concurrent versions of ELAS both require floating-point hardware, at least 1Mb of RAM, and approximately 70Mb of disk space. Both versions also require a COMTAL display device in order to display images. For the Sun, Masscomp, and Silicon Graphics versions of ELAS, the disk storage required is approximately 115Mb, and a minimum of 8Mb of RAM is required for execution. The Sun version of ELAS requires either the X-Window System Version 11 Revision 4 or Sun OpenWindows Version 2. The Masscomp version requires a GA1000 display device and the associated "gp" library. The Silicon Graphics version requires Silicon Graphics' GL library. ELAS display functions will not work with a monochrome monitor. The standard distribution medium for the VAX version (ERL~10017) is a set of two 9-track 1600 BPI magnetic tapes in DEC VAX BACKUP format. This version is also available on a TK50 tape cartridge in DEC VAX BACKUP format. The standard distribution medium for the Concurrent version (ERL-10013) is a set of two 9-track 1600 BPI magnetic tapes in Concurrent BACKUP format. The standard distribution medium for the Sun version (SSC-00019) is a .25 inch streaming magnetic tape cartridge in UNIX tar format. The standard distribution medium for the Masscomp version, (SSC-00020) is a .25 inch streaming magnetic tape cartridge in UNIX tar format. The standard distribution medium for the Silicon Graphics version (SSC-00021) is a .25 inch streaming magnetic IRIS tape cartridge in UNIX tar format. Version 9.0 was released in 1991. Sun4, SunOS, and Open Windows are trademarks of Sun Microsystems, Inc. MIT X Window System is licensed by Massachusetts Institute of Technology.

Description: The Science and Technology Laboratory Applications Software (ELAS) was originally designed to analyze and process digital imagery data, specifically remotely-sensed scanner data. This capability includes the processing of Landsat multispectral data; aircraft-acquired scanner data; digitized topographic data; and numerous other ancillary data, such as soil types and rainfall information, that can be stored in digitized form. ELAS has the subsequent capability to geographically reference this data to dozens of standard, as well as user created projections. As an integrated image processing system, ELAS offers the user of remotely-sensed data a wide range of capabilities in the areas of land cover analysis and general purpose image analysis. ELAS is designed for flexible use and operation and includes its own FORTRAN operating subsystem and an expandable set of FORTRAN application modules. Because all of ELAS resides in one "logical" FORTRAN program, data inputs and outputs, directives, and module switching are convenient for the user. There are over 230 modules presently available to aid the user in performing a wide range of land cover analyses and manipulation. The file management modules enable the user to allocate, define, access, and specify usage for all types of files (ELAS files, subfiles, external files etc.). Various other modules convert specific types of satellite, aircraft, and vector-polygon data into files that can be used by other ELAS modules. The user also has many module options which aid in displaying image data, such as magnification/reduction of the display; true color display; and several memory functions. Additional modules allow for the building and manipulation of polygonal areas of the image data. Finally, there are modules which allow the user to select and classify the image data. An important feature of the ELAS subsystem is that its structure allows new applications modules to be easily integrated in the future. ELAS has as a standard the flexibility to process data elements exceeding 8 bits in length, including floating point (noninteger) elements and 16 or 32 bit integers. Thus it is able to analyze and process "non-standard" nonimage data. The VAX (ERL-10017) and Concurrent (ERL-10013) versions of ELAS 9.0 are written in FORTRAN and ASSEMBLER for DEC VAX series computers running VMS and Concurrent computers running MTM. The Sun (SSC-00019), Masscomp (SSC-00020), and Silicon Graphics (SSC-00021) versions of ELAS 9.0 are written in FORTRAN 77 and C-LANGUAGE for Sun4 series computers running SunOS, Masscomp computers running UNIX, and Silicon Graphics IRIS computers running IRIX. The Concurrent version requires at least 15 bit addressing and a direct memory access channel. The VAX and Concurrent versions of ELAS both require floating-point hardware, at least 1Mb of RAM, and approximately 70Mb of disk space. Both versions also require a COMTAL display device in order to display images. For the Sun, Masscomp, and Silicon Graphics versions of ELAS, the disk storage required is approximately 115Mb, and a minimum of 8Mb of RAM is required for execution. The Sun version of ELAS requires either the X-Window System Version 11 Revision 4 or Sun OpenWindows Version 2. The Masscomp version requires a GA1000 display device and the associated "gp" library. The Silicon Graphics version requires Silicon Graphics' GL library. ELAS display functions will not work with a monochrome monitor. The standard distribution medium for the VAX version (ERL~10017) is a set of two 9-track 1600 BPI magnetic tapes in DEC VAX BACKUP format. This version is also available on a TK50 tape cartridge in DEC VAX BACKUP format. The standard distribution medium for the Concurrent version (ERL-10013) is a set of two 9-track 1600 BPI magnetic tapes in Concurrent BACKUP format. The standard distribution medium for the Sun version (SSC-00019) is a .25 inch streaming magnetic tape cartridge in UNIX tar format. The standard distribution medium for the Masscomp version, (SSC-00020) is a .25 inch streaming magnetic tape cartridge in UNIX tar format. The standard distribution medium for the Silicon Graphics version (SSC-00021) is a .25 inch streaming magnetic IRIS tape cartridge in UNIX tar format. Version 9.0 was released in 1991. Sun4, SunOS, and Open Windows are trademarks of Sun Microsystems, Inc. MIT X Window System is licensed by Massachusetts Institute of Technology.

Description: MacMultiview is an interactive tool for the Macintosh II family which allows one to display and make computations utilizing polarimetric radar data collected by the Jet Propulsion Laboratory's imaging SAR (synthetic aperture radar) polarimeter system. The system includes the single-frequency L-band sensor mounted on the NASA CV990 aircraft and its replacement, the multi-frequency P-, L-, and C-band sensors mounted on the NASA DC-8. MacMultiview provides two basic functions: computation of synthesized polarimetric images and computation of polarization signatures. The radar data can be used to compute a variety of images. The total power image displays the sum of the polarized and unpolarized components of the backscatter for each pixel. The magnitude/phase difference image displays the HH (horizontal transmit and horizontal receive polarization) to VV (vertical transmit and vertical receive polarization) phase difference using color. Magnitude is displayed using intensity. The user may also select any transmit and receive polarization combination from which an image is synthesized. This image displays the backscatter which would have been observed had the sensor been configured using the selected transmit and receive polarizations. MacMultiview can also be used to compute polarization signatures, three dimensional plots of backscatter versus transmit and receive polarizations. The standard co-polarization signatures (transmit and receive polarizations are the same) and cross-polarization signatures (transmit and receive polarizations are orthogonal) can be plotted for any rectangular subset of pixels within a radar data set. In addition, the ratio of co- and cross-polarization signatures computed from different subsets within the same data set can also be computed. Computed images can be saved in a variety of formats: byte format (headerless format which saves the image as a string of byte values), MacMultiview (a byte image preceded by an ASCII header), and PICT2 format (standard format readable by MacMultiview and other image processing programs for the Macintosh). Images can also be printed on PostScript output devices. Polarization signatures can be saved in either a PICT format or as a text file containing PostScript commands and printed on any QuickDraw output device. The associated Stokes matrices can be stored in a text file. MacMultiview is written in C-language for Macintosh II series computers. MacMultiview will only run on Macintosh II series computers with 8-bit video displays (gray shades or color). The program also requires a minimum configuration of System 6.0, Finder 6.1, and 1Mb of RAM. MacMultiview is NOT compatible with System 7.0. It requires 32-Bit QuickDraw. Note: MacMultiview may not be fully compatible with preliminary versions of 32-Bit QuickDraw. Macintosh Programmer's Workshop and Macintosh Programmer's Workshop C (version 3.0) are required for recompiling and relinking. The standard distribution medium for this package is a set of three 800K 3.5 inch diskettes in Macintosh format. This program was developed in 1989 and updated in 1991. MacMultiview is a copyrighted work with all copyright vested in NASA. QuickDraw, Finder, Macintosh, and System 7 are trademarks of Apple Computer, Inc.

Description: The accurate partitioning of available energy into sensible and latent heat flux is crucial to the understanding of surface atmosphere interactions. This issue is more complicated in arid and semi arid regions where the relative contribution to surface fluxes from the soil and vegetation may vary significantly throughout the day and throughout the season. A three component model to estimate sensible heat flux over heterogeneous surfaces is presented. The surface was represented with two adjacent compartments. The first compartment is made up of two components, shrubs and shaded soil, the second of open 'illuminated' soil. Data collected at two different sites in Nevada (U.S.) during the Summers of 1991 and 1992 were used to evaluate model performance. The results show that the present model is sufficiently general to yield satisfactory results for both sites.

Description: Since September 1991, the ERS-1 SAR (Synthetic Aperture Radar) has collected approximately 170 frames of ocean imagery on 28 passes over the western Gulf Stream in support of ESA experiment US8-2c. SAR signatures of the north wall are seen on nearly all passes, with modulation depth varying from 3% to 35% for 100 m samples. Many small and mesoscale circulation features associated with the Stream are evident. The detailed form of the signature varies considerably, however. Narrow bright or dark linear features appear to follow streamlines, and on one occasion a strong dark line was associated with an in situ measurement of a sharp current shear. Similarly, larger spatial scale changes in backscatter over the Stream were associated with in situ measurements of atmospheric stability transitions. Physical explanations for the narrow features are not so obvious. However, the accumulation of surfactants along converging current boundaries or local short wave straining and breaking appear plausible. These preliminary results strongly suggest that a wide swath (approximately 500 km) SAR with at least 100 m resolution would be a useful adjunct to existing satellite AVHRR (Advanced Very High Resolution Radiometer) imagery.

Description: ERS-1 SAR (Synthetic Aperture Radar) data were used to specify Winter physical processes on the surface of the Greenland Sea, and SSM/I (Special Sensor Microwave/Imager) data were used to characterize the regional behavior of the ice cover. Examination of the SSM/I data indicated that the convective water was likely to be confined to small (less than 100 km) domains near the ice edge. Using ERS-1 SAR data crossing the ice edge, it was possible to identify ice edge features that are very similar to modeled plumes; they have a diameter of about 100 m, a spacing of about 300 m, and cover an area about 20 by 90 km. This plume observation is the first such identification of convection. The plumes are topped by ice, and the return-water areas are open, indicating a freshened top layer of the sea and emphasizing the importance of this layer to convection.

Description: There is renewed interest in using optical remote sensing techniques for measuring and monitoring airborne toxins. Many instruments have been used to measure traces of atmospheric molecular species. Some optical remote sensing technology is in use for measuring or monitoring toxic or pollutant gases. The examples in this article provide a number of lessons that may be of use in the new field of optical remote sensing of toxic gases. Topics covered include the following: atmospheric properties, Fourier transform spectrometry, gas-filter correlation, differential absorption laser systems, aircraft missions, laser long-path instruments, differential optical absorption spectrometry, and ozone measurement.

Description: Global and regional temperature variations in the lower troposphere and lower stratosphere are examined for the period 1979-92 from Microwave Sounder Unit (MSU) data obtained by the Television Infrared Observation Satellite (TIROS)-N series of National Oceanic and Atmospheric Administration (NOAA) operational satellites. In the lower troposphere, globally-averaged temperature variations appear to be dominated by tropical El Nino (warm) and La Nina (cool) events and volcanic eruptions. The Pinatubo volcanic eruption in June 1991 appears to have initiated a cooling trend which persisted through the most recent data analyzed (July, 1992), and largely overwhelmed the warming from the 1991-92 El Nino. The cooling has been stronger in the Northern Hemisphere than in the Southern Hemisphere. The temperature trend over the 13.5 year satellite record is small (+0.03 C) compared to the year-to-year variability (0.2-0.4 C), making detection of any global warming signal fruitless to date. However, the future global warming trend, currently predicted to be around 0.3 C/decade, will be much easier to discern should it develop. The lower stratospheric temperature record is dominated by warm episodes from the Pinatubo eruption and the March 1982 eruption of El Chichon volcano.

Description: Several types of algorithms are generally used to process digital imagery such as Landsat data. The most commonly used algorithms perform the task of registration, compression, and classification. Because there are different techniques available for performing registration, compression, and classification, imagery data users need a rationale for selecting a particular approach to meet their particular needs. This collection of registration, compression, and classification algorithms was developed so that different approaches could be evaluated and the best approach for a particular application determined. Routines are included for six registration algorithms, six compression algorithms, and two classification algorithms. The package also includes routines for evaluating the effects of processing on the image data. This collection of routines should be useful to anyone using or developing image processing software. Registration of image data involves the geometrical alteration of the imagery. Registration routines available in the evaluation package include image magnification, mapping functions, partitioning, map overlay, and data interpolation. The compression of image data involves reducing the volume of data needed for a given image. Compression routines available in the package include adaptive differential pulse code modulation, two-dimensional transforms, clustering, vector reduction, and picture segmentation. Classification of image data involves analyzing the uncompressed or compressed image data to produce inventories and maps of areas of similar spectral properties within a scene. The classification routines available include a sequential linear technique and a maximum likelihood technique. The choice of the appropriate evaluation criteria is quite important in evaluating the image processing functions. The user is therefore given a choice of evaluation criteria with which to investigate the available image processing functions. All of the available evaluation criteria basically compare the observed results with the expected results. For the image reconstruction processes of registration and compression, the expected results are usually the original data or some selected characteristics of the original data. For classification processes the expected result is the ground truth of the scene. Thus, the comparison process consists of determining what changes occur in processing, where the changes occur, how much change occurs, and the amplitude of the change. The package includes evaluation routines for performing such comparisons as average uncertainty, average information transfer, chi-square statistics, multidimensional histograms, and computation of contingency matrices. This collection of routines is written in FORTRAN IV for batch execution and has been implemented on an IBM 360 computer with a central memory requirement of approximately 662K of 8 bit bytes. This collection of image processing and evaluation routines was developed in 1979.

Description: The Science and Technology Laboratory Applications Software (ELAS) was originally designed to analyze and process digital imagery data, specifically remotely-sensed scanner data. This capability includes the processing of Landsat multispectral data; aircraft-acquired scanner data; digitized topographic data; and numerous other ancillary data, such as soil types and rainfall information, that can be stored in digitized form. ELAS has the subsequent capability to geographically reference this data to dozens of standard, as well as user created projections. As an integrated image processing system, ELAS offers the user of remotely-sensed data a wide range of capabilities in the areas of land cover analysis and general purpose image analysis. ELAS is designed for flexible use and operation and includes its own FORTRAN operating subsystem and an expandable set of FORTRAN application modules. Because all of ELAS resides in one "logical" FORTRAN program, data inputs and outputs, directives, and module switching are convenient for the user. There are over 230 modules presently available to aid the user in performing a wide range of land cover analyses and manipulation. The file management modules enable the user to allocate, define, access, and specify usage for all types of files (ELAS files, subfiles, external files etc.). Various other modules convert specific types of satellite, aircraft, and vector-polygon data into files that can be used by other ELAS modules. The user also has many module options which aid in displaying image data, such as magnification/reduction of the display; true color display; and several memory functions. Additional modules allow for the building and manipulation of polygonal areas of the image data. Finally, there are modules which allow the user to select and classify the image data. An important feature of the ELAS subsystem is that its structure allows new applications modules to be easily integrated in the future. ELAS has as a standard the flexibility to process data elements exceeding 8 bits in length, including floating point (noninteger) elements and 16 or 32 bit integers. Thus it is able to analyze and process "non-standard" nonimage data. The VAX (ERL-10017) and Concurrent (ERL-10013) versions of ELAS 9.0 are written in FORTRAN and ASSEMBLER for DEC VAX series computers running VMS and Concurrent computers running MTM. The Sun (SSC-00019), Masscomp (SSC-00020), and Silicon Graphics (SSC-00021) versions of ELAS 9.0 are written in FORTRAN 77 and C-LANGUAGE for Sun4 series computers running SunOS, Masscomp computers running UNIX, and Silicon Graphics IRIS computers running IRIX. The Concurrent version requires at least 15 bit addressing and a direct memory access channel. The VAX and Concurrent versions of ELAS both require floating-point hardware, at least 1Mb of RAM, and approximately 70Mb of disk space. Both versions also require a COMTAL display device in order to display images. For the Sun, Masscomp, and Silicon Graphics versions of ELAS, the disk storage required is approximately 115Mb, and a minimum of 8Mb of RAM is required for execution. The Sun version of ELAS requires either the X-Window System Version 11 Revision 4 or Sun OpenWindows Version 2. The Masscomp version requires a GA1000 display device and the associated "gp" library. The Silicon Graphics version requires Silicon Graphics' GL library. ELAS display functions will not work with a monochrome monitor. The standard distribution medium for the VAX version (ERL~10017) is a set of two 9-track 1600 BPI magnetic tapes in DEC VAX BACKUP format. This version is also available on a TK50 tape cartridge in DEC VAX BACKUP format. The standard distribution medium for the Concurrent version (ERL-10013) is a set of two 9-track 1600 BPI magnetic tapes in Concurrent BACKUP format. The standard distribution medium for the Sun version (SSC-00019) is a .25 inch streaming magnetic tape cartridge in UNIX tar format. The standard distribution medium for the Masscomp version, (SSC-00020) is a .25 inch streaming magnetic tape cartridge in UNIX tar format. The standard distribution medium for the Silicon Graphics version (SSC-00021) is a .25 inch streaming magnetic IRIS tape cartridge in UNIX tar format. Version 9.0 was released in 1991. Sun4, SunOS, and Open Windows are trademarks of Sun Microsystems, Inc. MIT X Window System is licensed by Massachusetts Institute of Technology.

Description: Calibration of polarimetric radar systems is a field of research in which great progress has been made over the last few years. POLCAL (Polarimetric Radar Calibration) is a software tool intended to assist in the calibration of Synthetic Aperture Radar (SAR) systems. In particular, POLCAL calibrates Stokes matrix format data produced as the standard product by the NASA/Jet Propulsion Laboratory (JPL) airborne imaging synthetic aperture radar (AIRSAR). POLCAL was designed to be used in conjunction with data collected by the NASA/JPL AIRSAR system. AIRSAR is a multifrequency (6 cm, 24 cm, and 68 cm wavelength), fully polarimetric SAR system which produces 12 x 12 km imagery at 10 m resolution. AIRSTAR was designed as a testbed for NASA's Spaceborne Imaging Radar program. While the images produced after 1991 are thought to be calibrated (phase calibrated, cross-talk removed, channel imbalance removed, and absolutely calibrated), POLCAL can and should still be used to check the accuracy of the calibration and to correct it if necessary. Version 4.0 of POLCAL is an upgrade of POLCAL version 2.0 released to AIRSAR investigators in June, 1990. New options in version 4.0 include automatic absolute calibration of 89/90 data, distributed target analysis, calibration of nearby scenes with calibration parameters from a scene with corner reflectors, altitude or roll angle corrections, and calibration of errors introduced by known topography. Many sources of error can lead to false conclusions about the nature of scatterers on the surface. Errors in the phase relationship between polarization channels result in incorrect synthesis of polarization states. Cross-talk, caused by imperfections in the radar antenna itself, can also lead to error. POLCAL reduces cross-talk and corrects phase calibration without the use of ground calibration equipment. Removing the antenna patterns during SAR processing also forms a very important part of the calibration of SAR data. Errors in the processing altitude or in the aircraft roll angle are possible causes of error in computing the antenna patterns inside the processor. POLCAL uses an altitude error correction algorithm to correctly remove the antenna pattern from the SAR images. POLCAL also uses a topographic calibration algorithm to reduce calibration errors resulting from ground topography. By utilizing the backscatter measurements from either the corner reflectors or a well-known distributed target, POLCAL can correct the residual amplitude offsets in the various polarization channels and correct for the absolute gain of the radar system. POLCAL also gives the user the option of calibrating a scene using the calibration data from a nearby site. This allows precise calibration of all the scenes acquired on a flight line where corner reflectors were present. Construction and positioning of corner reflectors is covered extensively in the program documentation. In an effort to keep the POLCAL code as transportable as possible, the authors eliminated all interactions with a graphics display system. For this reason, it is assumed that users will have their own software for doing the following: (1) synthesize an image using HH or VV polarization, (2) display the synthesized image on any display device, and (3) read the pixel locations of the corner reflectors from the image. The only inputs used by the software (in addition to the input Stokes matrix data file) is a small data file with the corner reflector information. POLCAL is written in FORTRAN 77 for use on Sun series computers running SunOS and DEC VAX computers running VMS. It requires 4Mb of RAM under SunOS and 3.7Mb of RAM under VMS for execution. The standard distribution medium for POLCAL is a .25 inch streaming magnetic tape cartridge in UNIX tar format. It is also available on a 9-track 1600 BPI magnetic tape in DEC VAX FILES-11 format or on a TK50 tape cartridge in DEC VAX FILES-11 format. Other distribution media may be available upon request. Documentation is included in the price of the program. POLCAL 4.0 was released in 1992 and is a copyrighted work with all copyright vested in NASA.

Description: Remote terrestrial sensing (RTS) data is constantly being collected from a variety of space-based and earth-based sensors. The collected data, and especially 'value-added' analyses of the data, are finding growing application for commercial, government, and scientific purposes. The scale of this data collection and analysis is truly enormous; e.g., by 1995, the amount of data available in just one sector, NASA space science, will reach 5 petabytes. Moreover, the amount of data, and the value of analyzing the data, are expected to increase dramatically as new satellites and sensors become available (e.g., NASA's Earth Observing System satellites). Lockheed and other companies are beginning to provide data and analysis commercially. A critical issue for the exploitation of collected data is the dissemination of data and value-added analyses to a diverse and widely distributed customer base. Customers must be able to use their computational environment (eventually the National Information Infrastructure) to obtain timely and complete information, without having to know the details of where the relevant data resides and how it is accessed. Customers must be able to routinely use standard, widely available (and, therefore, low cost) analyses, while also being able to readily create on demand highly customized analyses to make crucial decisions. The diversity of user needs creates a difficult software problem: how can users easily state their needs, while the computational environment assumes the responsibility of finding (or creating) relevant information, and then delivering the results in a form that users understand? A software agent is a self-contained, active software module that contains an explicit representation of its operational knowledge. This explicit representation allows agents to examine their own capabilities in order to modify their goals to meet changing needs and to take advantage of dynamic opportunities. In addition, the explicit representation allows agents to advertize their capabilities and results to other agents, thereby allowing the collection of agents to reuse each others work.

Description: Weather forecasting has been called the second oldest profession. To do so accurately and with some consistency requires an ability to understand the processes which create the clouds, drive the winds, and produce the ever changing atmospheric conditions. Measurement of basic parameters such as temperature, water vapor content, pressure, windspeed and wind direction throughout the three dimensional atmosphere form the foundation upon which a modern forecast is created. Doppler radar, and space borne remote sensing have provided forecasters the new tools with which to ply their trade.

Description: Algorithms and techniques for use in the identification and location of large buildings in digitized copies of aerial photographs are developed and tested. The building data would be used in the simulation of objects located in the vicinity of an airport that may be detected by aircraft radar. Two distinct approaches are considered. Most building footprints are rectangular in form. The first approach studied is to search for right-angled corners that characterize rectangular objects and then to connect these corners to complete the building. This problem is difficult because many nonbuilding objects, such as street corners, parking lots, and ballparks often have well defined corners which are often difficult to distinguish from rooftops. Furthermore, rooftops come in a number of shapes, sizes, shadings, and textures which also limit the discrimination task. The strategy used linear sequences of different samples to detect straight edge segments at multiple angles and to determine when these segments meet at approximately right-angles with respect to each other. This technique is effective in locating corners. The test image used has a fairly rectangular block pattern oriented about thirty degrees clockwise from a vertical alignment, and the overall measurement data reflect this. However, this technique does not discriminate between buildings and other objects at an operationally suitable rate. In addition, since multiple paths are tested for each image pixel, this is a time consuming task. The process can be speeded up by preprocessing the image to locate the more optimal sampling paths. The second approach is to rely on a human operator to identify and select the building objects and then to have the computer determine the outline and location of the selected structures. When presented with a copy of a digitized aerial photograph, the operator uses a mouse and cursor to select a target building. After a button on the mouse is pressed, with the cursor fully within the perimeter of the building, the program scans from the position of the cursor to a perimeter position where a shift in grayscale is detected. Once at the perimeter, the process traces along it, around the building, until it eventually returns to the perimeter starting point. Spatial resolution limits cause the perimeter trace to be somewhat course so that a line straightening algorithm is employed. One result is that the building corner positions become more distinctly defined.

Description: It is known that an effective control system is the key condition for successful implementation of high-performance magnetic servo systems. Major issues to design such control systems are nonlinearity; unmodeled dynamics, such as secondary effects for copper resistance, stray fields, and saturation; and that disturbance rejection for the load effect reacts directly on the servo system without transmission elements. One typical approach to design control systems under these conditions is a special type of nonlinear feedback called gain scheduling. It accommodates linear regulators whose parameters are changed as a function of operating conditions in a preprogrammed way. In this paper, an on-line learning fuzzy control strategy is proposed. To inherit the wealth of linear control design, the relations between linear feedback and fuzzy logic controllers have been established. The exercise of engineering axioms of linear control design is thus transformed into tuning of appropriate fuzzy parameters. Furthermore, fuzzy logic control brings the domain of candidate control laws from linear into nonlinear, and brings new prospects into design of the local controllers. On the other hand, a self-learning scheme is utilized to automatically tune the fuzzy rule base. It is based on network learning infrastructure; statistical approximation to assign credit; animal learning method to update the reinforcement map with a fast learning rate; and temporal difference predictive scheme to optimize the control laws. Different from supervised and statistical unsupervised learning schemes, the proposed method learns on-line from past experience and information from the process and forms a rule base of an FLC system from randomly assigned initial control rules.

Description: Multiple images taken from similar locations and under similar lighting conditions contain similar, but not identical, information. Slight differences in instrument orientation and position produces mismatches between the projected pixel grids. These mismatches ensure that any point on the ground is sampled differently in each image. If all the images can be registered with respect to each other to a small fraction of a pixel accuracy, then the information from the multiple images can be combined to increase linear resolution by roughly the square root of the number of images. In addition, the gray-scale resolution of the composite image is also improved. We describe methods for multiple image registration and combination, and discuss some of the problems encountered in developing and extending them. We display test results with 8:1 resolution enhancement, and Viking Orbiter imagery with 2:1 and 4:1 enhancements.

Description: To assess the feasibility of planetary exploration missions using rovers, the French national agency CNES, with a consortium of European laboratories and industrial concerns, has initiated the Eureka project, 'Illustration of an Autonomous Robot for the Exploration of Space' (IARES). IARES is a demonstrator composed of a rover and a ground station, linked by telemetry and telecommand. It is aimed at verifying, on earth, robotic concepts developed by the RISP group of French laboratories (LAAS, INRIA, CERT, LETI) to perform scientific missions such as autonomous terrain sample collecting over large areas. To cope with the actual needs of planet exploration, IARES suitability is assessed through constraints on limited bandwidth, time delay and on-board resources. This autonomy relies heavily on robust onboard trajectory generation capabilities. This paper presents the main functions of the IARES navigation sub-system and shows how they are combined to allow movement in Mars-like environments. Section 2 gives an overall description of the IARES system. Section 3 details the functions of the Navigation sub-system, and finally, section 4 illustrates with a simple example the use of these functions.

Description: A network of satellite laser ranging (SLR) tracking systems with continuously improving accuracies is challenging the modelling capabilities of analysts worldwide. Various data analysis techniques have yielded many advances in the development of orbit, instrument and Earth models. The direct measurement of the distance to the satellite provided by the laser ranges has given us a simple metric which links the results obtained by diverse approaches. Different groups have used SLR data, often in combination with observations from other space geodetic techniques, to improve models of the static geopotential, the solid Earth, ocean tides, and atmospheric drag models for low Earth satellites. Radiation pressure models and other non-conservative forces for satellite orbits above the atmosphere have been developed to exploit the full accuracy of the latest SLR instruments. SLR is the baseline tracking system for the altimeter missions TOPEX/Poseidon, and ERS-1 and will play an important role in providing the reference frame for locating the geocentric position of the ocean surface, in providing an unchanging range standard for altimeter calibration, and for improving the geoid models to separate gravitational from ocean circulation signals seen in the sea surface. However, even with the many improvements in the models used to support the orbital analysis of laser observations, there remain systematic effects which limit the full exploitation of SLR accuracy today.

Description: Stennis Space Center personnel flew a Learjet equipped with instrumentation designed to acquire imagery in many spectral bands into areas most damaged by Hurricane Andrew. The calibrated airborne multispectral scanner (CAMS), a NASA-developed sensor, and a Zeiss camera acquired images of these areas. The information derived from the imagery was used to assist Florida officials in assessing the devastation caused by the hurricane. The imagery provided the relief teams with an assessment of the debris covering roads and highways so cleanup plans could be prioritized. The imagery also mapped the level of damage in residential and commercial areas of southern Florida and provided maps of beaches and land cover for determination of beach loss and vegetation damage, particularly the mangrove population. Stennis Space Center personnel demonstrated the ability to respond quickly and the value of such response in an emergency situation. The digital imagery from the CAMS can be processed, analyzed, and developed into products for field crews faster than conventional photography. The resulting information is versatile and allows for rapid updating and editing. Stennis Space Center and state officials worked diligently to compile information to complete analyses of the hurricane's impact.

Description: Utility companies are challenged to provide services to a highly dynamic customer base. With factory closures and shifts in employment becoming a routine occurrence, the utility industry must develop new techniques to maintain records and plan for expected growth. BellSouth Telecommunications, the largest of the Bell telephone companies, currently serves over 13 million residences and 2 million commercial customers. Tracking the movement of customers and scheduling the delivery of service are major tasks for BellSouth that require intensive manpower and sophisticated information management techniques. Through NASA's Commercial Remote Sensing Program Office, BellSouth is investigating the utility of remote sensing and geographic information system techniques to forecast residential development. This paper highlights the initial results of this project, which indicate a high correlation between the U.S. Bureau of Census block group statistics and statistics derived from remote sensing data.

Description: Environmental management, impact assessment, research and monitoring are multidisciplinary activities which are ideally suited to incorporate a multi-media approach to environmental problem solving. Geographic information systems (GIS), simulation models, neural networks and expert-system software are some of the advancing technologies being used for data management, query, analysis and display. At the 140,000 acre John F. Kennedy Space Center, the Advanced Software Technology group has been supporting development and implementation of a program that integrates these and other rapidly evolving hardware and software capabilities into a comprehensive Mapping, Analysis and Planning System (MAPS) based in a workstation/local are network environment. An expert-system shell is being developed to link the various databases to guide users through the numerous stages of a facility siting and environmental assessment. The expert-system shell approach is appealing for its ease of data access by management-level decision makers while maintaining the involvement of the data specialists. This, as well as increased efficiency and accuracy in data analysis and report preparation, can benefit any organization involved in natural resources management.

Description: One objective of the Mission to Planet Earth (MTPE) program involves comparing data from various instruments on multiple spacecraft to obtain a total picture of the Earth's systems. To correlate image data from instruments on different spacecraft, these spacecraft must be able to image the same location on the Earth at approximately the same time. Depending on the orbits of the spacecraft involved, complicated operational details must be considered to obtain such observations. If the spacecraft are in similar orbits, close formation flying or synchronization techniques may be used to assure coincident observations. If the orbits are dissimilar, the launch time of the second satellite may need to be restricted in order to align its orbit with that of the first satellite launched. This paper examines strategies for obtaining coincident observations for spacecraft in both similar and dissimilar orbits. Although these calculations may be performed easily for coplanar spacecraft, the non-coplanar case involves additional considerations which are incorporated into the algorithms presented herein.

Description: Since 1986, NASA's Commercial Remote Sensing Program (CRSP) at Stennis Space Center has supported commercial remote sensing partnerships with industry. CRSP's mission is to maximize U.S. market exploitation of remote sensing and related space-based technologies and to develop advanced technical solutions for spatial information requirements. Observation, geolocation, and communications technologies are converging and their integration is critical to realize the economic potential for spatial informational needs. Global positioning system (GPS) technology enables a virtual revolution in geopositionally accurate remote sensing of the earth. A majority of states are creating GPS-based reference networks, or high accuracy reference networks (HARN). A HARN can be defined for a variety of local applications and tied to aerial or satellite observations to provide an important contribution to geographic information systems (GIS). This paper details CRSP's experience in the design and implementation of a HARN in Mississippi and the design and support of future applications of integrated earth observations, geolocation, and communications technology.

Description: The temporal and spatial distribution of African savanna grassland fires has been examined, and the areal extent of these fires has been estimated for the subequatorial African continent. African savanna fires have been investigated using remote sensing techniques and imagery collected by low-light sensors on Defense Meteorological Satellite Program (DMSP) satellites and by the Advanced Very High Resolution Radiometer (AVHRR) which is aboard polar orbiting National Oceanic and Atmospheric Administration (NOAA) satellites. DMSP imagery has been used to map the evolution of savanna burning over all of the African continent and the analysis of AVHRR imagery has been used to estimate the areal extent of the burning in the southern hemispheric African savannas. The work presented primarily reflects the analysiscompleted for the year 1987. However, comparisons have been made with other years and the representativeness of the 1987 analysis is discussed.

Description: A concept for coupling the remote sensing derived fraction of the absorbed photosynthetic active radiation (FAPAR) with a functional ecosystem model was developed. The study was named the Belfix procedure. The quantification of changes in carbon dynamics at the ecosystem level is a key issue in studies of global climatic change effects at the vegetation atmosphere interface. An operational procedure, for the determination of carbon fluxes at the regional scale (Belgian territory), is presented. The approach allows for the determination of the sink function of vegetation for carbon (dioxide). The phyto- and litter mass, photosynthetic assimilation, autotroph and heterotroph carbon fluxes and net ecosystem exchange (NEE) of carbon, were evaluated. The results suggest that a single solution can be obtained for ecosystem rates and states, applying an iterative procedure, based on minimizing the change in maximal seasonal green phytomass in function of yearly FAPAR temporal profiles. Total phytomass values obtained are in close range with those obtained by ground sampling.

Description: The potential for remote sensing of ocean wave direction using passive polarimetric microwave observations was investigated. A fixed-beam 91.65 GHz polarimetric radiometer was mounted on the NASA DC-8 aircraft during the Tropical Ocean Global Atmosphere/Coupled Ocean Atmosphere Response Experiment (TOGA/COARE January - February 1993). Several experiments were performed during which the DC-8 was flown in constant bank-angle turns at approximately 1.5 km altitude to obtain azimuthal scans of the sea surface at fixed observation angles. Data at 65 deg from nadir are consistent with previous findings using 19 and 37 GHz Special Sensor Microwave Imager (SSM/1) satellite observations and support the claim that a broadband emission mechanism is responsible for the azimuthal brightness signatures. Accordingly, a tilted-facet geometrical optics (GO) model of the surface was developed to investigate emission from deterministic and random striated surfaces. Laboratory measurements of polarimetric emission at 92 GHz from small-amplitude water-waves corroborate this model.

Description: The Earth Observations Commercial Applications Program (EOCAP) is described. This video explains how EOCAP has aided in the development of new and commercial products.

Description: This project involves collaborative research with Stephen W. Pacala and Simon A. Levin of Princeton University to calibrate, test, and analyze models of heterogeneous forested landscapes containing a diverse array of habitats. The project is an extension of previous, NASA-supported research to develop a spatially-explicit model of forest dynamics at the scale of an individual forest stand (hectares to square kilometer spatial scales). That model (SORTIE) has been thoroughly parameterized from field studies in the modal upland environment of western Connecticut. Under our current funding, we are scaling-up the model and parameterizing it for the broad range of upland environments in the region. Our most basic goal is to understand the linkages between stand-level dynamics (as revealed in our previous research) and landscape-level dynamics of forest composition and structure.

Description: This report describes Aerojet's methods and procedures used to control and administer contractual schedules for the EOS/AMSU-A program. Included are the following: the master, intermediate, and detail schedules; critical path analysis; and the total program logic network diagrams.

Description: This document defines the responsibilites for the management of the like-cycle development of the flight software installed in the AMSU-A instruments, and the ground support software used in the test and integration of the AMSU-A instruments.

Description: This simultaneous collection of HIS spectral measurements aboard the ER-2 during STORM-FEST provided a means to explore calibration problems in the infrared bands of the Wildfire instrument. Large discrepancies in brightness temperatures were noted in Wildfire bands designed to sample the 'wings' of the strong ozone absorption band centered at 9.6 microns, where the atmospheric transmittance changes rapidly with wavelength. Examination of interchannel relationships in Wildfire data and subsequent comparison to Wildfire data synthesized from the HIS measurements suggests that a wavelength shift in the channel spectral response from those determined in the laboratory may have occurred. Based on comparisons from several flights, this spectral shift has been empirically determined to be about 0.15 micron. It is speculated that this problem resulted from a slight misalignment of the spectrometer grating or other optical elements, or was a result of extreme range in temperatures experienced by the instrument throughout the course of an ER-2 flight. A consequence of this temperature fluctuation may be a change in a position of the grating in the optical path and could result in the variations in channel spectral response during flight. These findings for Wildfire may have significant bearing on future use of the MAS because of the similarities to the original Wildfire configuration.

Description: A conceptual radiometer design study was performed to determine the optimum design approach for spaceborne radiometers in low Earth orbit. Radiometric system configurations which included total power radiometers, unbalanced Dicke radiometers, and balanced Dicke, or as known as noise injection, radiometers were studied. Radiometer receiver configurations which were analyzed included the direct detection radiometer receiver, the double sideband homodyne radiometer receiver, and the single sideband heterodyne radiometer receiver. Radiometer system performance was also studied. This included radiometric sensitivity analysis of the three different radiometer system configurations studied. Both external and internal calibration techniques were analyzed. An accuracy analysis with and without mismatch losses was performed. It was determined that the balanced Dicke radiometer system configuration with direct detection receivers and external calibrations was optimum where frequent calibration such as once per minute were not feasible.

Description: One essential parameter used in the estimation of radiative and turbulent heat fluxes from satellite data is surface temperature. Sea and land surface temperature (SST and LST) retrieval algorithms that utilize the thermal infrared portion of the spectrum have been developed, with the degree of success dependent primarily upon the variability of the surface and atmospheric characteristics. However, little effort has been directed to the retrieval of the sea ice surface temperature (IST) in the Arctic and Antarctic pack ice or the ice sheet surface temperature over Antarctica and Greenland. The reason is not one of methodology, but rather our limited knowledge of atmospheric temperature, humidity, and aerosol vertical, spatial and temporal distributions, the microphysical properties of polar clouds, and the spectral characteristics of snow, ice, and water surfaces. Over the open ocean the surface is warm, dark, and relatively homogeneous. This makes SST retrieval, including cloud clearing, a fairly straightforward task. Over the ice, however, the surface within a single satellite pixel is likely to be highly heterogeneous, a mixture of ice of various thicknesses, open water, and snow cover in the case of sea ice. Additionally, the Arctic is cloudy - very cloudy - with typical cloud cover amounts ranging from 60-90 percent. There are few observations of cloud cover amounts over Antarctica. The goal of this research is to increase our knowledge of surface temperature patterns and magnitudes in both polar regions, by examining existing data and improving our ability to use satellite data as a monitoring tool. Four instruments are of interest in this study: the AVHRR, ATSR, SMMR, and SSM/I. Our objectives are as follows. Refine the existing AVHRR retrieval algorithm defined in Key and Haefliger (1992; hereafter KH92) and applied elsewhere. Develop a method for IST retrieval from ATSR data similar to the one used for SST. Further investigate the possibility of estimating surface temperature from passive microwave data (in conjunction with AVHRR clear sky samples) through the use of 'effective emissivities' and physical relationships between skin temperature and subsurface temperature. Use the general method outlined in MK93 to calculate a 12-year record of clear sky equivalent surface temperatures, or possibly all-sky snow-ice interface physical temperatures, from SMMR and SSM/I, compare these temperatures to climatologies, ECMWF modeled surface temperatures, and surface temperatures predicted by a 2-D ice model. And intercompare several ice surface retrieval methods and validate them against ground measurements from the Swiss Camp on the Greenland ice sheet. Additionally, we intend to develop a surface temperature product based on AVHRR data and possibly blended with drifting buoy and meteorological station temperatures.

Description: The advantages of having Geosat Follow-On in a Geosat orbit flying simultaneously with Topex Follow-On in a Topex/Poseidon orbit are examined. The orbits are evaluated using two criteria. The first is the acute crossover angle. This angle should be at least 40 degrees in order to accurately resolve the slope of sea level at crossover locations. The second is tidal aliasing. In order to solve for tides, the largest constituents should not be aliased to a frequency lower than two cycles/year and should be at least one cycle discrete from one another and from exactly two cycles/year over the mission life. The results show that TFO and GFO in these orbits complement each other. Both satellites have large crossover angles over a wide latitude range. In addition, the Topex orbit has good aliasing characteristics for the M2 and P1 tides for which the Geosat orbit has difficulty.

Description: The Space Shuttle Main Engine (SSME) has been undergoing extensive flight certification and developmental testing, which involves some 250 health monitoring measurements. Under the severe temperature, pressure, and dynamic environments sustained during operation, numerous major component failures have occurred, resulting in extensive engine hardware damage and scheduling losses. To enhance SSME safety and reliability, detailed analysis and evaluation of the measurements signal are mandatory to assess its dynamic characteristics and operational condition. Efficient and reliable signal detection techniques will reduce catastrophic system failure risks and expedite the evaluation of both flight and ground test data, and thereby reduce launch turn-around time. The basic objective of this contract are threefold: (1) develop and validate a hierarchy of innovative signal analysis techniques for nonlinear and nonstationary time-frequency analysis. Performance evaluation will be carried out through detailed analysis of extensive SSME static firing and flight data. These techniques will be incorporated into a fully automated system; (2) develop an advanced nonlinear signal analysis topographical mapping system (ATMS) to generate a Compressed SSME TOPO Data Base (CSTDB). This ATMS system will convert tremendous amount of complex vibration signals from the entire SSME test history into a bank of succinct image-like patterns while retaining all respective phase information. High compression ratio can be achieved to allow minimal storage requirement, while providing fast signature retrieval, pattern comparison, and identification capabilities; and (3) integrate the nonlinear correlation techniques into the CSTDB data base with compatible TOPO input data format. Such integrated ATMS system will provide the large test archives necessary for quick signature comparison. This study will provide timely assessment of SSME component operational status, identify probable causes of malfunction, and indicate feasible engineering solutions. The final result of this program will yield an ATMS system of nonlinear and nonstationary spectral analysis software package integrated with the Compressed SSME TOPO Data Base (CSTDB) on the same platform. This system will allow NASA engineers to retrieve any unique defect signatures and trends associated with different failure modes and anomalous phenomena over the entire SSME test history across turbo pump families.

Description: Motorized cable systems for transporting infrared thermometers have been used successfully during several international field campaigns. Systems may be configured with as many as four thermal sensors up to 9 m above the surface, and traverse a 30 m transect. Ground and canopy temperatures are important for solving the surface energy balance. The spatial variability of surface temperature is often great, so that averaged point measurements result in highly inaccurate areal estimates. The cable systems are ideal for quantifying both temporal and spatial variabilities. Thermal emissivity is also necessary for deriving the absolute physical temperature, and measurements may be made with a portable measuring box.

Description: This conference reviewed the recent developments in remote monitoring of surface temperatures, which will be significant in future global change studies. Various techniques to derive surface temperature from existing and future remote sensing systems such as earth observing system (EOS) are discussed. Five sessions were held: (1) The nature of the problem of remote sensing of surface temperatures; (2) Surface temperature measurements from current satellites; (3) Modeling and surface observations of various techniques to measure temperature and/or emissivity, modeling of vegetation; (4) The effects of variable spectral emissivity from the determination of surface kinetic temperature using multispectral thermal infrared measurements; and (5) Future satellite systems including EOS/ASTER, EOS/MODIS-N, and EOS/AIRS.

Description: This Earth Observing System (EOS) directory is divided into two main sections: white and yellow pages. The white pages list alphabetically the names and addresses -- including e-mail, phone, and fax when available -- of all individuals involved with EOS, from graduate students to panel members to program management and more. The yellow pages list the names, affiliation, and phone number of participants divided by project management, program management, individual project participants, interdisciplinary investigations (listed alphabetically by PI), the Science Executive Committee, various panels, platforms, working groups, fellowships, and contractors.

Description: Instruments of the Earth Radiation Budget Experiment (ERBE) are operating on three different Earth-orbiting spacecraft. The Earth Radiation Budget Satellite (ERBS) is operated by the National Aeronautics and Space Administration (NASA), and the NOAA 9 and NOAA 10 weather satellites are operated by the National Oceanic and Atmospheric Administration (NOAA). This paper is the third in a series that describes the ERBE mission in-orbit environments, instrument design and operational features, and data processing and validation procedures. This paper describes the in-flight operations for the ERBE instruments aboard the ERBS and NOAA 10 spacecraft for the period from February 1987 through February 1990. Validation and archival of radiation measurements made by ERBE instruments during this period were completed in May 1992. This paper covers normal and special operations of the spacecraft and instruments, operational anomalies, and the responses of the instruments to in-orbit and seasonal variations in the solar environment.

Description: First results of the Walnut Gulch '92 (Arizona, U.S.) experiment concerning the combined use of radar backscattering (ERS-1) and thermal infrared (LANDSAT TM (Thematic Mapper)) data to estimate surface sensible heat flux are reported. The first step investigates the potential use of ERS-1 SAR (Synthetic Aperture Radar) images for surface soil moisture monitoring of the watershed using five calibrated images acquired during the year 1992 (dry to wet conditions). Results show that despite the typical low level of biomass of semi arid rangeland, an attenuation of the soil backscatter (up to 2 dB) can occur during the rainy season mainly due to the vegetation characteristics. A statistical relationship is then used to retrieve the volumetric surface soil moisture from ERS-1 backscattering (sensitivity of 0.23 dB/% moisture) with a resulting root mean square error of 1.3% of soil moisture. In a second step a semi empirical approach based on energy balance relates soil temperatures to this estimated surface soil moisture. Vegetation temperature is then deduced from soil temperatures and LANDSAT TM composite temperature in order to estimate sensible heat flux according to a two layer type model providing an RMSE of 29 W/sq m.

Description: This glossary is one of a series of NASA publications designed to familiarize educators with global change issues and Mission to Planet Earth. The series enables teachers to enhance classroom studies with hands-on activities, including satellite images. Concepts and terms related to the global environment and the impact of human activities on the planet are presented.

Description: Formed in Jan. 1992, the Panel to Review EOSDIS Plans was charged with advising NASA on its plans for developing the Earth Observing System (EOS) Data and Information System (EOSDIS). Specifically, the panel was asked to do the following: assess the validity of the engineering and technical underpinnings of the EOSDIS; assess its potential value to scientific users; suggest how technical risk can be minimized; and assess whether current plans are sufficiently resilient to be adaptable to changing technology and requirements such as budget environments, data volumes, new users, and new databases. The panel completed an interim report (Addendum A) and transmitted it to NASA and other interested parties in the government on 9 Apr. 1992. Because of a delay in NASA's plans to select the contractor for EOSDIS, the panel was not able to complete its review of the program according to the original government request. With the issuance of a letter report (Addendum B) on 28 Sep. 1992, the panel became inactive until such time as NASA could release the details of the contractor's proposed architecture, schedule, and costs for developing EOSDIS. In early 1993, NASA awarded the contract for the EOSDIS Core System (ECS). On 20 Apr. 1993, NASA asked the panel to reconvene to do the following: ( 1) complete its review of NASA's approach to the EOSDIS architecture and implementation; (2) appraise NASA's responses to the panel's previous recommendations; and (3) review the planning for EOSDIS in the context of NASA's role in the Global Change Data and Information System (GCDIS) implementation plan. To respond to the NASA charge, the panel met three times in 1993 including sessions with NASA officials and the EOSDIS contractor. In addition, several of the panel members visited individual Distributed Active Archive Centers (DAAC's) to obtain additional views of EOSDIS. The panel has now obtained substantial information on the EOSDIS budget, contractor work program, and current baseline architecture that was not previously available, due to procurement restrictions. This report presents the panel's findings and recommendations based on this additional information.

Description: A research and modeling strategy is presented for development of distributed hydrologic models given by a combination of remotely sensed and ground based data. In support of this strategy, two experiments Moonsoon'90 and Walnut Gulch'92 were conducted in a semiarid rangeland southeast of Tucson, Arizona, (U.S.) and a third experiment, the SALSA-MEX (Semi Arid Land Surface Atmospheric Mountain Experiment) was proposed. Results from the Moonsoon'90 experiment substantially advanced the understanding of the hydrologic and atmospheric fluxes in an arid environment and provided insight into the use of remote sensing data for hydrologic modeling. The Walnut Gulch'92 experiment addressed the seasonal hydrologic dynamics of the region and the potential of combined optical microwave remote sensing for hydrologic applications. SALSA-MEX will combine measurements and modeling to study hydrologic processes influenced by surrounding mountains, such as enhanced precipitation, snowmelt and recharge to ground water aquifers. The results from these experiments, along with the extensive experimental data bases, should aid the research community in large scale modeling of mass and energy exchanges across the soil-plant-atmosphere interface.

Description: Directional thermal radiance from vegetation depends on many factors, including the architecture of the plant canopy, thermal irradiance, emissivity of the foliage and soil, view angle, slope, and the kinetic temperature distribution within the vegetation-soil system. A one dimensional model, which includes the influence of topography, indicates that thermal emissivity of vegetation canopies may remain constant with view angle, or emissivity may increase or decrease as view angle from nadir increases. Typically, variations of emissivity with view angle are less than 0.01. As view angle increases away from nadir, directional infrared canopy temperature usually decreases but may remain nearly constant or even increase. Variations in directional temperature with view angle may be 5C or more. Model predictions of directional emissivity are compared with field measurements in corn canopies and over a bare soil using a method that requires two infrared thermometers, one sensitive to the 8 to 14 micrometer wavelength band and a second to the 14 to 22 micrometer band. After correction for CO2 absorption by the atmosphere, a directional canopy emissivity can be obtained as a function of view angle in the 8 to 14 micrometer band to an accuracy of about 0.005. Modeled and measured canopy emissivities for corn varied slightly with view angle (0.990 at nadir and 0.982 at 75 deg view zenith angle) and did not appear to vary significantly with view angle for the bare soil. Canopy emissivity is generally nearer to unity than leaf emissivity may vary by 0.02 with wavelength even though leaf emissivity. High spectral resolution, canopy thermal emissivity may vary by 0.02 with wavelength even though leaf emissivity may vary by 0.07. The one dimensional model provides reasonably accurate predictions of infrared temperature and can be used to study the dependence of infrared temperature on various plant, soil, and environmental factors.

Description: Aircraft photopolarimetric observation of cloud and snow fields made by the POLDER (Polarization and Directionality of the Earth Reflectance) instrument during the EUCREX (European Cloud Radiation Experiment) and RACER (Research Antarctica Coastal Ecosystem Rates) campaigns are presented. Over clouds, the polarized component of the reflectance at the wavelength of 450 nm and scattering angles of 90 to 100 deg is sensitive to the molecular optical thickness between the cloud top and aircraft altitudes and, therefore, may be used for cloud altimetry. Liquid water clouds and snow exhibit similar spectral and bidirectional characteristics, but distinct polarization signatures. In the rainbow region (scattering angles of about 140 deg), water droplets strongly polarize incident sunlight while snow crystals do not, making it possible to distinguish the two types targets by scanning the angular polarization.

Description: Several vegetation indices were developed by ratioing or linear combinations of different spectral bands to characterize vegetation status with remote sensing measurements. These indices are primarily sensitive to vegetation, but also to non vegetation related factors such as soil background variations, atmospheric conditions, and sensor viewing geometries. Consequently, there is a need to quantify these effects when utilizing these vegetation indices. A sensitivity analysis of existing vegetation indices was made using both modeled spectral data and ground based remote sensing measurements. The analysis was made with respect to soil background, atmosphere, and sensor viewing geometries. General criteria to evaluate vegetation indices were established, and based on these criteria, a new index was developed. The new index was developed by adapting the reflectance in blue region for the atmospheric corrections in the Modified Soil Adjusted Vegetation Index (MSAVI). The resultant Atmosphere Soil Vegetation Index (ASVI) was compared with other indices and it increased vegetation sensitivity while further reducing soil and atmospheric effects. However, differences found among these vegetation indices may not be statistically significant, and further studies are, therefore, needed with satellite and ground based data.

Description: The effects of the atmosphere and surface on sunlight backscattered to space by the ocean may be substantially reduced by using the unpolarized component of reflectance instead of total reflectance. At 450 nm, a wavelength of interest in ocean color remote sensing, and for typical conditions, 45% of the unpolarized reflectance may originate from the water body instead of 20% of the total reflectance, which represents a gain of a factor 2.2 in useful signal for water composition retrieval. The best viewing geometries are adjacent to the glitter region; they correspond to scattering angles around 100 deg, but they may change slightly depending on the polarization characteristics of the aerosols. As aerosol optical thickness increases, the atmosphere becomes less efficient at polarizing sunlight, and the enhancement of the water body contribution to unpolarized reflectance is reduced. Since the perturbing effects are smaller on unpolarized reflectance, at least for some viewing geometries, they may be more easily corrected, leading to a more accurate water-leaving signal and, therefore, more accurate estimates of phytoplankton pigment concentration.

Description: Thermal infrared data of LANDSAT Thematic Mapper (TM) are hardly used, probably due to the difficulties met when trying to correct them for atmospheric effects. A method for correcting these data was designed, based on surface energy balance estimation of known wet and dry targets included in the TM image to be corrected. This method, only using the image itself and local meteorological data was tested and validated on various surfaces: agricultural, forest and rangeland. The root mean square error on corrected temperatures is on the order of 1C.

Description: Spatial distributions of soil moisture over an agricultural watershed with a drainage area of 60 ha were derived from two NASA microwave remote sensors, and then used as a feedback to determine the initial condition for a distributed water balance model. Simulated hydrologic fluxes over a period of twelve days were compared with field observations and with model predictions based on a streamflow derived initial condition. The results indicated that even the low resolution remotely sensed data can improve the hydrologic model's performance in simulating the dynamics of unsaturated zone soil moisture. For the particular watershed under study, the simulated water budget was not sensitive to the resolutions of the microwave sensors.

Description: A geocoding procedure for remotely sensed data of airborne systems in rugged terrain is affected by several factors: buffeting of the aircraft by turbulence, variations in ground speed, changes in altitude, attitude variations, and surface topography. The current investigation was carried out with an Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) scene of central Switzerland (Rigi) from NASA's Multi Aircraft Campaign (MAC) in Europe (1991). The parametric approach reconstructs for every pixel the observation geometry based on the flight line, aircraft attitude, and surface topography. To utilize the data for analysis of materials on the surface, the AVIRIS data are corrected to apparent reflectance using algorithms based on MODTRAN (moderate resolution transfer code).

Description: High-spatial-resolution microwave radiometer sensing from space with reasonable swath widths and revisit times favors large aperture systems. However, with traditional precision antenna design, the size and weight requirements for such systems are in conflict with the need to emphasize small launch vehicles. This paper describes tradeoffs between the science requirements, basic operational parameters, and expected sensor performance for selected satellite radiometer concepts utilizing novel lightweight compactly packaged real apertures. Antenna, feed, and radiometer subsystem design and calibration are presented. Preliminary results show that novel lightweight real aperture coupled with state-of-the-art radiometer designs are compatible with small launch systems, and hold promise for high-resolution earth science measurements of sea ice, precipitation, soil moisture, sea surface temperature, and ocean wind speeds.

Description: Lidar measurements using pseudonoise code modulated AlGaAs lasers are reported. Horizontal path lidar measurements were made at night to terrestrial targets at ranges of 5 and 13 km with 35 mW of average power and integration times of one second. Cloud and aerosol lidar measurements were made to thin cirrus clouds at 13 km altitude with Rayleigh (molecular) backscatter evident up to 9 km. Average transmitter power was 35 mW and measurement integration time was 20 minutes. An AlGaAs laser was used to characterize spectral properties of water vapor absorption lines at 811.617, 816.024, and 815.769 nm in a multipass absorption cell using derivative spectroscopy techniques. Frequency locking of an AlGaAs laser to a water vapor absorption line was achieved with a laser center frequency stability measured to better than one-fifth of the water vapor Doppler linewidth over several minutes. Differential absorption lidar measurements of atmospheric water vapor were made in both integrated path and range-resolved modes using an externally modulated AlGaAs laser. Mean water vapor number density was estimated from both integrated path and range-resolved DIAL measurements and agreed with measured humidity values to within 6.5 percent and 20 percent, respectively. Error sources were identified and their effects on estimates of water vapor number density calculated.

Description: A technique for generation of a 2-D space map by traveling a short distance is described. The space to be mapped can be classified as: (1) space without obstacles, (2) space with stationary obstacles, and (3) space with moving obstacles. This paper presents the methodology used to generate a 2-D map of an unknown navigation space. The ability to minimize the redundancy during traveling and maximize the confidence function for generation of the map are advantages of this technique.

Description: This project is continuing along the lines of the semiannual report dated January 1993. Four major tasks have been addressed: analysis of variability in the seasonal snow of interior and arctic Alaska, the interpretation of microwave brightness temperature across Alaska on transects from south to north, study of nonclimatic controls which affect glaciers, and the location of glacier facies boundaries.

Description: The Goddard VLBI group reports the results of analyzing Mark 3 data sets acquired from 110 fixed and mobile observing sites through the end of 1992 and available to the Space Geodesy Program. Two large solutions were used to obtain site positions, site velocities, baseline evolution for 474 baselines, earth rotation parameters, nutation offsets, and radio source positions. Site velocities are presented in both geocentric Cartesian and topocentric coordinates. Baseline evolution is plotted for the 89 baselines that were observed in 1992 and positions at 1988.0 are presented for all fixed stations and mobile sites. Positions are also presented for quasar radio sources used in the solutions.

Description: Project GOSAP is a multi organizational effort to determine how best to use remote sensing technology, and ERS-1 data in particular, to address offshore problems and operations faced by the exploration and marine engineering industries, in the Gulf of Mexico. Remotely sensed data integrated with sea truth are used to quantify meteorologic and oceanographic events, to detect and track ocean currents and gyres, to image the sea floor, map subsurface geology, or detect oil seeps from orbital altitudes. Participants are evaluating the potential for satellite based offshore exploration, ocean engineering, and environmental applications using combined satellite and airborne measurements constrained by real time sea truth.

Description: During the first half of our second project year we have accomplished the following: (1) acquired a new AVHRR data set for the Beaufort Sea area spanning an entire year; (2) acquired additional ATSR data for the Arctic and Antarctic now totaling over seven months; (3) refined our AVHRR Arctic and Antarctic ice surface temperature (IST) retrieval algorithm, including work specific to Greenland; (4) developed ATSR retrieval algorithms for the Arctic and Antarctic, including work specific to Greenland; (5) investigated the effects of clouds and the atmosphere on passive microwave 'surface' temperature retrieval algorithms; (6) generated surface temperatures for the Beaufort Sea data set, both from AVHRR and SSM/I; and (7) continued work on compositing GAC data for coverage of the entire Arctic and Antarctic. During the second half of the year we will continue along these same lines, and will undertake a detailed validation study of the AVHRR and ATSR retrievals using LEADEX and the Beaufort Sea year-long data. Cloud masking methods used for the AVHRR will be modified for use with the ATSR. Methods of blending in situ and satellite-derived surface temperature data sets will be investigated.

Description: The Long Duration Exposure Facility (LDEF) was placed in low-Earth orbit (LEO) in 1984 and recovered 5.7 years later. The LDEF was host to several individual experiments specifically designed to characterize critical aspects of meteoroid and debris environment in LEO. However, it was realized from the beginning that the most efficient use of the satellite would be to examine the entire surface for impact features. In this regard, particular interest centered on common exposed materials that faced in all LDEF pointing directions. Among the most important of these materials was the tray clamps. Therefore, in an effort to better understand the nature of particulates in LEO and their effects on spacecraft hardware, residues found in impact features on LDEF tray clamp surfaces are being analyzed. This catalog presents all data from clamps from Bay B of the LDEF. NASA Technical Memorandum 104759 has cataloged impacts that occurred on Bay B (published March 1993). Subsequent catalogs will include clamps from succeeding bays of the satellite.

Description: Backscatter cross section measurements from the ERS-1 Active Microwave Instrument (AMI) scatterometer were reprocessed to vector winds using the Freilich-Dunbar model function and a meteorologically aided ambiguity removal scheme. This consistent data set was used to examine the wind field over the Southern Ocean from 20 to 60 deg South. The large number of ERS-1 measurements allows relatively accurate calculation of annual mean wind, stress, and curl fields as well as overall statistics of the winds at mid to high southern latitudes. The long duration of the data time series allows preliminary examination of low frequency (semi annual) wind variability.

Description: A detailed gravity field map of the mid Arctic Ocean, spreading ridge system was produced on the basis of ERS-1 satellite altimetry data. Areas of special concern, the Barents and Kara Seas, and areas surrounding the islands of Svalbard, Frans Josef Land and Novoya Zemlya are reviewed. ERS-1 altimetry covers unique Arctic and Antarctic latitudes above 72 degrees. Before ERS-1 it was not possible to study these areas with satellite altimetry. Gravity field solutions for the Barents Sea, portions of the Arctic Ocean and the Norwegian sea are shown. The largest gravity anomalies occur along the Greenland fracture zone as well as along transform faults near Svalbard.

Description: Remote sensing has become important in the ocean sciences, especially for research involving large spatial scales. To estimate the in-water constituents through remote sensing, whether carried out by satellite or airplane, the signal emitted from beneath the sea surface, the so called water-leaving radiance (L(w)), is of prime importance. The magnitude of L(w) depends on two terms: one is the intensity of the solar input, and the other is the reflectance of the in-water constituents. The ratio of the water-leaving radiance to the downwelling irradiance (E(d)) above the sear surface (remote-sensing reflectance, R(sub rs)) is independent of the intensity of the irradiance input, and is largely a function of the optical properties of the in-water constituents. In this work, a model is developed to interpret r(sub rs) for ocean water in the visible-infrared range. In addition to terms for the radiance scattered from molecules and particles, the model includes terms that describe contributions from bottom reflectance, fluorescence of gelbstoff or colored dissolved organic matter (CDOM), and water Raman scattering. By using this model, the measured R(sub rs) of waters from the West Florida Shelf to the Mississippi River plume, which covered a (concentration of chlorophyll a) range of 0.07 - 50 mg/cu m, were well interpreted. The average percentage difference (a.p.d.) between the measured and modeled R(sub rs) is 3.4%, and, for the shallow waters, the model-required water depth is within 10% of the chart depth. Simple mathematical simulations for the phytoplankton pigment absorption coefficient (a(sub theta)) are suggested for using the R(sub rs) model. The inverse problem of R(sub rs), which is to analytically derive the in-water constituents from R(sub rs) data alone, can be solved using the a(sub theta) functions without prior knowledge of the in-water optical properties. More importantly, this method avoids problems associated with a need for knowledge of the shape and value of the chlorophyll-specific absorption coefficient. The simulation was tested for a wide range of water types, including waters from Monterey Bay, the West Florida Shelf, and the Mississippi River plume. Using the simulation, the R(sub rs)-derived in-water absorption coefficients were consistent with the values from in-water measurements (r(exp 2) greater than 0.94, slope approximately 1.0). In the remote-sensing applications, a new approach is suggested for the estimation of primary production based on remote sensing. Using this approach, the calculated primary production (PP) values based upon remotely sensed data were very close to the measured values for the euphotic zone (r(exp 2) = 0.95, slope 1.26, and 32% average difference), while traditional, pigment-based PP model provided values only one-third the size of the measured data. This indicates a potential to significantly improve the accuracy of the estimation of primary production based upon remote sensing.

Description: Detectors that will be used for planetary missions must have their responses calibrated in a reproducible manner. In addition, it is important to characterize a detector system at uneven portions of its life cycle, for example after exposure to different amounts of radiation. A calibration and response characterization facility has been constructed at Schlumberger-Doll Research for all types of gamma- and x-ray detectors that may be used for planetary measurement. This facility is currently being tested. Initial use is expected for the MARS 94 detectors. The facility will then also be available for calibrating other detectors as well as arrays of detectors such as the NEAR detector with its central Nal(TI) crystal surrounded with a large BGO crystal. Cadmium telluride detectors are investigated for applications in space explorations. These detectors show an energy resolution of 5 keV for the 122 keV 57Co line. Earlier reported polarization effects are not observed. The detectors can be used at temperatures up to 100 C, although with reduced energy resolution. The thickness of standard detectors is limited to 2 mm. These detectors become fully efficient at bias voltages above 200 V. Initial results for a 1 cm thick detector show that the quality of the material is inferior to the thinner standard detectors and hole trapping affects the pulse height. A detailed characterization of the detector is in progress. Prototypes of photomultipliers based on a Channel Electron Multiplier (CEM) are being built to study their performance. Such photomultipliers promise better timing characteristics and a higher dynamic range while being more compact and of lower in weight.