Session
Technical Session VI: The Year Ahead
Abstract
This paper presents the range of coverage options available to TopSat like small satellites, both singly and in a small constellation. TopSat is a low-cost, high resolution and image quality, optical small satellite, due for launch in October 2004. In particular, the paper considers the use of tuned, repeat ground track orbits to improve coverage for selected ground targets, at the expense of global coverage. TopSat is designed to demonstrate the capabilities of small satellites for high value remote sensing missions. It is a 108kg, sun-synchronous satellite, designed to provide 2.5m resolution imagery direct to users in the vicinity of the imaged area. Its objectives are to demonstrate the capability to cost performance available from small satellites, the utility of direct reception of remotely sensed imagery, and the affordability of constellations and individually owned assets. A description of the satellite, and update on the development and flight build of the satellite is given, as of June 2003. Two coverage improving augmentations to the TopSat satellite are discussed, namely the addition of a propulsion system and more capable attitude actuators. With limited orbit control, achievement and maintenance of tuned orbits, and phasing of a constellation within orbits, become practicable. TopSat is an agile small satellite, allowing boresight reorientation required for slews during imaging. The capability for performing multiple images in a single target pass is considered, with the existing and improved torque actuator implementations. Similar options for performing stereo imaging with 2 formation flying TopSats are outlined. Reconfiguration of repeat ground track orbits for a single satellite is analysed in terms of fuel cost and drift orbit options. A one day repeat orbit case is presented which would allow daily coverage of a fixed target, with orbit reconfiguration required to allow global access. A typical mission for such a satellite is summarised, along with practical requirements for the propulsion system. Coverage options for constellations of between 2 and 4 satellites are then also scrutinised, with fuel estimates for the most promising options explored. Again, the benefits that could be achieved by using repeat ground track orbits are weighed against the fuel requirements, to maintain and reconfigure such a constellation. The TopSat mission is a collaboration between four UK partners. QinetiQ are leading the mission and providing data handling and ground segment elements. Rutherford Appleton Laboratory (RAL) are developing the camera, Surrey Satellite Technology Limited (SSTL) are providing the bus, and InfoTerra are responsible for developing potential data markets. The programme is jointly funded by the UK Ministry of Defence (MoD) and by the British National Space Centre (BNSC).
Presentation Slides
Coverage Options for a Low cost, High Resolution Optical Constellation
This paper presents the range of coverage options available to TopSat like small satellites, both singly and in a small constellation. TopSat is a low-cost, high resolution and image quality, optical small satellite, due for launch in October 2004. In particular, the paper considers the use of tuned, repeat ground track orbits to improve coverage for selected ground targets, at the expense of global coverage. TopSat is designed to demonstrate the capabilities of small satellites for high value remote sensing missions. It is a 108kg, sun-synchronous satellite, designed to provide 2.5m resolution imagery direct to users in the vicinity of the imaged area. Its objectives are to demonstrate the capability to cost performance available from small satellites, the utility of direct reception of remotely sensed imagery, and the affordability of constellations and individually owned assets. A description of the satellite, and update on the development and flight build of the satellite is given, as of June 2003. Two coverage improving augmentations to the TopSat satellite are discussed, namely the addition of a propulsion system and more capable attitude actuators. With limited orbit control, achievement and maintenance of tuned orbits, and phasing of a constellation within orbits, become practicable. TopSat is an agile small satellite, allowing boresight reorientation required for slews during imaging. The capability for performing multiple images in a single target pass is considered, with the existing and improved torque actuator implementations. Similar options for performing stereo imaging with 2 formation flying TopSats are outlined. Reconfiguration of repeat ground track orbits for a single satellite is analysed in terms of fuel cost and drift orbit options. A one day repeat orbit case is presented which would allow daily coverage of a fixed target, with orbit reconfiguration required to allow global access. A typical mission for such a satellite is summarised, along with practical requirements for the propulsion system. Coverage options for constellations of between 2 and 4 satellites are then also scrutinised, with fuel estimates for the most promising options explored. Again, the benefits that could be achieved by using repeat ground track orbits are weighed against the fuel requirements, to maintain and reconfigure such a constellation. The TopSat mission is a collaboration between four UK partners. QinetiQ are leading the mission and providing data handling and ground segment elements. Rutherford Appleton Laboratory (RAL) are developing the camera, Surrey Satellite Technology Limited (SSTL) are providing the bus, and InfoTerra are responsible for developing potential data markets. The programme is jointly funded by the UK Ministry of Defence (MoD) and by the British National Space Centre (BNSC).
