ESA GNC Conference Papers Repository

The Copernicus Imaging Microwave Radiometer (CIMR) is a European Earth Observation mission consisting of 2 satellites (with an option of the extension to the third one). It will provide high resolution global monitoring of the Earth surface emissions across various frequency bands, in particular floating sea ice parameters. The 3-axis stabilized spacecraft(s) will operate in a sun synchronous orbit with 817 km altitude. The instrument features a deployable mesh reflector with the diameter of 8 meters and its feed cluster, which rotates at 8 rpm to produce a 1900km wide ground swath. The CIMR mission is currently in the C/D development phase and is being developed by a European space consortium with Thales-Alenia-Space Rome as a prime contractor. The unique configuration consisting of the 3-axis stabilized platform and a spinning instrument poses various technical challenges for the AOCS design. The design drivers have been identified as follows: •Provision of onboard angular momentum management to accommodate for large rotating instrument. •Sophisticated spacecraft dynamic phenomena caused by a)flexibility of the deployable rotating antenna b)static and dynamic unbalance of the rotating instrument c)fuel sloshing •Capability to perform collision avoidance maneuvers throughout nominal operation and controlled reentry at the end of mission lifetime •Managing the onboard Fault Detection, Isolation and Recovery (FDIR) with the objective of maximizing the scientific operation. This paper gives an overview of the CIMR AOCS design, in particular •Description of the avionics hardware setup •Basic AOCS modes and transitions •FDIR concept description Besides the general overview few critical design solutions developed for CIMR will be presented in more detail: •Static and dynamic unbalance on-board estimation using gyro rate measurements and compensation through active balancing system •Preliminary design of onboard control laws that meet the performance requirements and guarantee the overall systems stability and robustness in presence of undesired coupling caused by internal disturbances, flexible dynamics, and time-varying uncertainties. •Controlled reentry manoeuvre through multiple apogee thruster firings in presence of critical drag at perigee passages.