Multi-Mission Synergies In Routine Operations Of Low Earth Orbiting Satellites

Abstract

The German Space Operations Center currently operates five low Earth orbit satellites in routine phase. The supported missions are the GRACE-mission (two satellites with an along track separation of 200km), the TerraSAR-X/TanDEM-X mission (two satellites in close formation flight at few hundred meters distance) and the Firebird mission with an infra-red camera on the spacecraft TET-1. The Firebird mission will be extended by a second spacecraft BIROS in near future. Effort has been spent to exploit synergy potentials in operations of these spacecraft. Since 2014 they are controlled in a multi-mission control room to facilitate combined operations for the multi-mission flight support team. The concept of the multi-mission layout of the control room will be described in this paper. Control room activities of low Earth orbiting satellites are driven by ground stations passes. Maximal synergies are possible whenever the ground station passes of the different missions are homogenously distributed over the day. In this case a minimum of multi-mission flight personnel is able to support the different missions sequentially. However, the timing of the ground station passes may not be chosen freely as the visibility times of ground stations are given by the combination of orbit and the geolocation of the available ground stations. In order to avoid conflicts with support times of other satellites a choice between different visibilities in sub sequential orbits is, in some cases, compliant with the mission’s operations concept and requirements. Another option might be the selection of alternative ground stations in different parts of the world. The operational integration of new ground stations in the mission’s network with an appropriate connection line is a precondition. The missions TerraSAR-X/TanDEM-X and GRACE comprise two spacecraft each. In both cases the spacecraft orbit fly in close spatial proximity and both missions use ground stations of the German Aerospace Center (DLR) in Germany, namely Weilheim in southern part, and Neustrelitz in northern part. One ground station supports the first satellite of the mission, the other ground station the second satellite of the same mission. As a consequence the support times in the control room for the two spacecraft are practically identical. In order to open-up the possibility to support parallel passes with a minimum of staff the operational task during passes needs to be reduced and simplified. This is done by assistance of automatic processes taking care of certain pass preparation functions, commanding and post pass activities or by the restriction of active interaction to one satellite only. The concept ideas are described in the paper. A further complication exists by the fact that the satellites of the GRACE mission do not have a sun synchronous orbit. The passes of the Grace satellites move in daytime in contrast to the ones of the TanDEM-X/TerraSAR-X mission and the TET-1 spacecraft. As a consequence the overall support pattern changes from day to day. An extreme accumulation of support times is possible. In order to avoid extreme situations a multi-mission pass planning process has been initiated.