The paper describes the system implementation for SPECTRA, which is one of the candidates for the future ESA Earth Explorer Core Missions. The system will enable observations of defined land targets in various spectral bands from the Visible into the Thermal IR and with variable directions of observations. These observations will provide samples of the Bi-directional Reflectance Distribution Function of vegetation. To monitor variations in time of the vegetation properties, the observations will be performed with a revisit of 3 days, assuming cloud-free conditions.

EarthCARE is one of the candidates for the future ESA Earth Explorer Core Missions. The mission major objective is to determine, in a radiatively consistent manner, the global distribution of vertical profiles of cloud and aerosol field characteristics. A major innovation of the EarthCARE mission is to include both active and passive instruments together on a single platform, which allows a complete 3-D spatial and temporal picture to be developed of the radiative flux field at the top of the atmosphere and the Earth's surface. While the active instruments provide vertical cloud profiles, the passive instruments (mainly the multi-spectral imager) provide supplementary horizontal data to allow extrapolation of the 3-D cloud and aerosol characteristics. The EarthCARE payload is composed of five instruments: an Atmospheric Lidar, a Cloud Profiling Radar, a Fourier Transform Spectrometer, a Multi-Spectral Imager and a Broad Band Radiometer. The mission baseline is a sun synchronous orbit with 10.30 descending node crossing time and an altitude around 400 km. EarthCARE is an ESA mission proposed in collaboration with NASDA.

WALES (Water vapour Lidar Experiment in Space) is one of the three candidate missions that are currently considered for the future ESA Earth Explorer missions. The objective of the mission is to provide better insight into the distribution of water vapour and aerosol in the upper troposphere and lower stratosphere for research and applications in climatology and numerical weather prediction. This is to be achieved by providing globally accurate profiles of water vapour concentration. A direct detection Differential Absorption Lidar has been studied in the frame of the WALES mission pre-phase A. The lidar is based on high power laser emitting several wavelengths in the 920-950 nm range, each wavelength being tunable and frequency locked. The backscatter signal is collected through a large telescope and filtered through narrow band filters. The concept and the expected performance of the instrument are discussed in this paper.

WALES is one of the three candidate missions that are currently considerd for the future ESA Earth Explorer missions. The objective of the mission is to provide better insight into the distribution of water vapor and aerosol in the upper troposphere and lower stratosphere for research and applications in climatology and numerical weather prediction. This is to be achieved by providing globally accurate profiles of water vapor concentration. A direct detection Differential Absorption Lidar has been studied in the frame of the WALES mission pre-phase A. The lidar is based on high power laser emitting several wavelengths in the 920-950 nm range, each wavelength being tunable and frequency locked. The backscatter signal is collected through a large telescope and filtered through narrow band filters. The concept and the expected performance of the instrument are discussed in this paper.

The ALADIN Instrument is a Doppler Wind Lidar, which will be launched in 2007 aboard the ESA Core Explorer Aeolus Mission. The main purpose of this payload is the measurement of tropospheric wind profiles on a global scale. The concept is based on a solid-state Nd:YAG laser associated with a direct detection frequency receiver. Astrium-SAS is prime contractor for the development of ALADIN. This program includes in particular the development of a Pre Development Model for the critical parts of the instrument. This paper describes the flight instrument design and reviews the achievements of the PDM activities: this will cover in particular the development status of the engineering models of the CCD detectors, front-end units and spectrometers.

Global Change Observation Mission (GCOM) is a follow on mission of ADEOS, ADEOS2 and TRMM. 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 geo-physical parameters which are critical to understand global change phenomena, especially phenomena related to climate change. Those parameters include, but not limited to, optical thickness of aerosols and clouds, water and energy fluxes, carbon fluxes, sink and source of greenhouse gases, etc. The measurements of geophysical parameters will continue more than 15 years after the launch of ADEOS2. The first generation satellites of GCOM after ADEOS2 is now composed of 3 satellites, i.e. GCOM-A1, GCOM-B1, and GPM core satellite. The target of GCOM-A1 is to monitor stratospheric and upper tropospheric greenhouse gases and ozone as well as ozone related constituents. The target of GCOM-B1 is to measure geophysical parameters which are uncertain in the today's climate models. GPM core satellite is a follow on of TRMM and the target of GPM core satellite is to measure precipitation. GPM mission is composed of GPM core satellite and 8 constellations of microwave radiometers. GCOM-A1 will carry 3 instruments, i.e. OPUS (Ozone and Pollution Ultra-violet Sounder), SOFIS (Solar Occultation Fourier Interferometric Sounder : ILAS follow on), and SWIFT (Stratospheric Wind Interferometer). GCOM-B1 will carry three core instruments, i.e. SGLI (GLI follow on), AMSR2 (AMSR follow on) and alpha-Scat (SeaW-inds follow on). Other instruments may be added based on an AO process. GPM core satellite will carry 2 instruments, i.e. DPR (Dual Precipitation Radar) and a microwave radiometer. The orbit of GCOM-B1 will be a sun synchronous orbit, which is almost the same as ADEOS2. The orbits of GCOM-A1 and GPM core satellite will be around 70 degree inclination orbit and the altitudes will be 700km and 400km, respectively. These 3 satellites are planned to be launched in 2008.

The SWIFT instrument is an imaging, field-widened Michelson interferometer designed to measure stratospheric winds passively from orbit by detecting the Doppler shift of naturally occurring O3 thermal emission. It has been selected for flight on NASDA's GCOM-A1 satellite, scheduled for launch in 2007. It is similar in principle to the Wind Imaging Interferometer (WINDII) on UARS but whereas WINDII operates in the visible with a CCD detector, SWIFT will operate at a wavelength of 8.823μm and use a HgCdTe array detector. This spectral region is very crowded with emission lines and a substantial effort was needed to select appropriate candidate lines. Designing filters for this instrument has also proved to be challenging because of the narrow bandwidth required to isolate the emission line, combined with the need to fill the field of view and minimize the effects of thermal drifts. SWIFT will carry blackbody sources for responsivity calibrations and three NH₃ cells that provide a narrow emission line to be used as a secondary phase standard. This paper discusses the design of the filters for SWIFT and associated calibration issues.

Of all the water on the Earth, only 3% is drinkable and two thirds of that water is locked away in polar ice. Precipitation constantly renews our fresh water resources and the latent heat it releases is the principal source of energy that drives atmospheric circulation and weather disturbances. It is the principal indicator of the rate of global water cycle and can also be used effectively as input for numerical weather forecasting. The Global Precipitation Measurement (GPM), a cooperative effort of the National Aeronautics and Space Administration (NASA) and Japan's National Space Development Agency (NASDA), aims to gather precipitation and related data globally. It will build upon the legacy of the extremely successful Tropical Rainfall Measuring Mission and will extend the spatial and temporal coverage of precipitation measurement to identify trends in the Earth's global water cycle, further explore the structure of rainfall to improve efforts to predict climate, and provide high quality rainfall accumulation products. GPM envisions a core satellite, up to eight constellation satellites, local ground validation sites and regional high quality rain gauge networks, and a global precipitation data system. It is anticipated that NASDA will provide the core satellite's dual frequency precipitation radar, its launch vehicle, and a constellation satellite. GPM's flexible architecture enables other international and domestic participants to provide enhancements incrementally as plans permit. The European Space Agency (ESA) is currently studying contribution satellite, EGPM, as an Earth Explorer Opportunity Mission. GPM is now in the Formulation Phase and is one of the highest priorities among the new missions for which NASA's Earth Science Enterprise seeks final approval. GPM launches are targeted to begin in 2007.

Even the youngest child knows that the sea is salty. Yet, routine, global information about the degree of saltiness and the distribution of the salinity is not available. Indeed, the sea surface salinity measurement is a key missing measurement in global change research. Salinity influences circulation and links the ocean to global change and the water-cycle. Space-based remote sensing of important global change ocean parameters such as sea-surface temperature and water-cycle parameters such as precipitation have been available to the research community but a space-based global sensing of salinity has been missing. In July 2002, the National Aeronautical and Space Administration (NASA) announced that the Aquarius mission, focused on the global measurement of sea surface salinity, is one of the missions approved under its ESSP-3 program. Aquarius will begin a risk-reduction phase during 2003. Aquarius will carry a multi-beam 1.4 GHz (L-band) radiometer used for retrieving salinity. It also will carry a 1.2 GHz (L-band) scatterometer used for measuring surface roughness. Aquarius is tentatively scheduled for a 2006 launch into an 8-day Sun-synchronous orbit. Aquarius key science data product will be a monthly, global surface salinity map at 100 km resolution with an accuracy of 0.2 practical salinity units. Aquarius will have a 3 year operational period. Among other things, global salinity data will permit estimates of sea surface density, or buoyancy, that drives the ocean's three-dimensional circulation.

The NASA NPOESS Preparatory Project (NPP) is designed to collect radiometric data to make comprehensive measurements of atmospheric temperature and humidity, and cloud and aerosol properties. NPP will provide NASA with continuation of global change parameters after the Earth Observing System Terra and Aqua missions. In addition, NPP will provide a pre-operational risk reduction demonstration and validation of three critical instruments for the National Polar-Orbiting Operational Environmental Satellite System (NPOESS). NPP is a joint mission with NASA, NOAA, and the Department of Defense. NPP will launch in 2006 and operate in a sun synchronous descending node orbit, with a 10:30 AM equator crossing time. This paper discusses the NPP mission and the design of the satellite. The key Earth System Science observations that are to be taken are highlighted, along with the key Environmental Data Records (EDRs) that NPP will provide. The Key EDRs for which NPP will provide data are vertical moisture profile, vertical temperature profile, imagery, sea surface temperature, and soil moisture. The mission concept, including the satellite and ground system architecture, combines elements provided by NASA, the DoD, and NOAA. One of the driving requirements is providing complete EDRs within 180 minutes of observation, with a goal of within 90 minutes or less. For the NPOESS spacecraft the goal is 15 minutes from time of observation.

NASA's Earth Science Mission Operations and Systems (ESMOS) Project is responsible for developing and operating sensor data capture, processing and delivery systems on behalf of NASA's Earth Science Enterprise (ESE). As the volume of sensor data being collected by the next generation of Earth observing satellites continues to dramatically increase, the demand for timely data delivery has correspondingly increased. The ESMOS Project has utilized a variety of techniques and methodologies to provide sensor data to the end user, and has collected a series of lessons learned with regard to the most efficient implementations based on the needs of the end user. This paper discusses the successes achieved and the pitfalls encountered by NASA, NOAA and ESA and makes recommendations for changes and enhancements to maximize future mission sensor data processing.

ASTER (Advanced Thermal Emission and Reflection Radiometer) was launched on December 19th, 1999, from Vandenberg, California, USA, and has been circulating the Earth on a NASA platform called Terra. After the Initial Checkout Phase, ASTER started the normal operation on September 20th, 2000, and ERSDAC started ASTER data distribution on December 1st, 2000. Data Acquisition by ASTER is quite stable at a daily rate of about 600 scenes. The resulting total number of acquired scenes is 439 thousands scenes as of June 28th, 2002. This number is equivalent to more than ten times the number of scenes covering all the land areas on the earth. ASTER GDS takes an operational sequence in which the observation schedule is updated by using Cloud Prediction Data immediately before the observation. Therefore, this scheduling operation allows us to acquire the data with less cloud cover. All the acquired data are downloaded at NASA and are shipped to ERSDAC via physical media and, for some small number, via network. All the acquired data are processed to Level 1A at ASTER GDS first, and the total number as of June 28th, 2002, is about 352 thousands scenes. Next, Level 1B processing is performed for the data requested by users and the data with less than 20% cloud cover. The total number of Level 1B data is about 80 thousands scenes as of June 28th, 2002.

An image correlation tool, which can calculate co-variance of sub-images with an arbitrary window size, was developed. The tool has been applied to the evaluation of image quality of ASTER data products. Other application to the DEM creation is presented. The tool is also promising for the image navigation method to detect the attitude fluctuation of the satellite.

The advanced spaceborne thermal emission and reflection radiometer (ASTER) was developed by the MInistry of Economy, Trade and Industry (METI) for installation in the EOS-AM1 spacecraft. 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 the infrared detectors for the SWIR and TIR subsystems. Two cryocoolers have been operating in orbit for over 22000 hours. The temperature of each detector was stabilized in the allowable temperature range. Long-term data have been acquired on the cooling performance and power consumption under normal operation for each cryocooler, the following are described; outline of ground test results and performance of the ASTER cryocooler in orbit for over 22000 hours.

The Atmospheric IR Sounder (AIRS) on the EOS Aqua spacecraft is an IR spectrometer/radiometer which covers the 650-2700 cm^-1 region of the spectrum with 2378 spectral channels. The EOS Aqua was launched on 4 May 2002 from Vandenburg AFB, California, in to a 705km high, sun synchronous orbit. First test of the radiometric calibration using the analysis of (observed-calculated) for data from a single, relatively cloud free 2500×2500 km area of the subtropical Atlantic ocean confirm absolute radiometric accuracy of better than 0.5K. The spectral information in the data also suggests that the analyzed region contained more moisture than the NCEP analysis. Based on these results we expect that the assimilation of AIRS data into the forecast to result in major medium range weather forecast improvements and that the data set recorded by AIRS during its nominal seven year lifetime will be a major resource for climate studies.

Recently the performance verification phase of the Ozone Monitoring Instrument (OMI) was successfully completed and the calibration has started. The OMI is a next generation imaging spectrograph suitable for trace gas retrieval using the UV-Visible wavelength range. The instrument combines a wide field-of-view (114 degrees) with high spatial resolution enabling trace gas retrieval in the troposphere and providing continuous monitoring. The paper summarises the important performance aspects for the OMI such as the spectral, radiometric, polarisation, viewing and stray light properties of the instrument. It focuses on some aspects that we consider of particular importance such as polarisation scrambling and diffuser features. These features can potentially mix with trace gas absorption features and thereby form error sources. Historically an important issue is the spectral stray light at the steep gradient in the Earth shine radiance around 300 nm. In this paper we show that OMI has a very good stray light performance at these wavelengths. The OMI will be launched on NASA's EOS-AURA satellite early 2004.

This paper focuses on the 'spectral' aliasing phenomenon that may produce distortions on remotely sensed spectra acquired by hyper-spectral push-broom sensors and that arises because of an inadequate sampling rate. The analysis of the aliasing appearance has been performed on a set of at-sensor radiance spectra computed stemming from some spectral libraries with spectral resolution sufficiently high for our aims. A general procedure to evaluate aliasing in spectral remote sensing data has been proposed. A model for the system modulation transfer function of a hyper-spectral push-broom sensor (like PRISM) has been developed by taking into account the different contributions due to optics, electronics, detector, spectrometer dispersion. By using this sensor model, the set of high resolution spectra has been processed in order to obtain the related set of simulated acquired spectra; also a corresponding set of not aliased spectra has been produced. Several score indexes have been considered among those proposed in literature and the three most effective have been implemented and applied to evaluate the aliasing produced in the acquired data. Aliasing evaluation has been first performed onto the simulated spectra without atmospheric and radiometric correction. Afterwards 'ideal' correction based on the knowledge of the ground irradiance and the atmospheric transmittance spectrum has been implemented, hence the aliasing evaluation has been performed also onto the reconstructed set of spectra (atmospherically and radiometrically corrected). Results are presented in the paper. To remove the constraints of the 'ideal correction', a simple atmospheric correction model has been implemented and applied to the simulated spectra radiometrically corrected; a qualitative evaluation of the reconstructed spectra has been performed.

A new airborne imaging spectrometer introduced: the ARES (Airborne Reflective Emissive Spectrometer) to be built by Integrated Spectronics, Sydney, Australia, financed by DLR German Aerospace Center and the GFZ GeoResearch Center Potsdam, Germany, and will be available to the scientific community from 2003/2004 on. The ARES sensor will provide 160 channels in the solar reflective region (0.45-2.45 μm) and the thermal region (8-13 μm). It will consists of two separate coregistered optical systems for the reflective and thermal part of the spectrum. The spectral resolution is intended to be between 12 and 15 nm in the solar wavelength range and should reach 150nm in the thermal. ARES will be used mainly for environmental applications in terrestrial ecosystems. The thematic focus is thought to be on soil sciences, geology, agriculture and forestry. Limnologic applications should be possible but will not play a key role in the thematic applications. For all above mentioned key application scenarios the spectral response of soils, rocks, and vegetation as well as their mixtures contain the valuable information to be extracted and quantified. The radiometric requirements for the instrument have been modelled based on realistic application scenarios and account for the most demanding requirements of the three application fields: a spectral bandwidth of 15 nm in the 0.45-1.8 μm region, and 12 nm in the 2 - 2.45 μm region. The required noise equivalent radiance is 0.005, 0.003, and 0.003 mWcm-2sr-1μm-1 for the spectral regions 0.45-1 μm, 1 - 1.8 μm, and 2 - 2.45 μm, respectively.

A hyperspectral Hadamard transform imager is presented. It is based on a flat field spectrometer and a spatial light modulator. Compared to a typical dispersive pushbroom imaging spectrometer, the signal-to-noise-ratio can be increased by 1 ... 2 orders of magnitude for typical dimensions of the hyperspectral data cube. Applicable spatial light modulators include individually addressable MEMS based light modulators such as micro mirrors or newly developed micro shutters as well as mechanical slit positioning systems which are characterized by a fixed, movable pattern. In contrast to the individually addressable devices, the number of operational modes of the slit positioning system is constrained by the mask design, but high pixel numbers and high optical quality can be achieved by a mature and relatively simple micro machining technology. A detailed analysis of the relative performance of hyperspectral Hadamard transform, Fourier transform and hypothetical optimal imaging spectrometers with particular respect to the dimensions of the hyperspectral data cube and the composition of the detector noise reveals a considerable signal-to-noise advantage of the Hadamard transform imaging spectrometer over the Fourier transform imaging spectrometer for domination of read noise and a large number of spectral bands. In case the noise is dominated by dark current noise, the Hadamard transform imaging spectrometer can achieve 50% of the maximum possible sensitivity which is given by the hypothetical optimal imaging spectrometer. In contrast to the Fourier transform imaging spectrometer, the Hadamard transform imaging spectrometer is also suitable for use with short wavelengths.

SPOT5, the fifth satellite of the SPOT remote sensing satellite family was successfully launched on the 4th of May 2002. SPOT5 is designed to ensure continuity of data acquisition and space image services but also to provide users with advanced products. It flies two identical cameras named HRG (High Resolution Geometry) providing a 2.5 m and a 5 m resolution in a panchromatic mode and a 10 m resolution in a multi-spectral mode, still keeping a 60-km ground field. Stereo application is part two of the SPOT5 mission; the satellite flies a specific High Resolution Stereo instrument (HRS) made up of two telescopes allowing a 20° fore view and a 20° aft view over a 120-km swath, sampling the landscape every 5m. VEGETATION2, a wide field of view imaging radiometer complements the mission thanks to its daily coverage of the earth. The paper presents the mission, the commissioning phase that followed the satellite launch, the assessment of the image quality and the first calibration results.

In order to increase SPOT5 panchromatic resolution, CNES adopted in 1995 a quincunx sampling mode named THR: two CCD linear arrays shifted in the focal plane deliver two images shifted by 0.5 pixel. Such a sampling scheme has been shown to meet Shannon sampling requirement at first order, thus optimizing the whole system. Meeting Shannon requirement means blurred images, since the MTF has low values at Nyquist frequencies. This leads to a complex on ground THR processing chain, including three steps : quincunx interleaving/interpolation, deconvolution and denoising. The first two steps consist of convolutions which are realized in the Fourier domain but the third one uses a complex spatial-frequency analysis thanks to a wavelet packet decomposition. During the in-flight commissioning period which starts immediately after launch and spreads over two months, the best fitted THR processing chain parameters have been computed to assess the image quality of the final THR restored product. The goals of this paper is to present the principles of the THR sampling mode, to detail how the in-flight commissioning of SPOT5 THR mode has been realized and to present its conclusions.

The SPOT5 remote sensing satellite was launched in May 2002. It provides SPOT service continuity above and beyond SPOT4 operation but the SPOT5 system also significantly improves the SPOT service with the new characteristics of its two HRG (High Resolution Geometry) cameras and its HRS (High Resolution Stereo) camera. SPOT5's first two months of life in orbit were dedicated to instrument calibration and the assessment of image quality performances. During this period, the CNES team used specific target programming to compute image correction parameters and estimate the performance of the image processing chain, at system level. This paper focuses on the relative radiometric performances of the different spectral bands for the three instruments, deduced from in-flight measurements. For each spectral band, a radiometric model gives the ratio between detector response and input radiance. This model takes the architecture of the onboard image chain into account. Calibration provides the normalisation parameters (dark currents and relative inter-detector sensitivities) used to correct the images. The quality of the corrected images is quantified through several signal-to-noise ratio measurements based on different techniques. These methods are presented and their accuracy is discussed. Finally, a comparison is given between flight measurements and ground measurements.

As compared to other SPOT satellites, SPOT5 geometric accuracy is improved : a stellar sensor unit allows absolute location accuracy of 60 meters; geometric resolution is 10 meters for multispectral mode, 5 meters for panchromatic mode and 2,5 meters for THR mode; HRS along track stereoscopic mode leads to 10 meters accuracy digital terrain models. This paper presents the results of in-flight geometric characterization of SPOT5 remote sensing satellite established during the first two months of SPOT5's life in orbit. Calibration of the viewing model has been performed : platform's biases and modelization of mirror positioning are measured thanks to a triangulation process using images acquired on several targets around the world chosen for their referential ground control points. Geometric performances of THR mode was precisely measured thanks to the comparison of the two images of the quincunx mode. Multispectral registration was measured using correlation methods. The viewing model includes a description of the focal plane with each detector viewing angle. This description was improved for HRS and HRG cameras thanks to a reference composed of a set of aerial photographs. Finally, a first evaluation of HRS' DTM accuracy has been done by comparison to a reference DTM over FRANCE.

The MTF (Modulation Transfer Function) is a means of characterizing the spatial resolution of the instruments. So, the MTFs of HRG and HRS cameras are parts of image quality parameters assessed during the in-flight commissioning phase. Vibrations during the launch and transition from air to vacuum may defocus the HRG cameras and degrade their MTF. Therefore, SPOT5 HRG cameras are refocused before measuring their MTF. The paper first describes the HRG focusing procedure that uses both cameras viewing the same landscape: the focus of one camera is changed while the other is fixed and used as a reference. Results are given for each camera in terms of best focus and focus variation in the field of view. These results are compared to those provided by an autotest system, on-board each HRG camera, that images a high frequency periodic pattern while the focus is changed. Then, MTF measurements are presented. The MTF of HRG cameras is measured by imaging a spotlight that aimed at the satellite; the results are compared with pre-flight measurements. Besides, the MTF of HRS cameras is assessed by imaging landscapes with edge patterns; the main objective is to compare the two HRS cameras.

The European Space Agency has undertaken exploratory studies to define future space borne microwave instruments for application in numerical weather prediction (NWP) and climate research in the 2015 to 2020 time frame. Teams involving scientist and industrial partners were following an approach that in a first stage reviewed and defined the user requirements for both applications. NWP requires mainly existing observables at an improved spatial and temporal resolution, and in addition operational observation of ice clouds. Climate user requirements are quite similar but do not call for the same temporal resolution and additionally observations of cirrus and surface parameters are needed. The user requirements were translated into system requirements that, at this point appear challenging but in most cases feasible in the envisaged time frame. The industrial teams traded the user requirements, system requirements and implementation issues. The derived mission and instrument concepts include improved cross-track sounders with AMSU heritage as well as conical scanning instruments (partly including sounding capabilities) on polar orbiting platforms.

This paper reports about the status of the actual performance prediction and some selected investigations within the system engineering for the TerraSAR-X satellite, which will be implemented in a Public-Private-Partnership between the German Aerospace Center (DLR) and the ASTRIUM GmbH. The main sensor parameters and modes of operation are summarized. Image simulations based on X-band data from the E-SAR sensor of DLR give an impression on the expected image quality with respect to geometric and radiometric resolution. Different realization possibilities for the dual polarization mode are investigated and the actual baseline for this mode is described. The potential of two independent receiving channels is analyzed and the paper reports about possible additional features as investigated so far.

The goal of the NASA/NASDA GLobal Precipitation Mission (GPM) is to provide frequent global rainfall observations, using a satellite cluster based on a 'core' platform and a number of 'drone' satellites large enough to provide a repeat observation cycle of about 3 hours. ESA has proposed a contribution to GPM in the form of a drone satellite, with a scheduled launch foreseen by 2007. The 'E-GPM' Drone satellite is currently studied within the frame of the ESA Earth Opporutnity Missions Program, and involves many innovative aspects, among which are: (i) a 5 band, 13 channel conical scan radiometer, operating at 18.7, 23.8, 36.5, 89 and 157 GHz for rainfall water content and ice content estimation of the atmosphere; (ii) a Nadir pointing Precipitation Radar embarked in order to enhance the overall accuracy of precipitation estimates, operating at 35.6 GHz. The radar will provide high quality estimates of vertical profile precipitation; (iii) an implementation on a small satellite based on Alcatel's multi-mission PROTEUS Platform, already flying with the JASON altimetry satellite launched in 2001. This presentation summarizes the definition of the E-GPM satellite, from the scientific requirements to the satellite and instrument design, performance, and budget.

The primary mission of a wind scatterometer is to determine wind speed and direction over the ocean. This is achieved by performing a set of radar cross-section measurements at different azimuth view-angles over the resolution cell, and inverting the backscatter model, a so-called geophysical model function (GMF), to extract the wind information using the azimuth anisotropy of the radar backscatter by sea-surface in presence of wind. A new concept of rotating fanbeam radar was introduced which operates in C-band. The present paper describes an analysis of the new concept by means of wind retrieval simulations and an investigation of advanced features such as multi-beam, dual-polarisation, dual-frequency and polarimetric capabilities in improving the wind retrieval accuracy. End-to-end simulations of the complete system are performed starting from wind-fields which are sampled by the scatterometer model. The simulated radar echos are then converted to sets of backscattering coefficients (sigma-naught) which are inverted to obtain again the wind-fields containing measurement errors and noise. The performance of the system is assessed by analysing the quality of retrieved wind as functions of the instrument configuration and characteristics (parameters).

The non-linear electric field dependence of ferroelectric thin films can be used to design frequency and phase agile components. Tunable components have traditionally been developed using mechanically tuned resonant structures, ferrite components, or semiconductor-based voltage controlled electronics, but they are limited by their frequency performance, high cost, hgih losses, and integration into larger systems. In contrast, the ferroelectric-based tunable microwave component can easily be integrated into conventional microstrip circuits and attributes such as small size, light weight, and low-loss make these components attractive for broadband and multi-frequency applications. Components that are essential elements in the design of a microwave sensor can be fabricated with ferroelectric materials to achieve tunability over a broad frequency range. It has been reported that with a thin ferroelectric film placed between the top conductor layer and the dielectric material of a microstrip structure, and the proper DC bias scheme, tunable components above the Ku band can be fabricated. Components such as phase shifters, coupled line filters, and Lange couplers have been reported in the literature using this technique. In this wokr, simulated results from a full wave electromagnetic simulator are obtained to show the tunability of a matching netowrk typically used in the design of microwave amplifiers and antennas. In addition, simulated results of a multilayer Lange coupler, and a patch antenna are also presented. The results show that typical microstrip structures can be easily modified to provide frequency agile capabilities.

The Robotic Lunar Observatory (ROLO) project has developed a spectral irradiance model of the Moon that accounts for variations with lunar phase through the bright half of a month, lunar librations, and the location of an Earth-orbiting spacecraft. The methodology of comparing spacecraft observations of the Moon with this model has been developed to a set of standardized procedures so that comparisons can be readily made. In the cases where observations extend over several years (e.g., SeaWiFS), instrument response degradation has been determined with precision of about 0.1% per year. Because of the strong dependence of lunar irradiance on geometric angles, observations by two spacecraft cannot be directly compared unless acquired at the same time and location. Rather, the lunar irradiance based on each spacecraft instrument calibration can be compared with the lunar irradiance model. Even single observations by an instrument allow inter-comparison of its radiometric scale with other instruments participating in the lunar calibration program. Observations by SeaWiFS, ALI, Hyperion and MTI are compared here.

The MODIS Protoflight Model (PFM) on-board the Terra spacecraft has been in operation for more than two and half years since its launch on December 18, 1999. In addition to the on-board calibrators (OBCs), the observations of the moon have been planned monthly with carefully chosen viewing conditions. The data from these observations is used to support the instrument's on-orbit calibration and characterization. In this paper, we describe the use of lunar observations for monitoring the MODIS reflective solar bands (RSB) radiometric stability and discuss related applications. For Terra MODIS, the lunar views have also been used to derive correction parameters for the optical leak among the photoconductive (PC) detectors (bands 31-36), to characterize the electronic crosstalk under different focal plane operational configurations, and to track on-orbit band-to-band registration (BBR). The same strategies are being applied to the Aqua MODIS (Flight Model 1 - FM1) launched on May 4, 2002. The lunar observation results from both instruments are compared.

Launched in April 1999, the Landsat-7 ETM+ instrument is in its fourth year of operation. The quality of the acquired calibrated imagery continues to be high, especially with respect to its three most important radiometric performance parameters: reflective band instrument stability to better than ±1%, reflective band absolute calibration to better than ±5%, and thermal band absolute calibration to better than ± 0.6 K. The ETM+ instrument has been the most stable of any of the Landsat instruments, in both the reflective and thermal channels. To date, the best on-board calibration source for the reflective bands has been the Full Aperture Solar Calibrator, which has indicated changes of at most -1.8% to -2.0% (95% C.I.) change per year in the ETM+ gain (band 4). However, this change is believed to be caused by changes in the solar diffuser panel, as opposed to a change in the instrument's gain. This belief is based partially on ground observations, which bound the changes in gain in band 4 at -0.7% to +1.5%. Also, ETM+ stability is indicated by the monitoring of desert targets. These image-based results for four Saharan and Arabian sites, for a collection of 35 scenes over the three years since launch, bound the gain change at -0.7% to +0.5% in band 4. Thermal calibration from ground observations revealed an offset error of +0.31 W/m² sr um soon after launch. This offset was corrected within the U. S. ground processing system at EROS Data Center on 21-Dec-00, and since then, the band 6 on-board calibration has indicated changes of at most +0.02% to +0.04% (95% C.I.) per year. The latest ground observations have detected no remaining offset error with an RMS error of ± 0.6 K. The stability and absolute calibration of the Landsat-7 ETM+ sensor make it an ideal candidate to be used as a reference source for radiometric cross-calibrating to other land remote sensing satellite systems.

The Remote Sensing Group at the University of Arizona has recently shown the successful use of a cross-comparison approach between the high spatial resolution sensor Enhanced Thematic Mapper Plus (ETM+) on the Landsat-7 platform and the 1-km footprint of the Moderate Resolution Imaging Spectroradiometer (MODIS). This work showed that these two sensors compared to better than 5% in solar reflective bands not affected by atmospheric absorption. In this paper, the work is extended to include the 1-km spatial resolution sensor SeaWiFS as part of a three-way comparison. The method described here relies on data ground-based reflectance data to estimate the surface reflectance in the MODIS and SeaWiFS bands based on surface reflectance data derived from ETM+. The cross-comparison takes into account changes in solar zenith angle due to the time separation in overpass times of the three sensors and the differing view angles between SeaWiFS and the other two sensors (MODIS and ETM+, while 40 minutes apart view the test site with the same view angle). Also included are corrections due to the spectral differences between the sensors. Results show that the at-sensor reflectance agrees to better than 4% in the solar reflective for bands not affected by atmospheric absorption and view angles out to 35 degrees.

Aqua MODIS, also known as the MODIS Flight Model 1 (FM1), was launched on May 4, 2002. It opened its nadir aperture door (NAD) on June 24, 2002, beginning its Earth observing mission. In this paper, we present early results from Aqua MODIS on-orbit calibration and characterization and assess the instrument's overall performance. MODIS has 36 spectral bands located on four focal plane assemblies (FPAs). Bands 1-19, and 26 with wavelengths from 0.412 to 2.1 microns are the reflective solar bands (RSB) that are calibrated on-orbit by a solar diffuser (SD). The degradation of the SD is tracked using a solar diffuser stability monitor (SDSM). The bands 20-25, and 27-36 with wavelengths from 3.75 to 14.5 microns are the thermal emissive bands (TEB) that are calibrated on-orbit by a blackbody (BB). Early results indicate that the on-orbit performance has been in good agreement with the predications determined from pre-launch measurements. Except for band 21, the low gain fire band, band 6, known to have some inoperable detectors from pre-launch characterization, and one noisy detector in band 36, all of the detectors' noise characterizations are within their specifications. Examples of the sensor's short-term and limited long-term responses in both TEB and RSB will be provided to illustrate the sensor's on-orbit stability. In addition, we will show some of the improvements that Aqua MODIS made over its predecessor, Terra MODIS (Protoflight Model - PFM), such as removal of the optical leak into the long-wave infrared (LWIR) photoconductive (PC) bands and reduction of electronic crosstalk and out-of-band (OOB) thermal leak into the short-wave infrared (SWIR) bands.

ENVISAT, ESA's ENVironmental research SATellite, has been launched successfully on 1 March 1st 2002. On-board, MEdium Resolution Imaging Spectrometer MERIS, is responding nominally. The results from the first six-months of in-flight verification and characterization of the instrument will be presented. The evolution of the instrument radiometric response based on the radiometric calibration results using the on-board diffusers will be discussed. The results from dedicated spectral characterization campaigns based on the spectral features of the sun (Fraunhofer), atmospheric oxygen and Erbium (doped diffuser) will be presented, and the instrument's spectral model derived will be discussed.

The measurement and long-term monitoring of global total ozone by ultraviolet albedo measuring satellite instruments require accurate and precise determination of the Bi-directional Reflectance Distribution Function (BRDF) of laboratory-based diffusers used in the pre-launch calibration of those instruments. To assess the ability of laboratories to provide accurate UltraViolet (UV) diffuse BRDF measurements, a BRDF measurement comparison was initiated by the NASA Total Ozone Mapping Spectrometer (TOMS) Project. From December 1998 to September 1999, NASA's Goddard Space Flight Center (GSFC), TPD TNO (formerly the TNO Institute of Applied Physics), and the National Institute of Standards and Technology (NIST) made BRDF measurements on four Spectralon diffusers used in the pre-launch calibration of three TOMS instruments. The diffusers were measured at the six TOMS wavelengths and at the incident and scatter angles used in the TOMS pre-launch calibration. The participation of GSFC, TPD TNO, and NIST in the comparison establishes a link between the diffuser calibrations of the on-orbit TOMS instruments, the Ozone Monitoring Instrument (OMI), and a national standards laboratory. The results of the comparison show that all of the BRDF measurements on the four diffusers agreed within +0.85 % to -1.10 % of the average BRDF and were well within the combined measurement uncertainties of the participating laboratories.

We present a calibration approach for the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) based on the reflectance properties of the instrument's onboard diffuser. This technique uses SeaWiFS as a reflectometer, measuring the reflected solar irradiance from the Earth and from the onboard diffuser. Since the sun is the common source of light for both measurements, the ratio of the SeaWiFS-measured radiances from the Earth and the diffuser provide the ratio for the reflectances of the two samples. The reflectance characterization of the onboard diffuser is the calibration reference for this approach. The result of the rationing technique is based on the linearity of the instrument's resopnse to the intensity of the input light. The calibration requires knowledge of the reflectance of the onboard diffuser at the start of the SeaWiFS mission, the response of the instrument bands, in digital numbers, for measurements of the diffuser at that time, and the change of the instrument's response over time after the start of the mission.

The Earth Radiation Budget Satellite carried a nonscanning radiometer package for the measurement of the solar radiative flux which is reflected by the Earth and the outgoing longwave radiation from the Earth. These fluxes are measured by wide field-of-view radiometers, which are active cavity radiometers (ACRs) having apertures which are open to radiation from the Earth from one limb to the other. The reflected shortwave radiative flux is measured by an ACR which has a quartz dome over the aperture to cut out the OLR component. The instrument has operated for over 15 years, producing an unbroken data record of Earth radiation budget form one instrument. However, the during this time the dome degraded due to diret solar radiation during sun rise and sunset at the spacecraft. The degradation is taken into account by rotating the instrument every 2 weeks so as to view the Sun, which serves as a calibration target. However, the solar dosage varies over the surface of the dome, so that its degradation is not uniform. Moreover, the spacecraft operates so as to always have one side to the Sun, so that one side of the dome gets more exposure than the other. The question then arises as to what is the pattern of solar dosage and the resulting non-uniform degradation on the measurements? This paper computes the pattern of solar exposure of the dome.

Two critical requirements of any calibration source are short and long-term operational stability and repeatability. Source monitoring is necessary in quantifying overall source performance including stability and repeatability. The NASA GSFC Code 920.1 Radiance Calibration Facility (RCF) developed a Filter Radiometer Monitoring System (FRMS) to continuously monitor the performance of its integrating sphere calibration sources. FRMS bands are in the 0.4 -2.4 μm region, with several bands selected to coincide with common remote sensing bands. The FRMS was designed and fabricated in the year 2000. Early in 2001, the FRMS was reconfigured prior to being deployed on the RCF 180cm integrating sphere. This paper describes the instrument modifications resulting from the FRMS reconfiguration and presents FRMS monitor data for three RCF integrating sphere sources.

NPL, in conjunction with many NMIs, has been seeking to improve the accuracy of its primary scales of spectral irradiance and radiance. In common with other laboratories this has been done through the use of an ultra-high temperature blackbody characterized using filter radiometers calibrated against a cryogenic raediometer. While such work is of importance to the Earth Observation community, it is also recognized that of at least equal importance is an improvement in the quality of the scales that are provided to the end user. This paper will describe new transfer standard sources of both spectral radiance and iradiance that have been developed not only to improve accuracy to the end user, but also to provide it in a form that is both robust and convenient to use. For example the radiance source has a spatial non-uniformity of <0.05% over a 50 mm diameter aperture and can maintain its accuracy for more than 100 hrs of operation.

The Traceable Radiometry Underpinning Terrestrial- and Helio-Studies (TRUTHS) mission offers a novel approach to the provision of key scientific data wtih unprecedented radiometric accuracy for Earth Observation (EO) and solar studies, which will also establish well-calibrated reference targets/standards to support other SI missions. This paper will present the TRUTHS mission and its objectives. TRUTHS will be the first satellite mission to calibrate its instrumentation directly to SI in orbit, overcoming the usual uncertainties associated with drifts of sensor gain and spectral shape by using an electrical rather than an optical standard as the basis of its calibration. The range of instruments flown as part of the payload will also proivde accurate input data to improve atmospheric radiative transfer codes by anchoring boundary conditions, through simultaneous measurements of aerosols, particulates and radiances at various heights. Therefore, TRUTHS will significantly improve the performance and accuracy of Earth observation misison with broad global or operational aims, as well as more dedicated missions. The providision of reference standards will also improve synergy between missions by reducing errors due to different calibration biases and offer cost reductions for future missions by reducing the demands for on-board calibration systems. Such improvements are important for the future success of strategies such as Global Monitoring for Environment and Security and the implementation and monitoring of international treaties such as the Kyoto Protocol. TRUTHS will achieve these aims by measuring the geophysical variables of solar and lunar irradiance, together with both polarized and un-polarized spectral radiance of the Moon, and the Earth and its atmosphere.

CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Spaceborne Observations) is an approved satellite mission being developed through collaboration between NASA and the French space agency CNES. The mission is scheduled for launch in 2004 and will operate for 3 years as part of a five-satellite formation called the Aqua constellation. This constellation will provide a unique data set on aerosol and cloud optical and physical properties and aerosol-cloud interactions that will substantially increase our understanding of the climate system and the potential for climate change.

The aim of this article is to estimate the revisiting time of an observated site. The revisiting time is the time elapsed between two successive possibilities of taking an image the same site by the same satellite. First, we suppose that the satellite has a cyclical and heliosynchronical orbit and that the imaging captor observes perpendicularly to the motion of the satellite. Then, we talk about how we can use the results of this algorithm to estimate the revisiting time without a computer and under the constraint of obtaining an image without a great geometrical deformation. To do this, we use the curves calculated by our algorithm and which have in x-axis the latitude of the observated site and in y-axis the view angle of the image. These results could be a great help for scientits who need to simply estimate the operationnal potential of a particular satellite in the field of short revisiting time applications.

There is a significant interest in the Earth Science remote sensing community in substantially increasing the number of observations relative to the current frequency of collection. The obvious reason for such a push is to improve the temporal and surface coverage of measurements. However, there is little analysis available in terms of benefits, costs and optimized set of sensors needed to make these necessary observations. This is a complex problem that should be carefully studied and balanced over many boundaries. For example, the question of technology maturity versus users' desire for obtaining additional measurements is noncongruent. This is further complicated by the limitations of the laws of physics and the economic conditions. With the advent of advanced technology, it is anticipated that developments in spacecraft technology will enable advanced capabilities to become more affordable. However, specialized detector subsystems, and precision flying techniques may still require substantial innovation, development time and cost. Additionally, the space deployment scheme should also be given careful attention because of the high associated expense. Nonetheless, it is important to carefully examine the science priorities and steer the development efforts that can commensurate with the tangible requirements. This paper outlines a possible set of architectural concepts, operational scenarios and potential benefits of one scheme versus another. It further makes some suggestions where one can draw boundary conditions to incrementally solve this predicament.

A spectrometer named Radiation Explorer in the Far InfraRed (REFIR) is being proposed for a future space mission aimed at the spectral measurement in the far infrared of the Earth outgoing emission, with particular attention at the spectral regions that are not covered by any current or planned space mission. The instrument requirements include continuous operation in the spectral range of 100-1100 cm^-1 with a resolution of 0.5 cm^-1, 6.5 s acquisition time, signal-to-noise ration better than 100 in the ranges 400-600 and 650-800 cm^-1 and an accuracy of absolute calibration better than 0.5 K at 280 K at least in the range 400-650 cm^-1. To meet these requirements, a spectrometer based on a polarising interferometer with a new optical configuration has been designed. The main characteristics include dual input and output ports, optics of the interferometer with full tilt compensation, and measurement of both planes of polarisation of the source on a single detector. In preparation for a possible space mission, a BreadBoard version (REFIR/BB) of the Fourier transform spectrometer has been built. REFIR/BB will allow us to study the trade-off between all instrument parameters, to test the optical layout and to optimise the data acquisition strategy. In perspective the breadboard could be flown for test flight on aircraft or balloon platforms. This paper describes REFIR/BB characteristics and preliminary experimental results with particular attention to the acquisition strategy and the instrument characterisation. Tests were performed both in air, at ground level, and under vacuum.

For hot spot events as forest fires, volcanic activity or burning oil spills and coal seams a dedicate dspace instrumentation does not exist. With its successful launch end of October 2001 with the Indian Polar Satellite Launch Vehicle the German Aerospace Center starts closing this gap with the micro-satellite mission BIRD. As space segment serves a three-axis stabilized satellite of 92 kg including a contingent of over 30% for the scientific instruments. The main payload of the BIRD micro-satellite is the newly developed Hot Spot Recognition System. It's a dual-channel instrument for middle and thermal IR imagery based on cooled MCT line detectors. The miniaturization by integrated detector/cooler assemblies provides a highly efficient design. A complement for the hot spot detection is the wide-angle stereo-scanner WAOSS-B. It is a hardware re-use dedicated to vegetation and cloud assessment in the visible spectral range. Besides the main objective of hot spot detection the mission has to answer several technological questions of the operation of cooled detectors in space, special aspects of their adaptation to the satellite platform as well as their calibration.

The full commercial availability of very high resolution satellite data has opened up a number of new opportunities for the use of Earth Observation data. Today we can carry out many applications with EO data that only in the recent past were exclusive to airborne and in-situ surveys, despite the geographic limitations of such data and techniques. Satellite imagery can be acquired over any area globally, in a short time frame and at a given price, and thus can be made readily available.

The techniques for fusion of satellite images with different spatial resolutions aims to enhance the image quality, that allows a better visual interpretation. Ideally, the resulting image must keep the spectral resolution, leading to a more precise image segmentation and classification. Many different methods have been proposed to perform image fusion for medium resolution images (e.g., Landsat TM and SPOT). The launching of IKONOS satellite became possible the obtaining of high spatial resolution images (1 meter in panchromatic mode). These images have spatial information for mapping applications and analysis of urban areas. However, the multispectral images, that provide the most relevant information for thematic applications, are obtained with spatial resolution of 4 meters. This work compares the experimental results of 5 traditional methods (Band Substitution, IHS Transformation, HSV Transformation, Principal Component Substitution and High-Pass Filtering) applied to fusion of multispectral and panchromatic images of IKONOS, and evaluates the applicability of these methods for high resolution images. The analysis of the results are done by: 1) visual inspection, 2) statistical comparison by correlation coefficient, and 3) classification of the resulting image. The test area corresponds to an urban region with different types of land cover.

Method and exemplary results of modeling of light reflectance function related to sea polluted with crude oil are explained. Crude oil existing as surface film and as suspension in the bulk of water is considered. The Monte Carlo method of photons life simulation is used in order to specify upward light fluxes. Results of modeling of oil contaminants visibility in the sea indicates the role of inherent optical properties of the seawater, sun elevation, weather or sea-state - besides of obvious factors like film thickness, oil droplets concentration or depth of 'oil cloud'. On the other hand - either oil concentration or 'cloud' depth does not indicate linear relation with the value of contrast of polluted area.

The consistent end-to-end simulation of airborne and spaceborne remote sensing systems is an important task and sometimes the only way for the adaptation and optimization of a sensor and its observation conditions, the choice and test of algorithms for data processing, error estimation and the evaluation of the capabilities of the whole sensor system. The presented software simulator SENSOR (Software ENvironment for the Simulation of Optical Remote sensing systems) includes a full model of the sensor hardware, the observed scene, and the atmosphere in between. It allows the simulation of a wide range of optoelectronic systems for remote sensing. The simulator consists of three parts. The first part describes the geometrical relations between scene, sun, and the remote sensing system using a ray tracing algorithm. The second part of the simulation environment considers the radiometry. It calculates the at-sensor radiance using a pre-calculated multidimensional lookup-table taking the atmospheric influence on the radiation into account. Part three consists of an optical and an electronic sensor model for the generation of digital images. Using SENSOR for an optimization requires the additional application of task-specific data processing algorithms. The principle of the end-to-end-simulation approach is explained, all relevant concepts of SENSOR are discussed, and examples of its use are given. The verification of SENSOR is demonstrated.

There is an emerging demand for remote sensing technologies that can determine the surface characteristics of objects from the properties of reflected light. In particular, hyperspectral analysis of solar rays reflected from the Earth's surface is expected to play an increasingly important role in Earth environment observation. The National Aerospace Laboratory (NAL) has developed a new type of imaging spectropolarimeter for such analysis that uses a liquid crystal tunable filter (LCTF), and efforts are now under way to develop it into a practical aircraft or spacecraft on-board sensor system for Earth environment sensing. This paper first presents the concept and architecture of an Earth observation system using an LCTF optical sensor which can sense radiation in the 400-720 nm wavelength band. The results of laboratory experiments to evaluate the performance characteristics of the observation system, e.g. hyperspectral resolution, optional selection of the plane of polarization, etc. are then presented, and the results of preliminary image acquisition experiments that demonstrate the feasibility of acquiring of spectral images is also shown. Finally, the applicability of the LCTF spectropolarimeter to Earth observation is summarized based on the results of the laboratory and field evaluation experiments.

For the calibration of OMI a slit function measurement stimulus has been developed. The slit function is the monochromatic image of the entrance slit of the spectrometer on the detector. Accurate knowledge of this slit function for all wavelengths and field angles is very important both for the spectral calibration and for the DOAS retrieval algorithm. Determination of this function with a spectral line source is inaccurate, because of the detector resolution and incomplete, because of the limited number of discrete spectral lines, that are available. For accurate and complete measurement of the slit function an echelle monochromator has been developed, that offers a number of spectral lines, that can be scanned with a small wavelength step over the entire spectral range of OMI. The spectral bandwidth of these lines is about 0.1 x the spectral resolution of OMI and the wavelength step during scanning is even smaller. The wavelength scanning is performed by accurate rotation of the echelle. In this paper the scientific background of the slit function measurement, the stimulus and first OMI slit function calibration measurements are described.

The definition and preliminary design of a thermal imager for earth observation applications has been performed, justified by a thorough analysis of user requirements. A survey of international programmes and other sources have been used to derive the radiometric requirements at ground level. Then instrument requirements at top of atmosphere have been obtained by means of the usual split-window techniques for land and sea. Preliminary instrument radiometric performances have been estimated on the basis of a review of possible instrument concepts (detectors and scan modes). A trade-off analysis between instrument requirements and performances led to the identification of two classes of instruments - the first based on high performance, cooled infrared detectors, and the second relying on microbolometer technology, with lower performance but not constrained by the need for a cryocooler. The applications feasible by means of each of them have been identified. The chosen instrument baseline was that using uncooled microbolometers, for which the best spatial and radiometric resolution achievable has been assessed, in order to cover as many applications as possible in view of the analysis of requirements. The selected baseline has been further detailed, up to a complete outline of the instrument, in order to confirm the achievable performance and assure its feasibility.

Mitchel and O-Brien observed in 1989 that a passive satellite measurement using the oxygen A-band could exhibit a precision better than 1% when used to make a surface pressure measurement. We will present a design and performance simulation for a Fabry-Perot interferometer based instrument which should exceed this level of performance. The design is small, inexpensive and rugged.

A concept of the cryogenic-optical sensor based on competitive adaptive sensitive elements applicable to a gravity meter sensor is considered. The sensor element is based on a magnetic levitation phenomenon, high-precision optical registration of levitating body mechanical coordinates, and robust signal processing tools. A controlled self-bearing probe dynamics is analyzed. An optimization approach to highly sensitive measurement of weak signal is presented. An optimization method which allows the extraction of the Lyapunov exponents from nonlinear chaotic dynamics of a macroscopic superconducting probe is described. Simulation results support the mathematical, and the system characteristics are thus optimized.

Many remote sensing instruments include the detection of photon/particle events, position decoding and time-of-hit measurement. Microchannel plates (MCPs) are widely used to detect photons and particles for position sensing and relative time of impact in imaging and time-of-flight (TOF) spectrometers. Two dimensional delay lines are used for fast and accurate readout of MCPs. Instruments that use these techniques are Neutral Atom Imagers and Particle Spectrometers to study planetary magnetospheres; photon counting detectors for spectrographic imaging in the far-UV and extreme-UV to study the earth's aurora and airglow; laser range finders. In all these there is a requirement of accurate and/or fast time interval measurement. An advance TOF system-on-a-chip has been developed that includes the complete signal processing electronics for MCP readout: two channels (start- stop) of amplifiers and constant fraction discriminators (CFDs), an 11-bit Time to Digital Converter (TDC), and control/readout logic. The TOF chip is capable for a time resolution of <50ps including time walk and time jitter, the dead time is as low as 0.5us; the power dissipation is a function of counting rate and time resolution-for resolution of ~100ps the power is <20mW at rates <100K/sec and <50mW at rates <1M/sec. The TOF chip flies on the NASA/IMAGE spacecraft launched in 2000 and is part of many other science instruments such as particles and fields, and laser altimeter on MESSENGER.

A brief description on the optical path and circuit of the IR system is presented. After analyzing the behavior of the pyroelectric detector detecting instrument response to the radiation, a complex performance parameter automated measurement system is put forward. And the response time is measured by the step response method, which founded the experimental basis for the detecting instrument's correct operation.

The National Aerospace Laboratory of Japan has developed a new type of optical sensor, an imaging spectropolarimeter which uses a liquid crystal tunable filter, for airborne and satellite-based remote sensing of the Earth's environment. Ground-based field experiments conducted as a preliminary to flight evaluations have demonstrated the feasibility of acquiring spectral images of objects irradiated by solar rays, and confirmed that solar rays reflected from different targets have characteristic spectropolarimetric properties. This paper first presents an outline of the developed spectropolarimeter. Next, the apparatus and procedures for the field experiments are described. The spectropolarimetric characteristics of solar rays reflected from a range of targets are then shown by relative radiance as the results of analyzed experimental data, and spectral images acquired at various wavelengths and polarization angles are shown. Plans to evaluate the sensor in a flight environment are described. Possible applications of the optical sensor are also introduced: observation of water quality deterioration in brackish lakes, applications to agro-environmental science, and applicability to a fish-finding system. Finally, it is concluded that results of the field experiments demonstrate that the way has been paved for determining surface characteristics from the optical sensor output.

The Infrared Atmospheric Sounding Interferometer (IASI) is a Fourier-Transform Spectrometer (FTS) that will be launched on the European METOP meteorological platform. IASI is to be used operationally to derive vertical profiles of temperature, humidity and composition of the atmosphere. This paper describes the IASI simulator model (ISM) developed in order to generate realistic instrument data measurements needed to test the signal processing algorithms as well as test performance improvement and measurement software. The simulator takes as input an atmospheric or calibration scene and a detailed description of the instrument parameters and produces a realistic sampled interferogram out of the Analog to Digital Converter (ADC). The instrument model includes all FTS relevant optical, mechanical and electronic phenomena such as: self-emission, double modulation, spectrum channel, position and time-dependent shear, position and time-dependent tilt, speed fluctuations, finite field of view, chromatism, noise, detector non-linearity, sampling laser wavelength and power fluctuations, etc. Both the science and the metrology signals are simulated. The validated models come from the heritage of a simulator developed 8 years ago for the ESA Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) that have evolved with various internal projects. A software tool coded in JAVA-2 and running on Windows based system integrates all the models. A graphical user-interface allows the edition of input parameters, the generation of intermediary results (modulation efficient, Instrument Line Shape (ILS), spectral power on the detector, etc.) and the visualization of results.

A spectroscopic camera has been developed which has spectral resolution of less than 1.5nm in the ultraviolet (UV) and visible wavelength bands (320-580 nm). Its main components are a specially coated UV objective lens, a UV Acousto-Optic Tunable Filter (AOTF) with a thermo-electric cooling system, and a imaging system based on a high-gain avalanche rushing amorphous photoconductor (HARP) developed by NHK Science and Technical Research Laboratories. Research is currently under way to develop the hyperspectral camera into a sensor package for airborne and ultimately space-based remote sensing applications. This paper presents the basic principle and configuration of the hyperspectral camera, and gives details of tests to measure its performance. The results of spectral resolution tests analyzing very close two spectra from a helium-discharge lamp demonstrate the camera's high spectral resolution performance. Full color and spectral images obtained by a spectrometry experiment are also presented to demonstrate the camera's hyperspectral capabilities.

The Scanning High-resolution Interferometer Sounder (S-HIS) instrument is a cross track scanning Fourier-transform interferometer with 0.5 wavenumber resolution. It uses three detectors to cover the upwelling earth spectrum over the range from 3.3 to 17 microns. Vibration experienced during flight on aircraft platforms can cause a significant level of spectrally correlated noise in the calibrated spectra. To allow this interferometric noise to be removed by analysis, a wavefront tilt measurement system that monitors vibration induced optical tilts has been incorporated into the S-HIS instrument. This two-axis tilt measurement system records small changes in wavefront alignment during the data collection of both scene and blackbody interferograms. In general, both amplitude-modulation and sample-position errors can result from these tilts. Here we show that the modulation errors that dominate the interferometric noise in the S-HIS shortwave band can be significantly reduced by using the wavefront tilt measurements to model and remove the interferometric errors. The validation of our vibration induced tilt error model with blackbody data demonstrates a correction technique applicable to correcting all types of scene data.

The development of a rotating detection system in space is proposed to assist in locating typical isotropicaly distributed burst-events. The system is based on several small angular openings (for example, 5 degrees opening each), bundled into a rotating detection system array, using a controlled stepper motor. A transmission device in the system will transmit the detected signals to an analyzing computer. In this work we simulated the response of rotating monitoring systems, using three different monitoring algorithms, in order to compare each system's efficiency according to its monitoring pattern. Burst-events counting on a spherical surface were simulated as a system, with a one or more detectors located on the center of a sphere. The burst-events monitoring was simulated in Monte Carlo calculations in three separate modules, describing several courses for the detectors’ angular translations. The burst-events position was randomly changed at steps analogous to the monitoring period. The scored events resulting from each of the three algorithms were very similar, for 106 steps as well as for 107 steps. Enhancing the results statistics, by a factor of ten increase of the number of burst-events in the simulations, showed that the random monitoring algorithm is a three fold more efficient scoring compare to the other two patterned monitoring algorithms.

Global transparency is founded on the Open Skies philosophy and its precept of non-discriminatory access. Global transparency implies that anyone can have anytime, anyplace access to a wide-array of remotely sensed imagery. The custom of non-discriminatory access requires that datasets of interest must be affordable, usable, and obtainable in a timely fashion devoid of political, economic or technical obstacles. Thus, an assessment of the correlation between the availability of satellite imagery and changes in governmental policies, pricing fluctuations of data, and advances in technology is critical to assessing the viability of global transparency. The Open Skies philosophy was originally proposed at the 1955 Geneva Summit to advocate mutually beneficial aerial reconnaissance missions over the USSR and the US as a verification tool for arms control and non-proliferation agreements. However, due to Cold War tensions, this philosophy and the custom of non-discriminatory were not widely adopted in the civilian remote sensing community until the commissioning of the Landsat Program in 1972. Since this time, commercial high-resolution satellites have drastically changed the circumstances on which the fundamental tenets of this philosophy are based. Since the successful launch of the first of this satellite class, the IKONOS satellite, high-resolution imagery is now available to non-US governments and an unlimited set of non-state actors. As more advanced capabilities are added to the growing assortment of remote sensing satellites, the reality of global transparency will rapidly evolve. This assessment includes an overview of historical precedents and a brief explanation of relevant US policy decisions that define non-discriminatory access with respect to US government and US based corporate assets. It also presents the dynamics of the political, economic, and technical barriers that may dictate or influence the remote sensing community's access to satellite data. In conclusion, this analysis considers strategies for balancing the dual-use nature of hyperspectral and high-resolution satellite imagery and discusses the potential impact of these policies on gloal transparency.

The Center for GeoSpatial Workforce Development is embarking on a new era in education by developing a repository of dynamic online courseware authored by the foremost industry experts within the remote sensing and GIS industries. Virtual classrooms equipped with the most advanced instructions, computations, communications, course evaluation, and management facilities amplify these courses to enhance the learning environment and provide rapid feedback between instructors and students. The launch of this program included the objective development of the Model Curriculum by an independent consortium of remote sensing industry leaders. The Center's research and development focus on recruiting additional industry experts to develop the technical content of the courseware and then utilize state-of-the-art technology to enhance their material with visually stimulating animations, compelling audio clips and entertaining, interactive exercises intended to reach the broadest audience possible by targeting various learning styles. The courseware will be delivered via various media: Internet, CD-ROM, DVD, and compressed video, that translates into anywhere, anytime delivery of GeoSpatial Information Technology education.

Cultural resource management archaeology in the United States concerns compliance with legislation set in place to protect archaeological resources from the impact of modern activities. Traditionally, surface collection, shovel testing, test excavation, and mechanical stripping are used in these projects. These methods are expensive, time consuming, and may poorly represent the features within archaeological sites. The use of remote sensing techniques in cultural resource management archaeology may provide an answer to these problems. Near-surface geophysical techniques, including magnetometry, resistivity, electromagnetics, and ground penetrating radar, have proven to be particularly successful at efficiently locating archaeological features. Research has also indicated airborne and satellite remote sensing may hold some promise in the future for large-scale archaeological survey, although this is difficult in many areas of the world where ground cover reflect archaeological features in an indirect manner. A cost simulation of a hypothetical data recovery project on a large complex site in Mississippi is presented to illustrate the potential advantages of remote sensing in a cultural resource management setting. The results indicate these techniques can save a substantial amount of time and money for these projects.

At present retrieval methods in remote sensing image database are mainly based on spatial-temporal information. The increasing amount of images to be collected by the ground station of earth observing systems emphasizes the need for database management with intelligent data retrieval capabilities. The purpose of the proposed method is to realize a new content based retrieval system for remote sensing images database with an innovative search tool based on image similarity. This methodology is quite innovative for this application, at present many systems exist for photographic images, as for example QBIC and IKONA, but they are not able to extract and describe properly remote image content. The target database is set by an archive of images originated from an X-SAR sensor (spaceborne mission, 1994). The best content descriptors, mainly texture parameters, guarantees high retrieval performances and can be extracted without losses independently of image resolution. The latter property allows DBMS (Database Management System) to process low amount of information, as in the case of quick-look images, improving time performance and memory access without reducing retrieval accuracy. The matching technique has been designed to enable image management (database population and retrieval) independently of dimensions (width and height). Local and global content descriptors are compared, during retrieval phase, with the query image and results seem to be very encouraging.

Space missions involve the download,from space to ground, of many raw images per day. The analysis and sharing of these huge amounts of data is a big challenge for the remote sensing community. The emerging computational grid technologies are expected to make feasible the creation of a computational environment handling many PetaBytes of distributed data, tens of thousands of heterogeneous computing resources, and thousands of simultaneous users from multiple research institutions. The first results obtained in an experiment aiming to demonstrate the use of grid technology for remote sensing applications will be shown. The experiment has been carried out within the DataGrid project funded by the European Union.

The Elkhorn Slough area is a major wildlife reserve, and important wetlands area along the central coast of California. As part of the ongoing study of this area, accurate classifications of the areas within the slough are needed. The objective of this work was to use the 4-m spatial resolution, 4-color sensor on the IKONOS satellite. A manually constructed classification map was used to train the spectral classifiers. As the work evolved, a problem emerged due to the relatively high spatial resolution. Regions of interest such as oak woodlands have highly variable spectral elements when observed at high spatial resolution. As a consequence, the refinement of the regions of interest obtained from the original classification map required not only the elimination of erroneous spectral elements; but also required inclusion of a range of spectra, as opposed to the traditional approach of selecting pure exemplars. Modest success was obtained from the classification effort. As a consequence, additional virtual bands were created by constructing texture features from the higher spatial resolution panchromatic band. This enabled spectrally similar classes such as trees and cultivated fields to be distinguished.

The objective of this study was to process and integrate Landsat-TM images along with aerial photography, for the identification of water outflows in the coastal area of south Attiki peninsula. Digital image processing of Landsat data facilitated the identification of water outflows. Thermal anomalies have been detected by visual interpretation in the coastal areas. Air-photographs interpreted to map linear features and analyze the tectonic structure. A DEM along with field geological data used to verify the results and model the information. Water outflow patterns along coastal areas can be seen or inferred from the satellite images. Thermal anomalies due to water outflows have been identified on the FCC of thermal - with mid - infrared bands. These coincide with areas where fresh water outflows or liquid pollution wastes are found. Discharges of thermal waters into the sea have been detected corresponding, mainly, to coastal springs. Combined interpretation of Landsat data with air-photographs identified the main sources of water outflows and the regional tectonic structure. Such data constitute an ideal base for these studies by comparison or superposition with the other data, and effectively monitor changes in regional scales. Regional hydro-geological or geothermic investigations could be helped by the results of this study.

Goal of this work is to investigate and compare different compression methodologies from the viewpoint of spectral distortion introduced in hyperspectral pixel vectors. The main result of this analysis is that, for a given compression ratio, near-lossless methods, i.e., with constrained pixel error, either absolute or relative, are more suitable for preserving the spectral discrimination capability among pixel vectors, which is the principal outcome of spectral information. Therefore, whenever a lossless compression is not practicable, the use of near-lossless compression is recommended in such application where spectral quality is a crucial point.

Utilization of Pan Chromatic and Multi Spectral Remote Sensing Imagery is wide spreading and becoming an established business for commercial suppliers of such imagery like ISI and others. Some emerging technologies are being used to generate Hyper-Spectral imagery (HSI) by aircraft as well as other platforms. The commercialization of such technology for Remote Sensing from space is still questionable and depends upon several parameters including maturity, cost, market reception and many others. HSI can be used in a variety of applications in agriculture, urban mapping, geology and others. One outstanding potential usage of HSI is for water quality monitoring, a subject studied in this paper. Water quality monitoring is becoming a major area of interest in HSI due to the increase in water demand around the globe. The ability to monitor water quality in real time having both spatial and temporal resolution is one of the advantages of Remote Sensing. This ability is not limited only for measurements of oceans and inland water, but can be applied for drinking and irrigation water reservoirs as well. HSI in the UV-VNIR has the ability to measure a wide range of constituents that define water quality. Among the constituents that can be measured are the pigment concentration of various algae, chlorophyll a and c, carotenoids and phycocyanin, thus enabling to define the algal phyla. Other parameters that can be measured are TSS (Total Suspended Solids), turbidity, BOD (Biological Oxygen Demand), hydrocarbons, oxygen demand. The study specifies the properties of such a space borne device that results from the spectral signatures and the absorption bands of the constituents in question. Other parameters considered are the repetition of measurements, the spatial aspects of the sensor and the SNR of the sensor in question.

Like every measurement device, lidar systems need the possibility to have their results certified according to the criteria of present-day quality assurance. To this aim guidelines are needed. KRdL, the German Commission on Air Pollution Prevention, has been quite active in this field and issued several guidelines on lidar systems and measurements; a few more are actually in preparation. The present paper gives a brief account of the intended purpose, of the procedure followed to get the guidelines written, discussed, approved, and issued, of some of the differences to guidelines for in-situ measurement systems, and of lidar-specific problems and how these problems have been solved. As an example, parts of the guideline "Ground-based remote sensing of visual range - Visual range LIDAR" are presented, emphasizing the difficulties involved when visibility definitions are extended for remote sensing instruments covering a large measuring volume.

The remote sensing laboratory belongs to the Earth Observation, Remote Sensing and Atmospheric Research division of INTA. INTA is a government research organization of the Spanish Department of Defense. INTA has been performing airborne remote sensing campaigns since 1975. The Remote Sensing Laboratory is devoted to the application and development of both aerial and space remote sensing technqiues. It owns both, personnel and technology suitable to perform flight campaigns in order to acquire remote sensing images and, with the help of precise image processing techniques, extract useful information. Currently has two different airborne platforms, for remote sensing and for atmospheric research, and is in the process of specification of a new platform for generation research. INTA is partner of the Concerted Action 'European Fleet for Airborne Research'. This paper describes the INTA platform, sensors, systems and its integration in the aircraft. The experience in airborne remote sensing campaigns also described. The research campaigns performed show their application in comparison with satellite remote sensing. Some examples of this are, evaluation of future space sensors, calibration and validation of images acquired by operative space platforms, environmental impact of ecological distasters, ocean surfaces characteristics, wetland mapping and fire analysis.

ASTER is a high-resolution optical sensor for observing the Earth on the Terra satellite. ASTER consists of three radiometers, VNIR in the visible and near-infrared region, SWIR in the shortwave infrared region, and TIR in the thermal infrared region. The pre-flight calibration of VNIR and SWIR adopted the working standard large integrating sphere whose radiance levels were traceable to the primary standard fixed-point blackbody. The on-board calibration devices of VNIR and SWIR were two halogen lamps and photodiode monitors. The on-board lamp calibration showed a little shift while launch. In orbit three bands of VNIR showed a rapid decrease in the output signal while all SWIR bands remained stable. The TIR on-board blackbody was calibrated against a standard blackbody from 100 K to 400 K in a vacuum chamber before launch. The TIR is unable to see the dark space. The temperature of the on-board blackbody of TIR remains at 270 K in the short-term calibration for the offset calibration, and is varied from 270 K to 340 K in the long term calibration for the offset and gain calibration. The long term calibration just after launch seemed consistent with the prelaunch calibration but showed a decrease in orbit.

The IKONOS satellite has been operational since January 2000 and was the first commercial satellite collecting imagery with 1 meter resolution. The current life expectancy of the satellite is 10 years. Since the launch, Space Imaging Inc. (the owner of the satellite) supplied IKONOS imagery to users in many vertical markets, such as: agriculture, defense, oil & gas and telecommunications. This oral presentation will give comprehensive information about IKONOS and the future: * Block II, the successor of IKONOS. Space Imaging expects to launch in 2004 a new high-resolution satellite, ensuring both continuity and (for some years) a tandem operation with IKONOS, greatly improving the availability of imagery. * Space Imaging affiliates. IKONOS imagery collected, processed and sold by regional affiliates. These regional affiliates are strategically located around the world, like Japan Space Imaging (Tokyo), Space Imaging Middle East (Dubai) and Space Imaging Eurasia (Ankara, Turkey). * Technical briefing IKONOS. IKONOS (compared to other commercial high-resolution satellites) has superior collection capabilities. Due to, the higher orbit altitude, local reception of the imagery, bi-directional scanning and the high agility of the satellite, is the IKONOS satellite capable to collect the imagery relative quickly.