Battery Operations for the TET–1 Spacecraft

Kurzfassung

The TET–1 satellite serves as a technology demonstrator within the On-Orbit Verification (OOV) program with the goal of providing German space companies and research institutions with the opportunity to test their equipment on actual spacecraft. It was launched on July 22, 2012, by a Russian Soyuz/Fregat into a Sun-synchronous Orbit with an LTAN of 11:27 UTC. The satellite is powered by nickel-hydrogen batteries during eclipse. The operations team became aware of several issues shortly before and after the launch which created some challenges for battery operation. Some battery cells had undergone reversal prior to launch which seems to have created an imbalance between them. Also, the overall temperature within the satellite and that of the batteries turned out to be higher than predicted and the battery voltage slightly exceeded the limit for payload operations. This paper describes in detail the circumstances in which these issues arose, wherever possible their causes and how they were dealt with. The capacity of the TET–1 spacecraft’s batteries is found to have increased from 12 Ah to about 14 Ah without any significant increase in temperature. Data gained at a later point in time also suggest a positive effect of the reconditioning.