Ground Segment Design for On-Orbit Servicing Missions at GSOC

Abstract

The interest in On-Orbit Servicing (OOS) space missions is growing. Such missions pose challenging requirements to ground segment design for these mission types. Especially when robotic elements, like rovers or robotic manipulators, come into play, legacy and proven ground segment concepts need revision and mission type-specific upgrade. Driven by the strategy to enable support of such missions in near-Earth space, the German Space Operation Center (GSOC) undertakes significant effort to achieve the desired readiness on technical and operational levels. This publication gives an overview about current activities at GSOC from a system engineering point of view and describes current mission preparation activities and future design tasks. The presented technological developments are of generic nature; however, a two-satellite, low-Earth orbit (LEO) mission with a robotic manipulator, which dominantly drives communication requirements, is taken as example to illustrate the presented concepts. That mission type is a very likely candidate for near-term OOS missions because of two reasons: First, the growing number of space debris poses a non-negligible threat to space operations, with large inoperable satellites in polar orbits of heights between 700 and 900 kilometers being the most vulnerable ones. Second, the life-time extension of valuable space assets may be a cost-saving alternative to the replacement by a new satellite. Active space debris removal and OOS almost inevitably require robotic in-space elements. If tele-operated in LEO regime, robotic mission operations can even take place under telepresence conditions, i.e., with visual and haptic feedback. For robotic tele-presence to function, a near-realtime communication environment with low latency and low jitter is therefore required. GSOC currently specifies the required equipment for innovative telecommand and telemetry communication chains and a generic ground segment design that supports Launch and Early Operations Phase and routine operation phases of OOS missions. Before presenting related current research activities and future development, implementation, test and validation plans, the authors describe recent and past achievements in that context. The identification of design-driving requirements is then followed by the technology development plan to address these requirements. This part also includes a description of those ground segment design entities that can be derived from established and proven concepts, such as backup and redundancy, network support, scheduling, archiving and replay, offline processing, multimission flight support, monitoring and control software, etc. The final part elaborates on the test and validation concept of the entire ground segment, which constitutes of the concept of subsequent tests of increasing complexity. Due to the special character of envisaged mission types, particularly adapted tests will however be necessary. Furthermore, for the envisaged two-satellite mission type, special two-crew concepts must be developed and validated through simulations starting from single-satellite simulations to two-satellite simulations involving realtime telepresence operations under most realistic conditions. This publication concludes with an outlook on OOS-related development and qualification activities over the next years and the possible extension on OOS missions in geostationary orbit (GEO).