ESA GNC Conference Papers Repository

CryoSat-2 was launched from Baikonur on 8th of April 2010 aboard a modified Dnepr ICBM, the so-called SS18 Satan. Following the ascent and separation from the launch vehicle the Flight Operations Segment (FOS) in ESOC, Darmstadt started the operations to configure the satellite into the correct mode to acquire science; switching on units, configuring software and ensuring that the satellite health and performance was as expected. Following the 3 days of LEOP, the spacecraft entered the Commissioning Phase, characterized by the check out and performance evaluation of the AOCS units and the acquisition of the reference orbit. Cryosat-2 AOCS is based on magnetometers and Coarse Earth and Sun sensor for the Earth pointing attitude determination and Sun Acquisition, while DORIS and star trackers for fine pointing and orbit knowledge. Cold gas thrusters and magneto-torquers are used for the control in all modes. This paper will describe the switch on activities and acquisition of fine attitude during LEOP. It will then describe the implementation of the strategy to acquire the final scientific orbit. Finally it will address the unexpected problems encountered with the AOCS units on- board, their implications at operational level and the implemented solution.