Herschel Status Report - December 2009
With about 6 months of operational experience with Herschel, test are performed for refinements to the initially conservative slew time predictions in the scientific mission planning chain to reduce the margins and to better match the real behaviour of the space observatory. When implemented this would lead to an even more efficient operation of Herschel and a gain in observing time of several weeks over the course of the mission.
The spacecraft is operating nominally on prime chains throughout.
The first Direct Liquid Content Measurement has been performed as planned on 25 November. This measurement assesses the remaining amount of liquid helium for the spacecraft's active cooling system, which directly determines Herschel's lifetime for scientific observations. The measurement results were very close to predictions, and confirm the anticipated lifetime of just under 4 years after launch.
Star tracker warm pixels
Although there is not yet a complete understanding as to the physical cause of the phenomenon of "warm" pixels on the star tracker CCD (these pixels carry additional charge but appear and disappear on a timescale of hours), there is now a quantitatively better understanding of its impact on astrometry. This helps to determine how to at least partly compensate for this effect afterward in the data processing.
By the beginning of December, in terms of required observing time half of the Science Demonstration Phase and more than 250 hours of Key Programme observations had been performed.
PACS and SPIRE continue to operate nominally. Both instruments have concluded their Performance Verification Phase activities and most of their standard operating modes have been released for public use.
Based on observations carried out using these modes it is currently being assessed together with the Principal Investigators of the 42 Key Programmes whether updates are required before these observations are released for execution as part of the Routine Science Phase. Such changes are sometimes required because a particular observing mode has been replaced by another one, or based on actual results from the Science Demonstration Phase. This approach is part of making the most of Herschel, for the benefit of its observers and the mission itself.
The HIFI recovery has progressed significantly. Both ESA and the HIFI consortium were informed of the investigation results, the measures taken to eliminate the recurrence of the suspected anomaly, and the recovery steps and plans. Elements of the redundant HIFI chain have since been switched on again and a Short Functional Test has been successfully conducted on 7 December. Some critical operations, involving the local oscillators and their redundant electronics, will be performed after New Year.
During the reporting period, mission operations have been conducted with the support of the ESA New Norcia ground station. Observational data stored on-board Herschel was received on ground during communication passes lasting approximately three hours.
The ground segment is operating nominally. Data products are generated routinely and ingested into the Herschel Science Archive (HSA).
- January 2010: Complete switch on of HIFI
- March 2010: Herschel Observatory Routine Science Phase Readiness Review