The improvements of the second-generation SPOT satellites increase Earth observation capabilities in three main ways: - the spectral range has been extended by adding a new infrared band to the HRV imaging instrument, now known as the HRVIR*, - the satellite's lifetime has been extended from 2.5 to 5 years, - the repetitivity of medium spatial resolution acquisitions has been increased by, adding "Vegetation", a new wide field of view instrument with the same spectral bands as the HRVIR. Its frequent image acquisi-tions can therefore be used to supplement the fewer observations made by the HRVIR. These improvements have been made to the SPOT 4 satellite which is to be launched in 1994. The first part of this article describes the main characteristics of the Vegetation payload's mission and gives a brief description of the payload itself. The second part looks at the payload's main sub-assembly, the imaging instrument. Like the HRVIR, this ins-trument has no constantly moving mechanical parts. The choice of a "static" solution (electronic scanning) for a wide field of view instrument has led us to conceive and develop (1) new technological solutions for the optical parts (2), a high-performance image electronics common to all spectral bands (3) and an onboard calibration device.

This paper provides the main outcomes from studies dedicated to the Visible and Infrared Radiometer (VIRI) for Meteosat Second Generation (MSG) geosynchronous satellite to be launched in 1995. These studies are performed by MATRA Space Branch with the collaboration of TPD (NL), Marconi (UK), BAe (UK) and Aerospatiale (F) and supported by European Space Agency (ESA) and Centre National d'Etudes Spatiales (CNES). The objective of MSG is to ameliorate the service already offered by the operational Meteosat serie in order to fit the rapid development of high resolution numerical weather prediction models. This is reflected in the requirements for VIRI which can be regarded as very ambitious as calling for simultaneous improvements in spatial, spectral, temporal and radiometric resolutions. Associated with those are stringent requirements on channel registration and the need to implement a really efficient on-board calibration. The instrument feasibility is primarily dictated by the spatial resolution, from which are derived the aperture diameter and the number of detectors. The preferred instrument concept is described with particular attention to the optical, radiometric and calibration aspects and to the infrared' detection cooling technique.

Already well-known in optical technology through major space programmes such as the Meteosat IR (Infra-Red) imager and the Spot HRV (High Resolution Visible) camera, Matra has found it necessary to expand the capabilities of their Instrumentation Division in order to match the trend towards passive microwave radiometry. Note that this evolution is not viewed as a fundamental gap but rather as a natural extension of the spectrum towards larger wavelengthes, allowing for complementary observations. So far, a number of contracts have been won and the related activities, including the development of airborne demonstration instruments aiming at preparing future space applications, are shortly presented in this paper.

Space era has recently made the geophysicists, biologists and geochemists communities aware of the new opportunity to gather earth related data everywhere on the planet by the same space-borne instrument. The emerging space technologies, while giving access to a longer orbital life duration, are allowing a long term data continuity that disciplines such as climatology, geoeconomics, ecology or natural ressources assessment could take advantage of Projects like LANDSAT 6, SPOT 4/5, and various international Polar Platforms are now being developed with a driving requirement of four to six years life duration. Among these new technologies, pushbroom type sensors offer potentially a good radiometric sensitivity and a long life duration. The question is to assess their ability to make the quantitative physical measurements needed for geophysical applications. A complex process made of calibration techniques and inversion algorithms must be designed to establish a link between raw push broom data and physical measurements. This paper describes the efforts undertaken by the Centre National d'Etudes Spatiales within the SPOT program to develop this process of conversion of the pushbroom data into terrestrial and marine surface reflectances in the visible and middle infrared regions. The modelizations and associated coefficients playing a role in the process are defined and the measurements techniques of these coefficients as well as the used inversion algorithms are reviewed.

The "Reflective Optics System Imaging Spectrometer" (ROSIS) is a compact, programmable imaging spetrometer based on a CCD matrix detector array. The instrument has been designed specifically for the monitoring of water color and of natural chlorophyll fluorescence in order to quantitatively derive pigments, suspended matter and yellow substance distributions in the marine environment. However, its high spectral resolution of ≤ 5 nm also permits many new applications in atmospheric physics and vegetation monitoring. An airborne prototype of ROSIS is jointly developed at present by M BB, GKSS and DFVLR. The instrument concept, the scope of applications and the relationship to ESA's Earth Observation Programme and to NASA's Earth Observation System is discussed.

The forthcoming scenario of remote sensing satellites is characterised by a growing utilization of Synthetic Aperture Radar (SAR) sensors. Among these sensors, the NASA SIR-C (in combination with German/Italian X-SAR), the Canadian Radarsat, the Japanese JERS-1 and the European ERS-1 will produce high resolution, day and night, cloud penetrating images of the earth in different microwave frequency bands and polarisations. The German Aerospace Research Establishment (DLR) is primarily engaged in the processing and distribution of SAR data from ERS-1 and X-SAR. The German Remote Sensing Data Center (DFD) of the DLR will be one of the Processing and Archiving Facilities (PAF) responsible for the off-line high precision image generation and geocoding of the radar images (Noack, 1987). The latter item, the satellite data geocoding element, is a fairly new subsytem for an operational satellite data processing chain. The need for such a system grows within the user community during the last few years. The different aspects in generation and utilisation of geocoded products with special emphasis on SAR geocoded digital images is presented in this paper.

Within the development of THOMSON-CSF thinned CCDs (576 x 384 pixels), a characterization program of evaluation in ultraviolet imaging is pursued. The description of this program is given with the quantum efficiency measured in the 200-3000Å wavelength range. Some preliminary data on the 2200-3000 Å quantum efficiency have been presentedl. New evaluations of this CCD in the ultraviolet and extreme ultraviolet ranges are reported with some details about the method and the implementation of the measurement.

The European Space Agency (ESA) will launch the first European remote sensing satellite ERS-1 with a Synthetic Aperture Radar (SAR) in September 1990. The German Remote Sensing Data Center of the German Aerospace Research Establishment DLR is presently implementing under ESA contract a SAR data processing facility that will process ERS-1 SAR data with high precision and high throughput. The design of this facility is based on the most recent technology and can be characterized as follows. The SAR processing facility is implemented as distributed processing system utilizing powerful UNIX based workstations, all attached to a high performance, vendor-independent local area network, high speed array processors for signal processing, large solid-state memories as data buffers for near real-time processing and optical disk for the archival and distribution of data. Important algorithmic and software aspects are the use of modified Range/Doppler algorithm for the generation at radiometrically accurate digital SAR images, the use of digital elevation models for the precise geometric registration of SAR images over land and their presentation in different map pro-jections, and the use of Ada as programming language for most new software developments. 'A centralized data. and facility management is being implemented, using commercial relational database management software for cataloguing and order handling, and applying knowledge engineering software for adaptive scheduling. This paper presents the German ERS-1 SAR data processing facility in terms of hardware and software and briefly describes the products that will be generated.

Earth observation from space becomes more important for global monitoring of air-pollution, unusual meteorological circumstances, and disaster preventions of the Earth. In paticular, observations in the infrared region from a geostationary orbit brings great advantage for the above purposes. To improve geometric and radiometric resolutions and also to shorten observing intervals, NASDA now develops a new device "IRCCD" (Infra-Red Charge Coupled Device) for a spaceborne infrared radiometer covering wavelength beyond 10gm . This paper describes detection mechanisms and test results of experimentally fabricated test devices for IRCCD and gives a breaf description of a cryogenic refrigerator maintaining the IRCCD at around 70K.

A "time dilation" push-broom imaging CCD sensor is being considered for certification of landing and roving sites for the Mars Rover/Sample Return Mission. It would be used to certify several candidate sites of 10 km by 10 km. Rocks and holes of size 1 m and larger will be identified using an optical sensor with 0.25 m resolution. This requires a large aperture camera and a camera pointing control system designed for high accuracy and stability. The imaging time is stretched out by a factor of 8 over the time required to fly directly over the imaged site to reduce the data rate and to increase the exposure time. Six parallel data strings are used to reduce the data rate through each string to a manageable 25 Mbps.

In this paper we discuss the importance of scene registration for several tasks in the automated interpretation of aerial imagery. These tasks are structure matching, stereo matching, and stereo visualization. While the process of registration and matching has traditionally been treated as separate problems, particularily in the case of stereo matching, we describe techniques that may unify these processes.

We present a technique for measuring the area of mesa shaped features of constant height and irregular outline starting from a pair of stereo images captured above the feature. Our method is based on correlating the sign images of the Laplacian of Gaussian convolution of the two grey-level images'. We generalise this method to measure the volume of an irregularly shaped pile of material, such as a blob of sol-der paste which has been applied to a circuit board in preparation for reflow soldering.

A method for the automatic registration of imagery and maps is presented, using a combination of photogram-metric and active contour model techniques. Roads appearing on the map and in the imagery are modeled as active contours, and their positions in the image determined by energy minimization on an energy surface calcu-lated as a function of edge strength. The rest positions of the contour models in the image are required to be projections of their map positions, thus maintaining the known shape of the roads. The image orientation parameters are refined as part of the road location process, yielding a simultaneous, consistent determination of the road locations and the imaging parameters and allowing well-determined features to assist the location of weaker ones.

The PEGASUS system, developed by Autometric, Inc., is a cost-effective, versatile softcopy workstation which can be used to extract terrain and feature data from digital imagery. This workstation can work with monoscopic as well as stereoscopic imagery, and a large variety of types of imagery are supported. Automatic digital terrain model (DTM) extraction is augmented by a semi-automatic edit capability based on a floating cursor tied to a real-time photogrammetric loop. The initial feature extraction capabilities include a semi-automated procedure to collect the point, line, and polygon data which is the foundation of map generation, map revision, and change detection. Target applications for the PEGASUS workstation include perspective scene generation, mission planning support, map data edit and revision, precise mensuration, line-of-sight applications, and industrial photo-grammetry. Key advantages of the PEGASUS workstation is that the hardware is commercial-off-the-shelf (COTS) and an extensive amount of COTS software is included with the system. Photogrammetric and geo-handling software developed by Autometric is combined with the image processing and rendering tools of the PIXAR II and the graphics and window capabilities of the Silicon Graphics 4D to produce a complete system. This paper discusses the functionality and performance of the PEGASUS workstation as well as its hardware architecture. Functions treated include the real-time photogrammetric loop; image warping and DTM collection; feature data collection, editing, and display.

The satellite ISO (Infrared Space Observatory) is to be launched in 1993, it will be equipped with four scientific instruments prepared for observation in the 2.5 to 200,μm wavelength range. One of them, the ISOCAM camera, is achieved under the management of CEA-SAp and will give pictures in the 2.5 - 5.5 μm and 4 - 17,μm ranges. This paper presents the main characteristics of the long wavelength channel (LWC) detector of ISOCAM which has been specially achieved by CEA-LIR for this mission.

This article discusses a number of the major problems confronting the development of present day semiconducting IR focal plane detectors for large array space based applications, shows that an entirely new detector technology based on superconductivity may circumvent many of these difficulties, provides detailed data on the characteristics of these devices and outlines the development program underway to exploit this new technology.