This PDF file contains the front matter associated with SPIE Proceedings Volume 8889, including the Title Page, Copyright information, Table of Contents, Invited Panel Discussion, and Conference Committee listing.

Five programs, i.e. TRMM, AMSR-E, ASTER, GOSAT and GCOM-W1 are going on in Japanese Earth Observation programs. ASTER has lost its short wave infrared channels. AMSR-E stopped its operation, but it started its operation from Sep. 2012. GCOM-W1 was launched on 18, May, 2012 and is operating well as well as TRMM and GOSAT. ALOS (Advanced Land Observing Satellite) was successfully launched on 24th Jan. 2006. ALOS carries 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). Unfortunately, ALOS has stopped its operation on 22nd, April, 2011 by power loss. GOSAT (Greenhouse Gas Observation Satellite) was successfully launched on 29, January, 2009. GOSAT carries 2 instruments, i.e. a green house gas sensor (TANSOFTS) and a cloud/aerosol imager (TANSO-CAI). The main sensor is a Fourier transform spectrometer (FTS) and covers 0.76 to 15 μm region with 0.2 to 0.5 cm^-1 resolution. SMILES (Super-conducting Millimeter wave Emission Spectrometer) was launched on September 2009 to ISS and started the observation, but stopped its operation on April 2010. After the unfortunate accident of ADEOS2, JAXA still have plans of Earth observation programs. Next generation satellites will be launched in 2012-2015 timeframe. They are, GCOM-C (ADEOS-2 follow on), and GPM (Global Precipitation Mission) core satellite. 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). GCOM-C1 will be launched on fiscal 2016, GPM core satellite will be launched on 2014 and EarthCare will be launched on 2015. ALOS F/O satellites are divided into two satellites, i.e. SAR and optical satellites. The first one of ALOS F/O is called ALOS 2 and will carry L-band SAR. It will be launched on fiscal 2013. JAXA is planning to launch follow on of optical sensors on ALOS. GOSAT2 project is going to start and will be launched on 2018.

The Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) is one of the five sensors on the NASA’s Terra satellite on orbit since December 1999. ASTER consists of three radiometers, the Visible and Near InfraRed (VNIR), the Short-Wave InfraRed (SWIR) and Thermal InfraRed (TIR) whose spatial resolutions are 15 m, 30 m and 90 m, respectively. Unfortunately the SWIR image data are saturated since April 2008 due to the offset rise caused by the cooler temperature rise, but the VNIR and the TIR are taking Earth images of good quality. The VNIR and the TIR experienced responsivity degradation while the SWIR showed little change. From the lamp calibration, Band 1 decreased the most among three VNIR bands and 31% in thirteen years. The VNIR has the electrical calibration mode to check the healthiness of the electrical circuits through the charge coupled device (CCD). Four voltage levels from Line 1 to Line 4, which are from 2.78 V to 3.10 V, are input to the CCD in the onboard calibration sequence and the output digital numbers (DNs) are detected in the images. These input voltages are monitored as telemetry data and have been stable up to now. From the electrical calibration we can check stabilities of the offset, gain ratio and gain stability of the electric circuit. The output level of the Line1 input is close to the offset level which is measured while observing the earth at night. The trend of the Line 1 output is compared to the offset level. They are similar but are not exactly the same. The trend of the even pixel and odd pixel is the same so the saturated offset levels of the odd pixel is corrected by using the even pixel trend. The gain ratio trend shows that the ratio is stable. But the ratio values are different from those measured before launch. The difference comes up to 10% for the Band 2. The correct gain ratio should be applied to the vicarious calibration result because the onboard calibration is measured with the Normal gain whereas the vicarious calibration often measures with the High gain. The cause of the VNIR responsivity degradation is not known but one of the causes might be the change of the electric circuit. The band 3 gain shows 16 % decrease whereas the gain changes of the band 1 and band 2 are 5% to 8%. The responsivity decrease after 1000 days since launch might be controlled by the electric circuit change.

The Advanced Land Observing Satellite-2 (ALOS-2) carries the state-of-the-art L-band Synthetic Aperture Radar (SAR) called PALSAR-2 which succeeds to the ALOS / PALSAR. PALSAR-2 will have enhanced performance in both high resolution and wide swath compared to PALSAR. It will allow comprehensive monitoring of disasters. Wider bandwidth and shorter revisit time will give better conference for INSAR data analysis such as crustal deformation and deforestation. The Proto Flight Test (PFT) of ALOS-2 has been conducted since June 2012. In parallel, the PFT of PALSAR-2 has been conducted since March 2012. As of August 2013, ALOS-2 system has completed the interface test with ground system and is preparing for the Vibration test, Acoustic test and Electromagnetic Compatibility test. After completing these tests, ALOS-2 will be transported to JAXA Tanegashima Space Center for launch. The initial commissioning phase of ALOS-2 is planned for six months which are comprised of LEOP (Launch and Early Orbit Phase) and initial Cal/Val phase. During the LEOP, all components will be checked with direct downlink via Xband and with data relay communication via JAXA’s DRTS (Data Relay Test Satellite). During the initial Cal/Val phase, the PALSAR-2 data will be verified and calibrated by using Corner Reflectors and Geometric Calibrator at ground. The data acquisition during the commissioning phase will be consistent with the systematic acquisition strategy prepared for the routine operation. This paper describes the current status and operation plan of ALOS-2.

ESA and JAXA plan to launch a satellite called EarthCARE (Earth Clouds, Aerosols and Radiation Explorer). The Cloud Profiling Radar (CPR), which will be the first millimeter-wave Doppler radar in space, is installed on this satellite as one of main sensors to observe clouds. This paper describes the design results and PFM performance of EarthCARE CPR.

Fourier transform spectrometer (FTS) has many advantages, especially for greenhouse gases and air pollution detection in the atmosphere, because a single instrument can provide wide spectral coverage and high spectral resolution with highly stabilized instrumental line function for all wavenumbers. Several channels are usually required to derive the column amount or vertical profile of a target species. Near infrared (NIR) and shortwave infrared (SWIR) spectral regions are very attractive for remote sensing applications. The GHG and CO of precursors of air pollution have absorption lines in the SWIR region, and the sensitivity against change in the amounts in the boundary layer is high enough to measure mole fractions near the Earth surface. One disadvantage of conventional space-based FTS is the spatial density of effective observation. To improve the effective numbers of observations, an imaging FTS coupled with a two-dimensional (2D)-camera was considered. At first, a mercury cadmium telluride (MCT)-based imaging FTS was considered. However, an MCT-based system requires a calibration source (black body and deep-space view) and a highly accurate and super-low temperature control system for the MCT detector. As a result, size, weight, and power consumption are increased and the cost of the instrument becomes too high. To reduce the size, weight, power consumption, and cost, a commercial 2D indium gallium arsenide (InGaAs) camera can be used to detect SWIR light. To demonstrate a small imaging SWIR-FTS (IS-FTS), an imaging FTS coupled with a commercial 2D InGaAs camera was developed. In the demonstration, the CH4 gas cell was equipped with an IS-FTS for the absorber to make the spectra in the SWIR region. The spectra of CH4 of the IS-FTS demonstration model were then compared with those of traditional FTS. The spectral agreement between the traditional and IS-FTS instruments was very good.

NASA’s Earth Science Division (ESD) conducts pioneering work in Earth system science, the interdisciplinary view of Earth that explores the interaction among the atmosphere, oceans, ice sheets, land surface interior, and life itself that has enabled scientists to measure global and climate changes and to inform decisions by governments, organizations, and people in the United States and around the world. The ESD makes the data collected and results generated by its space missions accessible to other agencies and organizations to improve the products and services they provide, including air quality indices, disaster management, agricultural yield projections, and aviation safety. Through partnerships with national and international agencies, NASA enables the application of this understanding. The ESD’s Flight Program provides the spacebased observing systems and supporting ground segment infrastructure for mission operations and scientific data processing and distribution that support NASA’s Earth system science research and modeling activities. The Flight Program currently has 15 operating Earth observing space missions, including the recently launched Landsat-8/Landsat Data Continuity Mission (LDCM). The ESD has 16 more missions planned for launch over the next decade. These include first and second tier missions from the 2007 Earth Science Decadal Survey, Climate Continuity missions to assure availability of key data sets needed for climate science and applications, and small-sized competitively selected orbital missions and instrument missions of opportunity utilizing rideshares that are part of the Earth Venture (EV) Program. The recently selected Cyclone Global Navigation Satellite System (CYGNSS) microsatellite constellation and the Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument are examples. In addition, the International Space Station (ISS) is being increasingly used to host NASA Earth observing science instruments. An overview of plans and current status will be presented.

The Global Precipitation Measurement (GPM) mission will advance the measurement of global precipitation, making possible high spatial resolution precipitation measurements. GPM will provide the first opportunity to calibrate measurements of global precipitation across tropical, mid-latitude, and polar regions. The GPM mission has the following scientific objectives: (1) Advance precipitation measurement capability from space through combined use of active and passive remote-sensing techniques; (2) Advance understanding of global water/energy cycle variability and fresh water availability; (3) Improve climate prediction by providing the foundation for better understanding of surface water fluxes, soil moisture storage, cloud/precipitation microphysics and latent heat release in the Earth's atmosphere; (4) Advance Numerical Weather Prediction (NWP) skills through more accurate and frequent measurements of instantaneous rain rates; and (5) Improve high impact natural hazard (flood/drought, landslide, and hurricane hazard) prediction capabilities. The GPM mission centers on the deployment of a Core Observatory carrying an advanced radar / radiometer system to measure precipitation from space and serve as a reference standard to unify precipitation measurements from a constellation of research and operational satellites. GPM, jointly led with the Japan Aerospace Exploration Agency (JAXA), involves a partnership with other international space agencies including the French Centre National d’Études Spatiales (CNES), the Indian Space Research Organisation (ISRO), the U.S. National Oceanic and Atmospheric Administration (NOAA), the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), and others. The GPM Core Observatory is currently being prepared for shipment to Japan for launch. Launch is scheduled for February 2014 from JAXA’s Tanegashima Space Center on an H-IIA 202 launch vehicle.

The EUMETSAT Polar System (EPS) will be followed by a second generation system, EPS-SG, in the 2020-2040 timeframe and contribute to the Joint Polar System being jointly set up with NOAA. Among the various missions which are part of EPS-SG, there are the Microwave Imager (MWI) and the Ice Cloud Imager (ICI). The MWI frequencies are from 18 GHz up to 183 GHz. All MWI channels up to 89 GHz measure both V and H polarisations. The primary objective of the MWI mission is to support Numerical Weather Prediction at regional and global scales. The MWI will not only provide continuity of measurements for some heritage microwave imager channels (e.g. SSM/I, AMSR-E) but will also include additional channels such as the 50-55 / 118 GHz bands. The combined use of these channels will provide more information on cloud and precipitation over sea and land. The ICI will provide measurements over the sub-millimetre spectral range contributing to an innovative characterisation of clouds over the whole globe. The ICI has channels at 183 GHz, 325 GHz and 448 GHz with single V polarisation and two channels at 243 GHz and 664 GHz with both V and H polarisation. The ICI’s primary objectives are to support climate monitoring and validation of ice cloud models and the parameterisation of ice clouds in weather and climate models through the provision of ice cloud products.

The Multi-viewing ,Multi-channel, Multi-polarisation Imager (3MI) of the EUMETSAT Polar System - Second Generation (EPS-SG) is a two-dimensional push broom radiometer dedicated to aerosol characterisation for climate monitoring, air quality forecasting and Numerical Weather Prediction (NWP). The purpose of the 3MI concept is to provide a multi-spectral (from 410 to 2130 nm), multi-polarisation (-60°, 0°, and +60°), and multi-angular (10 to 14 views) image of the Earth outgoing radiance at the top of the atmosphere (TOA) in order to accurately measure the aerosol load and thereby resolve the directional anisotropy and the microphysical properties of aerosol. The 3MI heritage comes from the Polarisation and Directionality of the Earth's Reflectances (POLDER) and Polarisation and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL), with 3 instruments launched since 1996.

The MetOp-SG programme is a joint Programme of EUMETSAT and ESA. ESA develops the prototype MetOp-SG satellites (including associated instruments) and procures, on behalf of EUMETSAT, the recurrent satellites (and associated instruments). Two parallel, competitive phase A/B1 studies for MetOp Second Generation (MetOp-SG) have been concluded in May 2013. The implementation phases (B2/C/D/E) are planned to start the first quarter of 2014. ESA is responsible for instrument design of six missions, namely Microwave Sounding Mission (MWS), Scatterometer mission (SCA), Radio Occultation mission (RO), Microwave Imaging mission (MWI), Ice Cloud Imager (ICI) and Multi-viewing, Multi-channel, Multi-polarisation imaging mission (3MI). The paper will present the main performances of the 3MI instrument and will highlight the performance improvements with respect to its heritage derived by the POLDER instrument, such as number of spectral channels and spectral range coverage, swath and ground spatial resolution. The engineering of some key performance requirements (multi-viewing, polarisation sensitivity, straylight etc.) will also be discussed. The results of the feasibility studies will be presented together with the programmatics for the instrument development. Several pre-development activities have been initiated to retire highest risks and to demonstrate the ultimate performances of the 3MI optics. The scope, objectives and current status of those activities will be presented. Key technologies involved in the 3MI instrument design and implementation are considered to be: the optical design featuring aspheric optics, the implementation of broadband Anti Reflection coatings featuring low polarisation and low de-phasing properties, the development and qualification of polarisers with acceptable performances as well as spectral filters with good uniformities over a large clear aperture.

GMES is a joint initiative of the European Commission (EC) and the European Space Agency (ESA), designed to establish a European capacity for the provision and use of operational monitoring information for environment and security applications. ESA’s role in GMES is to provide the definition and the development of the space- and ground-related system elements. GMES Sentinel-2 mission provides continuity to services relying on multi-spectral highresolution optical observations over global terrestrial surfaces. The key mission objectives for Sentinel-2 are: (1) to provide systematic global acquisitions of high-resolution multi-spectral imagery with a high revisit frequency, (2) to provide enhanced continuity of multi-spectral imagery provided by the SPOT series of satellites, and (3) to provide observations for the next generation of operational products such as landcover maps, land change detection maps, and geophysical variables. Consequently, Sentinel-2 will directly contribute to the Land Monitoring, Emergency Response, and Security services. The corresponding user requirements have driven the design towards a dependable multi-spectral Earthobservation system featuring the MSI with 13 spectral bands spanning from the visible and the near infrared to the short wave infrared. The spatial resolution varies from 10 m to 60 m depending on the spectral band with a 290 km field of view. This unique combination of high spatial resolution, wide field of view and large spectral coverage will represent a major step forward compared to current multi-spectral missions. The mission foresees a series of satellites, each having a 7.25-year lifetime (extendable to 12 years) over a 20-year period starting with the launch of Sentinel-2A foreseen by mid-2014. During full operations two identical satellites will be maintained in the same sun synchronous orbit with a phase delay of 180° providing a revisit time of five days at the equator.

The first Sentinel-2 satellites, which constitute the next generation of operational Earth observation satellites for optical land monitoring from space, are undergoing completion in the facilities at Astrium ready for launch end 2014. Sentinel-2 will feature a major breakthrough in the area of optical land observation since it will for the first time enable continuous and systematic acquisition of all land surfaces world-wide with the Multi-Spectral Instrument (MSI), thus providing the basis for a truly operational service. Flying in the same orbital plane and spaced at 180°, the constellation of two satellites, designed for an in-orbit nominal operational lifetime of 7 years each, will acquire all land surfaces in only 5 days at the equator. In order to support emergency operations, the satellites can further be operated in an extended observation mode allowing to image any point on Earth even on a daily basis. MSI acquires images in 13 spectral channels from Visible-to-Near Infrared (VNIR) to Short Wave Infrared (SWIR) with a swath of almost 300 km on ground and a spatial resolution up to 10 m. The data ensure continuity to the existing data sets produced by the series of Landsat and SPOT satellites, and will further provide detailed spectral information to enable derivation of biophysical or geophysical products. Excellent geometric image quality performances are achieved with geolocation better than 16 m, thanks to an innovative instrument design in conjunction with a high-performance satellite AOCS subsystem centered around a 2-band GPS receiver, high-performance star trackers and a fiberoptic gyro. To cope with the high data volume on-board, data are compressed using a state-of-the-art wavelet compression scheme. Thanks to a powerful mission data handling system built around a newly developed very large solid-state mass memory based on flash technology, on-board compression losses will be kept to a minimum. The Sentinel-2 satellite design features a highly flexible operational concept, allowing downlink of all mission data to a nominal X-band core ground stations network. In addition, users could receive mission data sets at selected X-band local user ground stations or through an Optical Communication Payload (OCP) via an inter-orbit optical link to a geostationary EDRS relay satellite at Ka-band user ground stations. Different priority schemes can be selected in flight to allow transmission of critical image data with the shortest possible latency. The system is designed for high system autonomy allowing for pre-programming of the operational schedule for 15 days in advance without interference from ground. Apart from the nominal and extended imaging modes, the satellites also feature a calibration mode to support regular in-orbit radiometric calibration of the instrument. Overall, the Sentinel- 2 satellites are designed to provide in-orbit availability for the instrument data greater than 97%, which fulfills the requirements of a fully operational system for multispectral Earth observation.

The MSI PFM campaign is built around 4 major steps : the focal planes alignment and testing, the telescope alignment and testing, the instrument performance testing and the instrument environmental qualification.. This paper presents the results of the first 3 steps covering major performance aspects of the Sentinel-2 Multi-Spectral Instrument.

The Tropospheric Monitoring Instrument, TROPOMI, is a passive UV-VIS-NIR-SWIR spectrograph, which uses sun backscattered radiation to study the Earth's atmosphere and to monitor air quality, on both global and local scale. It follows in the line of SCIAMACHY (2002) and OMI (2004), both of which have been very successful. OMI is still operational. TROPOMI is scheduled for launch in 2015. Compared with its predecessors, TROPOMI will take a major step forward in spatial resolution and sensitivity. The nominal observations are at 7 x 7 km² at nadir and the signal-tonoises are sufficient for trace gas retrieval even at very low albedos (2 to 5%). This allows observations of air quality at sub-city level. TROPOMI has reached CDR status and production of flight model units has started. Flight detectors have been produced and detector electronics is expected to be finished by mid-2013. The instrument control unit is undergoing extensive tests, to ensure full instrument functionality. Early results are promising and this paper discusses these H/W results, as well as some challenges encountered during the development of the instrument.

The PRISMA (PRecursore IperSpettrale della Missione Applicativa) Programme is an ASI (Agenzia Spaziale Italiana) hyperspectral mission for Earth observation based on a mono-payload single satellite: an Italian Consortium is in charge to realize the mission; Selex ES has the full responsibility of the hyperspectral payload composed by a high spectral resolution spectrometer optically integrated with a medium resolution panchromatic camera. The optical design permits to cover the wavelength range from 400 to 2500 nm and it is based on high transmittance optical assemblies, including a reflective common telescope in Three-Mirror Anastigmat (TMA) configuration, a single slit aperture, a panchromatic camera (700-900 nm) and a spectrometer having two channels (VNIR and SWIR), each one using an suitable prism configuration and spectrally separated by a beam splitter, conceived to minimize the number of optical elements. High performance MCT-based detectors represent the core of the instrument. To provide the required data quality for the entire mission lifetime (5 years), an accurate and stable calibration unit (radiometric and spectral) is integrated, for the in-flight instrument calibration. The thermal design has been based on a passive cooling system: a double stage radiator, suitable oriented and protected from unwanted heat fluxes, high performance heat pipes and an operational heaters network represent the solution adopted to achieve the required thermal stability.

The Fluorescence Explorer (FLEX) mission is currently subject to feasibility (Phase A) study as one of the two candidates of ESA’s 8th Earth Explorer opportunity mission. The FLuORescence Imaging Spectrometer (FLORIS) will be an imaging grating spectrometer onboard of a medium sized satellite flying in tandem with Sentinel-3 in a Sun synchronous orbit at a height of about 815 km. FLORIS will observe vegetation fluorescence and reflectance within a spectral range between 500 nm and 780 nm. It will thereby cover the photochemical reflection features between 500 nm and 600 nm, the Chlorophyll absorption band between 600 and 677 nm, and the red-edge in the region from 697 nm to 755 nm being located between the Oxygen A and B absorption bands. By this measurement approach, it is expected that the full spectrum and amount of the vegetation fluorescence radiance can be retrieved, and that atmospheric corrections can efficiently be applied. FLORIS will measure Earth reflected spectral radiance at a relatively high spectral resolution of ~0.3 nm around the Oxygen absorption bands. Other spectral band areas with less pronounced absorption features will be measured at medium spectral resolution between 0.5 and 2 nm. FLORIS will provide imagery at 300 m resolution on ground with a swath width of 150 km. This will allow achieving global revisit times of less than one month so as to monitor seasonal variations of the vegetation cycles. The mission life time is expected to be at least 4 years. The fluorescence retrieval will make use of information coming from OLCI and SLSTR, which are onboard of Sentinel-3, to monitor temperature, to detect thin clouds and to derive vegetation reflectance and information on the aerosol content also outside the FLORIS spectral range. In order to mitigate the technological and programmatic risk of this Explorer mission candidate, ESA has initiated two comprehensive bread-boarding activities, in which the most critical technologies and instrument performance shall be investigated and demonstrated. The breadboards will include representative optics and dispersive elements in a configuration, which is expected to be very close to the instrument flight configuration. This approach follows the guideline to reach, before it goes into the implementation phase, a technology readiness level of at least 5. It thereby requires a demonstration of predicted performance in a configuration, where the basic technological components are integrated with reasonably realistic supporting elements such that it can be tested in a simulated environment. We will report, within the limits of the competitive nature of the industrial studies, on the currently running or planned preparatory activities. We will present the mission configuration, the imposed instrument requirements and the identified instrument concepts as derived by the Phase A studies.

Since launch, Terra MODIS has successfully operated for more than 13 years and Aqua MODIS more than 11 years. High quality science data products are continuously produced from sensor calibrated radiance and reflectance, or the Level 1 (L1B) data products, and distributed to worldwide users for a broad range of studies of the earth’s land, ocean, and atmospheric properties and their changes over time. MODIS observations are made in 20 reflective solar bands (RSB) and 16 thermal emissive bands (TEB). The RSB are calibrated using data collected from its on-board solar diffuser and lunar observations, and the TEB are calibrated by an on-board blackbody (BB). On-orbit changes in the sensor’s spectral and spatial characteristics are monitored by an on-board spectroradiometric calibration assembly (SRCA). This paper presents an overview of both Terra and Aqua MODIS on-orbit operations, calibration activities, and methodologies applied from launch to present, and the current instrument status. It provides a summary of their radiometric, spectral, and spatial calibration and characterization performance. It discusses on-orbit changes in sensor characteristics and correction strategies applied to maintain the sensor calibration and level 1B (L1B) data quality, including lessons that could benefit future calibration efforts and other earth-observing sensors.

Terra and Aqua MODIS have successfully operated for more than 13 and 11 years since their launch in 1999 and 2002, respectively. The VIIRS instrument on-board the S-NPP launched in 2011 has also operated for nearly 2 years. Both MODIS and VIIRS make observations in the reflective solar and thermal emissive regions and their on-orbit calibration and characterization are provided by a set of on-board calibrators (OBC). In addition, lunar observations have been made on a regular basis to support sensor on-orbit calibration. This paper provides a brief overview of MODIS and VIIRS instrument on-orbit calibration and characterization activities. It describes the approaches and strategies developed to schedule and perform on-orbit lunar observations. Specific applications of MODIS and VIIRS lunar observations discussed in this paper include radiometric calibration stability monitoring and performance assessment of sensor spatial characterization. Results derived from lunar observations, such as sensor response (or gain) trending and band-to-band registration, are compared with that derived from sensor OBC. The methodologies and applications presented in this paper can also be applied to other earth observing sensors.

The Sentinel-2 multi-spectral instrument (MSI) will provide Earth imagery in the frame of the Global Monitoring for Environment and Security (GMES) initiative which is a joint undertaking of the European Commission and the Agency. MSI instrument, under Astrium SAS responsibility, is a push-broom spectro imager in 13 spectral channels in VNIR and SWIR. The instrument radiometric calibration is based on in-flight calibration with sunlight through a quasi Lambertian diffuser. The diffuser covers the full pupil and the full field of view of the instrument. The on-ground calibration of the diffuser BRDF is mandatory to fulfil the in-flight performances. The diffuser is a 779 x 278 mm² rectangular flat area in Zenith-A material. It is mounted on a motorised door in front of the instrument optical system entrance. The diffuser manufacturing and calibration is under the Centre Spatial of Liege (CSL) responsibility. The CSL has designed and built a completely remote controlled BRDF test bench able to handle large diffusers in their mount. As the diffuser is calibrated directly in its mount with respect to a reference cube, the error budget is significantly improved. The BRDF calibration is performed directly in MSI instrument spectral bands by using dedicated band-pass filters (VNIR and SWIR up to 2200 nm). Absolute accuracy is better than 0.5% in VNIR spectral bands and 1% in SWIR spectral bands. Performances were cross checked with other laboratories. The first MSI diffuser for flight model was calibrated mid 2013 on CSL BRDF measurement bench. The calibration of the diffuser consists mainly in thermal vacuum cycles, BRDF uniformity characterisation and BRDF angular characterisation. The total amount of measurement for the first flight model diffuser corresponds to more than 17500 BRDF acquisitions. Performance results are discussed in comparison with requirements.

In partnership with the European Commission and in the frame of the Copernicus program, the European Space Agency (ESA) is developing the Sentinel-2 optical imaging mission devoted to the operational monitoring of land and coastal areas. The Sentinel-2 mission is based on a satellites constellation deployed in polar sun-synchronous orbit. Sentinel-2 will offer a unique combination of global coverage with a wide field of view (290km), a high revisit (5 days with two satellites), a high resolution (10m, 20m and 60m) and multi-spectral imagery (13 spectral bands in visible and shortwave infra-red domains). The first satellite is planned to be launched in late 2014. In this context, the Centre National d’Etudes Spatiales (CNES) supports ESA to insure the cal/val commissioning phase. This paper provides first, an overview of the Sentinel-2 system and the image products delivered by the ground processing. Then the paper will present the ground segment, presently under preparation at CNES, and the various devices that compose it : the GPP in charge of producing the level 1 files, the “radiometric unit” that processes sensitivity parameters, the “geometric unit” in charge of fitting the images on a reference map, MACCS that will produce Level 2A files (computing reflectances at the Bottom of Atmosphere) and the TEC-S2 that will coordinate all the previous software and drive a database in which will be gather the incoming Level 0 files and the processed Level 1 files.

The Sea and Land Surface Temperature Radiometer (SLSTR) to be flown on ESA's Sentinel-3 mission is a multichannel scanning radiometer that will continue the 21-year datasets of the Along Track Scanning Radiometer (ATSR) series. As its name implies, measurements from SLSTR will be used to retrieve global sea surface temperatures to an uncertainty of <0.3K traced to international standards. To achieve these low uncertainties requires an end to end instrument calibration strategy that includes pre-launch calibration at subsystem and instrument level, on-board calibration systems and sustained post launch activities. The authors describe the preparations for the pre-launch calibration activities including the spectral response, instrument level alignment tests, solar and infrared radiometric calibration. A purpose built calibration rig has been designed and built at RAL space that will accommodate the SLSTR instrument, infrared calibration sources and alignment equipment. The calibration rig has been commissioned and results of these tests will be presented. Finally the authors will present the planning for the on-orbit monitoring and calibration activities to ensure that calibration is maintained. These activities include vicarious calibration techniques that have been developed through previous missions, and the deployment of ship-borne radiometers.

The standard procedure for wavelength calibration of monochromators in the visible and near infrared wavelength range uses low-pressure gas discharge lamps with spectrally well-known emission lines as primary wavelength standard. The calibration of a monochromator in the wavelength range of 350 to 2500 nm usually takes some days due to the huge number of single measurements necessary. The useable emission lines are not for all purposes sufficiently dense and at the appropriate wavelengths. To get faster results for freely selectable wavelengths, a new method for monochromator characterization was tested. It is based on measurements with a lambdameter taken at equidistant angles distributed over the grating's entire angular range. This method provides a very accurate calibration and needs only about two hours of measuring time.

The Centre Spatial de Liège in Belgium (CSL) has developed a stray light test facility for In Field and Out of Field of View stray light characterization of small Earth observation satellites. The first tested satellite is PROBA V, a small ESA satellite, developed by a Belgian consortium, dedicated to replace the SPOT VGT on SPOT missions. The test results demonstrate that the stray light performance of both PROBA V and the test facility are excellent and are in line with the model predictions. The new facility is designed for in-field and far field stray light characterization: intensities dynamic range up to 10⁸:1 for in-field and up to 10¹⁰:1 for far field stray light in the visible to SWIR spectral ranges. Moreover, from previous stray light tests performed at CSL, vacuum conditions are needed for reaching the 10^-10 rejection requirement mainly to avoid air/dust diffusion. To fulfill these requirements the stray light facility is built in one of CSL vacuum chamber located in a class 100. The large dynamic range required is achieved by using a high radiance point source allowing small diverging collimated beam. A lot of care is taken in the design of the collimator focal plane to provide a highly purely collimated luminance. Previous articles have presented the principle, the concept and a detailed analysis of the facility for stray light characterization of EO satellites. This paper goes a step forward with the presentation of actual test facility description and results obtained on PROBA V EO satellite. The achieved results are put in parallel to the modeled computed values.

Sensitive imaging systems with high dynamic range onboard spacecrafts are susceptible to ghost and stray-light effects. During the design phase, the Dawn Framing Camera was laid out and optimized to minimize those unwanted, parasitic effects. However, the requirement of low distortion to the optical design and use of a front-lit focal plane array induced an additional stray light component. This paper presents the ground-based and in-flight procedures characterizing the stray-light artifacts. The in-flight test used the Sun as the stray light source, at different angles of incidence. The spacecraft was commanded to point predefined solar elongation positions, and long exposure images were recorded. The PSNIT function was calculated by the known illumination and the ground based calibration information. In the ground based calibration, several extended and point sources were used with long exposure times in dedicated imaging setups. The tests revealed that the major contribution to the stray light is coming from the ghost reflections between the focal plan array and the band pass interference filters. Various laboratory experiments and computer modeling simulations were carried out to quantify the amount of this effect, including the analysis of the diffractive reflection pattern generated by the imaging sensor. The accurate characterization of the detector reflection pattern is the key to successfully predict the intensity distribution of the ghost image. Based on the results, and the properties of the optical system, a novel correction method is applied in the image processing pipeline. The effect of this correction procedure is also demonstrated with the first images of asteroid Vesta.

The TROPOMI Earth-observing instrument is the single payload on board ESA's Sentinel-5 Precursor mission. It is the successor of the Sciamachy instrument (ESA ENVISAT) and the OMI instrument (NASA EOS/Aura), and combines and improves the best of both instruments. TROPOMI copies the push broom observation geometry of OMI allowing for daily global coverage due to its instantaneous field of view of 108 degrees, or 2600 km swath on ground. From Sciamachy the 2305 - 2385 nm Short-Wave Infra-Red (SWIR) observational band is copied with which methane and carbon monoxide are observed. This paper reports on the development of the SWIR detector module and the detailed characterization of the 1000x256 SWIR Saturn detector array produced by Sofradir (F) as measured with the SRON-developed Front-End Electronics. The detailed characterization comprises not only the regular properties such as dark current, noise and photo-response, but also more complex characteristics including non-linearity and memory. Characterization of the detection module was performed for all operational parameters: detector temperature (135 - 145 K), bias voltage and integration time. Thanks to the detector-characterization program, the operational clocking of the detector could be optimized, resulting in significantly improved performance.

The SLSTRs are high accuracy radiometers selected for the GMES mission Sentinel-3 space component to provide SST data continuity respect to previous (A)ATSRs for climatology. Many satellites, each with 7.5-year lifetime, over a 20- year period are foreseen. Sentinel-3A will be launched in 2014 and Sentinel-3B at least 6 months later implying that two identical satellites will be maintained in the same orbit with 180° phase delay. Each SLSTR has an improved design respect to AATSR affording large near nadir and oblique view swaths (1400 and 740 km) for SST/LST global coverage at 1 km spatial resolution with a daily revisit time (with two satellites), appropriate for climate and meteorology. Clouds screening and other products are obtained with 0.5 Km spatial resolution in visible and SWIR bands while two additional channels are included to monitor high temperature events, such as forest fires. The two swaths are obtained with two conical scans and telescopes combined optically at a common focus, representing the input of a cooled Focal Plane Assembly, where nine channels are separated with dichroic and focalized on detectors with appropriate optical relays. IR and SWIR optics/detectors are cooled to 85 K by an active mechanical cryo-cooler with vibration compensation, while the VIS ones are maintained at a stable temperature. The opto-mechanical design and the expected electro-optical performance of the Focal Plane Assembly are described and the models predictions at system level are compared with experimental data acquired in the vacuum chamber in flight representative thermal conditions or in laboratory.

Two detectors, SWIR and VNIR, and relevant front-end electronics were developed in the frame of the PRISMA(Precursore Iperspettrale della Missione Applicativa) project, an hyperspectral instrument for the earth observation. The two detectors were of the MCT type and, in particular, the VNIR was realized by Sofradir by using the CZT(Cadmium Zinc Telluride substrate of the PV diodes) substrate removal to obtain the sensitivity in the visible spectral range. The use of the same ROIC permitted to design an unique front-end electronics. Two test campaigns were carried out: by Sofradir, only on the detectors, and by Selex ES, by using the PRISMA flight electronics. This latter tests demonstrated that was possible to obtain the same detector performance, with respect of those ones obtained by a ground setup, with a flight hardware in terms of noise, linearity and thermal stability.

Based on a large experience, Sofradir is conducting major space programs covering all the wavelength range from visible to VLWIR as Sentinel projects in the frame of the GMES / Copernicus European program or MTG detectors development and manufacturing for the future European meteorological satellites of third generation. Among all the space activity, a large part of the programs is based on SWIR detectors (with extension in visible spectral range on some of them). Thus the well-known Saturn and Neptune VISIR or SWIR detectors from Sofradir are widely used in numerous space applications to answer these needs. More recently, Sofradir developed in the frame of an ESA contract a new 1kx1k VISIR – SWIR detector with 15 μm pixel pitch for future space missions. In this paper, the last results on space programs involving VISIR – SWIR detectors are presented and discussed. A particular emphasis is also made on the new 1k² VISIR – SWIR detector for space applications which is presented with its performances.

Spatial applications are challenging infrared (IR) technologies requiring the best system performances. Usually, the need is a trade-off between the signal to noise ratio (SNR) and spatial response of the IR detector, and in particular the modulation transfer function (MTF) performance. MTF optimization requires a deep understanding of detector physics and the use of evaluation tools. This paper describes the optimization of an n-on-p Mercury Cadmium Telluride (MCT) pixel design using a MTF mathematical model to predict the performance.

We developed a Time Delay Integration (TDI) CCD image sensor that consists of four multispectral bands (B1-B4 zone) and one panchromatic band (P zone) in an integrated, compact package. The B zones have a horizontal resolution of 3k columns, with a pixel size of 28 μm x 28 μm. The P zone has a horizontal resolution of 12k columns, with a pixel size of 7 μm x 7 μm. The large pixel size of B zones provides excellent colour differentiation even under extremely low light intensity, while the small pixel size and the large pixel number of broad band zone (P zone) provides high resolution images within a wide spectrum range. By utilizing a particularly designed hybrid optical filter, the sensor is able to collect blue, green, red, and near infrared images with only negligible optical crosstalk. The sensor uses selectable outputs and data rate: 2 or 1 outputs running at 16.5 MHz (B1-B4 Zone) per output, and 8 or 4 outputs running at 33 MHz (P Zone) per output. Special design features minimize optical crosstalk between the image zones, and achieve a low signal noise: ≤ 85 e^- in B zone, and ≤ 35 e^- in P zone. To acquire spectral reflectance signatures with good fidelity, the image sensor must be very sensitive to weak light in some spectral bands and cannot be over exposed to light in other spectral bands. To fulfil this requirement, the sensor is designed to show a balanced responsivity in all the image zones. Over all, the sensor demonstrates outstanding performance, providing exceptional images that are crucial for remote sensing applications.

The DLR Institute of Planetary Exploration has proposed a novel design of a space instrument accommodated on a small satellite bus (SSB) that is dedicated to the detection of inner earth objects (IEOs) from a low earth orbit (LEO). The instrument design is based on a focal plane consisting of electron multiplied CCDs (EMCCD) operating at high frame rates for compensation of the spacecraft’s pointing jitter at very low effective readout noise. The CCD detectors operate at a nominal operating temperature of -80°C and at a frame rate of 5fps. It is well known, that CCD detectors are prone to space radiation. However, EMCCD, designed to detect very low light levels of a few electrons, have not yet been used in space. Therefore, investigations have been initiated and performed by DLR for evaluation of the performance of EMCCDs before and after radiation. The main scope of the investigations was the characterization of the charge transfer efficiency (CTE) at low light levels because of its key impact on the detection performance. The non-ionizing dose effects of space high energy particle radiation on the detector were simulated by 60MeV protons at two different fluence levels. The low light-CTE was measured with point light sources without and with background-light.

Global shuttering, sometimes also known as electronic shuttering, enables the use of CMOS sensors in a vast range of applications. Teledyne DALSA Global shutter sensors are able to integrate light synchronously across millions of pixels with microsecond accuracy. Teledyne DALSA offers 5 transistor global shutter pixels in variety of resolutions, pitches and noise and full-well combinations. One of the recent generations of these pixels is implemented in 12 mega pixel area scan device at 6 um pitch and that images up to 70 frames per second with 58 dB dynamic range. These square pixels include microlens and optional color filters. These sensors also offer exposure control, anti-blooming and high dynamic range operation by introduction of a drain and a PPD reset gate to the pixel. The state of the art sense node design of Teledyne DALSA’s 5T pixel offers exceptional shutter rejection ratio. The architecture is consistent with the requirements to use stitching to achieve very large area scan devices. Parallel or serial digital output is provided on these sensors using on-chip, column-wise analog to digital converters. Flexible ADC bit depth combined with windowing (adjustable region of interest, ROI) allows these sensors to run with variety of resolution/bandwidth combinations. The low power, state of the art LVDS I/O technology allows for overall power consumptions of less than 2W at full performance conditions.

CMOS Image Sensors (CIS) arrays have well proven their capabilities to address the growing need of space imaging from the GEO orbit within the visible and near infrared spectral bands. The main interesting features of CIS detectors for such applications are smearing-free capability, small pixel pitches even with large charge handling capacity, fine tuning of QE and MTF, low power dissipation, exposure control and good radiation behaviour. This paper will present new results obtained by our team in the field of development of such 2D arrays, including large format detectors (up to 12 million pixels), front and back side illuminations, 3T and 4T pixels, microlenses and different types of epitaxial layers/thicknesses. Radiometric and geometric characterisation results obtained for various devices will be presented.

Developing and testing advanced ground-based image processing systems for earth-observing remote sensing applications presents a unique challenge that requires advanced imagery simulation capabilities. This paper presents an earth-imaging multispectral framing camera simulation system called PayloadSim (PaySim) capable of generating terabytes of photorealistic simulated imagery. PaySim leverages previous work in 3-D scene-based image simulation, adding a novel method for automatically and efficiently constructing 3-D reflectance scenes by draping tiled orthorectified imagery over a geo-registered Digital Elevation Map (DEM). PaySim’s modeling chain is presented in detail, with emphasis given to the techniques used to achieve computational efficiency. These techniques as well as cluster deployment of the simulator have enabled tuning and robust testing of image processing algorithms, and production of realistic sample data for customer-driven image product development. Examples of simulated imagery of Skybox’s first imaging satellite are shown.

Collecting the earth’s critical climate signatures over the next 30 years is an obvious priority for many world governments and international organizations. Implementing a solution requires bridging from today’s scientific missions to ‘operational’ constellations that are adequate to support the future demands of decision makers, scientific investigators and global users for trusted data.

We present the results of an instrument concept study for a low cost terahertz sounder of the mesosphere and lower thermosphere (MLT). Recent advances in the development of Quantum Cascade Laser (QCL) technology to be used for Local Oscillators (LOs) mean that it has now become viable for the first time to build compact, low weight heterodyne receivers in the terahertz (THz) frequency range [28]. Some of the most important atmospheric constituents of the MLT region, e.g. atomic oxygen (O) and the hydroxyl radical (OH), can only realistically be measured at THz frequencies. The technical challenges of THz remote sensing result in a large uncertainly of the global distribution of these species. Recent research indicates that the MLT region exhibits links to processes associated with climate change. From this follows a strong need to measure the composition and dynamic of the MLT region more accurately and more comprehensively.

In the frame of the future satellite mission Meteosat Third Generation (MTG) undertaken by ESA, Thales Alenia Space, as satellite prime contractor, is responsible for the design, validation and monitoring of the geometric image quality. All final products delivered by the MTG mission will be geolocated on-ground by the Image Navigation Registration (INR) process. This process estimates the geolocation of every acquired sample thanks to a Kalman filter based on observables extracted from the images (e.g landmarks, stars) as well as auxiliary data such as orbit, attitude or scan mirror measurements. The paper presents the high-fidelity engineering tool developed to assess and analyze the future INR performances of the system. Compared to previous Meteosat generations based on spinning satellites, the 3-axis stabilisation increases the complexity of the INR model prediction by inducing high-frequency perturbations. In order to estimate the INR filter behaviour, realistic sets of image observables are simulated. The simulation takes into account all error sources affecting the pointing knowledge of each MTG instrument such as micro-vibrations, thermoelastic deformations, orbit estimation errors or instrument scan and spacecraft attitude knowledge performances. After simulating the INR process over the images, geometric performances as defined through MTG user specifications are assessed. Thus, the INR behaviour and the overall system performance can be predicted among different operational conditions. It is then possible to analyse the contribution of each perturbation to the final performances and to tune the INR filter with respect to the satellite behaviour.

The Sentinel 2 mission shall ensure the continuity and enhancement of Landsat and SPOT data and sustain operational land services in the frame of the Global Monitoring for Environment and Security (GMES) initiative. Sentinel-2 is designed to image the Earth’s landmasses from its orbit for at least 7.25 years. The Multi-Spectral Instrument (MSI), delivered by Astrium Toulouse, will provide high resolution imagery in 13 spectral channels extending from the Visible Near Infrared (VNIR, 400-1100 nm) to the Short Wave Infra-Red (SWIR, 1100-2500 nm) range, down to a resolution of 10 meters with an image width of 290 kilometers. A dichroic splitter device is located in back-focal path of the telescope. It allows splitting the incoming optical beam between VNIR and SWIR focal planes. It shall ensure an extremely high rejection, better than 1:1000, between both ranges while introducing negligible aberrations in reflected (VNIR) and transmitted (SWIR) paths. The splitter assembly consists of a wedged dichroic filter plate and a wedged compensator plate mounted in a common frame. Both plates are made of fused silica (Infrasil) and polished to lambda/40. The major challenges reside in the design complexity of the dichroic coating and in the deposition process control to ensure the required high uniformity of performances through the large aperture. The paper presents the final spectral and optical performances of this challenging sub-system. It also discusses the main difficulties that have been overpassed during the development and qualification phase.

Numerous space radar missions are presently envisioned to study the water cycle in the tropics. Among them, the DYCECT (DYnamique, énergie et Cycle de l'Eau dans la Convection Tropicale) mission, a French proposal (submitted to the French CNES Agency), could embark a Doppler radar (W-band or Ka-band) with scanning possibilities onboard a low-orbiting satellite. This instrument could be implemented in addition to a Passive Microwave Radiometer (PMR), and eventually an improved ScaraB-like broadband radiometer, and a lightning detection instrument. This package will document the ice microphysics and the heat budgets. Since the microphysics and the water and energy budgets are strongly driven by the dynamics, the addition of a Doppler radar with scanning possibilities could provide valuable information (3D wind and rain fields) and a large statistic of such critical information over the entire tropics and for all the stages of development. These new information could be used to better understand the tropical convection and to improve convection parameterization relevant for cloud and climate models. It could be used also to associate direct applications such as now-casting and risk prevention. The present study focuses on the feasibility of such 3D wind field retrieval from spaceborne radar. It uses a simulator of some parts of the spaceborne radar in order i) to evaluate the sensitivity of the retrieved wind fields to the scanning strategies and sampling parameters, and to the instrumental and platform parameters and ii) to determine the best parameters providing the most accurate wind fields.

A software tool for a simplified end-to-end simulation of data products from space-borne and airborne visible, nearinfrared and short-wave infrared imaging spectrometers, starting from either synthetic or airborne hyper-spectral data, has been developed and tested. Such a simulator is conceived as a preliminary aid tool (during phase 0⁄A) for the specification and early development of new Earth observation optical instruments, whose compliance to user’s requirements is achieved through a process of cost/performance trade-off. The proposed simulator is based on three principal core modules: the reflectance scenario simulator, the atmospheric simulator and the instrument simulator. High spatial/spectral resolution images with low intrinsic noise and the sensor/mission specifications are used as inputs. Examples of hyper-spectral and panchromatic images for existing and future instruments are reported, showing the capabilities for simulating target detection scenarios and image quality assessment. The Selex-ES simulator, as compared with other existing software, implements all modules necessary for a complete image simulation, allowing excellent flexibility and expandability for new integrated functions because of the adopted IDL-ENVI software environment. The simulation modeling has been validated and assessed through the matching between synthetized and true spectra acquired at ground and airborne level for clay soil mapping. A simulation of the same clay map at satellite scale has also demonstrated a more than acceptable agreement considering the coarser spatial resolution as compared to the airborne scale.

VTT Technical Research Centre of Finland has developed Tunable Fabry-Perot Interferometer (FPI) based miniaturized hyperspectral imager which can be operated from light weight Unmanned Aerial Vehicles (UAV). The concept of the hyperspectral imager has been published in the SPIE Proc. 7474, 8174 and 8374. This instrument requires dedicated laboratory and on-board calibration procedures which are described. During summer 2012 extensive UAV Hyperspectral imaging campaigns in the wavelength range 400 - 900 nm at resolution range 10 - 40 nm @ FWHM were performed to study forest inventory, crop biomass and nitrogen distributions and environmental status of natural water applications. The instrument includes spectral band limiting filters which can be used for the on-board wavelength scale calibration by scanning the FPI pass band center wavelength through the low and high edge of the operational wavelength band. The procedure and results of the calibration tests will be presented. A short summary of the performed extensive UAV imaging campaign during summer 2012 will be presented.

The geoCARB sensor uses a 4-channel slit-scan infrared imaging spectrometer to measure the absorption spectra of sunlight reflected from the ground in narrow wavelength regions. The instrument, which is to be hosted on a geostationary communication satellite, is designed to provide continual monitoring of greenhouse gas over continental scales, several times per day, with a spatial resolution of a few kilometers. The paper discusses the image navigation and registration (INR) of the geoCARB optical footprints on to the earth’s surface. The instrument acquires data in a step and stare mode with 4.08 s stare time and 0.34s step time on 1016 footprints spaced by 2.7 km at nadir in the NS direction along the slit, which is stepped in 3 km EW increments. Knowledge of the instrument line of sight is obtained through use of a dual-head star tracker system (STS), high-precision optical encoders for the scan mirrors, a GPS receiver, and a highly stable common optical bench to which the instrument components, the scan mirror assembly, and the heads of the STS are kinematically mounted. While attitude disturbances due to jitter and solar array flex affect spatial resolution, we show that the effect on INR is negligible. GeoCARB performs a star sighting every 30 minutes to compensate for its diurnal alignment variation relative to the STS, enabling a 1 sigma INR accuracy of 0.38 and 0.51 km at nadir in the NS and EW directions, respectively. Coastline identification may be used to improve accuracy by 6%, while an additional 20% improvement is achievable through identification of systematic errors via extensive post-processing. The paper quantifies all error sources and describes how each of them affects overall INR accuracy.

Raytheon Space and Airborne Systems (SAS) has designed, built and tested a 3.3-inch diameter fast steering mirror (FSM) for space application. This 2-axis FSM operates over a large angle (over 10 degree range), has a very high servo bandwidth (over 3.3 Khz closed loop bandwidth), has nanoradian-class noise, and is designed to support microradian class line of sight accuracy. The FSM maintains excellent performance over large temperature ranges (which includes wave front error) and has very high reliability with the help of fully redundant angle sensors and actuator circuits. The FSM is capable of achieving all its design requirements while also being reaction-compensated. The reaction compensation is achieved passively and does not need a separate control loop. The FSM has undergone various environmental testing which include exported forces and torques and thermal vacuum testing that support the FSM design claims. This paper presents the mechanical design and test results of the mechanism which satisfies the rigorous vacuum and space application requirements.

Compressive sensing (CS) is a new technology that investigates the chance to sample signals at a lower rate than the traditional sampling theory. The main advantage of CS is that compression takes place during the sampling phase, making possible significant savings in terms of the ADC, data storage memory, down-link bandwidth, and electrical power absorption. The CS technology could have primary importance for spaceborne missions and technology, paving the way to noteworthy reductions of payload mass, volume, and cost. On the contrary, the main CS disadvantage is made by the intensive off-line data processing necessary to obtain the desired source estimation. In this paper we summarize the CS architecture and its possible implementations for Earth observation, giving evidence of possible bottlenecks hindering this technology. CS necessarily employs a multiplexing scheme, which should produce some SNR disadvantage. Moreover, this approach would necessitate optical light modulators and 2-dim detector arrays of high frame rate. This paper describes the development of a sensor prototype at laboratory level that will be utilized for the experimental assessment of CS performance and the related reconstruction errors. The experimental test-bed adopts a push-broom imaging spectrometer, a liquid crystal plate, a standard CCD camera and a Silicon PhotoMultiplier (SiPM) matrix. The prototype is being developed within the framework of the ESA ITI-B Project titled “Hyperspectral Passive Satellite Imaging via Compressive Sensing”.

This study evaluates the performances of different algorithms for the retrieval of solar induced fluorescence of vegetation in both the telluric O₂-A and O₂-B bands of the atmospheric molecular oxygen, respectively at 760 nm and 687 nm. In particular, we evaluated the performances of three algorithms amongst those already applied by the scientific community: two of them are based on the use of two or three spectral bands (sFLD and 3FLD methods), while the third one exploits the information content of all the spectral channels in certain bands by applying a polynomial model for fluorescence and reflectance (SFM method). These were applied to a synthetic set of fluorescence data corresponding to different types of vegetation. The main technical specifications of the spectroradiometer have been outlined in terms of three different airborne operating scenarios, addressing different flight altitudes and speeds chosen on the basis of typical platforms suitable for operation from low-medium altitudes. The results underline that the high spectral resolution of the instrument plays a fundamental role for the determination of the value of fluorescence with a good precision and accuracy, as expected. Nevertheless, the extraction of the value of fluorescence in the O₂-A band is less critical than in the O₂-B band and, specifically, it is less sensitive to the spectral resolution of the spectroradiometer. Even at low spectral resolutions, however, the retrieval algorithms based on polynomial fitting provided better results than methods based on the use of spectral bands.

Linear APS-based sun sensor is a kind of sun sensor based on a linear array Active Pixel Sensor (APS) with low power consumption, small size, and small mass. It is integrated with optical, mechanical and electronic technologies. The main function of linear APS-based sun sensor is to realize two-axis measurement of solar aspect angle, determining the attitude of spacecraft. The image of the solar is projected on the linear image sensor through an N-shape aperture in front of it. By comparing the position shift of solar image projection on linear array APS, we can obtain the position of the sun relative to sensor. This paper analyzes the sources of system error and some specific solutions are proposed. The error compensation algorithm in the software designed makes the sun senor meet the accuracy requirements. The performance characteristics are as follows: FOV is ±64°x±64°; the accuracy of α-axis is better than 0.02° (3σ) in the FOV of less than 45°, and better than 0.03° (3σ) in other FOV; the accuracy of β-axis is better than 0.03° (3σ) in the whole FOV. Linear APS-based sun sensor was successfully carried by satellite on orbit in October 2012. On-orbit testing showed that it operates normally and the data curves prove the accuracy meets requirements.

Climate Modeling results show that about 50% of the Earth’s outgoing radiation and 75% of the atmospheric outgoing radiation are contained in the far infrared. Generally the earth is considered as a 220~230 K blackbody, and the peak breadth of the Earth’s outgoing radiation is around the wavelength of 10 micron. The atmospheric outgoing radiation are contained with five spectral intervals: the water vapor band from 6.33 to 6.85 microns, the ozone band from 8.9 to 10.1microns, the atmospheric window from 10.75 to 11.75 microns, the carbon dioxide band from 14 to 16 microns, and finally the rotational water vapor band from 21 to 125 microns. The properties of the carbon dioxide band is stable than other bands which has been chosen for the work Spectrum of the earth sensors. But the radiation energy of carbon dioxide band is variety and it is a function of latitude, season and weather conditions. Usually the luminance of the Earth’s radiation (14 to 16 μm) is from 3 to 7 W/m²Sr. Earth sensor is an important instrument of the Attitude and Orbit Control System (AOCS), and it is sensitive to the curve of the earth’s and atmospheric outgoing radiation profile to determine the roll and pitch angles of satellite which are relative to nadir vector. Most earth sensors use profile data gathered form Project Scanner taken in August and December 1966. The earth sensor referred in this paper is the conical scanning earth sensor which is mainly used in the LEO (Low Earth Orbit) satellite. A method to determine the luminance of earth’s and atmospheric outgoing radiation (carbon dioxide) using the earth sensor is discussed in this paper. When the conical scanning sensor scan form the space to the earth, a pulse is produced and the pulse breadth is scale with the infrared radiation luminance. Then the infrared radiation luminance can be calculated. A carbon dioxide radiance model of the earth’s and atmospheric outgoing radiation is obtained according the luminance data about with different latitudes and seasons which are measured form the conical scanning earth sensors of ZY-1 satellite. When the carbon dioxide radiance model has been collected, it can be fed directly to the earth sensors to improve their accuracy. It also can be supplied for the research of the content and distribution of carbon dioxide in the atmosphere.

In the near future a new class of EO-missions will be possible that combine both high resolution imaging and real-time imaging, and therefore will open up room for new fields of applications not feasible today. GEO remote sensing satellite is one of the most important applications of international remote sensing technology academia which has the advantage of real-t ime, continuous observation, rapid revisit capability and rapid response for small or medium scale objects. Currently the international researchers have reached the nadir looking Ground Sampling Distances (GSD) in the order of 20m for VNIR bands (0.45-0.90μm), CCD pixel spatial angle of about 0.55μrad, instantaneous swath of 300x300 km². This paper analyzes the complicated new features of imaging observation and imaging quality of the GEO optical remote sensing satellite different from LEO. For image quality, this paper points out all aspects and influencing factors of the imaging system chain. Using theoretical analysis, modeling and simulation methods, we research related factors and the degree of influence on the image quality of the satellite imagery full chain. Such research achievements can provide reference for the satellite system design and mission analysis of high-resolution GEO remote sensing satellites.

With the development of space technologies, satellite-based data link is becoming more and more popular due to its wide coverage. However, it needs tens of LEO satellites, short for Low Earth Orbiting satellites, to cover the whole Earth in real time. Therefore it requires huge investment to fulfill such an engineering. If several TDRS satellites, short for Tracking and Data Relaying Satellites, are included, the engineering investment might as well be acceptable. Herein, simulations of coverage and some particular performances are presented in three cases, i.e., a single LEO satellite plus one TDRS satellite, a single LEO satellite plus two TDRS satellite, a single LEO satellite plus three TDRS satellite. Simulations have shown that in the case of one LEO satellite and one TDRS satellite, the revisiting period is 5726s,which will shorten the revisiting period by 57%;the encounter frequency between one LEO and one TDRS is 11 times daily; the average duration for every encounter is 2128s. The performances of one LEO satellite and two TDRS satellites are presented as followings：the revisiting period is 2819s,which will shorten the revisiting period by 79%;the encounter frequency among one LEO and two TDRS is 23 times daily;the average duration for every encounter is 2049s.The performances of one LEO satellite and two TDRS satellites are presented as followings：the revisiting period is 1780s,which will shorten the revisiting period by 87%;the encounter frequency among one LEO and two TDRS is 34 times daily;the average duration for every encounter is 2067s. The above simulations have indicated TDRS satellites can greatly improve LEO satellite coverage and related performances. For china customers, the space orbits of TDRS are limited by either geographical positions or by orbital space regulation in equator. Such limitations make sparsely-distributed LEO satellites global real-time data link difficult, especially above western hemisphere. LEO satellite data link above some of the western hemisphere has to be retarded. Delayed data link are hardly acceptable for some emergency rescues. Before the constellation of tens of LEO communication satellites is deployed in space, it might be a good choice to realize LEO satellite data link via TDRS satellites for China users.

ALSAT-2A is the second Algerian Earth observation satellite build by Astrium together with the Algerian Space Agency and the first spacecraft of AstroSat-100 family. The spacecraft design is based on the Myriade platform and its power subsystem consists of GaAs solar array, Li-ion battery, power conditioning and distribution unit and harness. The purpose of a power subsystem is to ensure reliable delivery of electrical power compatible with payload under all foreseeable operational states, environments, and during all mission phases. The power subsystem is unarguably the most critical subsystem on a satellite. Reliability, efficiency and continuous operation of the power subsystem is essential to the successful fulfillment of ALSAT-2A mission, a failure even a brief interruption in the source of power can have catastrophic consequences for the spacecraft. Therefore, the power subsystem and its components, specially, the solar array must be checked carefully. In this context, this paper outlines the in-orbit performances of ALSAT-2A solar array wings from the period of July 2010 to March 2013. The 32 months telemetry data related to the solar array voltage, current and temperature will be analyzed. These parameters will be discussed in function of satellite power consumption.

The paper is devoted to the results of the star tracker 329K flight tests on board of the satellites Luch-5A and Luch-5B launched into geostationary orbit in December 2011 and November 2012 respectively. Emphasis is placed on accuracy and photometric characteristics of the star tracker 329K.