Herschel Status Report - October 2009
25 Oct 2009 17:53
Report for period 23 September to 21 October 2009
Mission operations of the Herschel space observatory continued nominally during the reporting period, with the spacecraft and subsystems all performing as expected. Investigations for the recovery of the HIFI instrument are progressing well, and a plan for switching on the instrument's back-up electronics is being finalized.
The spacecraft is operating nominally on prime chains throughout.
Autonomous star tracker switch-over
As of mid-October, Herschel was 70% through the Performance Verification Phase (PVP) of its three instruments. For PACS and the SPIRE photometer, PVP will likely be completed by the end of October with the exception of activities requiring Neptune as a target - this planet only becomes visible in November. HIFI remained switched off during the reporting period. In November Herschel will be conducting a mix of activities from four post-launch phases (Commissioning, Performance Verification, Science Demonstration and Routine Science Phases), because after the temporary unavailability of HIFI and the spectrometer part of SPIRE these two instruments will require re-commissioning and additional performance verification.
The cryogenic chains are working well and maintaining the PACS and SPIRE bolometers at their operating temperatures of 300 mK.
There now is a coherent and consistent picture of the likely sequence of events leading to the anomalous behaviour on 2 August. A chain of events led to an overload in some components in a power converter of the Local Oscillator Control Unit (LCU) on the instrument's prime electronics chain, causing the permanent failure of one of the diodes.
The investigation team's report is being drafted and the detailed HIFI recovery plan is being prepared for formal approval. The HIFI recovery scenario and timeline is currently being elaborated and, pending the formal approval of the proposed plans, it is anticipated to resume HIFI operations (re-commissioning on its redundant signal chain and completing its PVP) in the second half of November.