Three programs, i.e. TRMM, ADEOS2 and ASTER, are going on in Japanese Earth Observation programs. TRMM and ASTER are operating well, though TRMM operation after June 2005 is still unclear. ADEOS2 was failed, but AMSR-E on Aqua is operating. After the unfortunate accident of ADEOS2, JAXA still have plans of Earth observation programs. The first satellite which will be launched is ALOS (Advanced Land Observing Satellite). The tentative launch date is 1st, Sep. 2005. ALOS will carry three instruments, i.e., PRISM (Panchromatic Remote Sensing Instrument for Stereo Mapping), AVNIR-2 (Advanced Visible and Near Infrared Radiometer), and PALSAR (Phased Array L band Synthetic Aperture Radar). PRISM is a 3 line panchromatic push broom scanner with 2.5m IFOV. AVNIR-2 is a 4 channel multi spectral scanner with 10m IFOV. PALSAR is a full polarimetric active phased array SAR. PALSAR has many observation modes including full polarimetric mode and scan SAR mode. Next generation satellites will be launched in 2007-2009 timeframe. They are GOSAT (Greenhouse Gas Observation Satellite), GCOM-W and GCOM-C (ADEOS-2 follow on), and GPM (Global Precipitation Mission) core satellite. GOSAT will carry 2 instruments, i.e. a green house gas sensor and a cloud/aerosol imager. The main sensor is a Fourier transform spectrometer (FTS) and covers 0.76 to 15 μm region with 0.1 to 0.2 cm-1 resolution. GPM is a joint project with NASA and will carry two instruments. JAXA will develop DPR (Dual frequency Precipitation Radar) which is a follow on of PR on TRMM. Another project is EarthCare. It is a joint project with ESA and JAXA is going to provide CPR (Cloud Profiling Radar). Discussions on future Earth Observation programs have been started including discussions on ALOS F/O.

The scientific results, present status, and future plan of the ADEOS-II mission, especially for AMSR and GLI sensor, are presented in the paper. Five specific sensors aboard the ADEOS-II satellite were designed for making overall observation of land, atmosphere, ocean, and cryosphere from the sun-synchronous polar orbit. The AMSR and GLI are two of the primary sensors aboard the ADEOS-II satellite. The AMSR, a microwave scanner, retrieved the physical parameters related to global water cycle such as total precipitable water, cloud liquid water, precipitations and soil moisture. One the other hand, the GLI, a near ultraviolet to infrared imager, had captured many environmental events such as volcano eruptions, forest fires, and dust events with moderate spatial resolution of 250 m or 1 km. It also observed ocean colors, sea surface temperature, vegetation indices, aerosol and cloud properties, and precipitable water over land area. The ADEOS-II science activities continue in future. The primary objective of the next phase is the data utilization toward the future satellite missions, and the synergy of satellite data and climate models.

Since the launch in December of 1999, ASTER (Advanced Thermal Emission and Reflection Radiometer) has collected more than 1,000,000 scenes of data and generated more than 10,000 DEM and ortho-rectified images (Level 3A) from them, covering 20% of the whole land. The relative and absolute accuracy of geolocation and DEM will be discussed by comparing GCPs (Ground Control Point), GIS (Geographic Information System) and other existing topographic map. ASTER has shown very high geometric accuracy even if any GCP is not available. Contributing factors to this high accuracy are the stability and knowledge of the space craft orbit and attitude, ASTER sensors geometry, information on the Earth movement, algorithm to calculate the line of site vectors, and so on. Discussion will also cover the applicability of the DEM and ortho-rectified image data, based on the accuracy, and the discussion on further improvement.

Global precipitation measurement is essential not only for the research of the global change but also for the water resources management. Currently, satellite precipitation measurement is not sufficient for the detailed study of the precipitation and is far from enough for the water resources management which requires very high spatial and temporal resolution. To fill the gap at least partly, the Global Precipitation Measurement (GPM) was proposed jointly by US and Japan. The basic concept of the GPM is to provide three hourly global precipitation maps using eight constellation satellites equipped with microwave radiometers and a core satellite equipped with the Dual-frequency Precipitation Radar (DPR) and a microwave radiometer. The DPR which uses radiowaves of 13 and 35 GHz is now being developed in Japan. The DPR will observe 3D precipitation structure and will provide essential data for microwave rain retrieval. GPM is partly a follow-on mission of the Tropical Rainfall Measuring Mission (TRMM), but the GPM will extend the observation to cold regions where solid precipitation frequently exists. Rain retrieval algorithms that use the DPR data are also being developed. Using two wavelength data, two parameters in the raindrop size distribution could be retrieved, which would result in precise rain retrieval. The retreaval of solid precipitation rate is another challenge. The solid precipitation has another parameter of density which varies significantly. The hydrometeor shape also deviates significantly from a sphere. Several algorithms including a combination with the microwave radiometer would be applied to the DPR.

EarthCARE Phase-A study was successfully conducted in collaboration between ESA and Japan (JAXA and NICT). In this study, high sensitivity Cloud Profiling Radar (CPR) design with Doppler capability was studied and demonstrated that the CPR satisfies mission requirements, system resource and launcher constraint. As a result of the study, a nadir looking CPR at 94 GHz with a 2.5 m diameter antenna reflector is designed with sensitivity exceeding -36 dBZ of requirement at TOA with 10 km horizontal integration. The Doppler measurement is a new challenge to attain velocity accuracy less than 1 m/s in vertical direction. In parallel to the CPR system design, algorithm development efforts have been conducted through field campaign. A suite of measured quantities that are very similar combination to the EarthCARE data was collected and applied to the retrieval algorithm test.

Japan Aerospace Exploration Agency (JAXA) is proposing the Global Change Observation Mission (GCOM). The GCOM mission will take over the Advanced Earth Observing Satellite-II (ADEOS-II or Midori-II) mission and develop into long-term monitoring. The GCOM mission will consist of two series of medium size satellites: GCOM-W and GCOM-C (these names are provisional). Three consecutive generations of satellites with one year overlap will result in over 13 years observing period in total. Two observing instruments are proposed for the GCOM-W satellite: the Advanced Microwave Scanning Radiometer (AMSR) follow-on instrument and hopefully the scatterometer for measuring ocean vector winds like SeaWinds onboard Midori-II. To keep the continuous observation by AMSR-E on Aqua, the earliest launch date is desired by science community. Current proposed launch year is 2010. The AMSR follow-on instrument will be a multi frequency, dual polarized passive microwave radiometer that observes water-related geophysical parameters supporting the GCOM concept. To keep the earliest launch date, only minimum but essential modifications from AMSR-E are now being examined. Combination of AMSR follow-on instrument and the scatterometer will provide unique opportunity to generate a synergistic effect of the active and passive microwave measurement. This combination can provide some instrument-level advantages including attenuation and scattering correction for scatterometer. Furthermore, simultaneous measurements of water vapor, SST, precipitation, and sea surface winds are effective for investigating various time-space scale phenomena.

Regarding climate change, we have still large uncertainties to predict long-term variation, such as the global average temperature after 100 years. According to the report by Inter-governmental Panel for Climate Change (IPCC), one of the main factors of the uncertainties are from lack of understanding the process between aerosols and clouds. In order to accelerate the understandings of the process, observation of the aerosol over land is crucial. On the other hand, from the monitoring point of view, we do not have sufficient data to distinguish the effect of human activities on and near the land. The results of previous mission; ADEOS-2 Global Imager (GLI) suggests the 1 km ground resolution is not enough for distinguish the effect of human activities, such as deforestation, land cover change, pollution in coastal area, and so on. In this study, we designed a new sensor of which main ground resolution is 250 m, has wide spectral range (0.38~12 miron), rather wide swath for global observation and polarimetry function. The sensor named Second generation GLI (SGLI) consists of two sensors. The first one is conventional push broom type imager for visible and near infrared region with polarimetry channels. The second one is whisk broom sensor for shortwave and thermal infrared. SGLI has 11 channels in VNIR and 6 channels in infrared at nadir position, 2 channels with 3 polarization angles for polarimetry. The total mass of the sensor is around 400 kg. The new JAXA standard bus will carry it on the sun synchronous polar orbit at 10:30, Local Time of Descending Node. The proposed launch year is 2011.

Earth observation from the Stratospheric Platform (SPF) has several advantages over traditional airborne or spaceborne observations. Primarily, SPF can continuously monitor a specific area with higher spatial resolution over a longer period of time. We have developed the Earth Observation System for SPF-II (EOSS) for examining the feasibility of observation missions from the SPF and for demonstrating some sensor technologies. EOSS consists of three sensors: Wide-Angle Multi-band Sensor - Visible and Near-Infrared (WAMS-VNIR) for observation of vegetation and aerosol; Wide-Angle Multi-band Sensor - Thermal Infrared (WAMS-TIR) for monitoring distribution and time variation of land surface temperature; and High Resolution Sensor (HRS) for traffic observation. Observation mission tests were performed in October and November 2004. This paper describes the development of the sensor instruments and the results of SPF-II's Earth-observation mission.

NASA's early period of Mars remote sensing was highlighted by the Mariner (4, 6, 7) flybys and the Mariner 9 and Viking (1, 2) orbiters. In the mid 1990s, NASA returned to Mars with orbiters designed to take advantage of technological breakthroughs in imaging and spectroscopy. Mars Global Surveyor's Mars Orbiter Camera took 1.4 m/pixel resolution images while the Mars Orbiter Laser Altimeter's measurements produced highly accurate 3D relief maps. Mars Odyssey's Thermal Emission Imaging System provided data on surface infrared properties and Odyssey's neutron spectrometer measured up to 50% H₂O in the shallow subsurface. The Mars Reconnaissance Orbiter was launched in August 2006. MRO is equipped with six remote sensing instruments: (1) High Resolution Imaging Science Experiment will achieve sub-meter stereo image resolution; (2) Compact Reconnaissance Imaging Spectrometer for Mars will perform 18 m/pixel, 544 channel, infrared and thermal surface analyses; (3) the Context Camera will take regional context images with 6 m/pixel resolution; (4) Mars Color Imager will produce daily global images of the atmosphere and surface; (5) Mars Climate Sounder will study the temperature, dust, ice and water vapor content of the atmosphere as a function of altitude; and, (6) the Shallow Subsurface Radar will explore regional subsurface stratigraphy down to a kilometer. Future trends in Mars remote sensing will be considerably aided by telecommunications bandwidth improvements. The trend toward higher resolution and wider wavelength spectrometer investigations (with increased channels) will continue. Subsurface sounding to determine stratigraphy will improve and should take on a more prominent role.

NASA's Science Mission Directorate's Earth-Sun System Division (ESSD) uses the unique vantage point of space to understand and explore Earth and the Sun. The relationship between the Sun and the Earth is at the heart of a complex, dynamic system that researchers do not yet fully understand. The Earth-Sun system is comprised of diverse components that interact in complex ways, requiring unique capabilities for characterizing, understanding, and predicting change. Therefore, researchers need to understand the Sun, the heliosphere, and Earth's atmosphere, lithosphere, hydrosphere, cryosphere, and biosphere as a single connected system. At the center of the solar system is the Sun, a magnetically variable star. This variability has impacts on life and technology that are felt here on Earth and throughout the solar system. NASA is working to understand this planetary system because it is the only star-planet system researchers can investigate in detail. Using NASA's view from space to study the Earth-Sun system, researchers also can better predict critical changes to Earth and its space environment. NASA's ESSD has a critical role in implementing three major national directives: - Climate Change Research via Climate Change Science Program - Global Earth Observation System of Systems via the U.S. Group on Earth Observations (US GEO) - Vision for Space Exploration NASA Earth-Sun system science conducts and sponsors research, collects new observations from space, develops technologies and extends science and technology education to learners of all ages. NASA now has a system of spacecraft with the ability to characterize the current state of the Earth-Sun system. In the years ahead, NASA's fleet will evolve into constellations of smart satellites that can be reconfigured based on the changing needs of science and technology. From there we envision an intelligent and integrated observation network composed of sensors deployed in vantage points from the subsurface to deep space. Technical and programmatic details and status of representative Earth-Sun system missions will be presented.

The thickness of Arctic sea ice plays a critical role in Earth's climate and ocean circulation. An accurate measurement of this parameter on synoptic scales at regular intervals would enable characterization of this important component for the understanding of ocean circulation and the global heat balance. Presented in this paper is a low frequency VHF interferometer technique and associated radar instrument design to measure sea ice thickness based on the use of backscatter correlation functions. The sea ice medium is represented as a multi-layered medium consisting of snow, sea-ice and sea water, with the interfaces between layers characterized as rough surfaces. This technique utilizes the correlation of two radar waves of different frequencies and incident and observation angles, scattered from the sea ice medium. The correlation functions relate information about the sea ice thickness. Inversion techniques such as the genetic algorithm, gradient descent, and least square methods, are used to derive sea ice thickness from the phase information related by the correlation functions. The radar instrument is designed to be implemented on a spacecraft and the initial test-bed will be on a Twin Otter aircraft. Radar system and instrument design and development parameters as well as some measurement requirements are reviewed. The ability to obtain reliable phase information for successful ice thickness retrieval for various thickness and surface interface geometries is examined.

Measurements of the column CH₄, CO and CO₂ are high priorities of the NPOESS Pre-Planned Product Improvement (P3I) data sets. Risk reduction for existing NPOESS instruments, including mitigation of daytime CO₂ SWIR non-LTE effects, is also a high priority. We have proposed an NPOESS Instrument Of Opportunity (IOO) to address these priorities. It consists of two grating mapping spectrometers (GMSs). One that would acquire measurements with high spectral resolution Δv < 0.13 cm^-1 of CH₄, CO and H₂O absorption lines in reflected sunlight in the VSWIR region 4281 to 4301 cm^-1, and another for measurements with Δv < 0.30 cm^-1 in the SWIR region 2355 to 2430 cm^-1. The IOO will acquire spectra on a crosstrack swath from nadir to 55 degrees (about 1400 km on the ground) on footprints that are about 1.55 and 3.1 km on a side at nadir for the two GMS, respectively. The small footprint facilitates cloud screening, and identification of pollution hotspots. We use linear error analysis (LEA, based on the Rodgers [1] paper) to estimate the proposed IOO's performance. The LEA indicates that the IOO should be able to provide CH₄ and CO column retrieval over sunlit land (and from ocean glitter when it is viewed) that satisfies or exceeds NPOESS P3I Environmental Data Records (EDRs) requirements in all aspects except refresh where the IOO would provide every two days vs the once per day requirement. Further, it shows the VSWIR IOO data when used in combination with the NPOESS Cross Track Infrared Sounder (CrIS) [2] data should provide: (a) CO profile data with sensitivity to CO in near surface air that is enhanced compared to that in the current TERRA-MOPITT, ACQUA-AIRS and AURA-TES data sets because these are limited to thermal infrared measurements that lack sensitivity to CO in near surface air layer where there is little contrast between the air temperature and the ground surface temperature, (b) CH₄ profile with sensitivity in the near surface air layer that is crucial for identifying CH₄ sources/sinks (c) and significant improvement in the CrIS retrieved humidity in the near surface layer of air. We show the SWIR IOO data can be used for CO₂ column retrieval with near surface air layer sensitivity in the daytime. And also that in combination with CrIS SWIR data facilitates CO₂ SWIR non-LTE mitigation that is required for advanced sounding quality temperature profile (TP) retrieval from CO₂ SWIR data in daytime conditions. This provides risk reduction in case of degradation in the CrIS LWIR region data.

Global Precipitation Measurement (GPM) is an international Earth observing "System of Systems" that will initiate the measurement of precipitation, a key climate factor, globally. GPM is a joint initiative with the Japan Aerospace Exploration Agency (JAXA) and other international partners. It integrates previously planned and dedicated missions in a scalable and evolving constellation of multiple spacecraft and data processing and validation ground systems. Its science objectives are: - To improve ongoing efforts to predict climate by providing near-global measurement of precipitation, its distribution, and physical processes; - To improve the accuracy of weather and precipitation forecasts through more accurate measurement of rain rates and latent heating; and - To provide more frequent and complete sampling of the Earth's precipitation. GPM is a potential NASA contribution to the Global Earth Observation System of Systems (GEOSS) as envisioned by the intergovernmental ad hoc Group on Earth Observations (GEO) through the U.S. Group on Earth Observations (US GEO). GPM directly supports three of the nine societal benefits identified by the GEO. GPM is envisioned to consist of a core spacecraft to measure precipitation structure and to provide a calibration standard for the constellation spacecraft, an international constellation of NASA and contributed spacecraft to provide frequent precipitation measurements on a global basis, calibration/validation sites distributed globally with a broad array of precipitation-measuring instrumentation, and a global precipitation data system to produce and distribute global rain maps andclimate research products. GPM is now in formulation phase and recently began the acquisition of the GPM Microwave Imager (GMI), NASA's principal instrument. GPM launches are targeted to begin in 2010.

Tropospheric aerosols play a crucial role in climate and can cause a climate forcing directly by absorbing and reflecting sunlight, thereby cooling or heating the atmosphere, and indirectly by modifying cloud properties. The indirect aerosol effect may include increased cloud brightness, as aerosols lead to a larger number of smaller cloud droplets (the so-called Twomey effect), and increased cloud cover, as smaller droplets inhibit rainfall and increase cloud lifetime. Both forcings are poorly understood and may represent the largest source of uncertainty about future climate change. In this paper we present results from various field experiments demonstrating the contribution that the multi-angle multi-spectral photopolarimetric remote sensing measurements of the NASA Glory mission will make to the determination of the direct and indirect radiative effects of aerosols.

The NASA Earth Science System Pathfinder (ESSP) mission Aquarius, will measure global ocean surface salinity with ~100 km spatial resolution every 7-days with an average monthly salinity accuracy of 0.2 psu (parts per thousand). This requires an L-band low-noise radiometer with the long-term calibration stability of less than or equal to 0.1 K over 7 days. A three-year research program on radiometer stability has addressed the radiometer requirements and configuration necessary to achieve this objective. The system configuration and component performance have been evaluated with radiometer test beds at both JPL and GSFC. The research has addressed several areas including component characterization as a function of temperature, system linearity, noise diode calibration, temperature control of components and optimum switching of the Dicke switch for lowest noise performance. A breadboard radiometer, utilizing microstrip-based technologies, has been built to demonstrate this long-term stability. This paper will present the results of the radiometer test program and details on the design of the Aquarius radiometer. The operational sequence that will be used to achieve the low noise and stability requirements will also be discussed.

The European Space Agency is pursuing the development of innovative Earth Observation missions to foster better scientific understanding of the system Earth and to respond to the requirements of the operational users. Six Earth Explorer missions (CRYOSAT, GOCE, SMOS, AEOLUS, SWARM, EarthCARE) are under development for launch between 2005 and 2012. They will provide to provide new critical information in a wide range of Earth science disciplines: ocean circulation, Earth's gravity and magnetic fields, the cryosphere, ocean salinity and soil moisture, magnetic field, aerosol-radiation-cloud interactions and the demonstration of the measurement of tropospheric wind fields. Application-oriented missions of the Earth Watch class are continuing with the METEOSAT series of geostationary meteorological satellites, the preliminary studies of the next-generation METEOSAT spacecraft and the forthcoming launch of the first spacecraft of the EPS/METOP series. Preparatory activities are underway for the series of operational missions, to provide data and services for Earth monitoring, in the frame of the GMES programme.

The EarthCARE (Earth Clouds, Aerosols and Radiation Explorer) mission has been recently selected as the 6^th ESA's Earth Explorer Mission. The mission 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 on a single platform, which allows for a complete 3-D spatial and temporal picture of the radiative flux field at the top of the atmosphere and the Earth's surface to be developed. While the active instruments provide vertical cloud profiles, the passive instruments (mainly the multi-spectral imager) provide supplementary horizontal data to allow for the extrapolation of the 3-D cloud and aerosol characteristics. The EarthCARE payload is composed of four instruments: an Atmospheric backscatter Lidar, a Cloud Profiling Radar, a Multi-Spectral Imager and a Broad Band Radiometer. The mission baseline is a sun-synchronous orbit with an altitude around 450 km. The EarthCARE mission is a cooperative mission with Japan (JAXA and NICT), which will provide the Cloud Profiling Radar. ESA will provide the ground segment and the rest of the space segment including the lidar, the imager and the broadband radiometer. The launch is planned for 2012.

The operational deployment of MSG-1 at the beginning of 2004, the first of a series of four Meteosat Second Generation (MSG) satellites, marks the start of a new era in Europe for the meteorological observations from the geostationary orbit. This new system shall be the backbone of the European operational meteorological services up to at least 2015. The time required for the definition and the development of new space systems as well as the approval process of such complex programs implies anyhow to plan well ahead for the future missions. EUMETSAT have initiated in 2001, with ESA support, a User Consultation Process aiming at preparing for a future operational geostationary meteorological satellite system in the post-MSG era, named Meteosat Third Generation (MTG). The first phase of the User Consultation Process was devoted to the definition and consolidation of end user requirements and priorities in the field of Nowcasting and Very Short Term Weather Forecasting (NWC), Medium/Short Range global and regional Numerical Weather Prediction (NWP), Climate and Air Composition Monitoring and to the definition of the relevant observation techniques. The following missions have been analysed and preliminary concepts studied: High Resolution Fast Imagery Mission (successor to MSG SEVIRI HRV mission); Full Disk High Spectral Resolution Imagery Mission (successor to the mission of other MSG-SEVIRI channels); Lightning Imagery Mission; IR Sounding Mission; UV-VIS-NIR Sounding Mission. After an initial post-MSG mission study (2003-2004) where preliminary instrument concepts were investigated allowing in the same time to consolidate the technical requirements for the overall system study, a pre-phase A study on MTG is on its final way for the overall system concept, architecture and programmatic aspects during 2004-2005 time frame. This paper provides an overview of the outcome of the MTG sensor concept studies conducted in the frame of the pre-phase A. It namely focuses onto the Imaging and Sounding Missions, highlights the resulting instrument concepts, establishes the critical technologies and introduces the study steps towards the implementation of the MTG development programme.

Pleiades is the highest resolution civilian earth observing system ever developed in Europe. This imagery programme is conducted by the French National Space Agency, CNES. It will operate in 2008-2009 two agile satellites designed to provide optical images to civilian and defence users. Images will be simultaneously acquired in Panchromatic (PA) and multispectral (XS) mode, which allows, in Nadir acquisition condition, to deliver 20 km wide, false or natural colored scenes with a 70 cm ground sampling distance after PA+XS fusion. Imaging capabilities have been highly optimized in order to acquire along-track mosaics, stereo pairs and triplets, and multi-targets. To fulfill the operational requirements and ensure quick access to information, ground processing has to automatically perform the radiometrical and geometrical corrections. Since ground processing capabilities have been taken into account very early in the programme development, it has been possible to relax some costly on-board components requirements, in order to achieve a cost effective on-board/ground compromise. Starting from an overview of the system characteristics, this paper deals with the image products definition (raw level, perfect sensor, orthoimage and along-track orthomosaics), and the main processing steps. It shows how each system performance is a result of the satellite performance followed by an appropriate ground processing. Finally, it focuses on the radiometrical performances of final products which are intimately linked to the following processing steps : radiometrical corrections, PA restoration, image resampling and PAN-sharpening.

Future planetary missions will require advanced, smart, low resource payloads (P/Ls) and satellites^1,2 to enable the exploration of the solar system in a more frequent, timely and multi-mission manner with reasonable cost. The concept of highly integrated payload architectures was introduced during the re-assessment of the payload of the BepiColombo Mercury Planetary Orbiter³. Considerable mass and power savings were achieved throughout the instrumentation by better definition of the instruments design, higher integration and identification of resource drivers⁴. Higher integration and associated synergy effects permit optimisation of the payload performance at minimum resource requirements while meeting demanding science requirements. This promising concept has been applied to a set of hypothetical Planetary Technical Reference Studies¹¹ (PTRS) on missions to Venus⁵, Jupiter/Europa⁶, Deimos⁷, Mars⁸ and the investigation of the Interstellar Heliopause⁹. The needs on future instrumentation were investigated for these mission concepts and potential instruments were proposed¹⁰. A demonstration programme is now proposed in form of an elegant breadboard that consists of a photon counting laser altimeter, a stereoscopic high resolution camera, and a broadband radiometric mapping spectrometer. The aim of the activity is to demonstrate to feasibility of such a miniaturised, low resource and highly integrated payload based on innovative instrument designs. The activity shall thereby provide a clear detailed definition of the technical and managerial aspects for implementation into potential future planetary space science missions.

Several organizations in the Netherlands are cooperating to develop user requirements and instrument concepts in the line of SCIAMACHY and OMI but with an increased focus on measuring tropospheric constituents from space. The concepts use passive spectroscopy in dedicated wavelength sections in the range of 300 to 2400 nm and wide angle, non-scanning, swath viewing. To be able to penetrate into the troposphere small ground pixels are used to obtain a fair fraction of cloud-free pixels and to allow precise detection of the sources of polluting gases. The trace gas products aimed for are O₃, NO₂, HCHO, H₂O, SO₂, Aerosol (optical depth, type and absorption index), CO and CH₄, covering science issues on air quality and climate. The main challenge in the instrument design is to obtain a good signal-to-noise for cloud free pixels and for low ground albedo and light levels. Also the retrieval of separated tropospheric and stratospheric column amounts from a nadir looking instrument is challenging. The paper discusses the user requirements and compares alternative measurement strategies. It explains the selection of passive UV-Visible-NIR spectroscopy and comes with an instrument concept which provides the current best realisation of the user requirements.

The paper presents the results of an extended analysis of image data sets acquired during the tandem-orbit configuration in 1999 for the purposes of radiometric cross-calibration of the Landsat-7 Enhanced Thematic Mapper Plus (ETM+) and Landsat-5 Thematic Mapper (TM) sensors. Earlier work focused on the tandem pair for the Railroad Valley Playa, Nevada (RVPN) site to tie down the Landsat-5 TM calibration based on the more accurate Landsat-7 ETM+ calibration. This paper describes new results based on as many as eight tandem image pairs. The additional tandem images are of vegetated areas for which little or no ground reference data were available. Increasing the number of tandem pairs yielded results for the Landsat 5 TM gain coefficients within approximately ± 1 % of the RVPN-based results in spectral bands 1, 2, 3 and 7, and within -2 % and -4 % of the RVPN-based results for spectral bands 4 and 5, respectively.

ESA currently builds the airborne hyper-spectral push broom imaging spectrometer APEX (Airborne Prism EXperiment) operating in the spectral range from 380 to 2500 nm. In the scope of the APEX project a large variety of characterization measurements will be performed, e.g., on-board characterization, frequent laboratory characterization, and vicarious calibration. The APEX instrument will only achieve its challenging measurement accuracy by regular calibration of the instrument between flight cycles. For that on-ground characterisation, a dedicated characterisation and calibration facility is necessary to enable a comprehensive and accurate calibration of the instrument. In view of the high relevance to scientific objectives, ESA is funding an external "Calibration Home Base" (CHB). It is located at DLR Oberpfaffenhofen and will be operational from 2006 on. The CHB provides all hard- and software tools required for radiometric, spectral and geometric on-ground characterisation and calibration of the instrument and its internal references and on-board attachments, and to perform measurements on polarisation- and straylight-sensitivity. This includes a test bed and the provision of the infrastructure. In this paper the calibration equipment and concept is outlined.

In July 2004 Nasa's AURA satellite was launched carrying the Dutch-Finnish Ozone Monitoring Instrument and since then it is producing high quality trace gas measurements of a.o. ozone and NO₂. The OMI is a non-scanning nadir viewing spectrograph with a wavelength coverage of 270 to 500 nm and a spectral resolution of 0.4 to 0.7 nm. It has a large spatial field-of-view of 114 degrees perpendicular to the flight direction and uses the resulting swath of 2600 km to measure the complete globe in a single day with ground pixels of nominally 13 km × 24 km. After a brief instrument overview, this paper discusses a number of in-flight performance issues, such as the wavelength calibration and the stray light correction. OMI's wavelength calibration is based on fitting the sun's Fraunhofer structures, both on sun irradiance spectra and Earth radiance spectra. For the latter the cloud structures impact the wavelength results via inhomogeneous illumination of the spectrometer slit. This is explained together with the basics of a correction algorithm. OMI has a carousel with three on-board sun diffusers. Measurements with the quartz volume diffuser will be used to show remaining diffuser features in the data. The measured irradiances are compared to the results obtained by convolving the high-resolution solar reference spectrum with the accurately calibrated spectral slit functions. In the in-flight measurement data in the wavelength range below 300 nm spatial stray light features are observed, resulting from clouds observed at wavelengths above 300 nm. These features are shown together with an explanation of the means to analyze the in-orbit stray light performance.

The Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the NASA EOS Aqua spacecraft has been in operation for more than three years since its launch in May 2002. MODIS is a multi-spectral cross-track scanning radiometer that has 20 reflective solar bands (RSB) from 0.41 to 2.2μm and 16 thermal emissive bands (TEB) from 3.7 to 14.4μm. It makes continuous observations that can be applied to a wide range of studies of the Earth's environment and climate. The sensor's in-flight calibration and characterization activities (radiometric, spatial, and spectral) are performed using a set of onboard calibrators (OBCs) that include a solar diffuser (SD), a solar diffuser stability monitor (SDSM), a blackbody, and a spectro-radiometric calibration assembly (SRCA). In this paper we present on-orbit performance of the Aqua MODIS onboard calibrators using its calibration data sets. We illustrate use of the SD for RSB calibrations and current trending of SD degradation. For the TEB calibration, we discuss BB temperature noise characterization, its short- and long-term stability, and the use of BB warm-up and cool-down cycles to track key TEB calibration parameters. The results of Aqua MODIS spatial and spectral characterization are also addressed. In general the overall Aqua MODIS on-orbit performance has been stable and satisfactory when compared to its design parameters, performance specifications, and pre-launch determined characteristics. In a number of areas, Aqua MODIS is performing better than its predecessor - Terra MODIS.

NASA's Earth Observing System (EOS) Terra spacecraft was launched in December 1999 and the Aqua spacecraft in May 2002. The Moderate Resolution Imaging Spectroradiometer (MODIS) is one of the key instruments for NASA's EOS missions, currently operated on both the Terra and Aqua spacecrafts. Together they have made continuous global observations for more than 8 years and led to many applications and studies for the Earth's system of land, oceans, and atmosphere. Compared to its heritage sensors, the MODIS was designed with more stringent requirements on the sensor's calibration accuracy and data product quality. Because of this it is equipped with a set of on-board calibrators (OBCs), including a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) for the reflective solar bands (RSB) calibration and a blackbody (BB) for the thermal emissive bands (TEB) calibration. In addition to the sensor's intrinsic design characteristics, the quality of MODIS data products depends on the quality of its on-orbit calibration and characterization and on its on-orbit performance. The primary objective of this paper is to provide an overview of MODIS on-orbit radiometric calibration approaches and a summary of the calibration uncertainties for both RSB and TEB (Terra and Aqua). This paper provides an update to our previous reports with considerations based on each sensor's characteristics identified pre-launch, measured and validated on-orbit. It also serves as a useful reference for the users of MODIS data products.

The Visible/Infrared Imager Radiometer Suite (VIIRS), built by Raytheon Santa Barbara Remote Sensing (SBRS) will be one of the primary earth-observing remote-sensing instruments on the National Polar-Orbiting Operational Environmental Satellite System (NPOESS). It will also be installed on the NPOESS Preparatory Project (NPP). These satellite systems fly in near-circular, sun-synchronous low-earth orbits at altitudes of approximately 830 km. VIIRS has 15 bands designed to measure reflectance with wavelengths between 412 nm and 2250 nm, and an additional 7 bands measuring primarily emissive radiance between 3700nm and 11450 nm. The calibration source for the reflective bands is a solar diffuser (SD) that is illuminated once per orbit as the satellite passes from the dark side to the light side of the earth near the poles. Sunlight enters VIIRS through an opening in the front of the instrument. An attenuation screen covers the opening, but other than this there are no other optical elements between the SD and the sun. The BRDF of the SD and the transmittance of the attenuation screen is measured pre-flight, and so with knowledge of the angles of incidence, the radiance of the sun can be computed and is used as a reference to produce calibrated reflectances and radiances. Unfortunately, the opening also allows a significant amount of reflected earthshine to illuminate part of the SD, and this component introduces radiometric error to the calibration process, referred to as earthshine contamination (ESC). The VIIRS radiometric error budget allocated a 0.3% error based on modeling of the ESC done by SBRS during the design phase. This model assumes that the earth has Lambertian BRDF with a maximum top-of-atmosphere albedo of 1. The Moderate Resolution Imaging Spectroradiometer (MODIS) has an SD with a design similar to VIIRS, and in 2003 the MODIS Science Team reported to Northrop Grumman Space Technology (NGST), the prime contractor for NPOESS, their suspicion that ESC was causing higher than expected radiometric error, and asked whether VIIRS might have a similar problem. The NPOESS Models and Simulation (M&S) team considered whether the Lambertian BRDF assumption would cause an underestimating of the ESC error. Particularly, snow, ice and water show very large BRDFs for geometries for forward scattered, near-grazing angles of incidence, and in common parlance this is called glare. The observed earth geometry during the period where the SD is illuminated by the sun has just such geometries that produce strongly forward scattering glare. In addition the SD acquisition occurs in the polar regions, where snow, ice and water are most prevalent. Using models in their Environmental Products Verification and Remote Sensing Testbed (EVEREST), the M&S team produced a model that meticulously traced the light rays from the attenuation screen to each detector and combined this with a model of the satellite orbit, with solar geometry and radiative transfer models that include the effect of the BRDF of various surfaces. This modeling showed that radiometric errors up to 4.5% over water and 1.5% over snow or ice. Clouds produce errors up to 0.8%. The likelihood of these high errors occurring has not been determined. Because of this analysis, various remedial options are now being considered.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), on the NASA Terra satellite, has three radiometers, the VNIR, SWIR and TIR. The TIR radiometer has five bands (10 to 14) in the thermal infrared region with a spatial resolution of 90 m. These TIR bands are radiometrically calibrated by a single onboard blackbody whose temperature can be changed between 270 K and 340 K. In the normal operation mode the blackbody is kept at 270 K, and a constant coefficient in a quadratic radiometric calibration equation for each detector is adjusted at that temperature before each Earth observation. Once in 33 days the gain term can be updated by a long term calibration in which the blackbody is measured at 270, 300, 320, and 340 K. The sensor response of all bands (particularly band 12) has been degrading since the launch, and periodical updating of the gain coefficient does not fully follow the degradation, so that the calibration error on level-1 products is sometimes unacceptable. We therefore have developed approximation equations for the coefficients to predict the most reasonable radiometric calibration coefficients (RCC) at the time of the observation. This will be implemented soon in the Level-1 data processing.

For the accurate radiometric calibration of earth observation instruments, diffusers are used as "white-references". In the framework of on-ground calibration campaigns of instruments such as SCIAMACHY, GOME2, OMI (all using on-board diffusers), which took place at TNO, a modulation of the reflectance signal in the spectral domain was discovered. The position and amplitude of the modulation depend on various factors: the diffuser material, the illumination and detection angles, the detection bandwidth, the wavelength, the used area of the diffuser and the way the diffuser is implemented in the optical design of the instrument (e.g. mesh, moving diffuser, ...). This modulation has been called Spectral Features. To achieve an accurate characterization of this effect TNO developed a dedicated Spectral Features set-up that allows the correlation of the Spectral Features sensitive parameters in order to minimize their effect. This paper gives an overview of the results of the commissioning activity of the dedicated Spectral Features set-up in the UV/VIS and of its extension to the NIR spectral range. Furthermore the results of the diffuser trade-off study performed in the framework of the ESA study (contract number 18432/04/NL/AR) are presented in this paper.

Today, both CCD and CMOS sensors can be envisaged for nearly all visible sensors and instruments designed for space needs. Indeed, detectors built with both technologies allow excellent electro-optics performances to be reached, the selection of the most adequate device being driven by their functional and technological features and limits. The first part of the paper presents electro-optics characterisation results of CMOS Image Sensors (CIS) built with an optimised CMOS process, demonstrating the large improvements of CIS electro-optics performances. The second part reviews the advantages of CMOS technology for space applications, illustrated by examples of CIS developments performed by EADS Astrium and Supaero/CIMI for current and short term coming space programs.

With the growth of huge volume markets (mobile phones, digital cameras...) CMOS technologies for image sensor improve significantly. New process flows appear in order to optimize some parameters such as quantum efficiency, dark current, and conversion gain. Space applications can of course benefit from these improvements. To illustrate this evolution, this paper reports results from three technologies that have been evaluated with test vehicles composed of several sub arrays designed with some space applications as target. These three technologies are CMOS standard, improved and sensor optimized process in 0.35μm generation. Measurements are focussed on quantum efficiency, dark current, conversion gain and noise. Other measurements such as Modulation Transfer Function (MTF) and crosstalk are depicted in [1]. A comparison between results has been done and three categories of CMOS process for image sensors have been listed. Radiation tolerance has been also studied for the CMOS improved process in the way of hardening the imager by design. Results at 4, 15, 25 and 50 krad prove a good ionizing dose radiation tolerance applying specific techniques.

Due to different local intra-pixel sensitivity and crosstalk between neighboring pixels, the Pixel Response Function of detectors (PRF - signal of the pixel as a function of a point source position) is generally non-uniform. This may causes problems in space application such as aperture photometry and astrometry (centroiding). For imaging applications, an important crosstalk yields to a loss of resolution, i.e. a poor image quality, commonly quantified by the Modulation Transfer Function (MTF). So, crosstalk study is of primary importance for our applications. A dedicated test chip (using a technology optimized for imaging applications) has been developed in order to get both MTF data and influence of the various areas of the pixel to its own response and the one of its neighbors. The results obtained with pixel kernels and direct MTF measurements, performed on the same chip at different wavelengths, are analyzed and compared in order to correlate them. So it is possible to draw conclusions -that can be applied at the design level - allowing to get a better MTF and to minimize errors on aperture photometry and centroiding computation.

The PLEIADES-HR Earth Observing system combines a high resolution panchromatic channel (0.7 m at nadir) and a multispectral channel allowing a 2.8 m resolution. This paper presents the main characteristics of the sensor equipped with filters for the multispectral channel. A long quadrilinear CCD sensor has been coupled to four long stripe filters. The CCD device provides four lines of 1500 pixels with 52 microns pitch. Each line is associated to a long stripe filter and allows to cover spectral bands from blue to near infra red spectrum. Performances of this sub-assembly are analyzed. Pixel response non-uniformity and relative spectral response have been measured and compared to individual performances of the CCD and the filters. Impacts of instrument optical interfaces on these parameters are included in this analysis. Residual spatial noise performances related to spectral response dispersion are presented.

Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Fire-fighting, predictive maintenance. process control and thermography are a few of the industrial applications which could take benefit from uncooled infrared detector. Therefore, to answer these markets, a 35 μm pixel-pitch uncooled IR detector technology has been developed enabling high performance 160 x 120 and 384 x 288 arrays production. Besides a wide-band version from uncooled 320 x 240 / 45 μm array has been also developed in order to address process control and more precisely industrial furnaces control. The ULIS amorphous silicon technology is well adapted to manufacture low cost detector in mass production. After some brief microbolometer technological background, we present the characterization of 35 μm pixel-pitch detector as well as the wide-band 320 x 240 infrared focal plane arrays with a pixel pitch of 45 μm.

SCD has recently presented an uncooled detector product line based on the high-end VO_x bolometer technology. The first FPA launched, named BIRD - short for Bolometer Infra Red Detector, is a 384x288 (or 320x240) configurable format with 25μm pitch. Typical NETD values for these FPAs range at 50mK with an F/1 aperture and 60 Hz frame rate. These detectors also exhibit a relatively fast thermal time constant of approximately 10 msec, as reported previously. In this paper, the special features of BIRD optimized for unattended sensor applications are presented and discussed. Unattended surveillance using sensors on unattended aerial vehicles (UAV's) or micro air vehicles (MAV's) , unattended ground vehicles (UGV's) or unattended ground sensor (UGS) are growing applications for uncooled detectors. This is due to their low power consumption, low weight, negligible acoustic noise and reduced price. On the other hand, uncooled detectors are vulnerable to ambient drift. Even minor temperature fluctuations are manifested as fixed pattern noise (FPN). As a result, frequent, shutter operation must be applied, with the risk of blocking the scenery in critical time frames and loosing information for various scenarios. In order to increase the time span between shutter operations, SCD has incorporated various features within the FPA and supporting algorithms. This paper will discuss these features and present some illustrative examples. Minimum power consumption is another critical issue for unattended applications. SCD has addressed this topic by introducing the "Power Save" concept. For very low power applications or for TEC-less (Thermo-Electric-Cooler) applications, the flexible dilution architecture enables the system to operate the detector at a number of formats. This, together with a smooth frame rate and format transition capability turns SCD's uncooled detector to be well suited for unattended applications. These issues will be described in detail as well.

Sofradir started to work in the field of space applications and especially in the earth observation domain in the beginning of the 1990s. Thanks to the work done with the support of the French Ministry of Defence, the European Space Agency, and the CNES, Sofradir has acquired a large know-how and became a major supplier for European space industry. Sofradir space technology is based on the use of a qualified Mercury Cadmium Telluride (MCT) technology hybridized with silicon readout circuit covering a bandwidth from 0.8 to 14 μm. Thanks to this technology Sofradir can answer most of the current space needs in terms of infrared instrument. Future space applications require also an extension of the sensitivity range of the infrared detectors to upper wavelength (typically higher than 15 μm) and to lower wavelength to offer infrared components able to operate both in the visible and short wave infrared range. Physically, MCT material is able to operate in the visible range and has a potential to offer a high quantum efficiency and large field factor thanks to the hybrid structure. Another issue of future space applications concerns the size and power consumption of the detectors and the associated cryogenic systems. Thanks to its activity, Sofradir has developed very compact cryogenic systems that can be used advantageously for space applications with limited adaptations and qualifications. This paper proposes an overview of Sofradir technology capabilities for space applications with an emphasis on new potential applications of MCT technology in visible range and for very long wave infrared components. This paper deals also with the capacity of Sofradir MCT and cryogenic technology to be used for both terrestrial and space applications. Finally, a review of the last results obtained in the development of infrared detectors for space applications is proposed.

Remote sensing programs require detectors with a variety of wavelengths. One example of remote sensing applications is the GOES-ABI program that requires linear arrays of detectors with cutoff wavelengths ranging from the visible to the VLWIR (λ_c ~ 15 μm). In order to target the variety of remote sensing applications, an internal task was conducted to develop detectors and linear arrays operating under nominal remote sensing applications. SWIR [λ_c(295 K) ~ 2.5 μm] test detectors have been measured as a function of temperature between 170 K and 295 K. At 200 K the R_oA values are in the 10⁶ ohm-cm² range. MWIR [λ_c(60 K) = 5.3 μm] and LWIR [λ_c(60 K) = 10.5 μm] HgCdTe detectors in a 320 x 6 array format have also been measured at 60 K. Within the arrays, the detector size is 40 μm x 50 μm. The MWIR detector array has a mean quantum efficiency of 89.2 % with a standard deviation to mean ratio, σ/μ = 1.51 %. The integration time for the focal plane array (FPA) measurements is 1.76 ms with a frame rate of 557.7 Hz. Operability values exceeding 99.5 % have been obtained. In addition, test diodes at the edge of the array that did not go through a read out integrated circuit (ROIC) were also measured and had quantum efficiency ~ 86 % that agreed well with the ~ 87 % quantum efficiency measured for detectors in the array that were located near the test detectors. The LWIR arrays, measured at 60K also had high operability with only ~ 3 % of the detectors having out of family response. Using best detector select (BDS) feature in the read out integrated circuit (ROIC), a feature that picks out the best detector in every row of six detectors, a 320 x 1 array with 100 % operability is obtained. For the 320 x1 array constituted using the BDS feature, a 100 % operable LWIR array with average NEI value of 1.94x10¹¹ ph/cm2/s at a flux of 7.0x10¹⁴ ph/cm²/s has been demonstrated.

Based on the mature and reproducible HgCdTe process developed by CEA-LETI-Infrared Laboratory and industrialized by Sofradir, two new detectors with a cut-off wavelength tuned between 9 μm and 12 μm have been developed. For compact LW cameras, Sofradir produces a high resolution 25 μm pitch 384×288 infrared focal plane array (IRFPA) with a cut-off wavelength between 9 μm and 10 μm, and an operational temperature between 77 and 85 Kelvin. The manufacturing of this detector relies on the standard HgCdTe production process with the latest uniformity improvements. For VLW applications such as spectroscopy or broadband low flux applications, an improved HgCdTe material with optimized Liquid Phase Epitaxy (LPE) and Photovoltaic (PV) detector process has been developed by LIR and Sofradir to get very low dark currents. These 30 μm pitch 320x256 detector arrays have cut-off wavelengths above 12 μm below 50 K and their dark current is compatible with very low flux applications. The performances of these new LW and VLW IR detectors are presented in this paper as well as the development trends for LW detectors at LETI and Sofradir.

Next generation, space-based, Sun-Earth System remote sensing missions place severe challenges on focal plane technologies to achieve their science goals. Among these are high sensitivity over a broad spectral range, small pixel size, fast readout, radiation tolerance, low power consumption, photometric accuracy & stability, and scalable mosaic technology for constructing large focal plane mosaics. Our Jet Propulsion Laboratory, Lawrence Berkeley National Laboratory, University of Alabama in Huntsville collaboration has begun the development of an Advanced Broadband Imager (ABI) to address these challenges for future Sun Solar System Connection science missions. We describe here the development of the delta-doped, high-purity, p channel charge coupled devices, which form the heart of the ABI imager, and our plans for future development. The current technical readiness levels of ABI component technologies are TRL 2 to TRL 4. Our proposed development program envisions achieving TRL 5 within 3 years with flight validation in the context of an Earth Sun System Science mission occurring within 6 years via the Quiet-Sun Transition Region Explorer EUV Telescope (Q-STREET) rocket-borne observatory.

Acreo is one of the leading producers of QWIP FPAs in the world and is also intensively running R&D activities. The European Space Agency has awarded Acreo the contracts "Far-IR Linear Detector Array" in 6-18 μm infrared range within the Darwin mission's frameworks and "Quantum Well Infrared Photodetector Arrays" in 11-15 μm range for Earth observation (EO). The Darwin project imposes hard requirements on the dark current, while for the EO project the operating temperature is a stringent constraint. The goal of both contracts is to establish and demonstrate the ultimate performance of Acreo's QWIP-technology for these applications at the highest possible operating temperature. For this purpose Acreo designed, grew and characterised QWIP material sensitive to different wavelengths in the range of 6-18 μm. To investigate transport properties and verify the validity of the hydrodynamic model of the dark current, experiments with varying numbers of quantum wells per thickness unit and periods were conducted. A structure for long infrared region with an increased number of periods revealed a drastic reduction of the dark current at transient temperature. The dependence of the capture probabilities on the electron energy in the miniband resulting in different dependencies of the photoconductive gain for the photo- and dark currents on the number of periods is suggested as the reason for that. Such hypothesis shows possibilities for improvement of the balance between the photo- and dark current. Optimisation of the photoconductive gain changes the geometrical parameters of the detector and requires optimisation of the optical coupling.

Standard GaAs/AlGaAs Quantum Well Infrared Photodetectors (QWIP) are from now seriously considered for the 3^rd generation of IR imagers for military markets. Since 2002, the THALES Group has been manufacturing sensitive arrays using QWIP technology based on AsGa techniques through THALES Research and Technology Laboratory. This QWIP technology allows the realization of large staring arrays for Thermal Imagers (TI) working in the IR band III (8-12 μm). A review of the current QWIP products is presented. In the past researchers claimed many advantages of QWIPs. Uniformity was one of these and is the key parameter for the production start. By presenting our first results of a 640x512 LWIR FPA at a pitch of 20μm we also demonstrate that very high performances can be achieved even with small pixels which opens the field for the realization of usable and affordable megapixel FPAs. Another advantage widely claimed in the past for QWIPs was the so-called band-gap engineering and versatility of the III-V processing allowing the custom design of quantum structure to fulfill the requirements of specific applications like very long wavelength (VLWIR) or multispectral detection. In this presentation, we present the performances of our first 256x256 MWIR / LWIR two color FPA at a pitch of 25 μm, and also the current status of QWIPs for VLWIR arrays (>15μm).

This paper presents the activities performed for the modelling and experimental characterisation of a pyroelectric infrared detector. The work focuses on a LiTaO3 sensor which has been used as detector in the Long Wavelength Channel of a double channel IR spectrometer devoted to the study of Mars atmosphere, the MarsExpress Planetary Fourier Spectrometer, PFS. The need for an experimental characterization arise from the need of modelling the complete spectrometer for a correct interpretation of the scientific data collected while orbiting around Mars. The sensor of interest has been characterised along with its amplifying and conditioning proximity electronics. Because of the final use of the detector, i.e. FTIR spectrometry, the experimental characterization focuses on the frequency response and non-linear behaviour which respectively affects spectral responsivity and the presence of spectral features ghosts. Mathematical models available in literature describing the pyroelectric phenomena usually neglect the dependence of thermal characteristics on temperature and are intrinsically linear, therefore unfit for our needs. Because of the lack of information about the detector building characteristics, an accurate a priori model could not be straightforward implemented. An a posteriori model, derived from an identification process based on the detector testing has been developed and validated in order to have a simulation tool for the full spectrometer. The sensor exhibit nonlinearities, depending on all factors influencing the sensing element average temperature: incident infrared power, housing temperature. These nonlinearities can be traced back to the dependence on temperature of thermal characteristics of the sensing element, pyroelectric coefficient and the thermal capacity of LiTaO3 and on the nonlinearity of the radiative heat exchanges.

Between 25-35% of the Earth's outgoing longwave radiation (OLR) lies in the far-infrared (FIR) spectral region from 0- 500cm^-1 where the emission is primarily due to water vapour located in the upper and mid troposphere. The local maximum in the absorption spectrum of ice means that high, cold cirrus clouds have a large effect on intensity of the OLR here. To date, no FIR measurements of the OLR have been made from space, resulting in a major gap in our understanding of the Earth's radiative energy budget. Such measurements will provide vital information about the spatial and temporal variability of the OLR with relation to upper tropospheric humidity and clouds which will better constrain radiation parameterisations in general circulation models. REFIR (the Radiation Explorer in the Far-Infrared) is a polarising interferometer designed to bridge this knowledge gap by measuring the OLR from 100-1100cm^-1 at a spectral resolution of 0.5cm^-1. This instrument's performance is critically dependent on the properties (transmittance and reflectance) of the wire grid polarisers it uses as beamsplitters. These properties have been measured at Imperial College and incorporated into a mathematical (Jones' matrix) model of the interferometer's performance to produce simulated interferograms and spectra. When coupled to a model of detectors suitable for the FIR spectral region, potential spectral noise characteristics of the calibrated radiance spectra produced by REFIR have been modelled. So far, cryogenically cooled detector systems are far preferable to ambient temperature detectors, although measurements with un-cooled devices with suitable accuracies are possible with longer integration times. The effects of the changing scene beneath the interferometer during the interferogram acquisition time have been analysed.

TELIS (TErahertz and submm LImb Sounder) is a cooperation between European institutes, DLR, RAL, and SRON, to build a three-channel balloon-borne heterodyne spectrometer for atmospheric research. Many atmospheric trace gases have their rotational transitions in the sub millimeter and THz range, yielding a very rich spectrum. Limb sounding results in very accurate vertical profiles. All three TELIS receivers will operate simultaneously. The 500 GHz channel is developed by RAL and will produce vertical profiles of BrO, ClO, O₃, and N₂O. The 1.8 THz channel is developed by DLR and will mainly target the OH radical, and will also measure HO₂, HCl, NO, NO₂, O₃, H₂O, O₂, and HOCl. Finally the 550 - 650 GHz channel is developed by SRON and IREE and will measure profiles of ClO, BrO, O₃ and its isotopologues, HCl, HOCl, H₂O and its isotopologues, HO₂, CO, NO, N₂O, HNO₃, CH₃Cl, and HCN. TELIS will fly on the MIPAS-B2 gondola. The two instruments together will yield the most complete set of stratospheric constituents. The qualification flight is foreseen in the winter of 2006/2007. The TELIS instrument serves as a test bed for many novel cryogenic heterodyne technology: novel low-noise cryogenic heterodyne mixer detectors, novel low-noise cryogenic intermediate-frequency amplifiers, novel back-end spectrometer. In the presentation these technologies will be discussed and compared with 'conventional' technology as applied in the Microwave Limb Sounder (MLS) on EOS-Aura, launched in 2004. Emphasis will be on the science and technology of the channel developed by SRON. It contains a Superconducting Integrated Receiver (SIR), which combines on a 4x4 mm² chip the low-noise Superconductor-isolator-Superconductor (SIS) mixer and its quasi-optical antenna, a superconducting phase-locked Flux Flow Oscillator (FFO) acting as Local Oscillator (LO) and SIS Harmonic Mixer (HM) for FFO phase locking. Latest test results and retrieval simulations will be presented.

This paper will discuss and compare recent refractive and catodioptric imager designs developed and manufactured at SunSpace for Multi Sensor Satellite Imagers with Panchromatic, Multi-spectral, Area and Hyperspectral sensors on a single Focal Plane Array (FPA). These satellite optical systems were designed with applications to monitor food supplies, crop yield and disaster monitoring in mind. The aim of these imagers is to achieve medium to high resolution (2.5m to 15m) spatial sampling, wide swaths (up to 45km) and noise equivalent reflectance (NER) values of less than 0.5%. State-of-the-art FPA designs are discussed and address the choice of detectors to achieve these performances. Special attention is given to thermal robustness and compactness, the use of folding prisms to place multiple detectors in a large FPA and a specially developed process to customize the spectral selection with the need to minimize mass, power and cost. A refractive imager with up to 6 spectral bands (6.25m GSD) and a catodioptric imager with panchromatic (2.7m GSD), multi-spectral (6 bands, 4.6m GSD), hyperspectral (400nm to 2.35μm, 200 bands, 15m GSD) sensors on the same FPA will be discussed. Both of these imagers are also equipped with real time video view finding capabilities. The electronic units could be subdivided into the Front-End Electronics and Control Electronics with analogue and digital signal processing. A dedicated Analogue Front-End is used for Correlated Double Sampling (CDS), black level correction, variable gain and up to 12-bit digitizing and high speed LVDS data link to a mass memory unit.

In recent years the Italian Space Agency funded a feasibility study for an aerospace imaging interferometer for Earth Observation. The instrument, named ALISEO (Aerospace Leap-frog Imaging Stationary Interferometer for Earth Observation), belongs to the class of the so called "stationary interferometers," and it operates in the common path Sagnac configuration not employing any moving parts to generate phase delay. ALISEO acquires the target image as modulated by a pattern of autocorrelation functions of the energy coming from each target's location. The complete interferogram is retrieved introducing relative source-observer motion. In order to calibrate the optical-path-difference (OPD) axis of the raw interferograms, a set of measurements have been carried out illuminating a double planar diffuser system by He-Ne lasers operating at different wavelengths. Standard reflectance tiles together with diffusers doped with Holmium and Rare Earths have been used to verify the wavelength calibration of the instrument. Finally, a procedure for raw data pre-processing aimed at retrieving at-sensor radiance spectra is developed taking into account the issues of dark signal subtraction, spectral instrument response compensation, effects of vignetting, and Fourier back-transform algorithm.

The Remote Sensing Laboratory at INTA owns and operates an 80-band airborne hyperspectral line-scanner radiometer, alias AHS. This instrument is based on previous airborne hyperspectral scanners as MIVIS and MAS. This instrument has been installed in the INTA´s aircraft (CASA C-212), and integrated with a GPS/INS. The acquired imagery is processed and archived by INTA. For this purpose, a processing chain has been implemented at the INTA premises in Madrid. In this chain, raw data (level 0 product) is transformed to at-sensor radiance (level 1b) and later to geolocated at-sensor radiance (level 1c). Other processing levels, as atmospherically corrected reflectance, brightness temperature or surface emissivity could also be produced. The radiometric calibration is based on laboratory measurements using an integrating sphere for the reflective bands, and on in-flight blackbodies measurements for the thermal bands. The geolocation procedure is based on processing of GPS/INS data synchronized with the imagery collection. Finally, direct parametric georeferencing is achieved by means of the commercial software PARGE. The resulting system is available to the international remote sensing community through specific agreements (contractual or based on joint collaborations). As an example of the use of this system, an on-going project to evaluate water stress in olives in southern Spain is presented. In this project, high resolution thermal radiometry is used to evaluate tree temperature, while reflective bands are used for identifying individual trees and for simultaneous monitoring of plant health.

Collecting data using different sensors mounted on different platforms is the challenge of multisensorics. Applications in Synthetic Aperture Radar (SAR) normally lead to extreme bi- or multistatic constellations in the multisensorial case. This paper describes basic considerations concerning the geometry, especially the antenna steering for a bistatic SAR experiment. Using the TerraSAR-X as a transmitter and a SAR system mounted on a plane as a receiver we want to record experimental raw data for further processing. Because of the high difference between the velocity of the transmitter platform and that of the receiver platform relative to a point target, stripmap mode is not useful in this case. By operating the transmitter in sliding spotlight or spotlight mode and using antenna steering to provide footprint chasing on the side of the receiving system, a useful scene extension in azimuth can be achieved. This is of course at the cost of a shorter time interval in which the point target is both illuminated by the transmitter and seen by the receiver. First simulations of a point target response will show that nevertheless we can expect a useful Doppler bandwidth and thus an adequate resolution in azimuth.

Operational SAR satellite missions impose new requirements to on-board data compression such as a higher data reduction ratio, more flexibility, and faster data throughput. A recent approach is Entropy-Constrained Block Adaptive Quantization (ECBAQ). This method outperforms currently-used Block Adaptive Quantization with respect to Signal-to-Quantization-Noise-Ratio. The ECBAQ algorithm can be implemented using an architecture that is essentially not more complicated than that of a BAQ encoder and suitable for high-speed implementations. Moreover, the method features bit rate programmability with non-integer rates. This allows the SAR information throughput to be optimized for different types of applications. This paper presents a new ECBAQ version including a rate control loop, avoiding the need for the multiplexing of block variance levels into the compressed data stream and further reducing the complexity of the implementation. The presented method is very well suited for application with frequency domain data due to its high instantaneous dynamic range and non-integer rate capabilities. Preceded by an FFT device which transforms the data in both range and azimuth direction, more data reduction can be achieved by frequency filtering and decimation. In addition, using variable bit allocation matched to the SAR processor's weighting functions, even higher compression ratios can be achieved. Overall, the compression improvement may range over 100% as compared to the conventional BAQ method while maintaining the same image quality. In conclusion, FFT-ECBAQ is a strong candidate for application in future SAR missions.

This paper describes techniques that have been investigated in order to minimise RF interference effects between a 35.5GHz radar and a multi-frequency radiometer with one of its bands operating around 36.5 GHz. One of the main potential interference paths identified is direct coupling between the instruments' antennas: both instruments have high-gain, earth pointing reflector antennas. The instruments are to be accommodated on a small satellite and, unlike large multi- instrument platforms, it is not possible to use the satellite structure to isolate them. The radiometer antenna is scanned mechanically over a large sector and there are no feasible options for introducing baffles or shields in order to reduce the antenna coupling factor. Instead, techniques that have been looked at include frequency-domain filtering and time-domain blanking. Blanking is achieved using a PIN switch to isolate the input to the radiometer channel during the period when the radar is transmitting. Whilst the approach can reduce the effects of interference to acceptable levels there is the potential for the PIN switch to degrade the radiometer's performance in other ways. Although such switches have been used in Dicke switch radiometers there is little reported information on their use in total power radiometers as is proposed here. Therefore a programme of tests was conducted to investigate the stability and repeatability of a PIN switch placed in the front-end of a representative radiometer. These tests, the results obtained and the conclusions drawn are reported on.

The most precise navigation systems are commonly based on at least 3 laser gyros and 3 mechanical accelerometers, based on moving or tensioned elements. Laser gyro's "dead zone" guides to existence of additive subsystems, and mechanical accelerometer accumulate the "error of zero" and does not measure during the free fall of an object. Here is found that dead zone on laser gyro characteristics is a result of the precession of momentum of pulse of ring baghron. The necessity of precise laser gyro tuning in Alert city, Canada, is discussed. The method to minimize the precession and to avoid the dead zone on the output characteristics is proposed. Therewith new solutions for autonomous control and navigation are discussed. Here is proposed the autonomous unit of sensors of irregular movement without moving parts and without ring laser resonators, disposed motionless on the object to be measured, based on unique unified 6 mini modules of the autonomous resonatory devices (ARD's). Another new solution could be computer 3D-mouse without pad and with 3 independent outputs for each axis of irregular movement, or the gear of control, which could be arranged in the marker or pen. ARD theory, the experiments and testing are discussed.

According to the requirements of China National Scientific Data Sharing Program (NSDSP), the research and development of web oriented RS Image Publication System (RSIPS) is based on Java Servlet technique. The designing of RSIPS framework is composed of 3 tiers, which is Presentation Tier, Application Service Tier and Data Resource Tier. Presentation Tier provides user interface for data query, review and download. For the convenience of users, visual spatial query interface is included. Served as a middle tier, Application Service Tier controls all actions between users and databases. Data Resources Tier stores RS images in file and relationship databases. RSIPS is developed with cross platform programming based on Java Servlet tools, which is one of advanced techniques in J2EE architecture. RSIPS's prototype has been developed and applied in the geosciences clearinghouse practice which is among the experiment units of NSDSP in China.

TERRA MODIS band 31 was selected as the criterion for doing the radiometric cross-calibration of CBERS-02 IRMSS band 9 in this paper. From August to December, 2004, seven times day and night synchronous images of two sensors passing through the Lake Qinghai and Lake Taihu were selected to get the cross-calibration data. Using TERRA MODIS band 31 data to conduct out the at pupil radiance of CBERS-02 IRMSS band 9 based on the two sensors' spectrum matching, and then pick-up the DN values from the IRMSS data in the same area. A new model to calculate the radiometric calibration coefficients was carried out in this paper: multi-points linear regression method with 7 times day and night synchronous images at different dates and locations. This new method can obviously control the radiometric calibration uncertainties aroused by the single point method to do the in-flight calibration like CBERS-02 IRMSS, this kind of sensors can't collect the radiometric signals from the deep space. In this research, the radiometric calibration coefficients obtained through the linear regression method were 8.0567 (gain, unit: DN/ (W/m2/sr1/μm1)) and 47.892 (offset, unit: DN). Preliminary estimate of calibration coefficients using Shanghai area was carried out and the results showed that the calibration coefficients obtained from the linear regression method was with a similar precision to TERRA MODIS band 31's. This suit of calibration coefficients can satisfy the quantitative applications of CBERS-02 IRMSS thermal data.

The Chinese Marine Surveillance Plane B-3837 was devolved to East Sea Branch of State Oceanic Administration and made its virgin flight in May, 2004. So far, China Marine Surveillance Force has her own modern aerial equipments for marine law-execute with the advantage of functioning agilely and operation of larger surveillance coverage, providing powerful safeguard all-round, harmonious and sustainable development of coastal economy. On the plane, three remote sensing scanners have been equipped, including a marine airborne multi-spectrum scanner (MAMS), an optical-electronic platform, and an airborne hyperspectral system AISA+. Among them, MAMS, made by Shanghai Institute of Technology and Physics CAS, will be introduced in detail in this paper. We will describe the specification and characteristics of the multi-spectrum scanner, and then the bands configuration and use of these bands. After that are MAMS' construction and its imaging mode. At last we will focus on its potentiality for oceanic remote sensing.

Precise measurements of CH₄ in a column of near surface air, and in partial columns above this, would be very valuable in identifying sources/sinks of atmospheric CH₄, and its transport. For this purpose we have proposed a grating mapping spectrometer (GMS) for deployment as an Instrument of Opportunity (IOO) on the NPOESS that acquires data in the 2990 to 3050 cm^-1 spectral region. It will provide measurements of CH₄ absorption of sunlight in the weaker CH₄ features in the region, and of thermal emission in the stronger CH₄ features in the region. It is the combination of the two that provides the vertical information. The IOO will acquire spectra on a crosstrack swath centered on nadir, and with 1/2 width of 55 degrees on each side of nadir (about 2800 km full width swath on the ground for a nominal 828 km satellite altitude). This with footprints that are about 3.1 km on a side at nadir. The small footprint facilitates cloud screening, and identification of CH₄ source hotspots. A capability to project the slit to nadir along the direction from satellite to sun will be utilized for over the ocean viewing in order to facilitate measurements in solar glitter. It will obtain spectra with resolution n < 0.58 cm^-1 and sample spacing < 0.17 cm^-1. Based on the spectral characteristics and currently achievable very low-noise we do a linear error analysis (Rodgers, [1]) for the simultaneous retrieval of multi-column CH₄, humidity, and surface parameters and ¹³CH₄ total column. We show that useful multi-column CH₄ retrievals can be obtained, with good near surface sensitivity in sunlit conditions. We also show the ¹³CH₄ column can be retrieved with precision better than 3%. Retrieval of ¹³CH₄ column in the earth's atmosphere is analogous in difficulty to retrieval of the major CH₄ isotope column in the Martian atmosphere by a similar GMS deployed on a Mars orbiter. We show that H₂O vertical information can be retrieved from these measurements and discuss the potential for ethane column retrieval.

High spatial-spectral resolution space based observations in visible-near infrared VNIR portion of the spectrum are required for a variety of remote sensing applications including ocean color, land surface classification, and atmospheric monitoring. In conventional approaches, the spectral selectivity is accomplished by means of interferometry, a series of pass-band filters (channels), or grating based spectrometers selectively designed to cover the spetral domain of interest for a given application. Unfortunately, these schemes are not able to modify the spectral channels for different applications as may be required for an all purpose imager. To accomplish tunability, we examine the feasibility of using Fabry Perot technology and show that by using a dual etalon system, we can achieve sufficient sensitivity and spectral filtration for ocean color observations which are the most difficult radiometrically. System specifications are oultlined and signal to noise ratio (SNR) estimates are developed as a function of the pixel-pixel integration time. Finally, the effects of out of band signals are considered and it is shown that a signal inversion scheme can be used for accurate retrieval of signals.