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Due to the distance limitation of quantum communication via ground-based fibre networks, space-based quantum key distribution (QKD) is a viable solution to extend such networks over continental and, ultimately, over global distances. Compared to LEO, QKD from GEO would offer substantial advantages, i.e. large coverage, continuous link to ground stations (cloud cover limited), 24/24h operation (background limited), no tracking required, however, coming with large link losses seen the space-ground distance. TNO, together with Eutelsat and CGI-NL, performed a detailed study on the feasibility of QKD from GEO, including a high level system design of payload and ground segment. We conclude that QKD from GEO is technically feasible, and a favourable solution if the satellite needs to act as an untrusted node (that is, no security assumptions required for the space segment). However, the optimal solution, generating a higher value-for-money, is to use a hybrid system, implementing an untrusted and trusted mode BBM92 QKD protocol. In order to arrive at a minimum required secure bit rate of ~1 bit/s in untrusted mode, a 2x ~0.5m diameter telescope in the space segment is required with

The Euclid mission, of which the spacecraft is the essential space segment, is being developed to undertake the challenges of mapping the dark energy and dark matter distribution in the Universe. As the launch date is approaching (2nd half of 2022), the development of the spacecraft has successfully passed critical milestones with the manufacturing and integration of the telescope, instruments and service module. Each sub-element of the spacecraft has been qualified and their performance assessed. The assembly of the complete payload and spacecraft is currently on-going. The integrated optical performance end to end of the payload module is currently being assessed based on the as-built knowledge of the parts of the telescope and instruments.

In this paper, the authors have attempted to provide a comprehensive account of the Indian Regional Navigation Satellite System (IRNSS). The paper describes the coverage area, the space segment, ground segment, and user segment of IRNSS. The orbital parameters of all seven satellites in the IRNSS constellation have been reported. Some important definitions related to space crafts have been explained. The paper presents the method to estimate the receiver’s position and the algorithm involved. The paper also discusses various sources of error in position estimation. The paper gives a detailed description of the trajectories of all seven satellites in the constellation. The paper presents the Slant Tropospheric Delay (STD) obtained over the National Atmospheric Research Laboratory, Gadanki; National Institute of Oceanography, Goa; Regional Meteorological Centre, Kolkata; Indian Institute of Technology, Bhubaneswar; and Sona Synthetics, Kanakapura, Bangalore.

This Paper provides an overview on the first results of the Metop-C satellite, third and last part of the series of three Metop-satellites of the EUMETSAT Polar System (EPS). EPS is the European contribution to the Polar Meteorological Satellite Observing System. It forms a part of the Initial Joint Polar System (IJPS), formed with NOAA (National Oceanic and Atmospheric Administration). The Metop-C satellite, launched on the 7 November 2018 from the Guyana Space Centre in Kourou, and is finalizing its commissioning activities. The Metop satellites were developed in co-operation with the European Space Agency (ESA). Seven meteorological instruments (among 10) are embarked on Metop-C satellites (eight on Metop-A and –B where the HIRS/4 instrument was embarked as well). These are the IASI (Infrared Atmospheric Sounding Interferometer), developed by CNES in co-operation with EUMETSAT, the AVHRR (Advanced Very High Resolution Radiometer) and AMSU-A (Advanced Microwave Sounding Unit-A) instruments, provided by NOAA, the Microwave Humidity Sounder (MHS), developed by EUMETSAT and the GRAS (GNSS (Global Navigation Satellite System) Receiver for Atmospheric Sounding) instrument, the GOME-2 (Global Ozone Monitoring .-2) instrument and ASCAT (Advanced Scatterometer), developed by ESA as part of the space segment. Metop instrument data – in particular the sounding instruments - provide an essential contribution to global operational Numerical Weather Prediction (NWP). Climate monitoring and atmospheric composition monitoring and ocean and cryosphere observations are further application areas supported by Metop instrument data. Results from the commissioning phase and first application impacts will be presented. After its successful commissioning, there will be three Metop-satellites in orbit for about three years.

REMI (Reduced Envelope Multispectral Imager) is a new instrument developed by Ball Aerospace specifically for the Sustained Land Imaging (SLI) program. The goal of REMI is to meet the current Landsat mission requirements with a much smaller volume, lower cost payload. A lower single unit recurring cost enables economies of scale on multiple builds by leveraging non-recurring engineering costs. This lower cost enables multiple copies on-orbit at the same time for improved temporal sampling, an innovative approach to space segment reliability, and more frequent technology onramps. REMI achieves miniaturization through use of a common aperture for all spectral bands. REMI features a pointing mechanism that compensates for platform and ground motion while using cross-track, step-stare pointing to produce contiguous ground coverage in all spectral bands. The status of the REMI development and airborne flight testing will be presented.

The 3MI instrument is a multi-directional spectro-polarimeter to fly on-board the Metop-SG platform to be launched in 2022, as part of EUMETSAT’s EPS-SG system space segment. As for most of radiometers devoted to Earth Observing from space, the radiometric budget is a system budget which includes many contributors, from the raw detector signal-to-noise to the artefact introduced by the ground correction in level-1 processing. The straylight happening in the optics is one of these contributors which could sometimes become dominant in the system budget. In this context, it is required to constrain the instrumental design as well as the ground characterization and its correction by processing. This is supported by maintaining accurate understanding of the straylight and its behaviour from early on in the project in order to check its radiometric level and quantify the potential impact on the products. This paper will present the analysis done to understand and model the physical behaviour of 3MI’s straylight. Based on initial inputs from the instrument builders and assuming some simplification, a physical straylight model was derived. This model allows an easy implementation in a simulator able to add this straylight contribution to any type of images, particularly on very realistic scenes. Our physical model shows advantageous complementarity to the builder’s simulations in the sense it allows a better quantification on a wide variety of realistic images while specifications usually assume theoretical targets such as a knife-edge transition. Such a capability is needed for 3MI system activities, in particular to cope with any deviation to the performance requirements. This paper presents examples of 3MI straylight-impacted images simulated at EUMETSAT using as input 1/ a simulation of the straylight provided by the instrument builder (ESA and Leonardo), and 2/ a realistic test data set based on PARASOL and MODIS acquisitions from the A-train observatory generated by ICARE/LOA. This simulator will be used during the development of the 3MI instrument and its ground characterization in order to monitor the impact on products.

The paper deals with an analysis of Very High Throughput Satellite (VHTS) systems employing optical feeder links. As the capacities of newly announced next generation VHTS systems are exceeding the Terabit/s barrier, a large amount of investment needs to be directed not only to the space segment (as was the case traditionally), but also to the ground segment in support of the feeder links. To reduce this investment, satellite operators are reviewing various options and technologies for the feeder links, among which optical feeder links [1]. In this paper, different approaches are analysed for ground segment networks relying on Optical Ground Stations (OGS), exploring the concept of smart gateway diversity with N active OGS and P redundant ones, like is currently done in VHTS systems with RF feeder links. OGS locations are assessed in terms of aggregate availability and total cost for the satellite operator, which is an essential element for the viability of the VHTS system. Different options are assessed for the distribution of OGS gateway processing functions (local at OGS or centralised), and for their interconnection. The main technical challenges are discussed, identifying which technologies will be required for an operational VHTS system with OGS.

After more than 3 years of operational experiences with the Transportable Adaptive Optical Ground Station (T-AOGS) it is not any more the question whether optical communication through atmosphere is possible for Geo to ground applications. It is important to understand the performance of optical communication under different atmospheric-conditions and which the key parameters are to improve simplicity, robustness and availability of optical bi-directional satellite to ground links (SGL). We report within this paper on the characterization of the atmospheric channel for ground to GEO optical communication without adaptive optics correction in the uplink. Besides the telemetry data of the space segment and the T-AOGS, also a special measurement campaign was carried out using the 1m telescope of the ESA-OGS in parallel. An outlook for further analysis and activities is given.

We present the space qualification of a multi-channel mid-power booster optical fiber amplifier (OFA) suitable for 1550nm LEO satellite to ground laser communication downlinks. The end-to-end OFA development from conceptual design all the way through qualification testing followed ECSS-level Product Assurance guidelines for deployed materials, components and processes. The environmental qualification test programme relied on ECSS-E-10-03C which is the ESA standard for qualification testing of space segment hardware. The qualification results show robust functional and structural performance following stress at all 3 possible excitation axes with high level sine vibration, random vibration and mechanical shock as well as thermal cycling between survival and operating temperatures in vacuum condition. In addition to thermo-mechanical tests, proton and gamma radiation tests performed on component and sub-assembly level suggest that the OFA is capable to deliver its performance under ionizing and non-ionizing radiation levels found in the LEO orbit. The OFA has been delivered for system integration into the Optel-μ terminal, applicable to small satellite platforms.

We report the design of OPTEL-D which is an optical communication system for direct data transfer from deep space to earth. OPTEL-D extends the link distances of current optical communication systems to the deep space. The design covers the electrical, thermal, mechanical and optical challenges that such a link distance imposes to both the ground and the space segment. The detailed conceptual system design is presented together with its trade-offs and performance analyses. The space terminal is based on a modular approach which groups the fiber-optical, the opto-mechanical, and the electrical functions into separated modules for independent accommodation. The transmitter beam is provided by an amplitude modulated MOPA system operating at 1.5um. The opto-mechanical unit accomplishes beam forming and steering of the transmit beam as well as reception of the uplink channel. An electrical unit comprises power-conditioning, data-handling, and terminal control through its interfaces to the spacecraft. It is concluded that the OPTEL-D space terminal mass and power are 34 kg and 116 Watts. Depending on the ground station configuration, a data rate of several Mbps is reached over distances of >75 Mio kilometers. Critical assumptions on the receiver sensitivity were verified by tests and the results will be presented. The design of OPTEL-D was derived in collaboration with the European Space Agency to serve the Asteroid Impact Mission. Due to its modular approach using commercially available technology, it can be realized in a competitive schedule and cost frame providing flexible yet powerful data downlinks to most deep space missions.

In recent years, a number of commercial Earth observation missions have been initiated with the aim to gather data in the visible and near-infrared wavelength range. Some of these missions aim at medium resolution (5 to 10 m) multi-spectral imaging with the special background of daily revisiting. Typical applications aim at monitoring of farming area for growth control and harvest prediction, irrigation control, or disaster monitoring such as hail damage in farming, or flood survey. In order to arrive at profitable business plans for such missions, it is mandatory to establish the space segment, i.e. the spacecraft with their opto -electronic payloads, at minimum cost while guaranteeing maximum reliability for mission success. As multiple spacecraft are required for daily revisiting, the solutions are typically based on micro-satellites. This paper presents designs for multi-spectral opto-electric scanners for this type of missions. These designs are drive n by minimum mass and power budgets of microsatellites, and the need for minimum cost. As a consequence, it is mandatory to arrive at thermally robust, compact telescope designs. The paper gives a comparison between refractive, catadioptric, and TMA optics. For mirror designs, aluminium and Zerodur mirror technologies are briefly discussed. State-of-the art focal plane designs are presented. The paper also addresses the choice of detector technologies such as CCDs and CMOS Active Pixel Sensors. The electronics of the multi-spectral scanners represent the main design driver regarding power consumption, reliability, and (most often) cost. It can be subdivided into the detector drive electronics, analog and digital data processing chains, the data mass memory unit, formatting and down - linking units, payload control electronics, and local power supply. The paper gives overviews and trade-offs between data compression strategies and electronics solutions, mass memory unit designs, and data formatting approaches. Special emphasis will be put on space application aspects of these electronics solutions such as radiation total dose tolerance and single events robustness. Finally, software architecture and operational modes of commercial multi-spectral scanners are discussed. They are driven by operational requirements and mission constraints such as data takes per orbit, number of downlink ground stations, calibration needs, and mission schedule planning.

ESA is currently running two parallel, competitive phase A/B1 studies for MetOp Second Generation (MetOp-SG). MetOp-SG is the space segment of EUMETSAT Polar System (EPS-SG) consisting of the satellites and instruments. The Phase A/B1 studies will be completed in the first quarter of 2013. The final implementation phases (B2/C/D) are planned to start 2013. ESA is responsible for instrument design of five missions, namely Microwave Sounding Mission (MWS), Scatterometer mission (SCA), Radio Occultation mission (RO), Microwave Imaging mission (MWI), Ice Cloud Imaging (ICI) mission, and Multiviewing, Multi-channel, Multi-polarization imaging mission (3MI). This paper will present the instrument main design elements of the 3MI mission, primarily aimed at providing aerosol characterization for climate monitoring, Numerical Weather Prediction (NWP), atmospheric chemistry and air quality. The 3MI instrument is a passive radiometer measuring the polarized radiances reflected by the Earth under different viewing geometries and across several spectral bands spanning the visible and short-wave infrared spectrum. The paper will present the main performances of the instrument and will concentrate mainly on the performance improvements with respect to its heritage derived by the POLDER instrument. The engineering of some key performance requirements (multiviewing, polarization sensitivity, etc.) will also be discussed.

EUCLID is a mission to accurately measure the accelerated expansion of the universe. It has been selected for implementation with a launch planned for 2020. EUCLID will map the large-scale structure of the Universe over 15.000 deg2 of the extragalactic sky and it will measure galaxies out to redshifts of z=2 EUCLID consists of a 1.2 m telescope and two scientific instruments for ellipticity and redshift measurements in the visible and near infrared wavelength regime. We present a design for the EUCLID space segment, targeting optimum performance in terms of image quality and stability and maximum robustness with respect to performance, resources and instrument interfaces.

The Meteosat Third Generation (MTG) Programme will ensure the future continuity and enhancement of meteorological data from geostationary orbit as currently provided by the Meteosat Second Generation (MSG) system. The industrial prime contractor for the space segment is Thales Alenia Space (France), with a core team consortium including OHB System AG (Germany).

The Meteosat Third Generation (MTG) program will ensure the continuity and enhancement of meteorological data from geostationary orbit as currently provided by the Meteosat Second Generation (MSG) system. OHB-Munich, as part of the core team consortium of the industrial prime contractor for the space segment Thales Alenia Space (France), is responsible for the Flexible Combined Imager – Telescope Assembly (FCI-TA) as well as the Infrared Sounder (IRS).

The Meteosat Third Generation (MTG) Programme is being realised through the well-established and successful cooperation between EUMETSAT and ESA. It will ensure the continuity with, and enhancement of, operational meteorological and climate data from Geostationary Orbit as currently provided by the Meteosat Second Generation (MSG) system. The industrial Prime Contractor for the Space segment is Thales Alenia Space (France) with a core team consortium including OHB-Bremen (Germany) and OHB-Munich (Germany. This contract includes the provision of six satellites, four Imaging satellites (MTG-I) and two Sounding satellites (MTG-S), which will ensure a total operational life of the MTG system in excess of 20 years. A clear technical baseline has been established for both MTG-I and MTG-S satellites, and confirmed through a rigorous Preliminary Design Review (PDR) process that was formally concluded during 2013. Dedicated reviews have been held for all the main elements including the core instruments (Flexible Combined Imager (FCI) and Infrared Sounder (IRS)), the Platform (which is largely common for the two satellites), the Lightning Imager (LI) and the MTG-I and MTG-S satellites as a whole. The satellites and instruments are at the moment in preparation for the Structural and Thermal Models (STM). The FCI is designed to provide images of the Earth every 10 to 2.5 minutes in 16 spectral channels between 0.44 and 13.3 μm, with a ground resolution ranging from 0.5 km to 2 km. The on-board calibration is based on the use of a Metallic Neutral Density (MND) filter for VIS/NIR channels and a blackbody for the IR channels. This paper introduces the overall FCI design and its calibration concept covering VIS/NIR and IR domains and it describes how the use of the MND makes it possible to accurately correct the medium and long term radiometric drifts of the IR3.8 μm channel.

COSMO-SkyMed (CSK), is an Earth Observation joint program between Agenzia Spaziale Italiana (Italian Space Agency, ASI) and Italian Ministry of Defense (It-MoD). It consists of a constellation of four X Band Synthetic Aperture Radar (SAR) whose first satellite of has been launched on June 2007. Today the full constellation is fully qualified and is in an operative phase. The COSMO-SkyMed System includes 3 Segments: the Space Segment, the Ground Segment and the Integrated Logistic Support and Operations Segment (ILS and OPS) As part of a more complex re-engineering process aimed to improve the expected constellation lifetime, to fully exploit several system capabilities, to manage the obsolescence, to reduce the maintenance costs and to exploit the entire constellation capability for Civilian users a series of activities have been performed. In the next months these activities are planned to be completed and start to be operational so that it will be possible the programming, planning, acquisition, raw processing and archiving of all the images that the constellation can acquire.

The importance of optical time transfer serving as a complement to traditional microwave links, has been attested for GNSSes and for scientific missions. Single photon time transfer (SPTT) is a process, allowing to compare (subtract) time readings of two distant clocks. Such a comparison may be then used to synchronize less accurate clock to a better reference, to perform clock characterization and calibration, to calculate mean time out of ensemble of several clocks, displaced in space. The single-photon time transfer is well established in field of space geodesy, being supported by passive retro-reflectors within space segment of five known GNSSes. A truly two-way, active terminals work aboard of Jason-2 (T2L2) - multiphoton operation, GNSS Beidou (Compass) - SPTT, and are going to be launched within recent ACES project (ELT) - SPTT, and GNSS GLONASS – multiphoton operation. However, there is still missing comprehensive theoretical model of two-way (using satellite receiver and retroreflector) SPTT link incorporating all crucial parameters of receiver (both ground and space segment receivers), transmitter, atmosphere effects on uplink and downlink path, influence of retroreflector. The input to calculation of SPTT link performance will be among others: link budget (distance, power, apertures, beam divergence, attenuation, scattering), propagating medium (atmosphere scintillation, beam wander, etc.), mutual Tx/Rx velocity, wavelength. The SPTT model will be evaluated without the properties of real components. These will be added in the further development. The ground-to-space SPTT link performance of typical scenarios are modeled. This work is a part of the ESA study “Comparison of optical time-transfer links.”

Free Space Optical Communications (FSOC) is progressing continuously. With the successful in-orbit verification of a Laser Communication Terminal (LCT), the coherent homodyne BPSK scheme advanced to a standard for Free-Space Optical Communication (FSOC) which now prevails more and more. The LCT is located not only on satellites in Low Earth Orbit (LEO), with spacecrafts like ALPHASAT-TDP and the European Data Relay Satellite (EDRS) the LCT will also exist in Geosynchronous Orbit (GEO) in the near future. In other words, the LCT has reached its practical application. With existence of such space assets the time has come for other utilizations beyond that of establishing optical Inter-Satellite Links (ISL). Aeronautical applications, as for instance High Altitude Long Endurance (HALE) or Medium Altitude Long Endurance (MALE) Unmanned Aerial Systems (UAS) have to be addressed. Driving factors and advantages of FSOC in HALE/MALE UAS missions are highlighted. Numerous practice-related issues are described concerning the space segment, the aeronautical segment as well as the ground segment. The advantages for UAS missions are described resulting from the utilization of FSOC exclusively for wideband transmission of sensor data whereas vehicle Command and Control can be maintained as before via RF communication. Moreover, the paper discusses FSOC as enabler for the integration of air and space-based wideband Intelligence, Surveillance and Reconnaissance (ISR) systems into existent military command and control systems.

LOFT (Large Observatory For x-ray Timing) is one of four candidates for the M3 slot (launch in 2024, with the option of a launch in 2022) of ESAs Cosmic Vision 2015 – 2025 Plan, and as such it is currently undergoing an initial assessment phase lasting one year. The objective of the assessment phase is to provide the information required to enable the down selection process, in particular: the space segment definition for meeting the assigned science objectives; consideration of and initial definition of the implementation schedule; an estimate of the mission Cost at Completion (CaC); an evaluation of the technology readiness evaluation and risk assessment. The assessment phase is divided into two interleaved components: (i) A payload assessment study, performed by teams funded by member states, which is primarily intended for design, definition and programmatic/cost evaluation of the payload, and (ii) A system industrial study, which has essentially the same objectives for the space segment of the mission. This paper provides an overview of the status of the LOFT assessment phase, both for payload and platform. The initial focus is on the payload design status, providing the reader with an understanding of the main features of the design. Then the space segment assessment study status is presented, with an overview of the principal challenges presented by the LOFT payload and mission requirements, and a presentation of the expected solutions. Overall the mission is expected to enable cutting-edge science, is technically feasible, and should remain within the required CaC for an M3 candidate.

Euclid is an ESA Cosmic-Vision wide-field-space mission which is designed to explain the origin of the acceleration of Universe expansion. The mission will investigate at the same time two primary cosmological probes: Weak gravitational Lensing (WL) and Galaxy Clustering (in particular Baryon Acoustic Oscillations, BAO). The extreme precision requested on primary science objectives can only be achieved by observing a large number of galaxies distributed over the whole sky in order to probe the distribution of dark matter and galaxies at all scales. The extreme accuracy needed requires observation from space to limit all observational biases in the measurements. The definition of the Euclid survey, aiming at detecting billions of galaxies over 15 000 square degrees of the extragalactic sky, is a key parameter of the mission. It drives its scientific potential, its duration and the mass of the spacecraft. The construction of a Reference Survey derives from the high level science requirements for a Wide and a Deep survey. The definition of a main sequence of observations and the associated calibrations were indeed a major achievement of the Definition Phase. Implementation of this sequence demonstrated the feasibility of covering the requested area in less than 6 years while taking into account the overheads of space segment observing and maneuvering sequence. This reference mission will be used for sizing the spacecraft consumables needed for primary science. It will also set the framework for optimizing the time on the sky to fulfill the primary science and maximize the Euclid legacy.

The ESA Sentinels constitute the first series of operational satellites responding to the Earth Observation needs of the EU-ESA Global Monitoring for Environment and Security programme. The GMES space component relies on existing and planned space assets as well as on new complementary developments by ESA. In particular, as part of the GMES space component, ESA is currently undertaking the development of 3 Sentinels mission families. Each Sentinel is based on a constellation of 2 satellites in the same orbital plane. This configuration allows to fulfil the revisit and coverage requirements and to provide a robust and affordable operational service. The launch of the 2nd satellite is scheduled 18 months after the launch of the 1st spacecraft of the constellation. The lifetime of the individual satellite is specified as 7 years, with consumables allowing mission extension up to 12 years. The lifecycle of the space segment is planned to be in the order of 15-20 years. The strategy for Sentinel procurement and replacement over this period is being elaborated, but will likely result in a need for 4-5 satellites of each type if the desired robustness for the service that GMES will provide is to be achieved. This paper will describe the operational and observational capabilities of the Sentinel-1 mission based on the user requirements, including potential emergency requests. An example of a pre-defined mission timeline for each and every cycle will be given.

The next generation of NOAA's Geostationary Operational Environmental Satellite system, Series R (GOES-R) provides continuity of the GOES mission and improvement of its remotely-sensed environmental data. The GOES-R system consists of the Space and Ground Segments. The Space Segment consists of spacecraft bus, its remote-sensing instruments, and communications payloads; while the Ground Segment consists of all Earth-based functions, provides satellite operations and instrument product generation and distribution. This paper presents an overview of the GOES-R Ground Segment (GS) architecture as it continues to evolve consistent with the GOES-R Ground Segment Project (GSP) approved requirements documents. The GOES-R Ground Segment operates from three sites. The first is the NOAA Satellite Operations Facility (NSOF) in Suitland, MD which houses the primary Mission Management (MM), and selected Enterprise Management (EM), Product Generation (PG), and Product Distribution (PD) functions. The Wallops Command and Data Acquisition Station (WCDAS), located in Wallops, VA, provides the primary space communications services, EM and MM functions, and selected PG and PD functions. The third site is a geographically diverse remote backup facility (RBU) located at Fairmont, WV. The architecture has been developed to allow integrated operation within a geographically distributed framework. Because of the unique configuration of the Mission Management Element, the Wallops Command and Data Acquisition Site will have the ability to assume control of satellite operations in the event of an emergency - when authorized by the primary NSOF controllers. This concept allows the Enterprise Management element to have available a wide range of capabilities governed by operations policy rather than the need for system upgrades. This concept also provides flexibility for addition and deletion of modules for major functions. The use of Service Based Architecture concepts within the Product Generation element (PG) provides service interaction capabilities for product generation with only a fraction of the necessary overhead.

ESA and EUMETSAT have initiated joint preparatory activities for the formulation and definition of the Meteosat Third Generation (MTG) geostationary system to ensure the future continuity, and enhancement, of the current Meteosat Second Generation (MSG) system. The MTG programmatics are being established to ensure a seamless transition between the conclusion of the successful MSG operational system and the start of the new MTG operational system, with particular emphasis on continuity of the imagery missions. The MTG phase A studies were successfully concluded in December 2008 an re-consolidation phase B1 activities continued from January to July 2009. They were devoted to the MTG concept definition and requirements consolidation for meeting the User needs in the field of Nowcasting and Very Short Term Weather Forecasting (NWC), Medium/Short Range global and regional Numerical Weather Prediction (NWP), Climate, Air Quality and Composition Monitoring. The following missions have been analysed, measurement techniques studied and preliminary concepts established: - High Resolution Fast Imagery Mission (improved successor to MSG SEVIRI HRV mission) - Full Disk High Spectral Resolution Imagery Mission (improved successor to SEVIRI) - Lightning Imagery Mission - IR Sounding Mission - UV-VIS-NIR Sounding Mission Both space segment architecture and preliminary satellite and instrument concepts were investigated in the course of these studies, and a dual satellite configuration established comprising the Imaging satellite (MTG-I) and the sounding satellite (MTG-S). The study covered all elements to a level of detail allowing to establish a technical baseline, conclude on the feasibility of the system requirements and undertake preliminary programmatic evaluation. Riders to the Phase A studies (Phase B1 work) have been placed to further consolidate the satellite and payload definition and development, prior to the release of the Invitation To Tender (ITT) for the full space segment implementation in July 2009. This paper provides an overview of the conclusions of those MTG space segment studies. It summarises the conclusions reached for the satellites, and associated instruments relating to Imaging, IR Sounding and Lightning missions, with respect to achievable performances, including Radiometry and Image Navigation and Registration aspects.

ESA and EUMETSAT have initiated joint preparatory activities for the formulation and definition of the Meteosat Third Generation (MTG) geostationary system to ensure the future continuity, and enhancement, of the current Meteosat Second Generation (MSG) system. The MTG programmatics are being established to ensure a seamless transition between the conclusion of the successful MSG operational system and the start of the new MTG operational system, with particular emphasis on continuity of the imagery missions. The MTG phase A studies were successfully concluded in December 2008 an re-consolidation phase B1 activities continued from January to July 2009. They were devoted to the MTG concept definition and requirements consolidation for meeting the User needs in the field of Nowcasting and Very Short Term Weather Forecasting (NWC), Medium/Short Range global and regional Numerical Weather Prediction (NWP), Climate, Air Quality and Composition Monitoring. The following missions have been analysed, measurement techniques studied and preliminary concepts established: - High Resolution Fast Imagery Mission (improved successor to MSG SEVIRI HRV mission) - Full Disk High Spectral Resolution Imagery Mission (improved successor to SEVIRI) - Lightning Imagery Mission - IR Sounding Mission - UV-VIS-NIR Sounding Mission Both space segment architecture and preliminary satellite and instrument concepts were investigated in the course of these studies, and a dual satellite configuration established comprising the Imaging satellite (MTG-I) and the sounding satellite (MTG-S). The study covered all elements to a level of detail allowing to establish a technical baseline, conclude on the feasibility of the system requirements and undertake preliminary programmatic evaluation. Riders to the Phase A studies (Phase B1 work) have been placed to further consolidate the satellite and payload definition and development, prior to the release of the Invitation To Tender (ITT) for the full space segment implementation in July 2009. This paper provides an overview of the critical technologies as established in the course of MTG space segment studies. It summarises the undertakings carried out for pre-developing the necessary technologies for the associated instruments relating to Imaging, IR Sounding and Lightning missions. It provides the status of the pre-development activities including long wave IR detectors, cryo-coolers, cryogenic wiring, scan mechanism assemblies, LI detectors and narrow band filters.

EUMETSAT and ESA initiated in 2000 joint preparatory activities for the formulation and definition of the Meteosat Third Generation (MTG) geostationary system, to ensure continuity and improvement of current Meteosat Second Generation (MSG) services. MTG will become the backbone of the European operational meteorological applications taking the relay from MSG by 2017, and warranting the continuation of the earth imagery mission supported by the Spin Enhanced Visible and Infrared Imager (SEVIRI). The early program definition phases were devoted to the discussion and consolidation of end user requirements and their priorities in meteorology fields as Nowcasting and Very Short Term Weather Forecasting (NWC), Medium/Short Range global and regional Numerical Weather Prediction (NWP), Climate and Air Composition Monitoring and the identification of the relevant observation techniques. In the system conceptualization process, the following missions have been analyzed: - Full Disc High Spectral resolution Imagery (FDHSI) - High Resolution and Fast Imagery (HRFI) - Lightning detection Mission (LI) - IR Sounding Mission (IRS) - UV-VIS-NIR Sounding Mission as a payload complement (UVN). After pre-phase A mission studies (2003-2006), where preliminary instrument concepts were investigated allowing the consolidation of the most critical and demanding technical requirements, phase A studies were launched at the beginning of February (2007-2008) addressing both the space segment system feasibility and ground and operations programmatic aspects. The space segment, phase A level, studies covered the entire suite of optical instruments identified in the preliminary assessments including: 1) a flexible combined imager for both FDHSI and HRFI missions; 2) a Fourier Transform Spectrometer for IRS observations; and 3) a lightning detector sensor. The study of concepts and implementation of the UVN mission are covered by the efforts of ESA and the European Union (EU) in the framework of the Global Monitoring for Environment and Security (GMES) Sentinel 4 program. This paper provides an overview of the outcome of the MTG System analyses at the end of phase A confirming its technical feasibility, the key characteristics of the intended missions, and the progress accomplished in the definition of the satellite optical payloads.

The Group on Earth Observations (GEO) is driving a paradigm shift in the Earth Observation community, refocusing Earth observing systems on GEO Societal Benefit Areas (SBA). Over the short history of space-based Earth observing systems most decisions have been made based on improving our scientific understanding of the Earth with the implicit assumption that this would serve society well in the long run. The space agencies responsible for developing the satellites used for global Earth observations are typically science driven. The innovation of GEO is the call for investments by space agencies to be driven by global societal needs. This paper presents the preliminary findings of an analysis focused on the observational requirements of the GEO Energy SBA. The analysis was performed by the Committee on Earth Observation Satellites (CEOS) Systems Engineering Office (SEO) which is responsible for facilitating the development of implementation plans that have the maximum potential for success while optimizing the benefit to society. The analysis utilizes a new taxonomy for organizing requirements, assesses the current gaps in spacebased measurements and missions, assesses the impact of the current and planned space-based missions, and presents a set of recommendations.

Satellite serving offers a potential for extending the life of satellites and reducing launching and operating costs. Proximity operations are necessary for purpose of satellite serving. As the primary measurement system, optical system can provide the information of relative navigation in near field. The paper has two main contributions. Firstly, we summarize use of optical systems for guidance and navigation in the missions of proximity operations in aerospace. Their characteristics vary from the manned missions, which are performed by astronauts on-orbit, through semi-autonomous missions, wherein human operators on the ground segment issue high level directives and sensor-guided systems on the space segment guide the execution, to the full-autonomous missions, which are executed using unmanned space robotic systems. It comes to light that future space operations will be more autonomous. Secondly, we present a concept and framework of a vision system for satellite proximity operations, which is semi-autonomous and can treat with uncooperative satellites. The vision system uses visible and infrared sensors synchronously to acquire images, which solves the problem of data integrity introduced by ambient illumination and direct sunlight for visible sensor. The vision system uses natural features on the satellite surfaces instead of artificial markers for its operation, computes relative motion and structure of the target, and tracks features in image sequences. Selected algorithms of the system have been characterized in ground environment; they are undergoing systematic sets of adaptation for space.

ESA and EUMETSAT have initiated joint preparatory activities for the formulation and definition of the Meteosat Third Generation (MTG) geostationary system to ensure the continuity and improvement of the Meteosat Second Generation (MSG) system. The MTG will become the new system to be the backbone of the European operational meteorological services from 2015, in particular, will ensure the continuation of the imagery missions. The first phases were 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: The Flexible Combined Imager, an improvement of the actual MSG-SEVIRI Imager Lightning Imagery Mission IR Sounding Mission UV-VIS-NIR Sounding Mission as a payload complement from GMES. After pre-phase A mission studies (2003-2006), where preliminary instrument concepts were investigated allowing in the same time to consolidate the technical requirements for the overall system study, a phase A study on MTG has been launched at the beginning of February 2007 for the space segment system feasibility and programmatic aspects to be accomplished during 2007-2008 time frame. The space segment phase A study will cover all elements to the level of details allowing to conclude on the feasibility of the system and to produce cost estimates with a good level of confidence. This paper provides an overview of the outcome of the MTG space segment at the end of phase A, addressing the progress accomplished for the various payloads in terms of achievable performances including Radiometry and Image Navigation and Registration aspects. It namely focuses onto the Imaging and IR Sounding, Lightning Missions, introduces the UV-VIS-NIR Sounding mission concept status, establishes the critical technologies and introduces the way forward to the implementation of the MTG development programme.

ESA and EUMETSAT have initiated joint preparatory activities for the formulation and definition of the Meteosat Third Generation (MTG) geostationary system to ensure the continuity and improvement of the Meteosat Second Generation (MSG) system. The MTG will become the new system to be the backbone of the European operational meteorological services from 2015, in particular, will ensure the continuation of the imagery missions. The first phases were 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 pre-phase A mission studies (2003-2006), where preliminary instrument concepts were investigated allowing in the same time to consolidate the technical requirements for the overall system study, a phase A study on MTG has been launched at the beginning of February 2007 for the space segment system feasibility and programmatic aspects to be accomplished during 2007-2008 time frame. The space segment phase A study will cover all elements to the level of details allowing to conclude on the feasibility of the system and to produce cost estimates with a good level of confidence. This paper addresses an overview of the outcome of the MTG space segment progress (spacecraft concept, payload preliminary design studies) accomplished in the frame of the phase A. It namely focuses onto the Imaging and IR Sounding Missions, highlights the platform and resulting instrument concepts, establishes the critical technologies and introduces the study progress towards the implementation of the MTG development programme.

Due for launch in 2013, EarthCARE (Earth Clouds, Aerosols and Radiation Explorer) has been selected as ESA's sixth Earth Explorer Missions within its Living Planet Programme. Its payload aims at providing measurements, in a radiatively consistent manner, of the global distribution of vertical profiles of clouds and aerosol field 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 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. ESA and JAXA have initiated predevelopment activities to reduce technical and programmatic risks for the critical elements of the mission. Following a mission overview, this paper presents results of these pre-development activities mainly related to the ATLID instrument. The activities consist of designing, manufacturing and testing a functional representative model of the ATLID receiver critical units and laser source, of developing and assessing high-power pump laser diodes with extended lifetime and improved efficiency, and of demonstrating the performance of candidate detectors.

The Metop series of satellites constitutes the space segment for the EUMETSAT Polar System, the European contribution to the Initial Joint Polar System, being developed in co-operation with the National Oceanic and Atmospheric Administration (NOAA) of the USA, to provide meteorological data from the Polar Orbit. The first Metop satellite was launched on 19 October 2006 on a Soyuz launcher from the Baikonur Cosmodrome in Kazakhstan. Following the in-orbit commissioning of the spacecraft, Metop became the first European polar orbiting operational meteorological satellite. The Advanced Very High Resolution Radiometer (AVHRR), the High-resolution Infrared Radiation Sounder (HIRS) and the Advanced Microwave Sounding Unit-A (AMSU-A) instruments constitute the operational meteorological payload provided by NOAA that, in addition to the EUMETSAT provided Microwave Humidity Sounder (MHS), is flown on both, the NOAA Polar Orbiting Satellites (POES) and the EUMETSAT Metop satellites. Following the launch of Metop-A, an extensive in-orbit verification of the instruments was conducted with the involvement of EUMETSAT and NOAA/NASA as well as European and US Industry. In this paper the performance of the AVHRR, HIRS and AMSU-A instruments attained after the in-orbit verification of the Metop-A satellite is presented.

The EarthCARE (Earth Clouds, Aerosols and Radiation Explorer) mission has been recently selected as the 6th 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 EarthCARE (Earth Clouds, Aerosols and Radiation Explorer) mission has been recently selected as the 6th 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 next-generation National Oceanic and Atmospheric Administration (NOAA) Geostationary Operational Environmental Satellite (GOES-R series) is currently being developed by NOAA in cooperation with the National Aeronautics and Space Administration (NASA). The GOES-R series satellites represents a significant improvement in spatial, temporal, and spectral observations (several orders of magnitude) over the capabilities of the currently operational GOES-1 series and the about to be launched GOES-N series satellite. The GOES-R series will incorporate technically advanced third-generation instruments and spacecraft enhancements to meet evolving observational requirements of forecasting for the era 2012-2025. The GOES-R instrument complement being developed includes a Advanced Baseline Imager (ABI), a Hyperspectral Environmental Suite (HES), a GEO Lighting Mapper (GLM), a Solar Imaging Suite (SIS) and a Space Environment In-Situ Suite (SEISS). Also, candidates for a number of GOES-R Pre-Planned Product Improvements (P(sup 3)Is) includes a Geo microwave Sounder, a Coronograph, a Hyperspectral Imager, and a Solar Irradiance Sensor. Currently, the GOES-R Space Segment architecture is being evaluated as part of a GOES-R system end-to-end architecture study. The GOES-R notional baseline architecture is a constellation of two satellites (A-sat and B-sat) each nominally located at 75 degrees west longitude and at 135 degrees west longitude at geostationary altitude, 0 degrees inclination. The primary mission of the A-sat is to provide imaging from the ABI. The A-sat will also contain the SIS and the GLM. The primary mission of the B-sat is to provide sounding of the hemispherical disk of the earth from the HES. The B-sat also contains the SEISS. Both satellites have mesoscale capabilities for severe weather sounding or imaging. This paper overviews the GOES-R Space Segment development including satellite constellation trade-off, improvements and differences between the current and future instrument and spacecraft capabilities, and technology infusion.

The TerraSAR-X is a German national SAR- satellite system for scientific and commercial applications. It is the continuation of the scientifically and technologically successful radar missions X-SAR (1994) and SRTM (2000) and will bring the national technology developments DESA and TOPAS into operational use. The space segment of TerraSAR-X is an advanced high-resolution X-Band radar satellite. The system design is based on a sound market analysis performed by Infoterra. The TerraSAR-X features an advanced high-resolution X-Band Synthetic Aperture Radar based on the active phased array technology which allows the operation in Spotlight-, Stripmap- and ScanSAR Mode with various polarizations. It combines the ability to acquire high resolution images for detailed analysis as well as wide swath images for overview applications. In addition, experimental modes like the Dual Receive Antenna Mode allow for full-polarimetric imaging as well as along track interferometry, i.e. moving target identification. The Ground Segment is optimized for flexible response to (scientific and commercial) User requests and fast image product turn-around times. The TerraSAR-X mission will serve two main goals. The first goal is to provide the strongly supportive scientific community with multi-mode X-Band SAR data. The broad spectrum of scientific application areas include Hydrology, Geology, Climatology, Oceanography, Environmental Monitoring and Disaster Monitoring as well as Cartography (DEM Generation) and Interferometry. The second goal is the establishment of a commercial EO-market in Europe which is driven by Infoterra. The commercial goal is the development of a sustainable EO-business so that the e.g. follow-on systems can be completely financed by industry from the profit. Due to its commercial potential, the TerraSAR-X project will be implemented based on a public-private partnership with the Astrium GmbH. This paper will describe first the mission objectives as well as the project organisation and major milestones. Then an overview on the satellite as well as the SAR instrument is given followed by a description of the system design. Finally the principle layout of the TerraSAR-X Ground Segment and some remarks on the European context are presented.

The Next Generation Space Telescope will be the premier instrument for astrophysical research a decade from now. This paper describes the reference concept for the observatory being studied by a prime contractor team led by TRW and Ball Aerospace. We give an overview of the space segment of the mission, and the rationale for its heliocentric orbit at the Sun-Earth L2 Lagrangian point. At the time of this meeting many details of the engineering design are still open for trade studies. We highlight a few whose resolution will have implications for the scientific performance of the observatory, and for which preferences and recommendations from the scientific community are welcomed.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper presents design and performance of a high- precision star tracker which has been developed for use in the attitude determination and control system of MUSES-B spacecraft; the space segment of space VLBI program called VSOP (equals VLBI Space Observation Program). The MUSES-B is being prepared for launch in September 1996. The attitude control system is required to fulfill an overall pointing accuracy of 0.01 degrees (3 sigma) of an 8 meter-diameter VLBI antenna mounted on the spacecraft. The onboard attitude determination system is based on a reset type Kalman filter that assures the overall attitude determination accuracy of 19 arcseconds, using outputs from the star trackers and the gyroscope-based inertial sensors. For this purpose, the star tracker is designed to provide star position detection accuracy of 4 arcsec random (1 sigma) plus 15 arcsec bias error. This paper describes the design of the STTs, the performance analyses, and ground test results of the Protoflight Model.

The GOES I-M image navigation and registration (INR) system was developed and patented by Space Systems/Loral in response to NASA/NOAA pointing requirements of Imager and Sounder payloads. This INR system is divided into space segment and ground segment. The space segment consist of image motion compensation (IMC) system that compensates for deterministic errors caused by orbit and attitude motions and mirror motion compensations system that compensates for spacecraft attitude motion caused by Imager and Sounder scanner mirror motion. The ground segment consists mainly of Orbit and Attitude Tracking System (OATS) that determines the IMC orbit and attitude coefficients from star, landmark, and range measurements.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Originating out of a SDIO-funded, Phase 1 study effort, two ground systems and an orbiting EO payload/spacecraft were the primary equipment for the RME. The RME was originally conceived to be a shuttle deployed experiment. Shortly after program start, the Challenger disaster occurred, with the promise of extensive delays. A completely new space segment was to be designed incorporating a free-flying spacecraft. During the midphase of the program, a variety of launch vehicles were envisioned to replace the shuttle, requiring the BASD team to design accommodations for Delta, Atlas, and Titan, with a Delta launch being the final solution. The ground systems tracked the spacecraft and illuminated it with green and blue beacon lasers. The Payload Experiment Package (PEP) housed the bisection tracker, a key innovation central to the experiment. The bisection tracker acquired both beacons and controlled steerable mirrors to accomplish fine tracking of the two cooperative beacons. In the process, the relay mirror was precisely positioned to enable a successful relay of a third infrared laser between the two ground sites via the orbiting spacecraft. Many of the key technologies employed in the PEP were originally developed for Ball laser communications research and development programs and other laser pointing efforts. The WAVE sensor package, built by ATA and integrated by Ball, measured the vibrations of the optical base structure on which it was mounted. These spacecraft vibration data are critical to the accurate pointing of space laser communication terminals.

Present large space-based remote sensing systems, and those planned for the next two decades, remain dichotomous and custom-built. An integrated architecture might reduce total cost without limiting system performance. An example of such an architecture, developed at The Aerospace Corporation, explores the feasibility of reducing overall space systems costs by forming a 'super-system' which will provide environmental, earth resources and theater surveillance information to a variety of users. The concept involves integration of programs, sharing of common spacecraft bus designs and launch vehicles, use of modular components and subsystems, integration of command and control and data capture functions, and establishment of an integrated program office. Smart functional modules that are easily tested and replaced are used wherever possible in the space segment. Data is disseminated to systems such as NASA's EOSDIS, and data processing is performed at established centers of expertise. This concept is advanced for potential application as a follow-on to currently budgeted and planned space-based remote sensing systems. We hope that this work will serve to engender discussion that may be of assistance in leading to multinational remote sensing systems with greater cost effectiveness at no loss of utility to the end user.

In the framework of past and future X-ray missions the SAX satellite, to be launched in March 1996, stands out for its very wide spectral coverage from 0. 1 to 200 keV, with well balanced performances of the low energy andhigh energy instrumentation. The sensitivity ofthe scientific payload will allow the exploitation of the full band of SAX also for weak sources (1/20 of 3C273), opening new perspectives in the study of spectral shape andvariability of several classes of objects. In this paper we briefly describe the main aspects of the mission, with particular regard to its scientific capabilities 1. OVERVIEW OF THE MISSION AND ITS INSTRUMENTS The X-ray Satellite SAX is a major program of the Italian space agency (ASI) with participation of the Netherlands space agency (NIVR). Prime industrial contractors are Alenia for the space segment and NuovaTelespazio for the Ground Segment. The mission development is supported by a consortium of scientific institutes4. SAX will be the first Xray mission (and, of the coming near$uture satellites, the only one) with the capability ofobserving sources over more than tree decades of energy from 0. 1 to 300 keV -with a relatively large area, a

Tropical radar environmental information system (TREIS) is a concept for a system of tropical forest monitoring based on satellite radar remote sensing. The approach is novel--starting from the ground up. TREIS offers a way around three major obstacles that are likely to preclude large-scale use of currently planned space radars: (1) high primary data cost; (2) complex and centralized ground segment infrastructure; and (3) a less than optimum radar wavelength. The proposed system is specified based on existing regional capabilities in data reception, processing, and utilization. The space segment uses existing AVHRR class data telemetry (625 Kbps), and partial on-board preprocessing of the P-band (75 cm) synthetic aperture data. Aggregate coverage of the earth''s tropical forests twice a year is achieved with ten look imagery of 20 km usable swath width and pixel spacing of 50 m. Image processing requires only work stations or high-end PC-class hardware which could be distributed over many regional centers. Data products could be prepared rapidly and inexpensively for regional use and for global inventory efforts such as those of the United Nations.

A new concept for a polar orbiting satellite dedicated to global change research and its extension to fulfill the meteorological operational mission in the morning orbit is studied by CNES and MATRA, with the support of EUMETSAT and a group of European scientists. Two options were investigated during the feasibility study called GLOB(MET)SAT, the first one, GLOBSAT, restricted to an IGBP-dedicated mission, and the second one, GLOBMETSAT, combining this research mission and the operational met-mission specified by EUMETSAT. The mission objectives, the associated requirements, and the instruments accommodated are presented and discussed, as well as the main results of the phase A study for the space segment. The system configurations, characteristics, performances and the development plan are described. Both options prove feasible and compatible with a target launch date in the 1996-97 timeframe and preserve a significant growth potential. The use of the MK-2 platform developed for the SPOT-4 program and of other recurrent hardware elements appears a significant cost-saving, schedule-securing and reliability factor in both options. In the same line, the GLOBMETSAT system combining the environment and meteorological missions is of mutual benefit for both missions, in terms of reliability, cost sharing and use of platform resources, while keeping each mission independent and unaffected by the other.

The German 'Atmospheric and Environmental Research Satellite, ATMOS'-program has been started in early 1989 under responsibility of the DLR. It is concerned with the measurement and analysis of atmospheric trace gases for the investigation of the ozone layer disturbance and the amplification of the greenhouse effect as well. Marine and terrestrial biosphere observation additionally is of great interest because of dramatically increasing human impact on the environment. The paper deals with the description of the scientific objectives of the ATMOS mission with focus on the tropospheric and stratospheric exchange processes, the chemistry of trace gases and the interaction of the biosphere and atmosphere. An optimized orbit concept is proposed and a comprehensive data management and information system is introduced. The space segment consists of a modular platform accommodated by a service module and a payload module with some growth potential to be open for involvement of international partners. The measurement principles of the four basic ATMOS instruments are described and their configurations are illustrated due to the present development status.

The requirements for characterization and calibration of instruments for the Earth Observing System space segment are defined in terms of tracking the Level 1 data for a sensor. The data must be traceable over the 15 year program, and must provide corrections for radiometric, spectral and geometric coefficients which capture the combined design and performance characteristics of the sensor. These requirements are then developed for MODIS-N to identify a set of techniques which can be used in the laboratory, spacecraft integrator's facility and in-orbit. The in-orbit of the so-called reflectance and radiance methods are reviewed, and the cross-calibrations available between HIRIS and MODIS through these techniques are listed. A scheme for the use of all available tools for instrument performance is provided as a Figure showing an estimated time interval over which each tool is expected to be useful. The final calibration strategy and plan must be developed through the understanding of a useful strategy for each of these candidate mechanisms.

The objective of the Space Infrared (SIRE) Sensor program is to measure LWIR radiation of natural and man made sources in space. Measurements will be used to support development and operation of space based space surveillance systems. This paper describes the planned concept for operating SIRE as a non-deployed payload within the payload bay of the Orbiter. The operations concept is prefaced with an overview of the SIRE system addressing the sensor, space segment, ground segment and supporting elements of the Space Trans-portation System. This is followed by a description of operational concepts and data processing that will be used within the ground segment during flights to plan, command and evaluate SIRE operations. This responsive system provides for inflight evaluation of data and replanning of measurements as necessary to accommodate operational perturbations from the Orbiter and react to unexpected measurement results.

This paper describes EOSAT's (The Earth Observation Satellite Company), plans for operating the Landsat System in the Landsat-6,7 era, (1985 to 1995). The paper will provide background information relative to EOSAT, and an overview of the planned configurations of both the space segment (Spacecraft and Enhanced Thematic Mapper), and the ground segment (Space-craft Operations Center, Data Capture Site, EOSAT Processing Center) for Landsats 6 and 7. The planned enhancements to the Landsat-6/7 Thematic Mappers will be described in some detail including the implementation of a Panchromatic Band of detectors providing 15m spatial resolution on both ETM sensors, and the possible inclusion on the Landsat-7 ETM of as many as five bands of thermal detectors with 120/60 meter spatial resolution.