ISCO: Algorithms for Space GNSS Guaranteed Positioning: Integrity for Space Corridor

The dramatic increase of the number of satellites in LEO (Low Earth Orbit) has significantly increased the frequency of risky conjunction events between space objects, which if not properly handle, can lead to collision and to the creation of even more space debris. Alongside this observed increase in conjunctions events, the complexity of the ground operation for constellation management and collision avoidance became evident, pushing to the limit the current state-of-art procedure that require ad-hoc event analysis with ground operator and analyst in the loop. The only suitable solution is an increase in the spacecraft’s autonomy. In the past, many missions have demonstrated an autonomous control of the satellite to maintain a nominal Space Corridor / orbit slot. However up today there is no integrity concept embedded into the Space Corridor to guarantee that possible issues (e.g., current position is outside protection limits) are identified and immediately flagged/corrected. To face this challenge and contribute to the solution of the problem, ESA (European Space Agency) launched the ISCO (Algorithms for Space GNSS Guaranteed Positioning: Integrity for Space Corridor), project led by GMV, to provide this extra layer of integrity to the Space Corridor concept, including feared events impacting satellite POD. The activity focus is to define the Space Corridor and the whole integrity concepts required. Such concepts need to be adapted to cover not only the Position, Velocity and Timing (PNT) of the spacecraft, but also the propagation/forecast of its orbit (future position and associated covariance). This is needed to guarantee that the spacecraft is maintained within the allocated space corridor to create a bound that could be used for collision detection/avoidance and autonomous manoeuvring capabilities. In this paper, next three main aspects of the project will be presented, i.e.: i. Representative Use Case selection, ii. Space corridor definition, iii. High accuracy onboard PNT design and implementation. The developed Software will be provided by ESA under a Community License.