12 The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is a high spatial resolution multispectral imaging radiometer, and is onboard the NASA's Terra spacecraft launched on December 18, 1999. It spectrally covers the visible and near-infrared, short-wave- infrared, and thermal infrared regions with 14 spectral bands, and creates high-spatial-resolution (15-90 m) multispectral images of the Earth's surface. The observation performances of the ASTER instrument were evaluated by the early images, e.g. spatial resolution, modulation transfer functions (MTF), signal-to-noise-ratios (SNRs), band-to-band registrations, and so on. It was confirmed that the ASTER instrument generally exceeds the specified observation performance, and the early images exhibit excellent quality even in the preliminary processing level. In the initial check-out phase, ASTER was operationally used for intensive monitoring of volcanic eruptions in Japan, and successfully provided useful information to volcanologists.

12 The Multi-angle Imaging SpectroRadiometer (MISR) instrument was launched into polar orbit aboard the Terra spacecraft in December 1999, and collection of Earth imagery began in February 2000. MISR contains nine cameras pointed at fixed along-track directions, and acquires images with view angles at the Earth's surface ranging from 70.5 degree(s) forward of nadir to 70.5 degree(s) aftward. Each camera contains four CCD line arrays filtered to blue, green, red, and near-infrared wavelengths. Spatial sampling ranging from 275 m to 1.1 km is obtained over a 400-km swath width. Each area observed by MISR is imaged at all nine angles within a seven-minute period. MISR provides a unique approach to characterizing atmospheric aerosols, the surface, and clouds. This paper provides examples of MISR products derived from imagery acquired during the first six months of data collection.

12 There are 2 CERES scanning radiometer instruments aboard the TERRA spacecraft, one for mapping the solar radiation reflected from the Earth and the outgoing longwave radiation and the other for measuring the anisotropy of the radiation. Each CERES instrument has on-board calibration devices, which have demonstrated that from ground to orbit the broadband total and shortwave sensor responses maintained their ties to the International Temperature Scale of 1990 at precisions approaching radiances have been validated in orbit to +/- 0.3 percent (0.3 W m^-2sr^-1). Top of atmosphere fluxes are produced by use of the CERES data alone. By including data from other instruments, surface radiation fluxes and radiant fluxes within the atmosphere and at its top, shortwave and longwave, for both up and down components, are derived. Validation of these data products requires ground and aircraft measurements of fluxes and of cloud properties.

12 This paper describes the major activities that were conducted in order to complete the successful commissioning of the spacecraft and instruments. Included are activities which did not execute as planned and took significant effort and resolve it took to overcome. As a result, Terra is now beginning to produce world class science.

12 The Multi-angle Imaging SpectroRadiometer (MISR) is one of five instruments on the EOS/Terra spacecraft. MISR consists of nine Earth-viewing cameras which continuously acquire global data sets in view perspectives from nadir to 70 degree(s). In order to maintain the radiometric calibration of the cameras, the instrument is equipped with an on-board calibrator. Spectralon panels, deployed at bi-monthly intervals, reflect sunlight into the cameras to be tested. This reflected light is measured by photodiode detectors which define the radiometric scale and allow the sensor calibration to be achieved. There exists six sets of four spectrally filtered photodiodes. For the first of the in- flight experiments the analysis was focused on validating the performance of the on-board calibrator components. As a result of these studies one blue-filtered, light-trapped detector was selected as the primary standard. All other on- board photodiodes have now been adjusted to be in agreement. This procedure has allowed improved band-to-band and camera- to-camera calibrations, in that all camera calibrations are traceable to a single standard. With these procedures in place MISR now plans to calibrate once every two months. New radiometric response coefficients will be delivered to the processing center following each experiment. This paper reports on these validation studies, and the post-launch radiometric response of the MISR cameras as determined during the first six months of on-orbit MISR calibration.

12 MODIS (Moderate Resolution Imaging Spectroradiometer) was launched on board the NASA's Terra Earth Observing System (EOS AM-1) Satellite on December 18, 1999. We propose in this work operative split-window algorithms for retrieving sea surface temperature (SST) and land surface temperature (LST) using MODIS data. In order to attain our goal, the MODTRAN 3.5 radiative transfer code was used to predict radiances for MODIS channels 31 and 32. To analyze atmospheric effects, a set of radiosoundings was used to cover the variability of surface temperature and water vapor concentration on a worldwide scale. These simulated data were split into two sets which have very similar distributions in space and time. The first one was used to fit the coefficients of the algorithms for retrieving both SST and LST, while the second one was used to test the fitted coefficients. Later, a sensibility study, including the effects of noise, emissivity and water vapor content uncertainties, has been done using the error theory.

12 The ASTER system was launched successfully on board the Terra spacecraft on December 18, 1999. The system obtains multispectral images ranging from visible to thermal infrared region by combining three subsystems composed of four telescopes. To deliver data products with high quality from the viewpoint of the geolocation and band-to-band registration performance, the fundamental program called the Level-1 processing has been developed. The geometric validation procedure of ASTER, which consists of four telescopes and a cross-track pointing function, is carried out during the initial checkout period. Image matching method based on a cross-correlation function was used to register images of each band.

12 The Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) is a multispectral imaging radiometer with 14 spectral bands of VNIR, SWIR and TIR, 60 km imaging swath, and 15-90 m spatial resolution. It was launched on NASA's Terra (EOS AM-1) on December 18, 1999. The ASTER scheduling algorithm and the ASTER Scheduler software was developed in order to maximize the scientific content of each schedule. The Scheduler divides each day into a series of short timesteps (several seconds), for the purpose of prioritization. Prioritization is the process of ranking possible observations, so that the observation opportunities with higher scientific or programmatic value are given higher probabilities of being scheduled. The Scheduler uses the prioritization function to calculate a priority for each potential observation. The prioritization function uses information from all data acquisition request parameters requesting a possible observation. After calculating all the priority, the Scheduler generates 24 hour schedule, namely One Day Schedule (ODS). At each point in this process, the Scheduler checks to make sure that no operating constraints are being violated. Finally, the ODS is transmitted to EOS Operation Center (EOC) every day.

12 ASTER (Advanced Spaceborne Thermal Emission and Reflection radiometer) which has been developed by MITI (Ministry of International Trade and Industry) and JAROS was successfully launched on December 18 10:57 PST on the satellite called Terra by the Launch Vehicle Atlas II. On the ground, ASTER Ground DATA System (ASTER GDS) has been developed also by MITI and ERSDAC together with EOSDIS (EOS Data and Information System) that has been developed by NASA and GSFC (Goddard Space Flight Center). Currently, Terra is orbiting around the Earth on the nominal polar orbit and ASTER is collecting data from all over the world. The comprehensive operation of Terra is performed by GSFC, while ASTER operation is conducted by ASTER GDS. As of September 2000, ASTER is working well and producing good image data of VNIR (Visible and Near Infrared Radiometer), SWIR (Short Wavelength Infrared Radiometer) and TIR (Thermal Infrared Radiometer). The details at the development stage of ASTER GDS have been described three times in foregoing SPIE Conferences. In this paper, the first data and experiences during the Initial Checkout will be discussed.

12 The Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) was one of the mission instruments selected by NASA to fly on the EOS-AM1 spacecraft. The EOS- AM1 (Terra) spacecraft was launched from Vandenberg Air Force Base, December 18, 1999. The ASTER consists of a visible and near-infrared radiometer (VNIR), a short-wave infrared radiometer (SWIR) and a thermal infrared radiometer (TIR). Two cryocoolers are required to cool down the infrared detectors for the SWIR and the TIR. Two cold plates act as a heatsink for each compressor unit and maintain in temperature in the range between 20 degree(s)C and 25 degree(s)C by a capillary-pump heat-transfer system (CPHTS). Therefore, environmental temperature conditions are the same for the two compressor units. While the TIR expander unit is thermal controlled by a local radiator with a heat pipe, the SWIR expander unit employs radiative cooling for thermal control. The performance of ASTER cryocooler was evaluation to operate normally, based on the data obtained in the functional checkout in orbit. The SWIR cryocooler cools the detector to the operating temperature of 77 K in the cooldown time of 22 minutes. The TIR cryocooler cools the detector to the operating temperature of 80 K in the cooldown time of 23 minutes. The temperature of each detector was stabilized in the allowable temperature range. A clear image was obtained in the initial checkout of each radiometer in their observation mode.

12 Global Change Observation Mission (GCOM) is a follow on mission of ADEOS and ADEOS2. It is under phase A study in NASDA (National Space Development Agency of Japan). GCOM is not a series of satellites but a mission and its concept is to continuously monitor geophysical parameters which are critical to understand global change phenomena, especially phenomena related to climate change. The measurements of geophysical parameters will continue more than 15 years after the launch of ADEOS2. The first generation of GCOM is now composed of 2 satellites, i.e. GCOM-A1 and GCOM-B1. The target of GCOM-A1 is to monitor greenhouse gases distribution and ozone as well as ozone related constituents from oblique orbit. The target of GCOM-B1 is to measure geophysical parameters which are uncertain in today's climate models. Those parameters include, but not limited to, optical thickness of aerosols and clouds, thermal fluxes, carbon fluxes, sink and source of greenhouse gases, etc. GCOM-B1 will carry three core instruments, i.e. SGLI (GLI follow on), AMSR2 (AMSR follow on), alpha-Scat (SeaWinds follow on). Another candidate instrument is ATRAS (IMG follow on). The orbit of GCOM-B1 will be a sun synchronous orbit, which is almost the same as ADEOS2. GCOM- B1 is especially powerful for the monitoring of oceanic processes. It can observe sea surface temperature, ocean color and sea surface winds simultaneously by 3 sensors, i.e. SGLI, alpha-Scat and AMSR2. GCOM-A1 is planned to be launched in Feb. 2005 while GCOM-B1 is planned to be launched in Aug. 2006.

12 GCOM is the big mission that does global change monitoring and make the long term data sets for 15 years from satellite data. The GLI series sensor is one of core sensor of this mission. The first series GLI is installed in ADEOS-2 that is launched in 2001. Also, SGLI is installed to GCOM-B1 that is launched in 2006. SGLI is one of GLI series sensor. GLI series sensor is multiband medium spatial resolution imager such as MODIS. Those sensors are classified as general-purpose radiometers capable of serving various earth observation missions. The advancement of remote sensing technologies means that wide ranging remote sensing data is now available to make more accurate products regarding the middle as well as lower atmosphere, ocean, land and cryosphere. The SGLI sensor will be a multipurpose, multiband, medium resolution, visual infrared imager and an advanced version of the GLI. Its main characteristic will be the possession of many channels of which the wavelength specifications and field of view are optimized for a specific target.

12 The Meteosat Second Generation (MSG) program consists of a series of 3 geostationary satellites. The objectives for this program have been defined by the European meteorological community led by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) and the European Space Agency (ESA). The first MSG satellite (MSG-1) is currently being developed by ESA and scheduled for launch in the year 2002. MSG-2 and MSG-3 will be procured by ESA on behalf of EUMETSAT. They will be built by European industry under ESA contract and are scheduled for launch in 2004 and 2009. EUMETSAT will launch and operate the three satellites and provide data until 2014. This paper focuses on the foreseen in-flight verification and calibration of the main payload on board the MSG satellites: the Spinning Enhanced Visible and Infrared Imager (SEVIRI). It commences with a brief description of the main elements of the MSG satellite and the SEVIRI instrument. Then the in-flight verification approach for functional and performance specifications will be presented. Finally, the paper will provide the envisaged in-flight calibration method for the SEVIRI instrument.

12 Atmospheric remote sensing with the O₂ A-band has a relatively long history, but most of these studies were attempting to estimate surface pressure or cloud-top pressure. Recent conceptual studies have demonstrated the potential of spaceborne high spectral resolution O₂ A- band spectrometers for retrieval of aerosol and cloud optical properties. The physical rationale of this new approach is that information on the scattering properties of the atmosphere is embedded in the detailed line structure of the O₂ A-band reflected radiance spectrum. The key to extracting this information is to measure the radiance spectrum at very high spectral resolution. Instrument performance requirement studies indicate that, in addition to high spectral resolution, the successful retrieval of aerosol and cloud properties from A-band radiance spectra will also require high radiometric accuracy, instrument stability, and high signal-to-noise measurements. To experimentally assess the capabilities of this promising new remote sensing application, the NASA Langley Research Center is developing an airborne high spectral resolution A-band spectrometer. The spectrometer uses a plane holographic grating with a folded Littrow geometry to achieve high spectral resolution (0.5 cm^-1 and low stray light in a compact package. This instrument will be flown in a series of field campaigns beginning in 2001 to evaluate the overall feasibility of this new technique. Results from these campaigns should be particularly valuable for future spaceborne applications of A-band spectrometers for aerosol and cloud retrievals.

12 The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a high-resolution Fourier Transform Infrared (FTIR) limb sounding spectrometer, developed as one of the ESA payload instruments for the ENVISAT satellite. MIPAS is designed to measure concentration profiles of atmospheric constituents on a global scale over a period of several years and constitutes one of three ENVISAT instruments designed primarily for atmospheric chemistry research. The MIPAS Flight Mode (FM) test campaign was completed in 1999 and the instrument was then integrated on the ENVISAT platform, which now undergoes environmental and system testing. The launch is foreseen in 2001 by an ARIANE-5 launcher into an 800 km polar orbit. This paper gives an overview of the MIPAS instrument design, describes its calibration scheme, presents the performance as measured in the test campaigns, summarizes the characterization activities and outlines the principal operations to be performed during MIPAS commissioning in orbit.

12 SkyMed/Cosmo is a research project, supported by the Italian Space Agency, devoted to develop a satellite constellation for the monitoring of the Earth surface in the optical and microwave spectral ranges. The system is devised for such operational purposes as disaster monitoring and observation of marine and terrestrial ecosystems over regional scale, and will be characterized by a very short re-visitation time. Nowadays the SkyMed/Cosmo project is expected to equip some satellites with different optical sensors comprising also a hyperspectral push-broom imager, having not less than roughly 40 spectral bands with a spectral resolution of 10 nm and radiometric resolution of 12 bit. This is a remarkable achievement that also requires a lot of theoretical and experimental work to be executed. An airborne hyperspectral instrument was selected for simulating the performance of this advanced push-broom satellite-based imager and our Institute was charged for carrying out some research and experiments. The selected airborne instrument is the VIRS-200, a push-broom hyperspectral sensor manufactured by the Officine Galileo and operating in the visible and near infrared spectral ranges (from 400 nm up to 1000 nm). This sensor measures a reflectance spectrum constituted of 20 spectral samples (tuneable channels) whose wavelength position can be user- selected with a step-increment of 2.5 nm. The bandwidth of each spectral channel is 2.5 nm and the spectral samples are digitized with a quantization accuracy of 10 bits.

12 IASI is a key instrument of the payload on METOP, a European meteorological platform. METOP will provide meteorology with atmosphere emission spectra, allowing to set atmosphere temperature and moisture profiles with high accuracy. In order to achieve these specifications, several new and innovative technologies and technical answers have had to be developed. Among them, the reference laser of IASI presents challenging concepts and widely uses the last commercial developments of telecommunication technologies. The reference laser is frequency locked onto a molecular reference absorption line providing a very stable frequency behavior over the several year duration of the instrument life. The principle is well known for atomic clocks and has been adapted to the commercial availability of reliable telecommunication lasers. Semiconductor laser modules, optical fibers and fibered components are used to achieve a compact and reliable subsystem. The availability of such space compliant frequency stabilized laser sources opens new opportunities in the field of optical metrology such as interferometry and multi- aperture telescope co-phasing.

12 During the past two years the company LH Systems and the German Aerospace Center (DLR) have developed the commercial airborne digital sensor ADS40 based on the three-line principle. By assembling additional CCD lines into the same focal plane, the sensor is capable of generating a number of color images. In the first part, the sensor system itself is introduced shortly. The main concept and the key features are described and an overview of the data processing scheme is given. After that, we will focus on the results of test flights. The emphasis is placed on the properties of the overall system including the sensor itself, platform, airplane, and inertial measurement unit. The effect of using staggered CCD lines is discussed. Flights over well known test areas are used to prove the accuracy of derived data products, DEMs, color images, and ortho-images. Differences in data processing methods are pointed out in comparison to sensor systems based on CCD matrices or film.

12 An end-to-end simulation is a valuable tool for sensor system design, development, optimization, testing, and calibration. This contribution describes the radiometry module of the end-to-end simulation tool SENSOR. It features MODTRAN 4.0-based look up tables in conjunction with a cache-based multilinear interpolation algorithm to speed up radiometry calculations. It employs a linear reflectance parameterization to reduce look up table size, considers effects due to the topology of a digital elevation model (surface slope, sky view factor) and uses a reflectance class feature map to assign Lambertian and BRDF reflectance properties to the digital elevation model. The overall consistency of the radiometry part is demonstrated by good agreement between ATCOR 4-retrieved reflectance spectra of a simulated digital image cube and the original reflectance spectra used to simulate this image data cube.

12 The increasing use of probabilistic methods, such as the Monte Carlo ray-trace (MCRT) method, in thermal radiation and optical modeling, has created a general awareness in the community of the need for a protocol to predict, to a specified level of confidence, the uncertainty of the results obtained using these methods. This paper presents such a protocol applied to models of radiometric channels used in space-based Earth observations. It is anticipated that the same protocol, with suitable modification, may be extended to data from actual instruments. The authors and their colleagues have developed a powerful generic MCRT- based computational environment that, among other features, is capable of simulating radiative exchange among surfaces and within enclosures. As in any MCRT thermal- radiative/optical model, the spatial resolution and accuracy of the results obtained depend on the fineness of the mesh, the number of rays traced, and the accuracy of directional and spectral surface property models. The protocol presented in this paper identifies and quantifies the contribution of these factors to the ultimate uncertainty in predicted results and to their related confidence intervals.

The methods of matching digital filtration of chirp-signa's in time domain are studied in this work. The advantages of this kind of processing in comparison to the processing on fast convolutions in frequency domain are demonstrated. The chirp signal aid smoothing window parameters have been studied to increase the ratio of the main lobe to side lobes of compression radio pulses. To increase the efficiency of the differential processing of location signals in time domain, the use of noise-like signal representation in sign delta modulation format (SignDM) has been proposed. The SignDM codes are determined by comparing the values of differences between signal samples in PCM formats with a differential zone, which is defined apriori. These codes belong to the set {-1, 0, l}. SignDM's sampling rate is equal to Nyquist's frequency. The resolution of matching filtration depending on the changing of differential zone is studied by computer simulations. The peculiarities of creating analog signals on the basis of the noise-like codes have been presented in this work, too. The stmcture of matching filter (MF) with Sign DM is represented, too.

12 An IR sensor based on a linear array of poly Si-Ge bolometers is presented. The bolometers are surface micromachined devices employing a suspended structure to achieve thermal insulation from the substrate. Linear arrays of 64 elements have been connected to the readout chip by means of a ceramic substrate realizing a hybrid sensor. The CMOS readout chip provides a pulsed bias for the bolometers, amplification of the signal and multiplexes the output in an analog line. At room temperature an NETD of 300mK has been achieved, while the maximum readout speed is 1kHz.

12 PRISM, a panchromatic stereomatic sensor with 2.5m resolution, is planned to be launched in 2003. Because observing data rate of PRISM is very high, lossy data compression will be applied on the board satellite in order to decrease the downlink data rate to ground receiving stations. The object of this study is to evaluate influences of the lossy data compression, atmospheric effects and S/N of the sensor for terrain elevation measurement. As the results, the following conclusions were given. Firstly, low S/N increases mean elevation error under the restriction that forward/backward viewing vectors converge within two pixels. Secondly, data compression and turbid atmosphere decrease the mean elevation error, preferably. Thirdly, data compression ratio of 1/6 is recommended in practical operation of PRISM. In this case, mean elevation error less than or equal to 3m can be achieved without relation of atmospheric condition and S/N.

12 Since 1995, the CEOS Calibration/Validation (Cal/Val) Database has provided the international Earth remote sensing science community with a) a central repository for information on current and planned Calibration/Validation activities and b) a means to foster collaboration on common Cal/Val issues. The Cal/Val Database uses an ORACLE relation database management system to store the data and is accessed via the World Wide Web (WWW) using PERL scripts to search and query the database. The search queries are structured such that users can define any combination of fields, either through selection of valids, or by directly typing the information. All query results are displayed in the text form. The text displays are interactive allowing the user to point and click to access more detailed information. System functionality provides an on-line form of all of the three questionnaires for submitting new information and allows a user with the assigned password to edit archived information for their facility. This functionality allows users to update information, as it becomes available. In 2000, the Cal/Val database was updated through a process of additional surveying of existing and planned Cal/Val capabilities to support the NASA's Earth Science Enterprise (ESE) and other international Earth observing missions. A set of three updated questionnaires was prepared: one for calibration laboratories, one for test sites, and one for field instruments. The information requested included: a description of the facility, instruments available, instrument characteristics, types of measurements performed, programs/projects that have used the facility, etc. These questionnaires with cover letter were mailed to over 250 research groups that included CEOS members and facilities within the USA. The information collected from worldwide facilities was used to construct and update this on-line database for use not only by the CEOS members, but also the broader international Earth science community.

12 A new facility is presented designed for the absolute and relative radiometric calibration of space instruments. All parts of the facility, thermal vacuum system, software, electronics and even the layout of the facility, are subordinate to the quality of the measurements. For each part is explained, how and why, the design of this particular part is contributing to improvement of the calibration.

12 The Landsat-7 ETM+ incorporates three on-board calibration devices: (1) an internal calibrator, (2) a partial aperture solar calibrator and (3) a full aperture solar calibrator. The internal calibrator consists of two tungsten lamps and optical and mechanical components to transfer the light to the primary and cooled focal planes. In the present contribution we analyze the ETM+ internal calibrator signal in several spectral bands and model them functionally using several instrument-state quantities available in the Landsat-7 telemetry. Models were tested and compared in terms of their complexity, explanatory power and fit to the data. The intent of such models is to provide a way to correct for the internal calibrator instabilities and allow for its more precise usage in calibrating ETM+ data on-orbit. Some of the computer models we developed can be accessed interactively on the World Wide Web.

12 The Total Ozone Mapping Spectrometer - Flight Model 5 (TOMS- 5), aboard the QuikTOMS spacecraft, is designed to continue the measurement of the total column amount of ozone in the atmosphere in order to monitor the global trend. Since the predicted total ozone change due to man-made sources is very small, an accurate calibration of the measuring instrument is required. Since in the TOMS-5 experiment the total ozone amount is determined from the ratio of the measurement of the solar backscattered ultraviolet Earth radiance to the incident solar irradiance, the accuracy of the calibration of the instrument sensitivity to this ratio measurement is critical. The prelaunch calibration of TOMS-5 was designed to achieve a ratio calibration accuracy of 1% in addition to the uncertainties of the standards used. Multiple calibration techniques were employed to ensure the self- consistency of results of different techniques to eliminate any systematic errors. TOMS-5 prelaunch radiometric calibration was performed twice, one in 1996 and the second in 1999 due to the launch delay. The ratio calibration was reproduced within 0.5% from the tests of 1996 to those of 1999 while the calibration of the individual measurement modes agreed among the various techniques to within 1%.

12 Currently, the moon is being used as a radiometric target to determine on-orbit relative shifts or shifts in the responses of certain spacecraft shortwave sensors. Along these lines, the 1998 Tropical Rainfall Measuring Mission (TRMM) Spacecraft/Clouds and the Earth's Radiant Energy System (CERES) thermistor bolometer sensor observations of lunar radiances were analyzed to evaluate the feasibility using the lunar radiances to calibrate the CERES sensor responses. Over a 5 to 110 degree phase angle range, the CERES sensors were used to measure: broadband shortwave (0.3 micrometers to 5.0 micrometers ) moon-reflected solar filtered radiances; broadband total (0.3 micrometers to more than 100 micrometers ) moon- reflected solar and moon-emitted longwave filtered radiances; and narrowband window (8 micrometers to 12 micrometers ) moon- emitted longwave filtered radiances. The TRMM/CERES on-orbit radiance measurements are tied to an International Temperature Scale of 1990 (ITS-90) modeled radiometric scale at uncertainty levels approaching 0.2% (0.2 Wm^-2sr^-1). Therefore, the TRMM/CERES measurements should be useful in forecasting the precisions of scheduled CERES lunar measurements from the NASA Terra and Aqua Spacecraft platforms near phase angle of 22 and 55 degrees, respectively. The 7-degree phase angle, 1998 CERES shortwave, total, and window measurements yielded lunar filtered radiances of approximately 4.5+/- 0.2, 24.4+/- 0.5, and 4.5+/- 0.2 Wm^-2sr^-1, respectively. These lunar measurements indicate that broadband shortwave radiances can be characterized at the 5% uncertainty range. The 7-degree, shortwave lunar radiances were found to be approximately 1.5 and 3 times brighter greater the corresponding radiances found at the 22-degree and 55-degree phase angles, respectively. Therefore, the Terra and Aqua CERES lunar shortwave measurements near 22.5- degree and 55-degree phase angles should yield projected precisions in the 7% and 15% range, respectively. The CERES lunar filtered radiance are presented and discussed. Research efforts are outlined briefly for comparing the total sensor broadband and window narrowband longwave lunar radiances during the January 9, 2001 lunar eclipse.

A program to characterize the brightness of the Moon for use with spacecraft calibration is continuing its operation. Observations are made over the wavelength range 350—2500 nm in 32 passbands, almost half of which approximate existing spacecraft bands. Observations of bright stars provide instrument calibration, measure atmospheric extinction, and provide an absolute calibration pathway. The processed data from this project currently contain over 40 000 Lunar images. Photometric models of the total Lunar irradiance are generated from image irradiance sums. Independent radiance models for '- 250000 pixel locations in the calibrated image projection are also calculated, allowing accurate treatment of spacecraft viewing geometries. Within the phase angle range 5_900,the uncertainty in the relative irradiance models is less than 1.5%. At a constant phase angle, the irradiance uncertainty due to libration is significantly lower. These uncertainties are small enough to establish the Moon as a good calibrator for tracking relative instrument stability. The uncertainty in the absolute radiance scale is currently 6—10%, but relative and absolute model uncertainties are expected to decrease with further analysis and as more observations are added to the dataset during the next few years.

Two critical requirements of a calibration source are short- and long-term operational stability and repeatability. Monitoring the source is an asset in determining the origin of temporal changes, thus increasing confidence in source performance and quantifying repeatability. Monitor data which fall outside established parameters indicate that the source requires maintenance or re-calibration against the standard. The NASA GSFC Code 920. 1 Radiance Calibration Facility (RCF) has developed a Filter Radiometer Monitoring System (FRMS) to continuously monitor the performance of its integrating sphere calibration sources in the 400-2400nm region. Sphere output change mechanisms include lamp aging, coating (BaSO4) deterioration, and water vapor level. FRMS wavelength bands are selected to be sensitive to changes caused by these mechanisms. Several FRMS bands coincide with common remote sensing instrument bands.

The Atmospheric Infrared Sounder represents a quantum leap in spaceborne sounding instruments with 2,378 infrared spectral channels ranging in wavelength from 3.5to 15.5 microns. AIRS was built by NASA subcontractor Lockheed Martin Sanders (LM Sanders) in Lexington, Massachusetts and is scheduled for launch on the NASA EOS-Aqua spacecraft in December 2000. Characterization of this high spectral resolution infrared spectrometer involved extensive laboratory testing in a thermal vacuum environment at cold optical temperatures. This paper summarizes the results of that testing and gives a detailed report on the spectral, radiometric, and spatial performance of the AIRS. Based on the excellent prelaunch calibration and results of data simulation, AIRS data should significantly improve global weather forecasts and provide an important new tool for climate research.

CLOUDS is a project co-funded by the EC under FP-4 (Environment and Climate), conducted by 12 European partners (7 scientific institutes and 5 industrial companies), also cooperating with NOAA/ETL. It is the mission study of a monitoring satellite to perform measurements necessary to describe cloud-radiation interaction in operational models for climate and long-term weather prediction. Complementary to missions for process study (Picasso-Cena, CloudSat, .. . ), CLOUDS addresses the monitoring aspect. As such, it has to comply with requirements of sufficiently frequent observing cycle, and operational sustainability. This prevents using active systems (radar and lidar) and leads to consider passive radiometry only, however exploiting as much as possible of the e.m. spectrum, with more polarisations and more viewing geometries. The paper reports on the instruments and system concepts developed to comply with the mission requirements. Six instruments are described, operating, respectively, in narrow channels of the UV/VIS/NIRISWIR, the TIRIFIR, the Sub-mm waves and the MW, in broad-band channels from UV to FIR, and in a relatively large-band channel of VIS/NIR. Several channels have three or four polarisations, all take images fore- and aft- (conical scanning), one has multi-angle-viewing capability. The overall system size is estimated as 900 kg mass, 1600 W power, 1 .1 Mbps data rate for real-time S-band transmission and 30 Mbps data rate for global data recovery in X-band.

Improved weather forecast and climate monitoring rely on a better quantification of soil moisture (SM) and sea surface salinity (SSS). The most accurate way to measure them from remote sensors is by using radiometers at L band, where the sensitivity of the brightness temperature is maximum and the atmosphere is almost transparent. In order to provide a global coverage of these basic parameters within a revisit time of 3 days and 30-50 Km spatial resolution, the SMOS mission was recently selected by ESA in the frame of the Earth Explorer Opportunity Missions. The sensor being considered for this mission (called MIRAS) uses the concept of 2D interferometric radiometry1'2'3, and is scheduled to be launched in 2005. A demonstrator consisting of a number of receivers is now under development by CASA (E) by contract with ESA. This work presents the block diagram of a single receiver chain in the SMOS instrument and its main requirements in terms of mission tradeoffs.

The GPS/MET experiment was the first active atmospheric microwave occultation experiment using the existing GPS Li and L2 frequencies to measure the atmospheric refractive index. One major limitation to this tecimique is that the presence of water vapor in amounts typically found in the lower troposphere (below 5-7 km) causes an ambiguity between the contributions of dry air and moisture to the refractive index. Additionally the profiles of other gases, such as ozone, cannot be measured using the Li and L2 frequencies. A new satellite remote sensing technique to independently monitor atmospheric water vapor and ozone is under development. It will include small satellites with both transmitter and receiver capabilities on each. The frequencies will be located around the 22 and 183 GHz water vapor and the i95 GHz ozone absorption lines. The receivers will also have the capability to observe the Li and L2 GPS frequencies. Simulation studies show that this new active occultation technique has the potential to provide accurate profiles of water vapor and ozone, as well as refractivity, temperature and pressure.

Three CERES (Clouds and the Earth's Radiant Energy System) Instruments are currently in orbit, one instrument is on the TRMM (Tropical Rainfall Measuring Mission) spacecraft launched in November, 1997 and two instruments are on the Terra spacecraft launched in December, 1999. The Aqua/CERES is scheduled to loft two additional CERES instruments in December, 2000. Three CERES Instrument Simulation Systems have been built which mimic the microprocessor-controlled operational characteristics of each instrument to a high degree. The original CERES engineering development models developed by NASA and TRW Space and Electronics Group were modified to provide the gimballed azimuth and elevation real-time simulation in synchronization with the embedded control processors. The simulators are used to perform testing and functional validation of custom commands and command sequences prior to the actual uploading to the individual orbiting instruments. The architecture of the benchtop simulation hardware matches that of the individual instruments and each operates in conjunction with the associated unmodified TRW developed flight software to assure a virtual reproduction of the performance of each instrument. Performance results of command sequences for calibration maneuvers and other simulation scenarios are presented.

The description of the testing for EUV-spectrometer of Space Patrol of the soft X-ray and extreme ultraviolet radiation of Sun is presented. The wavelength calibration was made in vacuum chamber with a window from MgF2. It allows to get spectra in three channels at wavelengths above 1 13 nm. Particularly attention is paid to discussion of observed noises. Analysis of sources of these noises is presented and method of their decreasing at measurements of spectra of Solar ionizing radiation is shortly discussed.

Current extended wavelength InGaAs detectors (<1 .7 pm) grown on InP are limited by the lattice-mismatch and consequent introduction of dislocations in the absorbing layer. In order to overcome these limits, GaAs based compliant substrates have been introduced for the growth of extended wavelength InGaAs detectors. In a first stage up to 3.8% lattice-mismatched InGaAs growth by MOVPE on GaAs compliant substrates has been investigated. Cross-hatch free surface morphology is obtained for epilayers with a thickness exceeding up to 50times the Matthews-Blakeslee critical thickness. X-ray diffraction (XRD) indicates a reduced FWHM (Full Width Half Maximum) and tilting of the InGaAs lattice-mismatched epitaxial layers, thus suggesting a reduced misfit dislocation density (at the interface). Consequently highly mismatched (5-6%)and thick (1-2 tim) InGaAs layers for the development of InGaAs detectors up to 2.5 jim, were grown on GaAs compliant substrates. Dark current measurements on the InGaAs detectors developed on compliant substrates indicate a comparable dark current level as for ordinary GaAs substrates, but a significant improvement in dark current uniformity. Current research includes the fabrication and use of dual material compliant substrates, e.g. InGaAs layers bonded on GaAs or other host substrates (Ge, .. .), for the growth of less than 2-3% latticemismatched InGaAs based detectors.

12 The VISIR instrument has been designed as a lightweight facility to be embarked on future low Earth orbit operational satellites whose mission requirements include monitoring of open oceans, coastal zones and land surface areas. The instrument consists of an imaging spectrometer working in the visible range, dual-band thermal infrared radiometer and a single-band imager in the short-wave infrared. The instrument provides two operational modes, namely the global mode (ground pixel 1200 m, swath 1200 km) and the regional mode (ground pixel 300 m, swath 100 km) with steering capability. The high radiometric performances achieved in both operational modes show the capability to detect very small radiometric changes such as those induced by typical variations of the water quality parameters (chlorophyll, suspended sediments, yellow substance) and surface temperature anomalies. VISIR can achieve many of the MERIS and ATSR/AVHRR performance characteristics within a considerable smaller envelope that can lead to a more affordable instrument. The performances are achieved thanks to a newly designed high-performance (f/2.0 optical spectrometer based on a double-Schmidt configuration, the use of hybrid CMOS detectors for the VNIR and uncooled microbolometers for the TIR, and a hybrid whiskbroom scanning technique. This solution is an excellent compromise as regards the cost/benefit ratio, achieving many of the performances required for a coastal zone earth watching mission, with considerable simplifications with respect to equivalent existing instruments that can lead to much more affordable budgets in terms of mass, power and cost. The spectrometer has the potential to match other type of applications in different spectral bands and/or with different spatial and spectral resolution.

12 The BGIS 2000 was developed by Ball for submeter remote imaging of the Earth surface. Ball is presently building 2 of these systems for the EarthWatch QuickBird Program. The first system will be launched in the Fall of 2000. This paper will detail the system design, and performance characteristics.

12 The Netherlands based National Aerospace laboratory NLR and the co-located Geomatics Business Park use the output of RAPIDS, a small 2.7m dish satellite data receiver system, on a daily basis. The satellite Earth observation data are real time downlinked from the three Spot satellites and the ERS-2 radar satellite and subsequently processed into images. After georeferencing and cutting into mapsheets, the data are sent to a value adding company, which is an expert in image interpretation and classification for e.g. agricultural purposes. The so extracted agricultural information is collected in a database that can be accessed by the subscribers day after day. A semi-automatic georeferencing system has been integrated so the output data of the RAPIDS station can be implemented in, for example, a GIS directly. The database/GIS is a valuable tool for decision making with respect to land use, crop monitoring, flood monitoring, etc.

12 The majority of recently installed remote-sensing groundstations use computer-based data recorders (sometimes referred to as direct ingest or direct capture systems) rather than the high-density tape-recorders used in earlier systems. Direct ingest systems offer significant advantages over high-density recorders, including improved performance, lower initial and operating costs, better reliability and easier system automation. This paper describes a direct ingest system designed for use in new systems or in upgrades to existing systems. It is being used in several recently commissioned groundstations. The design accommodates applications ranging from a simple manually controlled data recorder to a fully automated data acquisition, quality-analysis, archiving and retrieval system. The only specialized hardware is a serial data I/O card that can transfer data at rates exceeding 400 Mb/s. All other functions, including real-time format synchronization and image generation, are carried out in software. The design is open, modular and flexible. The main components may be used separately or as part of a complete system. Satellites currently supported include ERS, KOMPSAT, Landsat-7, Radarsat and SPOT. End-users can easily customize the system to meet their own requirements and can integrate their own satellite-specific processing modules.

12 This assessment will concentrate on an analysis of the U.S. policy of shutter control and its potential impact on U.S. commercial remote sensing firms. The legal elements of this analysis focus an overview of the legality of recent regulations issued by the National Oceanic and Atmospheric Administration (NOAA) to regulate the collection and/or distribution of high-resolution satellite imagery. The policy elements of this analysis concentrate on the goals of this policy, namely to preserve the national security, foreign policy and international obligations of the U.S. government. Conclusions include an assessment that future launches and operations of commercial high-resolution satellites by other countries will undermine the ability of the U.S. government to control the flow of data and therefore make the policy of shutter control obsolete.

12 This paper reports the operational implementation of new techniques for the exploitation of remote sensing data (SAR and optical) in the framework of forestry applications. In particular, we present a new technique for standing timber volume estimation. This technique is based on remote sensing knowledge (SAR and optical synergy) and forestry knowledge (forest structure models), proved fairly accurate. To illustrate the application of these techniques, an operational commercial case study regarding forest concessions in Sarawak is presented. Validation of this technique by comparison of the remote sensing results and the database of the customer has shown that this technique is fairly accurate.

12 As sources of high resolution Earth imagery increase and sophisticated software tools for their analysis proliferate, opportunities abound to generate finer tuned information about our world. At the same time, users are challenged to manage ever-increasing quantities of complex digital assets. Lockheed Martin's Intelligent Library System (ILS), addresses the need for cost-effective management of expanding digital stores, streamlined workflow, and the extraction of information from detailed imagery. Intelligent Library System (ILS) was designed for rapid retrieval, automated processing and dissemination to distributed users. A flexible open architecture allows integration of new products into ILS' functional components: SmartArchiver and SmartAnalyst.

12 The emission behavior of road vehicles is usually estimated by application of emission factors and models. The validity of such factors or models in real world situations can be investigated by tunnel measurements, because road tunnels can be considered as big laboratories with well known boundary conditions. Tunnel experiments were carried out in the 10 km long Plabutschtunnel near Graz, Austria for a period of six weeks in November 1998 and another four weeks in May 1999. A UV- DOAS-system was operated in open-path mode located some 4 km inside the tunnel with pathlengths of 220 m to 430 m. To have an idea about the uniformity of the pollutant air mixture within the path, a comparison of NO₂ measurements performed with a standard chemiluminescent analyser (point measurement) and the DOAS system (open-path measurement) was done. Therefore a standard air quality monitoring-system (AQM) in a container was installed in a niche inside the tunnel on one end of the DOAS path. The analysis of data showed good agreement of emissions derived from the measurements with the existing PC and HDV emission factors for CO. This was not the case for benzene and NO_x emissions obtained from heavy duty vehicles.

12 The detection of benzene and other organic compounds in vehicle exhaust by FT-IR-spectroscopy is seriously limited by the strong interference of carbon dioxide and the rather weak absorption coefficient of the gases. Therefore, a measurement device was developed which separates the components of interest (mostly VOCs) from carbon dioxide, water and nitric oxide. In addition the VOCs have to be pre- concentrated. To avoid condensation of VOCs the measurements have to take place at higher temperatures. The vehicle exhaust was led through an activated charcoal tube where the organic compounds were adsorbed. Afterwards, the charcoal tube was heated in a furnace, the VOCs were desorbed thermically and were carried by (heated) nitrogen into a gas cell with a path-length of 10 m where the concentration of the different species was measured. With the help of this measurement device a lot of VOC- components like benzene, toluene, and xylene were detected successfully. Measurements were performed on an engine test bed and a chassis dynamometer for heavy duty vehicles. The detection limit of most of the VOCs was about 2 to 3 ppb for a sampling time of 20 min. Calibration measurements showed an accuracy of 15%.

12 Hyperspectral images are becoming more common and have considerable information content. Analysis tools must keep up with the changing demands and opportunities posed by the new datasets. Traditional tools such as image compression, and classification, both supervised and unsupervised, can be improved. Newly developed tools will enhance the commercial value of the data (e.g. tools capable of objective data cube quality evaluation). This paper discusses several new or improved analysis tools developed for use with hyperspectral images. The algorithm fundamental to many of these tools is the Spectral Similarity Scale (SSS). The SSS is an objective measure of spectral distance that quantifies differences in both magnitude (albedo) and direction (shape). This is a fundamental improvement in the description of distance between two spectra. The toolset described in this paper consists of: 1) image quality evaluation, which is an objective measurement of information content, image complexity, and subtlety; 2) hyperspectral image compression, which facilitates image storage and transmission; 3) processing-induced spectral change objectively quantifies spectral changes caused by image processing such as lossy compression. Using the SSS as the measure of spectral distance improves the performance of both supervised classification and unsupervised classification algorithms.