Extending the Envisat Mission - Impacts on Ground and Space Segment Operations

ESA’s Earth Observation (EO) satellite ENVISAT is a key source of remote sensing data for a multitude of Earth science disciplines and operational applications. Launched in 2002, ENVISAT’s nominal mission was scheduled to end in 2007. Given its excellent performance and the even increasing interest in the science data permanently collected by nine actively controlled instruments, the mission was extended until the end of 2010, when most of the onboard hydrazine will be exhausted. Concerns were however expressed about the expected data gap starting in 2010 between ENVISAT and the next generation of EO satellites, in particular the Sentinel missions. A new concept for extending the Envisat mission even beyond 2010 has therefore been analyzed and defined by the ESA internal “ENVISAT 2010+” project, which is based on an altitude lowering and a new orbit control concept. This approach will allow retaining high exploitation capabilities for the payload complement until end of 2013, while at the same time minimizing the impact on the space and the ground segment. Routine operations conducted from ESA’s control centre ESOC in Darmstadt, Germany, will however need to undergo substantial modifications in various areas. Following the ENVISAT orbit change, S-Band interferences are for instance predicted to occur during overlapping ENVISAT and ERS-2 ground station passes, affecting commanding, telemetry and ranging for these two EO missions operated from ESOC. Further aspects of the new ENVISAT orbit scenario include dynamic ground station allocation procedures, development of an automation tool for ENVISAT operations which is intended to ease the tasks of the operator, modified mission planning and simulator systems as well as necessary onboard updates and operations procedures.