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The regional coverage satellite constellations are in demand for fulfilling earth observation needs of specific user regions of interest as opposed to global coverage thus enhancing the revisit period for the area. In this paper, we present a few key mission aspects of the regional coverage constellation designed and operated by the Indian Space Research Organization (ISRO) in low earth orbit. ISRO developed three X-Band Synthetic Aperture Radar (SAR) Earth Observation satellites and placed them in three inclined orbit planes to enhance the Indian region's coverage. This is India's first inclined orbit constellation designed for remote sensing applications in low earth orbit. The satellites were built around a standard bus carrying a Synthetic Aperture Radar payload with a deployable Radial Rib Antenna (RRA). They were designed to achieve a high agility capability. As SAR sensors are capable of all-weather, day, and night imaging; thus, most suitable in inclined orbits where the illumination conditions vary continuously for imaging. Though the inclined orbits provide more revisit opportunities to the region of interest, their characteristics pose challenges in mission design and operations. Though the mission design and planning involved a host of elements, this paper brings out the details of a few key mission analysis elements, planning aspects and operations that were critical in the course of various mission phases. The mission analysis included mission-specific requirements like launch windows selection for the constellation and reference attitude generation specific to inclined orbit geometry. Mission planning had to take care of Radial Rib Antenna (RRA) deployment requirements which were very critical for the mission, apart from taking care of individual subsystem requirements. The SAR payload data product quality and targeting accuracy are very sensitive to the satellite image point range (vis-a-vis SAR operation data window). Extensive post-launch calibration activity was carried out to meet all these mission requirements and data product specifications. The challenge was in fixing the payload beam alignment and fixing the uncertainties in onboard and ground computations. The paper also describes the methods of fixing all possible error sources affecting the high-resolution SAR payload performance. • The regional coverage satellite constellations are in demand for area targets coverage. • Inclined orbit constellations are more suitable for regional coverage using SAR sensors. • Mission operations plans need to consider all the specific requirements of spacecraft systems. • Pre-launch and post -launch calibrations of sensors is mandatory for achieving system performance. [ABSTRACT FROM AUTHOR]

Abstract: With an array of Indian Remote Sensing Satellites (IRS), a wide variety of national applications have been developed as an inter-agency effort over the past 20 years. Now, the capacity of the programme has been extended into the global arena and IRS is providing operational data services to the global user community. The recently launched IRS satellite, Resourcesat-1, was placed into perfect orbit by India''s PSLV and is providing valuable imaging services. Resourcesat-1 is actually like 3 satellites “rolled” into one, imaging a wide field of 710km area at 55m resolution in multispectral bands from the AWiFS, 23m resolution in a systematic 142km swath from four bands of the LISS-3 and the 5.8m multi-spectral images from the most advanced sensor—LISS-4. Yet another aspect of Resourcesat-1 is it that it marks a “watershed” in terms of a quantum jump in technological capability that India has achieved compared to past missions. The mission has many newer features—the advanced imaging sensors, the more precise attitude and orbit determination systems, the satellite positioning system onboard, the mass storage devices and many other features. This mission has led IRS into a new technological era, and when combined with the technological capability of the forthcoming Cartosat missions, India would have developed technologies that will take us into the new generation of EO satellites for the coming years. This paper provides a detailed description of the Resourcesat-1 mission. From the applications point of view, Resourcesat-1 will open up new avenues for environmental monitoring and resources management—especially for vegetation assessment and disaster management support. The monitoring capability of this mission is also extremely important for a number of applications. The mission has global imaging and servicing capabilities and could be received through the Antrix-Space Imaging network, which markets Resourcesat-1 data worldwide. This paper also describes the applications potentials and global capabilities of the mission. Resourcesat-1 will have continuity and after that a new generation system will provide enhanced and more unique imaging services. Actually, India has a 25 years strategy for EO and a perspective of the same is also described in this paper. [Copyright &y& Elsevier]

Abstract: The mission of the COMPASS-1 picosatellite is to take pictures of the earth, to validate a space-borne GPS receiver developed by the German Aerospace Center, and to verify the proper operation of the magnetic attitude control system in orbit. The spacecraft was launched on April 28, 2008 from the Indian space port Sriharikota, as part of the PSLV-C9 world record launch that simultaneously brought ten satellites into orbit. The mission operations were carried out from the ground stations in Aachen and Tainan. Arising difficulties in the communication link were overcome with the support of individuals from the amateur radio community. After several months of mission operation, abundant housekeeping and mission data has been commanded, received and analyzed and is presented in this paper. [ABSTRACT FROM AUTHOR]