ALBERT

Description: In August and September of 1995 the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) was deployed to Brazil as part of the NASA Smoke Cloud Aerosol and Radiation experiment in Brazil (SCAR-B). AVIRIS measures spectra from 400 to 2500 nm at 10-nm intervals. These spectra are acquired as images with dimensions of 11 by up to 800 km with 20-m spatial resolution. Spectral images measured by AVIRIS are spectrally, radiometrically, and spatially calibrated. During the SCAR-B deployment, AVIRIS measured more than 300 million spectra of regions of Brazil. A portion of these spectra were acquired over areas of actively burning fires. Actively burning fires emit radiance in the AVIRIS spectral range as a function of temperature. This emitted radiance is expressed from the 2500-nm end of the AVIRIS spectrum to shorter wavelengths as a function of intensity and modeled by the Planck function.. The objective of this research and analysis was to use spectroscopic methods to determine the minimum high temperature of the most intense fires measured in the SCAR-B AVIRIS data set. Spectra measured by AVIRIS with hot sources have been previously examined for volcanic lava and fires in Brazil.

Description: Various locations in the southwestern U.S. are used to calibrate remote sensing instruments. This study shows how some of these targets compare in terms of albedo and homogeneity, and records the variation of these factors for a single location (Ivanpah Playa) over a period of one year. Results indicate that there is a great deal of variation among these targets in albedo, spectral flatness, and surface uniformity, and that these factors can change throughout the year.

Description: Among the most important short-term dynamic biological processes are diurnal changes in canopy water relations. Plant regulation of water transport through stomatal openings affects other gaseous transport processes, often dramatically decreasing photosynthetic fixation of carbon dioxide during periods of water stress. Water stress reduces stomatal conductance of water vapor through the leaf surface and alters the diurnal timing of stomatal opening. Under non-water stressed conditions, stomates typically open soon after dawn and transpire water vapor throughout the daylight period. During stress periods, stomates may close for part of the day, generally near mid-day. Under prolonged stress conditions, stomatal closure shifts to earlier times during the day; stomates may close by mid-morning and remain closed until the following morning - or remain closed entirely. Under these conditions the relationship between canopy greenness (e.g., measured with a vegetation index or by spectral mixture analysis) and photosynthetic fixation of carbon is lost and the remotely sensed vegetation metric is a poor predictor of gas exchange. Prediction of stomatal regulation and exchange of water and trace gases is critical for ecosystem and climate models to correctly estimate budgets of these gases and understand or predict other processes like gross and net ecosystem primary production. Plant gas exchange has been extensively studied by physiologists at the leaf and whole plant level and by biometeorologists at somewhat larger scales. While these energy driven processes follow a predictable if somewhat asymmetric diurnal cycle dependent on soil water availability and the constraints imposed by the solar energy budget, they are nonetheless difficult to measure at the tree and stand levels using conventional methods. Ecologists have long been interested in the potential of remote sensing for monitoring physiological changes using multi-temporal images. Much of this research has focused on day-to-day changes in water use, especially for agricultural applications. Ustin et al. showed seasonal changes in canopy water content in chaparral shrub could be estimated using optical methods. Vanderbilt et al. followed asymmetric diurnal changes in the reflectance of a walnut orchard, but could not attribute specific reflectance changes to specific changes in canopy architecture or physiology. Forests and shrub lands in California experience prolonged periods of drought, sometimes extending six months without precipitation. The conifer and evergreen chaparral communities common to the foothill region around the central valley of California retain their foliage throughout the summer and have low transpiration rates despite high net radiation and temperature conditions. In contrast, grasslands and drought resistant deciduous species in the same habitat are seasonally dormant in summer. Because of differences in the mechanisms of drought tolerance, rooting depth and physiology between different plant communities in the region, it is likely that they display differences in diurnal water relations. The presence of diverse plant communities provides an opportunity to investigate possible diurnal landscape patterns in water relations that could be observed by an airborne hyperspectral scanner. This investigation of AVIRIS data collected over forest and shrub land represents the continuation of a prior investigation involving spectral mixture analysis of diurnal effects in the same AVIRIS data set.

Description: Spectroscopy is used in the laboratory to measure the molecular components and concentrations of plant constituents to answer questions about the plant type, status, and health. Imaging spectrometers measure the upwelling spectral radiance above the Earth's surface as images. Ideally, imaging spectrometer data sets should be used to understand plant type, plant status, and health of plants in an agricultural setting. An Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data set was acquired over agricultural fields near Wallula, Washington on July 23rd, 1997. AVIRIS measures upwelling radiance spectra through 224 spectral channels with contiguous 10-nm sampling from 400 to 2500 nm in the solar-reflected spectrum. The spectra are measured as images of 11 by up to 800 km with 20-m spatial resolution. The spectral images measured by AVIRIS represent the integrated signal resulting from: the solar irradiance; two way transmittance and scattering of the atmosphere; the absorptions and scattering of surface materials; as well as the spectral, radiometric and spatial response functions of AVIRIS. This paper presents initial research to derive properties of the agricultural fields near Wallula from the calibrated spectral images measured by AVIRIS near the top of the atmosphere.

Description: The Southern Great Plains 1997 (SGP97) field experiment was conducted in Oklahoma during June-July 1997 to validate the models used for computing remote soil moisture using measurements by microwave radiometers. One of the objectives of SGP97 was to examine the effect of soil moisture on the evolution of the Atmospheric Boundary Layer (ABL) and clouds over the Southern Great Plains (SGP) during the warm season. The LASE (Lidar Atmospheric Sensing Experiment) airborne DIAL (Differential Absorption Lidar) system, which was flown autonomously on the NASA ER-2 aircraft during previous missions, was reconfigured to fly on the NASA P3 research aircraft. During SGP97 LASE was used to study the morning evolution of the ABL, particularly as manifested in the development of the convective boundary layer, and to study the influence of soil moisture variations on the development of ABL. The ABL development is strongly influenced by the surface energy budget, which is in turn influenced by soil moisture, mesoscale meteorology, clouds, and solar insolation. LASE data acquired during this mission are being used to study the ABL water vapor budget, the development of the ABL, spatial and temporal variabilities in the ABL, and the meteorological factors that influence the ABL development. This field experiment also permitted comparisons of LASE water vapor measurements with water vapor profiles acquired by radiosondes launched at the DOE (Department of Energy) Atmospheric Radiation Measurement (ARM) Southern Great Plain (SGP) site and at NASA/Wallops Flight Facility, as well as with measurements from other SGP97 aircraft.

Description: Imaging Spectroscopy enables the identification and mapping of surface mineralogy over large areas. This study focused on assessing the utility of Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data for environmental impact analysis over the Environmental Protection Agency's (EPA) high priority Superfund site Ray Mine, AZ. Using the Spectral Angle Mapper (SAM) algorithm to analyze AVIRIS data makes it possible to map surface materials that are indicative of acid generating minerals. The improved performance of the AVIRIS sensor since 1996 provides data with sufficient signal to noise ratio to characterize up to 8 image endmembers. Specifically we employed SAM to map minerals associated with mine generated acid waste, namely jarositc, goethite, and hematite, in the presence of a complex mineralogical background.

Description: The primary objective of the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program at the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) is to acquire in situ and remote sensing data to improve cloud and atmospheric radiative models and parameterizations. As a consequence of this program, a large number of atmosphere and surface measurements are being acquired at the ARM SGP CART central site. NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) overflew this site on August 1, 1997. AVIRIS measures the upwelling spectral solar radiance from 400 to 2500 nm at 10-nm intervals. From 20 km altitude, these calibrated spectra are acquired as images of 11 by up to 800 km with 20-by-20 m spatial resolution. These data were acquired at the ARM SGP CART Central Site to first investigate derivation of atmospheric parameters from the measured spectra, second study the variation of these parameters, and third demonstrate the inversion of the calibrated radiance spectra to apparent surface reflectance. These objectives have been pursued with AVIRIS data at other sites for atmospheric water vapor and derivation of apparent surface reflectance.

Description: Mineral maps generated for the Ray Mine, Arizona were analyzed to determine if imaging spectroscopy can provide accurate information for environmental management of active and abandoned mine regions. The Ray Mine, owned by the ASARCO Corporation, covers an area of 5700 acres and is situated in Pinal County, Arizona about 70 miles north of Tucson near Hayden, Arizona. This open-pit mine has been a major source of copper since 1911, producing an estimated 4.5 million tons of copper since its inception. Until 1955 mining was accomplished by underground block caving and shrinkage stope methods. (excavation by working in stepped series usually employed in a vertical or steeply inclined orebody) In 1955, the mine was completely converted to open pit method mining with the bulk of the production from sulfide ore using recovery by concentrating and smelting. Beginning in 1969 a significant production contribution has been from the leaching and solvent extraction-electrowinnowing method of silicate and oxide ores. Published reserves in the deposit as of 1992 are 1.1 billion tons at 0.6 percent copper. The Environmental Protection Agency, in conjunction with ASARCO, and NASA/JPL obtained AVIRIS data over the mine in 1997 as part of the EPA Advanced Measurement Initiative (AMI) (Tom Mace, Principal Investigator). This AVIRIS data set is being used to compare and contrast the accuracy and environmental monitoring capabilities of remote sensing technologies: visible-near-IR imaging spectroscopy, multispectral visible and, near-IR sensors, thermal instruments, and radar platforms. The goal of this effort is to determine if these various technologies provide useful information for envirorunental management of active and abandoned mine sites in the arid western United States. This paper focuses on the analysis of AVIRIS data for assessing the impact of the Ray Mine on Mineral Creek. Mineral Creek flows to the Gila River. This paper discusses our preliminary AVIRIS mineral mapping and environmental findings.

Description: Life at the surface of the Earth, over the last 400 m.y., evolved under conditions of decreased short-wave radiation (i.e., ultraviolet) relative to solar output due to absorption and scattering by constituents (e.g., ozone, water vapor, aerosols) in the upper atmosphere. However, a significant amount of ultraviolet radiation in the range from 280-320 nm, known as ultraviolet-B radiation, reaches the Earth's surface and has sufficient energy to be damaging to biologic tissue. Natural fluctuations in atmospheric constituents (seasonal variation, volcanic eruptions, etc.), changes in the orbital attitude of the Earth (precession, axial tilt, orbital eccentricity), and long-term solar variability contribute to changes in the total amount of ultraviolet radiation reaching the surface of the Earth, and thus, the biosphere. More recently, the atmospheric release of commercial propellants and refrigerants, known as chlorofluorocarbons (CFCs), has contributed to a significant depletion in naturally occurring ozone in the stratosphere. Thus, decreased stratospheric ozone has resulted in an increased UV-B flux at the Earth's surface which may have profound effects on terrestrial and marine organisms. In this study, we are investigating the effects of differing solar UV-B fluxes on alfalfa (Medicago sativa L.), an important agricultural crop. A long-term goal of this research is to develop spectral signatures to detect plant response to increased UV-B radiation from remote sensor platforms.

Description: The Environmental Research Aircraft and Sensor Technology (ERAST) program is a NASA initiative that seeks to demonstrate the application of cost-effective aircraft and sensor technology to private commercial ventures. In 1997-98, a series of flight-demonstrations and image acquisition efforts were conducted over the Hawaiian Islands using a remotely-piloted solar- powered platform (Pathfinder) and a fixed-wing piloted aircraft (Navajo) equipped with a Kodak DCS450 CIR (color infrared) digital camera. As an ERAST Science Team Member, I defined a set of flight lines over the largest coffee plantation in Hawaii: the Kauai Coffee Company's 4,000 acre Koloa Estate. Past studies have demonstrated the applications of airborne digital imaging to agricultural management. Few studies have examined the usefulness of high resolution airborne multispectral imagery with 10 cm pixel sizes. The Kodak digital camera integrated with ERAST's Airborne Real Time Imaging System (ARTIS) which generated multiband CCD images consisting of 6 x 106 pixel elements. At the designated flight altitude of 1,000 feet over the coffee plantation, pixel size was 10 cm. The study involved the analysis of imagery acquired on 5 March 1998 for the detection of anomalous reflectance values and for the definition of spectral signatures as indicators of tree vigor and treatment effectiveness (e.g., drip irrigation; fertilizer application).

Description: Following the launch of the Earth Observing System first morning (EOS-AM1) satellite, daily, global snow-cover mapping will be performed automatically at a spatial resolution of 500 m, cloud-cover permitting, using Moderate Resolution Imaging Spectroradiometer (MODIS) data. A technique to calculate theoretical accuracy of the MODIS-derived snow maps is presented. Field studies demonstrate that under cloud-free conditions when snow cover is complete, snow-mapping errors are small (less than 1%) in all land covers studied except forests where errors are greater and more variable. The theoretical accuracy of MODIS snow-cover maps is largely determined by percent forest cover north of the snowline. Using the 17-class International Geosphere-Biosphere Program (IGBP) land-cover maps of North America and Eurasia, the Northern Hemisphere is classified into seven land-cover classes and water. Snow-mapping errors estimated for each of the seven land-cover classes are extrapolated to the entire Northern Hemisphere for areas north of the average continental snowline for each month. Average monthly errors for the Northern Hemisphere are expected to range from 5 - 10%, and the theoretical accuracy of the future global snow-cover maps is 92% or higher. Error estimates will be refined after the first full year that MODIS data are available.

Description: Analysis of a time series of European Remote Sensing Satellite (ERS)-1 and -2, RADARSAT ScanSAR synthetic aperture radar (SAR) and Landsat images from 1973 to 1998, shows daily to interannual changes in Hofsjokull, a 923 sq km ice cap in central Iceland. A digital elevation model of Hofsjokull was constructed using interferometry, and then SAR backscatter coefficient (d) was plotted with elevation, and air temperature along a transect across the ice cap. Most of the a' changes measured along the transect are caused by a change in the state (frozen or thawed) of the surficial snow or ice when air temperature rises above or below about -5 to O C. Seasonal (sigma)deg patterns are identified in a 4-year time series of 57 ERS-1 and -2 images. In addition, June 1997 ScanSAR images display rapid changes in brightness that are tied closely to daily meteorological events. SAR and Landsat data were also used to measure changes in the areal extent of Hofsjokull, from 1973 to 1997, and to locate (sigma)deg and reflectance boundaries that relate to the glacier facies. Late-summer 1997 (sigma)deg and reflectance boundaries agree and are coincident with the approximate location of the fim line, and the January 1998 position of the equilibrium line as determined from ERS-2 data.

Description: Aerosol particles originate from man-made sources such as urban/industrial activities,rurning associated with land use processes, wind-blown dust, and natural sources. Their interaction with sunlight and their effect on cloud microphysics forms a major uncertainty in predicting climate change. Furthermore, the lifetime of only a few days causes high spatial variability in aerosol optical and radiative properties that requires global observations from space. Remote sensing of aerosol properties from space is reviewed both for present and planned national and international satellite sensors. Techniques that are being used to enhance our ability to characterize the global distribution of aerosol properties include well-calibrated multispectral radiometers, multispectral polarimeters, and multi-angle spectroradiometers. Though most of these sensor systems rely primarily on visible to mid-infrared spectral channels, the availability of of thermal channels to aid in cloud screening is an important additional piece of information that is not always incorporated into the sensor design. In this paper we describe the various satellite sensor systems being developed by Europe, Japan, and the U.S., and highlight the advantages and disadvantages of each of these systems for aerosol applications. An important underlying theme is that the remote sensing of aerosol properties, especially aerosol size distribution and single scattering albedo, is exceedingly difficult. As a consequence, no one sensor system is capable of providing totally unambiguous information, and hence a careful intercomparison of derived products from different sensors, together with a comprehensive network of ground-based sun-photometer and sky radiometer systems, are required to advance our quantitative understanding of global aerosol characteristics.

Description: Various configurations of a scanning satellite instrument are simulated by sampling realistic fields of nitrous oxide. Synoptic grids are computed from the resulting simulated orbital data and compared to the original sampled data fields. Results are compared with those obtained by flying a simulated satellite over low-resolution fields and fields that are static in time. Although increasing the number of instrument scan positions does provide more information along an orbital swath, using more than three to five scan positions does not significantly increase the accuracy of global synoptic grids using the gridding techniques described here.

Description: In this paper a fuzzy classification procedure is applied to polarimetric radar measurements, and street pixels are detected. These data are successively grouped into consistent roads by means of a dynamic programming approach based on the fuzzy membership function values. Further fusion of the 2D road network extracted and 3D TOPSAR measurements provides a powerful way to analyze urban infrastructures.

Description: This project focuses on the adaptation of human populations to their environments from prehistoric times to the present. It emphasizes interdisciplinary research to develop ecological baselines through the use of remotely sensed imagery, in situ field work, and the modeling of human population dynamics. It utilizes cultural and biological data from dated archaeological sites to assess the subsistence and settlement patterns of human societies in response to changing climatic and environmental conditions. The utilization of remote sensing techniques in archaeology is relatively new, exciting, and opens many doors.

Description: Vegetational changes are primary indicators of the present and future ecological status of the globe. These are changes which not only impact upon the primary productivity, but the total of the biogeochemical processes occurring on the planet. The impacts of global climatic and other environmental changes on vegetation must be monitored by some means in order to develop models which will allow us to predict long term effects. Large scale monitoring is now possible only with remote sensing systems, primarily passive reflectance, obtained by the use of satellite and aircraft platforms. However, passive reflectance techniques at this time are limited in their ability to detect subtle changes in the concentration and oxidation states of the many compounds involved in the light reactions of photosynthesis. Knowledge of these changes we consider to be fundamental in the remote assessment of both the rate and efficiency of photosynthesis and also the early detection of stress damage. The above factors pointed to the desirability of a sensing technique with the sensitivity and specificity necessary for detecting and quantifying those biological entities involved in photosynthesis. Another optical technique for vegetation monitoring is fluorescence. Previously, the lack of adequate excitation light sources and detector technologies have limited the use of fluorescence on intact plant leaves in the field. It is only recently with the advent of lasers with short pulse duration and advanced detector technologies that fluorescence measurements in the remote mode have become possible in the presence of ambient light.

Description: The use of TOMS (Total Ozone Mapping Spectrometer) satellite data demonstrates the recently developed technique of using satellite UV radiance measurements to detect absorbing tropospheric aerosols is effective over snow/ice surfaces. Instead of the traditional single wavelength (visible or infrared) method of measuring tropospheric aerosols, this method takes advantage of the wavelength dependent reduction in the backscattered radiance due to the presence of absorbing aerosols over snow/ice surfaces. An example of the resulting aerosol distribution derived from TOMS data is shown for an August 1998 event in which smoke generated by Canadian forest fires drifts over and across Greenland. As the smoke plume moved over Greenland, the TOMS observed 380 nm reflectivity over the snow/ice surface dropped drastically from 90-100% down to 30-40%. To study the effects of this smoke plume in both the UV and visible regions of the spectrum, we compared a smoke-laden spectrum taken over Greenland by the high spectral resolution (300 to 800 nm) GOME instrument with one that is aerosol-free. We also discuss the results of modeling the darkening effects of various types of absorbing aerosols over snow/ice surfaces using a radiative transfer code. Finally, we investigated the history of such events by looking at the nearly twenty year record of TOMS aerosol index measurements and found that there is a large interannual variability in the amount of smoke aerosols observed over Greenland. This information will be available for studies of radiation and transport properties in the Arctic.

Description: The Support Vector Machine provides a new way to design classification algorithms which learn from examples (supervised learning) and generalize when applied to new data. We demonstrate its success on a difficult classification problem from hyperspectral remote sensing, where we obtain performances of 96%, and 87% correct for a 4 class problem, and a 16 class problem respectively. These results are somewhat better than other recent results on the same data. A key feature of this classifier is its ability to use high-dimensional data without the usual recourse to a feature selection step to reduce the dimensionality of the data. For this application, this is important, as hyperspectral data consists of several hundred contiguous spectral channels for each exemplar. We provide an introduction to this new approach, and demonstrate its application to classification of an agriculture scene.

Description: Scale is an "innate" concept in geographic information systems. It is recognized as something that is intrinsic to the ingestion, storage, manipulation, analysis, modeling, and output of space and time data within a GIS purview, yet the relative meaning and ramifications of scaling spatial and temporal data from this perspective remain enigmatic. As GISs become more sophisticated as a product of more robust software and more powerful computer systems, there is an urgent need to examine the issue of scale, and its relationship to the whole body of spatiotemporal data, as imparted in GISS. Scale is fundamental to the characterization of geo-spatial data as represented in GISS, but we have relatively little insight on the effects of, or how to measure the effects of, scale in representing multiscaled data; i.e., data that are acquired in different formats (e.g., map, digital) and exist in varying spatial, temporal, and in the case of remote sensing data, radiometric, configurations. This is particularly true in the emerging era of Integrated GISs (IGIS), wherein spatial data in a variety of formats (e.g., raster, vector) are combined with multiscaled remote sensing data, capable of performing highly sophisticated space-time data analyses and modeling. Moreover, the complexities associated with the integration of multiscaled data sets in a multitude of formats are exacerbated by the confusion of what the term "scale" is from a multidisciplinary perspective; i.e., "scale" takes on significantly different meanings depending upon one's disciplinary background and spatial perspective which can lead to substantive confusion in the input, manipulation, analyses, and output of IGISs (Quattrochi, 1993). Hence, we must begin to look at the universality of scale and begin to develop the theory, methods, and techniques necessary to advance knowledge on the "Science of Scale" across a wide number of spatial disciplines that use GISs.

Description: In this paper a machine vision approach is applied to Interferometric Synthetic Aperture Radars (IFSAR) data to extract the most relevant built structures in a dense urban environment. The algorithm tries to cluster primitives (line segments) into more complex surfaces (planes) to approximate the 3D shape of these objects. Very interesting results starting from TOPSAR data recorded over S, Monica are presented.

Description: In August and September of 1995 the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) was deployed to Brazil as part of the NASA Smoke Cloud Aerosol and Radiation experiment in Brazil (SCAR-B). AVIRIS measures spectra from 400 to 2500 nm at 10-nm intervals. These spectra are acquired as images with dimensions of 11 by up to 800 km with 20-m spatial resolution. Spectral images measured by AVIRIS are spectrally, radiometrically, and spatially calibrated. During the SCAR-B deployment, AVIRIS measured more than 300 million spectra of regions of Brazil. A portion of these spectra were acquired over areas of actively burning fires. Actively burning fires emit radiance in the AVIRIS spectral range as a function of temperature. This emitted radiance is expressed from the 2500-nm end of the AVIRIS spectrum to shorter wavelengths as a function of intensity and modeled by the Planck function. The objective of this research and analysis was to use spectroscopic methods to determine the minimum high temperature of the most intense fires measured in the SCAR-B AVIRIS data set. Spectra measured by AVIRIS with hot sources have been previously examined for volcanic lava.

Description: In this paper, we investigate the feasibility of estimating aerodynamic roughness parameter from interferometric SAR (INSAR) measurements. The relation between the interferometric correlation and the rms height of the surface is presented analytically. Model simulations performed over realistic canopy parameters obtained from field measurements in boreal forest environment demonstrate the capability of the INSAR measurements for estimating and mapping surface roughness lengths over forests and/or other vegetation types. The procedure for estimating this parameter over boreal forests using the INSAR data is discussed and the possibility of extending the methodology over tropical forests is examined.

Description: Satellite altimeter data from TOPEX/POSEIDON and ERS-1 are used to examine seasonal and mesoscale variability of the Black Sea level. Consistent processing procedures of the altimeter measurements make it possible to determine the dynamical Black Sea level with an rms accuracy about 3 cm. It is shown that the Black Sea circulation intensifies in the winter-spring seasons and attenuates in summer-autumn. The seasonal variability of sea level is accompanied by a radiation of Rossby waves from the eastern coast of the basin. Mesoscale oscillations of the dynamical sea level are found to vary spatially and temporarily. Usually, strong eddy intensity is associated with instabilities of the Rim Current. Away from this circulation feature, in the deep basin, mesoscale variability is much smaller. Mesoscale variability has a strong seasonal signal, which is out of phase with the strength of the Rim Current.

Description: High spatial resolution (5 m) remote sensing data obtained using the airborne Thermal Infrared Multispectral Scanner (TIMS) sensor for daytime and nighttime have been used to measure thermal energy responses for 2 broad classes and 10 subclasses of vegetation typical of the Salt Lake City, Utah urban landscape. Polygons representing discrete areas corresponding to the 10 subclasses of vegetation types have been delineated from the remote sensing data and are used for analysis of upwelling thermal energy for day, night, and the change in response between day and night or flux, as measured by the TIMS. These data have been used to produce three-dimensional graphs of energy responses in W/ sq m for day, night, and flux, for each urban vegetation land cover as measured by each of the six channels of the TIMS sensor. Analysis of these graphs provides a unique perspective for both viewing and understanding thermal responses, as recorded by the TIMS, for selected vegetation types common to Salt Lake City. A descriptive interpretation is given for each of the day, night, and flux graphs along with an analysis of what the patterns mean in reference to the thermal properties of the vegetation types surveyed in this study. From analyses of these graphs, it is apparent that thermal responses for vegetation can be highly varied as a function of the biophysical properties of the vegetation itself, as well as other factors. Moreover, it is also seen where vegetation, particularly trees, has a significant influence on damping or mitigating the amount of thermal radiation upwelling into the atmosphere across the Salt Lake City urban landscape. Published by Elsevier Science Ltd.

Description: The effect of vegetation on passive microwave remote sensing of soil moisture is studied. The radiative transfer modeling work of Njoku and Kong is applied to a stratified medium of which the upper layer is treated as a layer of vegetation. An effective dielectric constant for this vegetation layer is computed using estimates of the dielectric constant of individual components of the vegetation layer. The horizontally-polarized brightness temperature is then computed as a function of the incidence angle. Model predictions are used to compare with the data obtained in the Huntsville '96, remote sensing of soil moisture experiment, and with predictions obtained using a correction procedure of Jackson and Schmugge.

Description: Volume mixing ratio profiles of the quantitatively significant NOy species NO, NO2, HNO3, HNO4, CINO3 and N2O5 were measured remotely form 8 to 38 km by the JPL MkIV FTIR solar absorption spectrometer during balloon flights from Fairbanks, Alaska on May 8 and July 8, 1997.

Description: We present a generalized raytracing inversion scheme which can be used when occultation data is acquired with a receiver within (e.g., on mountain top) or outside (i.e., in space) the atmosphere.

Description: Positive Systems has worked in conjunction with Stennis Space Center to design the ADAR System 5500. This is a four-band airborne digital imaging system used to capture multispectral imagery similar to that available from satellite platforms such as Landsat, SPOT and the new generation of high resolution satellites. Positive Systems has provided remote sensing services for the development of digital aerial camera systems and software for commercial aerial imaging applications.

Description: Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristics of the surface. This paper reviews the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.

Description: Scatterometry is a well established and heavily utilized technique that routinely provides vector wind measurements over the ocean with resolution cells on the order of 60 kilometers on a side(1,2,3).

Description: The SeaWinds scatterometer will fly on the NASA Quickscat spacecraft in 1998, and on the Japanese ADEOS-II mission in 2000. In addition to providing ocean surface wind estimates for use by weather forcasters, these flights will generate a global Ku-Band backscatter data set for a variety of climate studies.

Description: Design and operation of a high speed, low noise, wide dynamic range linear infrared multiplexer array for readout of infrared detectors with large detector capacitance is presented. Image lag related to abrupt transitions of signal currents is analyzed.

Description: A theoretical emission model of combined ocean surface and atmosphere is presented to predict the microwave emissivity of ocean. The modeled ocean surface is one-dimensional with a random rough profile.

Description: We hypothesize that the strong sensitivity of radar backscatter to surface dielectric properties, and hence to the phase (solid or liquid) of any water near the surface, should make space-borne radar observations a powerful tool for large-scale spatial monitoring of the freeze/thaw state of the land surface, and thus ecosystem growing season length.

Description: Polarimetric radar interferometry is much more sensitive to the distribution of oriented objects in a vegetated land surface than either polarimetry on interferometry alone. This paper shows that single-baseline polarimetric interferometry can be used to estimate vegetation heights and underlying topography, while at least two baselines are needed for randomly oriented volumes.

Description: The Ku-band dual-polarized backscatter signatures of ocean surfaces are described in this article with the airborne scatterometer measurements collected in the Hurricane Ocean Wind Experiment in September 1997.

Description: A technique was developed to improve spectral mixture analysis estimates of snow-covered-area in alpine regions through the use of multiple snow endmembers.

Description: We describe a pushbroom imaging spectrometer having a number of attractive features for remote sensing applications, including compact and simple form, good image quality, high effciency, and very low levels of distortion.

Description: The capability of current remote sensing tools and mathematical models to study the Great Lakes ice conditions is reported.

Description: The tidal signature in the middle atmospheric thermal structure (15-95 km) at Mauna Loa, Hawaii, (19.5is investigated using more than 145 hours of nighttime lidar measurements obtained during October 3-16, 1996 and October 2-11, 1997.

Description: Ocean backscatter signatures were measured by the Jet Propulsion Laboratory airborne NUSCAT K(sub u)-band scatterometer across the Gulf Stream sea surface temperature front. The measurements were made during the Surface Wave Dynamics Experiment (SWADE) off the coast of Virginia and Maryland in the winter of 1991.

Description: Wind taken from the National Aeronautics and Space Administration (NASA) scatterometer (NSCAT) is compared with the operational analysis from European Center for Medium-Rnage Forecast (ECMWF) for the entire duration (about 9 months) of the NSCAT mission.

Description: The National Space Development Agency of Japan's (NASDA) JERS-1 SAR began collecting data in 1995 for the Global Rain Forest Mapping Project (GRFM). The GRFM data quality has been examined for products resulting from both the NASDA and Alaska SAR facility's (ASF) processing facilities.

Description: The purpose of this paper is to provide an overview of the NSCAT instrument and sigma-0 computation, and to describe the process and the results of an intensive post-launch verification, calibration, and validation effort.

Description: The Lost Hills and Belridge oil felds are in the San Joaquin Valley, California. The major oil reservoir is high porosity and low permeability diatomite. Extraction of large volumes from shallow depths causes reduction in pore pressure and subsequent compaction, forming a surface subsidence bowl. We measure this subsidence from space using interferometric analysis of SAR (Synthetic Aperture Radar) data collected by the European Space Agency Remote Sensing Satellites (ERS-1 and ERS-2). Maximum subsidence rates are as high as 40 mm in 35 days or 〉 400 mm/yr, measured from interferograms with time separations ranging from one day to 26 months. The 8- and 26-month interferograms contain areas where the subsidence gradient exceeds the measurement possible with ERS SAR, but shows increased detail in areas of less rapid subsidence. Synoptic mapping of subsidence distribution from satellite data powerfully complements ground-based techniques, permits measurements where access is difficult, and aids identification of underlying causes.

Description: This paper illustrates an improved geophysical model function (GMF) for Ku-band ocean backstcatter at high winds and preliminary geophysical model function for polarimetric brightness temperatures acquired from aircraft measurements.

Description: A technique employed to extract higher resolution backscatter measurements from the SeaWinds pencil-beam scatterometer system is described. The unique methodology necessary to achieve very high radiometric accuracy for such measurements is discussed.

Description: In July of 1995 the Airborne Emission Spectrometer was deployed to Nashville, Tennessee to participate in the 1995 Ozone Study Intensive Campaign of the Southern Oxidants Study. AES is a high resolution mid-infrared interferometer that measures the spectrum of upwelling radiation in the 650-4250 cm-1 range.

Description: Satellite data from the advanced very high resolution radiometer (AVHRR) instrument were used to produce a general land cover distribution of temperate Asia (referred to hence as Central Asia) from 1982, starting with the NOAA-7 satellite, and continuing through 1991, ending with the NOAA-11 satellite. Emphasis was placed upon delineating the and and semi-arid zones of Central Asia (largely Mongolia and adjacent areas), mapping broad categories of aggregated land cover, and upon studying photosynthetic capacity increases in Central Asia from 1982 to 1991.

Description: TROPIX (Transfer Orbit Plasma Interaction Experiment) is both a scientific experiment and a flight demonstration of a solar electric propulsion space vehicle. The research supported by this grant resulted in the specific definition of magnetospheric and planetary science missions that can be uniquely implemented with SEP within the resources available in the MIDEX program. A plasma instrument suitable for inclusion on TROPIX was defined.

Description: Current and future earth observation programs depend on satellite measurements of radiance to retrieve the properties of clouds on a global basis. At present, this retrieval is made assuming that the clouds in the instrument field of view are plane parallel and independent of adjacent pixels. While this assumption is known to be false except in very limited cases, its impact can be evaluated, and if possible corrected, based on emerging theoretical techniques. In this study, the Spherical Harmonic Discrete Ordinate Method (SHDOM, Evans, 1996) has been used to assess the sensitivity of the retrieval to a variety of cloud parameters. SHDOM allows the plane parallel assumption to be relaxed and makes 2D and even 3D radiative solutions practical. A previous study (Chambers et al., 1996) assessed the effect of horizontal inhomogeneity in 45 LANDSAT scenes of boundary layer clouds over ocean. The four scenes studied here represent overcast, broken, scattered and strongly thermally forced cloud fields and are used to perform sensitivity studies to a wider variety of parameters. Comparisons are made at three solar zenith angles (theta (sub 0) = 0, 49, and 63 degrees) to avoid ambiguity in the results due to solar zenith angle.

Description: Development of a hydrologic model for the study of environmental conservation requires a comprehensive understanding of individual-storm affecting hydrologic and sedimentologic processes. The hydrologic models that we are currently coupling are the Simulator for Hydrology and Energy Exchange at the Land Surface (SHEELS) and the Distributed Runoff Model (DRUM). SHEELS runs continuously to estimate surface energy fluxes and sub-surface soil water fluxes, while DRUM operates during and following precipitation events to predict surface runoff and peak flow through channel routing. The lateral re-distribution of surface water determined by DRUM is passed to SHEELS, which then adjusts soil water contents throughout the profile. The model SHEELS is well documented in Smith et al. (1993) and Laymen and Crosson (1995). The model DRUM is well documented in Vieux et al. (1990) and Vieux and Gauer (1994). The coupled hydrologic model, SHEELS/DRUM, does not simulate sedimentologic processes. The simulation of the sedimentologic process is important for environmental conservation planning and management. Therefore, we attempted to develop a conceptual frame work for coupling a sediment yield model with SHEELS/DRUM to estimate individual-storm sediment yield from a watershed at a regional level. The sediment yield model that will be used for this study is the Universal Soil Loss Equation (USLE) with some modifications to enable the model to predict individual-storm sediment yield. The predicted sediment yield does not include wind erosion and erosion caused by irrigation and snow melt. Units used for this study are those given by Foster et al. (1981) for SI units.

Description: "Visit to an Ocean Planet" is an interactive, educational CD-ROM that reveals the importance of our oceans to global climate and life. It is designed to complement middle and high school science curricula, as well as to be enjoyed by the general public. The CD-ROM allows users to explore the Gulf of Mexico with satellite data, investigate the 1997-1998 El Nino, discover "what's up" with Earth-orbiting satellites, and learn about the real life oceanographers. The curriculum background material are arranged in the context of widely accepted teaching themes. The CD-ROM also highlights results from the TOPEX/Poseidon satellite launched by NASA and the Centre National Etudes Spatiales (CNES). It has been measuring our oceans since 1992. This product is a result of NASA's commitment to involve the educational community in endeavors to inspire America's students, create learning opportunities, and enlighten inquisitive minds.

Description: In this paper we investigated the possibility of using a shape-from-shading technique, applied to a Landsat MSS image, to create a high spatial resolution DEM of Austfonna, an ice cap in Svalbard.

Description: This study examines the ocean-atmosphere coupling patterns in time and space through a canonical correlation analysis of the fields.

Description: Traditional down-looking infrared techniques for the detection and study of clouds have difficulties when clouds are within approximately 200 mbar of the surface. This is because of the lack of thermal contrast between the surface and a low cloud. We present a technique that, using a prior knowledge of the total water column, allows a down-looking high spectral resolution infrared spectrometer to recognize when a significant fraction of its field-of-view contains optically thick clouds (low-altitute or not).

Description: Observations of Doppler velocity of hydrometeors form airborne Doppler weather radars normally contains a component due to the aircraft motion. Accurate hydrometeor velocity measurements thus require correction by subtracting this velocity from the observed velocity.

Description: An Airborne Multi-angle Imaging SpectroRadiometer (AirMISR) instrument has been developed to assist in validation of the Earth Observing System (EOS) MISR experiment.

Description: The community of researchers studying global climate change is preparing to launch the first Earth Observing System (EOS) satellite, EOS AM-1. The satellite will generate huge amounts of data, filling gaps in the information available to address critical questions about Earth's climate.

Description: We evaluate the ability of a dual frequency (C and Ku band) radar altimeter to detect rain events.

Description: This paper focuses mostly on satellite microwave observations from UARS MLS (Upper Atmosphere Research Satellite Microwave Limb Sounder) at 186.5 and 203.2 GHz.

Description: Electromagnetic waves travelling through the ionosphere undergo Faraday rotation of the polariztion vector which modifies the polarization and phase characteristics of the electromagnetic signal.

Description: Elevated cold CO2 emissions from the flank of Mammoth Mountain volcano on the southwest rim of the Long Valley Caldera, eastern California, have been the cause of over 100 acres of dead trees in that area since 1990.

Description: JPL/NASA's Earth remote sensing and deep-space exploration programs have been placing emphasis on their spacecraft's high-gain and large-aperture antennas. At the same time, however, low mass and small storage volume are demanded in order to reduce payload weight and reduce shroud size and thus reduce launch cost.

Description: The application of atmospheric models to AVIRIS and other spectral imaging data to derive surface reflectance requires that the sensor output be calibrated to absolute radiance. Uncertainties in absolute calibration are to be expected, and claims of 92% accuracy have been published. Measurements of accurate surface albedos and cloud absorption to be used in radiative balance calculations depend critically on knowing the absolute spectral-radiometric response of the sensor. The Earth Observing System project is implementing a rigorous program of absolute radiometric calibration for all optical sensors. Since a number of imaging instruments that provide output in terms of absolute radiance are calibrated at different sites, it is important to determine the errors that can be expected among calibration sites. Another question exists about the errors in the absolute knowledge of the exoatmospheric spectral solar irradiance.

Description: The research supported by this grant covered two projects: (1) a study of the luminosity dependence of the properties of atoll sources; and (2) a search for Doppler shifts in the pulse arrival times of the anomalous pulsar 4U 0142+61. Following the discovery of kilohertz quasi-periodic oscillations (QPOS) in Sco X-1 studies of the X-ray properties of atoll sources have been dominated by searches for these QPOS, and the study of their dependence on other source properties, such as X-ray luminosity and spectral state. In the project supported by grant NAG5-3269 we have detected kHz QPOs for several atoll sources. The physical interpretation of these QPO is as yet unclear, but simple models (such as the Keplerian beat frequency model) can probably be excluded. The results of this research have been reported. We have studied the X-ray pulsations of the anomalous X-ray pulsar 4U 0142+61 using the Rossi XTE. A detailed search for Doppler shifts did not lead to a positive detection. The upper limits exclude almost all types of possible companion stars, except white dwarfs. However, the latter can be excluded since anomalous X-ray pulsars are very young objects. We therefore conclude that anomalous X-ray pulsars are single neutron stars.

Description: This final report details the contract performance and analysis of research and development results obtained during the contract period. KT-Tech's research and development work results in the areas of registration of remotely sensed data and the test evaluation and porting of the Regional Validation Center software system are presented.

Description: A number of satellite sensor systems will collect large data sets of the Earth's surface during NASA's Earth Observing System (EOS) era. Efforts are being made to develop efficient algorithms that can incorporate a wide variety of spectral data and ancillary data in order to extract vegetation variables required for global and regional studies of ecosystem processes, biosphere-atmosphere interactions, and carbon dynamics. These variables are, for the most part, continuous (e.g. biomass, leaf area index, fraction of vegetation cover, vegetation height, vegetation age, spectral albedo, absorbed photosynthetic active radiation, photosynthetic efficiency, etc.) and estimates may be made using remotely sensed data (e.g. nadir and directional optical wavelengths, multifrequency radar backscatter) and any other readily available ancillary data (e.g., topography, sun angle, ground data, etc.). Using these types of data, neural networks can: 1) provide accurate initial models for extracting vegetation variables when an adequate amount of data is available; 2) provide a performance standard for evaluating existing physically-based models; 3) invert multivariate, physically based models; 4) in a variable selection process, identify those independent variables which best infer the vegetation variable(s) of interest; and 5) incorporate new data sources that would be difficult or impossible to use with conventional techniques. In addition, neural networks employ a more powerful and adaptive nonlinear equation form as compared to traditional linear, index transformations, and simple nonlinear analyses. These neural networks attributes are discussed in the context of the authors' investigations of extracting vegetation variables of ecological interest.

Description: The local variability of UV irradiance at the Earth's surface is mostly caused by clouds in addition to the seasonal variability. Parametric representations of radiative transfer RT calculations are presented for the convenient solution of the transmission T of ultraviolet radiation through plane parallel clouds over a surface with reflectivity R(sub s). The calculations are intended for use with the Total Ozone Mapping Spectrometer (TOMS) measured radiances to obtain the calculated Lambert equivalent scene reflectivity R for scenes with and without clouds. The purpose is to extend the theoretical analysis of the estimation of UV irradiance from satellite data for a cloudy atmosphere. Results are presented for a range of cloud optical depths and solar zenith angles for the cases of clouds over a low reflectivity surface R(sub s) less than 0.1, over a snow or ice surface R(sub s) greater than 0.3, and for transmission through a non-conservative scattering cloud with single scattering albedo omega(sub 0) = 0.999. The key finding for conservative scattering is that the cloud-transmission function C(sub T), the ratio of cloudy-to clear-sky transmission, is roughly C(sub T) = 1 - R(sub c) with an error of less than 20% for nearly overhead sun and snow-free surfaces. For TOMS estimates of UV irradiance in the presence of both snow and clouds, independent information about snow albedo is needed for conservative cloud scattering. For non-conservative scattering with R(sub s) greater than 0.5 (snow) the satellite measured scene reflectance cannot be used to estimate surface irradiance. The cloud transmission function has been applied to the calculation of UV irradiance at the Earth's surface and compared with ground-based measurements.

Description: From a flight dynamics perspective, the EOS AM-1 mission design and maneuver operations present a number of interesting challenges. The mission design itself is relatively complex for a low Earth mission, requiring a frozen, Sun-synchronous, polar orbit with a repeating ground track. Beyond the need to design an orbit that meets these requirements, the recent focus on low-cost, "lights out" operations has encouraged a shift to more automated ground support. Flight dynamics activities previously performed in special facilities created solely for that purpose and staffed by personnel with years of design experience are now being shifted to the mission operations centers (MOCs) staffed by flight operations team (FOT) operators. These operators' responsibilities include flight dynamics as a small subset of their work; therefore, FOT personnel often do not have the experience to make critical maneuver design decisions. Thus, streamlining the analysis and planning work required for such a complicated orbit design and preparing FOT personnel to take on the routine operation of such a spacecraft both necessitated increasing the automation level of the flight dynamics functionality. The FreeFlyer(trademark) software developed by AI Solutions provides a means to achieve both of these goals. The graphic interface enables users to interactively perform analyses that previously required many parametric studies and much data reduction to achieve the same result. In addition, the fuzzy logic engine .enables the simultaneous evaluation of multiple conflicting constraints, removing the analyst from the loop and allowing the FOT to perform more of the operations without much background in orbit design. Modernized techniques were implemented for EOS AM-1 flight dynamics support in several areas, including launch window determination, orbit maintenance maneuver control strategies, and maneuver design and calibration automation. The benefits of implementing these techniques include increased fuel available for on-orbit maneuvering, a simplified orbit maintenance process to minimize science data downtime, and an automated routine maneuver planning process. This paper provides an examination of the modernized techniques implemented for EOS AM-1 to achieve these benefits.

Description: Instruments of the Earth Radiation Budget Experiment (ERBE) have operated 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 one of a series that describes the ERBE mission, in-orbit environments, instrument design and operational features, and data processing and validation procedures. This paper also describes the in-flight operations for the ERBE nonscanner instruments aboard the ERBS, NOAA 9, and NOAA 10 spacecraft from January 1990 through December 1990. Validation and archives of radiation measurements made by ERBE nonscanner instruments during this period were completed in August 1996. 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: As part of NASA's Mission to Planet Earth, the first Clouds and the Earth's Radiant Energy System (CERES) instrument will be launched on the Tropical Rainfall Measuring Mission (TRMM) spacecraft from the Tanegashima launch site in Japan in November 1997. The instrument will measure the radiation budget incoming and outgoing radiant energy - of the Earth. The major feature of interest is clouds, which play a very strong role in regulating our climate. CERES will identify clear and cloudy regions and determine cloud physical and microphysical properties using imager data from a companion instrument. Validation efforts for the remote sensing algorithms will be intensive. As one component of the validation, the S'COOL (Students' Cloud Observations On-Line) project will involve school children around the globe in making ground truth measurements at the time of a CERES overpass. They will report cloud type, height, fraction, and opacity, as well as the local surface conditions. Their observations will be collected at the NASA Langley Distributed Active Archive Center (DAAC) and made available over the Internet for educational purposes as well as for use by the CERES Science Team in validation efforts. Pilot testing of the S'COOL project began in January 1997 with two local schools in Southeastern Virginia and one remote site in Montana. National testing in April 1997 involved 8 schools (grades 3 to high school) across the United States. Global testing will be carried out in October 1997. Details of the S'COOL project, which is mainly Internet-based, are being developed in each of these phases according to feedback received from participants. In 1998, when the CERES instrument is operational, a global observer network should be in place providing useful information to the scientists and learning opportunities to the students. Broad participation in the S'COOL project is planned, both to obtain data from a wide range of geographic areas, and to involve as many students as possible in learning about clouds and atmospheric science. This paper reports on the development phase of the S'COOL project, including the reaction of the teachers and students who have been involved. It describes the operational state of the S'COOL network, and identifies opportunities for additional participants.

Description: Significant accomplishments made during the present reporting period: (1) We expanded our "spectral-matching" algorithm (SMA), for identifying the presence of absorbing aerosols and simultaneously performing atmospheric correction and derivation of the ocean's bio-optical parameters, to the point where it could be added as a subroutine to the MODIS water-leaving radiance algorithm; (2) A modification to the SMA that does not require detailed aerosol models has been developed. This is important as the requirement for realistic aerosol models has been a weakness of the SMA; and (3) We successfully acquired micro pulse lidar data in a Saharan dust outbreak during ACE-2 in the Canary Islands.

Description: The Laser Vegetation Imaging Sensor (LVIS) is an airborne laser altimeter designed to quickly and extensively map surface topography as well as the relative heights of other reflecting surfaces within the laser footprint. Since 1997, this instrument has primarily been used as the airborne simulator for the Vegetation Canopy Lidar (VCL) mission, a spaceborne mission designed to measure tree height, vertical structure and ground topography (including sub-canopy topography). LVIS is capable of operating from 500 m to 10 km above ground level with footprint sizes from 1 to 60 m. Laser footprints can be randomly spaced within the 7 degree telescope field-of-view, constrained only by the operating frequency of the ND:YAG Q-switched laser (500 Hz). A significant innovation of the LVIS altimeter is that all ranging, waveform recording, and range gating are performed using a single digitizer, clock base, and detector. A portion of the outgoing laser pulse is fiber-optically fed into the detector used to collect the return signal and this entire time history of the outgoing and return pulses is digitized at 500 Msamp/sec. The ground return is then located using software digital signal processing, even in the presence of visibly opaque clouds. The surface height distribution of all reflecting surfaces within the laser footprint can be determined, for example, tree height and ground elevation. To date, the LVIS system has been used to monitor topographic change at Long Valley caldera, CA, as part of NASA's Topography and Surface Change program, and to map tree structure and sub-canopy topography at the La Selva Biological Research Station in Costa Rica, as part of the pre-launch calibration activities for the VCL mission. We present results that show the laser altimeter consistently and accurately maps surface topography, including sub-canopy topography, and vegetation height and structure. These results confirm the measurement concept of VCL and highlight the benefits of airborne prototypes of spaceborne instruments.

Description: Remotely sensed data allows archeologists and historic preservationists the ability to non-destructively detect phenomena previously unobservable to them. Archeologists have successfully used aerial photography since the turn of the century and it continues to be an important research tool today. Multispectral scanners and computer-implemented analysis techniques extend the range of human vision and provides the investigator with innovative research designs at scales previously unimaginable. Pioneering efforts in the use of remote sensing technology have demonstrated its potential, but it is the recent technological developments in remote sensing instrumentation and computer capability that provide for unlimited, cost-effective applications in the future. The combination of remote sensing, Global Positioning System (GPS) technology, and Geographic Information Systems (GIS) are radically altering survey, inventory, and modelling approaches.

Description: Surface air temperatures observed from stations around Antarctica have indicated predominantly positive trends which are as high as 0.4K per decade along the Antarctic Peninsula. Since the average air temperature during summer in the West Antarctic region is about -6 K, and since most of the stations are near coastal regions, it is important to know whether such trends are due to a local or large scale phenomenon. We analyzed about 19 years of infrared satellite data (1979-1997) to obtain a spatially detailed study of the variability of surface temperatures over the entire Antarctic region. We also analyzed potential impact of temperature changes over the sea ice cover using co-registered and nearly coincident microwave satellite data. The surface temperatures inferred from infrared data are shown to agree well with those observed from the limited number of Antarctic station data with a correlation coefficient of 0.98 and a standard deviation of less than 3K. The 19-year temperature data set shows positive trends of 0.12, 0.68, and 0.41 C per decade in ocean, sea ice and ice sheet surfaces, respectively. The sensitivity of the trend to record length was studied, using long term station data sets, and the results show that the trends start to stabilize at around 2 decades which is about the record length of satellite data. However, interannual fluctuations of the temperatures are large, especially in the ice sheets, and the 95% confidence level for the trends ranges from 0.12 to 1.22 for sea ice and from -0.74 to 1.55 C per decade for the ice sheet. In the sea ice regions, the position of the ice edge in winter with respect to the northernmost position of sea ice during the study period is also shown to be influenced by alternating warm and cold anomalies around the continent. This pattern is similar to that suggested by the presence of the Antarctic Circumpolar Wave (ACW) but the wavenumber appears to be predominantly mode 3 (instead of reported mode 2) for the Antarctic region. Unexpectedly, trends in the sea ice extent are found to be positive in most Antarctic sectors during the same period with the exception of the Bellingshausen and Amundsen Seas region.

Description: Oceanic islands represent an often overlooked aspect of the land surface of Earth, yet they are sensitive, natural laboratories for investigating the impacts of environmental change on landscapes and land-cover systems. For this reason, we have utilized the Canadian Space Agency's RADARSAT satellite to initiate a program for monitoring the landscapes of approximately 20 oceanic islands as part of the RADARSAT Background Mission. To date, we have analyzed high resolution SAR images of 12 islands that extend from the Arctic, throughout the Atlantic and Southern Indian oceans, and into the equatorial Pacific. We have selected islands for monitoring on the basis of their known or suspected history of landscape change in association with environmental factors or anthropogenic effects.

Description: The term 'scale', both in space and time, is central to remote sensing and geographic information systems (GIS). The emergency and widespread use of GIS technologies, including remote sensing, has generated interest in addressing scale as generic Issue, and in the development and implementation of techniques for dealing explicitly with the vicissitudes of scale as a multidisciplinary issue. Traditionally, the paper map has been used as the primary conveyor of 'scale', represented by the ratio between the distance as measured between pairs of points on the map and distance as measured between the same pairs of points on the Earth's surface. GIS and remote sensing, however, have expanded upon the paper map and now provide opportunities for representing multiscale representations; that is databases or models that contain spatial and temporal data that have been obtained and stored at different scales.

Description: Advanced Microwave Scanning Radiometer (AMSR) will be flown on-board of the Japanese Advanced Earth Observing Satellite-II (ADEOS-II) and United States Earth Observation System (EOS) PM-1 satellite. AMSR is a passive microwave radiometer with frequency ranges from 6.9 GHz to 89 GHz. It scans conically with a constant incidence angle of 55 deg at the Earth's surface. The swath width is about 1600 km. With a large antenna, AMSR will provide the best spatial resolution of multi-frequency radiometer from space. This provides us an opportunity to improve the snow parameter retrieval. Accurate determination of snow parameters from space is a challenging effort. Over the years, many different techniques have been used to account for the complicated snow parameters such as the density, stratigraphy, snow grain size, temperature variation of the snow-pack. Forest type, fractional forest cover and land use type also need to be considered in developing an improved retrieval algorithm. However, snow is such a dynamic variable, snow-pack parameter keeps changing once the snow is deposited on the earth surface. Currently, NASDA and NASA are developing AMSR snow retrieval algorithms. These algorithms are now being carefully tested and evaluated using the SSM/I data. Due to limited snow-pack data available for comparison, this activity is progressing slowly. However, it is clear that in order to improve the snow retrieval algorithm, it is necessary to model the metamorphism history of the snow-pack.

Description: We have investigated the role of biological processes in the C-isotopic dynamics of the aquatic ecosystems in Taylor Valley, Antarctica. This cold desert ecosystem is characterized by the complete lack of vascular plants, and the presence of algal mats in ephemeral streams and perennially ice covered lakes. Streams having abundant algal mats and mosses have very low sigma CO2 concentrations, as well as the most depleted delta C-13 values (-4%). Previous work has shown that algal mats in these streams have delta C-13 values averaging -7.01%. These values are similar to those observed in the algal mats in shallow areas of the lakes in Taylor Valley, where CO2 is thought to be colimiting to growth. These low Sigma CO2 concentrations, and delta C(13) signatures heavier than the algal mats, suggest that CO2 may be colimiting in the streams, as well. Streams with little algal growth, especially the longer ones in Fryxell Basin, have higher Sigma CO2 concentrations and much more enriched isotopic signatures (as high as +8%). In these streams, the dissolution of isotopically enriched, cryogenic CaCO3 is probably the major source of dissolved carbonate. The delta C(13) geochemistry of Antarctic streams is radically different from the geochemistry of more temperate streams, as it is not affected by terrestrially produced, isotopically depleted Sigma CO2. These results have important implications for the understanding of "biogenic" carbonate that might have been produced from aquatic ecosystems in the past on Mars.

Description: From 1987 through 1997 the Airborne Visible-InfraRed Imaging Spectrometer has matured into a remote sensing instrument capable of producing prodigious amounts of high quality data. Using the NASA/Ames ER-2 high altitude aircraft platform, flight operations have become very reliable as well. Being exclusively dependent on the ER-2, however, has limitations: the ER-2 has a narrow cruise envelope which fixes the AVIRIS ground pixel at 20 meters; it requires a significant support infrastructure; and it has a very limited number of bases it can operate from. In the coming years, the ER-2 will also become less available for AVIRIS flights as NASA Earth Observing System satellite underflights increase. Adapting AVIRIS to lower altitude, less specialized aircraft will create a much broader envelope for data acquisition, i.e., higher ground geometric resolution while maintaining nearly the ideal spatial sampling. This approach will also greatly enhance flexibility while decreasing the overall cost of flight operations and field support. Successful adaptation is expected to culminate with a one-month period of demonstration flights.

Description: Cooperative research in microwave remote sensing between the Hydrological Sciences Branch of the NASA Goddard Space Flight Center and the Earth Sciences Faculty of the Vrije Universiteit Amsterdam began with the Botswana Water and Energy Balance Experiment and has continued through a series of highly successful International Research Programs. The collaboration between these two research institutions has resulted in significant scientific achievements, most notably in the area of satellite-based microwave remote sensing of soil moisture. The Botswana Program was the first joint research initiative between these two institutions, and provided a unique data base which included historical data sets of Scanning Multifrequency Microwave Radiometer (SN4NM) data, climate information, and extensive soil moisture measurements over several large experimental sites in southeast Botswana. These data were the basis for the development of new approaches in physically-based inverse modelling of soil moisture from satellite microwave observations. Among the results from this study were quantitative estimates of vegetation transmission properties at microwave frequencies. A single polarization modelling approach which used horizontally polarized microwave observations combined with monthly composites of Normalized Difference Vegetation Index was developed, and yielded good results. After more precise field experimentation with a ground-based radiometer system, a dual-polarization approach was subsequently developed. This new approach realized significant improvements in soil moisture estimation by satellite. Results from the Botswana study were subsequently applied to a desertification monitoring study for the country of Spain within the framework of the European Community science research programs EFEDA and RESMEDES. A dual frequency approach with only microwave data was used for this application. The Microwave Polarization Difference Index (MPDI) was calculated from 37 GHz data and used to derive the one-way canopy transmissivity. Using a simple radiative transfer model, this information was combined with horizontally polarized 6.6 GHz SMMR observations to derive a 9-year time series of soil moisture for all of Spain at a one quarter degree spatial scale. Both day and night SMMR observations were used independently, in order to check the consistency of the results. A first order Fourier Transform was performed on the mean monthly soil moisture values to identify major characteristics of time series such as trend, amplitude, and phase shift.

Description: We describe an automated algorithm (MEMSCAG) for mapping subpixel snow covered area (SCA) and snow grain size with AVIRIS data. The algorithm is based on the multiple endmember approach to spectral mixture analysis in which the spectral endmembers and the number of endmembers can vary on a pixel-by-pixel basis. This approach accounts for surface cover heterogeneity within a scene. The mixture analysis runs on endmembers from a spectral library of snow, vegetation, rock, soil, and lake ice spectra. Snow endmembers of varying grain size were produced with a radiative transfer model. All non-snow endmembers were collected with a portable field spectrometer. Mapping is performed through sequential 2-endmember, 3-endmember, and 4- endmember mixture model runs, each subject to constraints on RMS, residuals, fractions and priority. Grain size is determined by the grain size of the snow endmember used in the optimal mixture model. We apply MEMSCAG to AVIRIS data collected over Mammoth Mountain, CA and the northern site of the BOREAS in Manitoba, Canada. MEMSCAG produces appropriate snow covered area estimates in all regions. A preliminary comparison of grain size estimates from MEMSCAG with field measurements demonstrates high accuracy.

Description: Two Landsat Thematic Mapper (TM) images, from July 1984 and July 1992, were used to identify land use/cover changes in the urban and suburban fringe of the city of Huntsville, Alabama. Image difference was the technique used to quantify the change between the two dates. The eight-year period showed a 16% change, mainly from agricultural lands to urban areas generated by the settlement of industrial, commercial, and residential areas. Visual analysis of the change map (i.e., difference image) supported this phenomenon by showing that most changes were occurring in the vicinity of the major roads and highways across the city.