Herschel Status Report - December 2011 and January 2012
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 were discussed end November, to see how it can best be put to use. Herschel's absolute pointing error is confirmed to be reduced to about 1 arcsecond. As a result of this supreme pointing, as compared to the specifications, higher order effects can now be seen. Beyond feeding back the improved knowledge into the re-processing of already gathered data, two measures have been agreed to be implemented to improve the pointing for future observations:
- higher order corrections (i.e. smaller than the two earlier updates in July and September 2011) in the on-board star tracker model will be uploaded to the spacecraft,
- the on-board star catalogue will be updated to exclude high proper motion stars and stars of lesser positional accuracy to the maximum extent possible.
After a long quiet period in autumn 2011, the instruments are again occasionally affected by single-event-upset induced bit flips in memory, sometimes leading to small losses in observing time. Apart from these few events, operations for all three instruments, PACS, SPIRE and HIFI, have been nominal during the reporting period. Indeed, the six-month average of executing observations still exceeds the pre-launch expectations, by more than 1 hour per day.
A large solar flare occurred on 23 January 2012 with a proton flux 40 times higher than the maximum observed by Herschel so far (see also "Solar flare - January 2012" in the right-hand menu). There is no damage to any of the three instruments. Possible degradations to the observations taken during this period were investigated. It was found that fortunately none of the observations taken during the Solar storm were affected to a degree that they would have to be repeated.
Ground segment operations have been nominal and 100% of the data continues to be recovered. As of 23 January 2012, the approximate completion of the different programme parts was:
|KPGT||Key Programme Guaranteed Time||:||98%|
|KPOT||Key Programme Open Time||:||98%|
|GT1||First in-flight Guaranteed Time||:||98%|
|OT1||First in-flight Open Time, high priority||:||56%|
|First in-flight Open Time, lower priority||:||2%|
|GT2||Second in-flight Guaranteed Time||:||22%|
For more details of the different programme parts, see the "overview of Herschel observing" linked from the right-hand menu.
The second, and final, in-flight Call for Open Time Proposals (OT2) for observing with Herschel was closed in mid-September 2011. Well over 500 proposals had been received and were reviewed by the Herschel Observing Time Allocation Committee. The committee's recommendations have now been endorsed and communicated to the proposers. Over 370 proposals have been accepted. The scheduling of priority 1 observations from these OT2 programmes has started.
Throughout the reporting period, mission operations have been conducted with the support of ESA's New Norcia ground station; except on 16 December, when ESA's Cebreros ground station was used instead. Observational data stored on-board Herschel was received on ground during daily communication passes, each lasting approximately three hours.
The ground segment is operating nominally. Data products are generated routinely and ingested into the Herschel Science Archive (HSA).
- 14 May 2012: Third launch anniversary of Herschel.