HFI operations

All satellite operations, including those for the HFI instrument were under ESA MOC responsibilty for obvious safety reasons. The HFI instrument operations were nevertheless delegated to the HFI Instrument Operations Team (IOT), set up within the HFI consortium and under the HFI Principal Investigator responsibility. Instrument management, operations and parameter monitoring were thus prepared and controlled by the IOT and serviced by MOC either in near real time during the DTCP or uploaded in the satellite mission timeline for deferred execution. The HFI instrument health and science data quality was monitored daily by the IOT from launch till the end of the HFI extension mission phase. Apart from ground based tests, different operations phases occurred, as listed below.

• 14/05/2009-18/05/2009 Launch Early Operational Phase.
• 18/05/2009-09/07/2009 Commissioning Phase. The operations during this phase were under ESA's Planck Project responsibilty. The main HFI activities were functional tests of the instrument and its cooldown to 100 mK. Given the performance, the helium flow was set to the minimal one giving an End Of Life estimation of the second half of January 2012.
• 10/07/2009-12/08/2009 Calibration and Performance Verification Phase. The operations during this phase were under the responsibility of ESA's Planck Science Office. The main HFI operations were performance tests and activities to measure the effects of several systematics. The only instrument failure happened on the 6th of August, where the electronic part of the 4-K cooler was switched off, probably due to a major cosmic particle. It has to be noted that no tuning of the HFI parameters were executed in-flight until the end of the full HFI mission, except in December 2009 for an adjustment of the on-board numerical compression parameters.
• 12/08/2009-28/11/2010 HFI Nominal mission.
• 28/11/2010-13/01/2012 HFI Extended mission.
• 13/01/2012-03/10/2013 LFI "only" extension phase.

The detailed operational timeline for HFI is given in this annex.