ERS-2 platform disposal operations

Abstract

ERS marked in many ways Earth observation at the European Space Agency. When ERS-1 was launched in 1991, it was one of the most sophisticated spacecraft ever built in Europe. It accomplished, together with its successor ERS-2, a major scientific mission covering a period of more than 20 years. During this extended period, the mission had to respond to new requirements while the actual capabilities of the ERS-2 spacecraft were declining. At the end of the mission, the mitigation of space debris had become a priority and posed a final challenge. Disposal operations were prepared to lower the orbit and to "passivate" the ageing spacecraft. The development and the execution of these operations are presented with a particular emphasis on the influence of the platform design and of its status at the time of execution. In order to give an overview of the platform status at the beginning of the disposal phase, its design is presented together with a short in-flight history of major failures and on-board software modifications. The ability of the spacecraft to comply with space debris mitigation recommendations is then analyzed before the development and the execution of the disposal operations is described in detail.

A Satellite Retires - The ERS-2 Deorbiting in Summer 2011

“…The attitude control was severely affected by the limited availability of the gyros onboard 3,7 . Three of the original 6 gyros already failed after an increase in noise between 1997 and 2000 and two further showed a degraded performance.…”

“…1) In Phase 1 maneuvers would be performed in pairs at opposite positions in the orbit (PSO) to decrease the semi-major axis and maintain a circular orbit. The duration of individual burns was limited to 300 seconds to al-low operations with both the "mono-gyro" and as backup the "gyroless" mode 3 . Goal was to lower the semimajor axis by at least 100 km (to less than 700 km altitude).…”

“…Gyro6 was used for piloting, Gyro4 configured for potential Safe Mode cases and Gyro3 was switched on, but not used for piloting. First signs of increasing gyro noise became immediately obvious 3 . 65.8 kg of hydrazine were spent for a total semi-major axis change of 110.9 km (see Table 3 for a performance summary).…”

“…While this paper provides an overview of the deorbiting background and activities, platform related details can be found in Ref. 3.…”