The Operations Concept for Tandem-L – From Mission Goals to Spacecraft Requirements

Kurzfassung

Tandem-L is a highly innovative L-band SAR mission for the global observation of dynamic processes on the Earth’s surface with unprecedented quality and resolution. Two identical satellites of ~3000 kg will fly in a variable formation with separations between 500 meters and 20 kilometers. Thanks to a Large Deployable Reflector and digital beam forming techniques Tandem-L will support the science community with unique data in the areas of the biosphere, geosphere, cryosphere, and hydrosphere. The mission was proposed by the DLR Microwaves and Radar Institute and is currently in the requirements definition phase. The German Space Operations Center (GSOC) has participated since the early phase of the project during the development of the mission operations concept and by reviewing the studies from industrial partners. As DLR is responsible for contracting the space segment supplier, the recent goal has been to derive satellite system requirements from the mission requirements as well as from operational strategies. New technical opportunities and standards were analyzed and considered in the operations approach. Simultaneously, a working group was established to collect lessons learnt from previous missions operated at GSOC. This paper presents the mission operations concept and the new challenges compared to the precursor missions TerraSAR-X and TanDEM-X. Drivers are amongst others the volume of generated mission data of more than 8 terabytes per day, the highly variable formation, and the effects of the radar reflector on the orbit determination accuracy. Additionally, the derived satellite system requirements are discussed with a focus on the propulsion system, mutual radar illumination, the AOCS safe-mode, GNSS performance, the Ka-band downlink, and the on-board schedule.