Herschel Status Report - November 2011
25 Nov 2011 15:05
Report for period 13 October to 21 November 2011
Mission operations of the Herschel space observatory continued nominally during the reporting period, with the spacecraft and subsystems all performing as expected.
The spacecraft continues to be in good health and is operating nominally.
The improved knowledge of effects that contribute to the pointing accuracy of the Herschel observatory will be discussed end November, to see how it can be put to use in further improving both the pointing accuracy during an observation and the post-observation reconstruction of the observatory's actual attitude.
Following two star tracker focal plane corrections, which were uploaded to the observatory earlier this year (see status reports from June to October 2011), Herschel's Absolute Pointing Error is about 1 arcsecond.
After more than three months of operations that were free of disruptions by any Single Even Upset (SEU) in the instrument processors a few SEUs were observed in rapid succession: one for HIFI, one for SPIRE, and four spontaneous changes in PACS voltages generated by their DECMEC device. For HIFI and PACS there was no impact on the science (HIFI was not observing at the time). For SPIRE several hours of observing time were lost. Apart from these SEUs, operations for all three instruments have been nominal during the reporting period.
An in-depth analysis of all SPIRE housekeeping data since launch has been performed by the SPIRE team, and the circumstances that produce a one second offset in the SPIRE on-board clock are now understood. Fortunately this anomaly occurs very infrequently (only four occasions in the 2.5 years since launch), and because it can also be reliably detected from housekeeping data and corrected for in the science products it will not be necessary to correct for it on-board.
Ground segment operations have been nominal and 100% of the data continues to be recovered. As of 11 November 2011, the approximate completion of the different programme parts was:
For more details of these different programme parts, see the "overview of Herschel observing" linked from the right-hand menu.
The second, and final, call for Open Time Proposals (OT2) for observing with Herschel was closed in mid-September. The Herschel Observing Time Allocation Committee has completed its review of the well over 500 submitted proposals. The outcome of the review, when endorsed, is expected to be communicated to proposers before the end of November.
A routine station-keeping manoeuvre, or orbit correction manoeuvre, was performed on 12 November. These routine manoeuvres ensure the spacecraft maintains its correct orbit about L2.