Herschel Status Report - December 2012 and January 2013
The spacecraft continues to be in good health and is operating nominally.
At launch, in 2009, Herschel's cryostat was filled with over 2300 litres of superfluid liquid helium, weighing about 335 kg. The helium is steadily used by the spacecraft's active cooling system to cool the payload, so the amount of remaining coolant directly determines Herschel's lifetime for scientific observations. Best estimates for the date of the exhaustion of the liquid helium (LHe) fall in the second-half of March this year.
The planning for post-LHe-exhaustion engineering tests on the instruments and on the spacecraft is being tuned up.
After Herschel has completed its operational lifetime for scientific observations, the spacecraft will leave its current orbit around L2 and will be injected into a no-return heliocentric orbit. In this context "no-return" means not returning to the potential well of the Earth-Moon system for at least 300 years. The window for the manoeuvre required to put the spacecraft in its final heliocentric orbit opens on 5 May 2013.
Operations for all three instruments, PACS, SPIRE and HIFI, have been nominal during the reporting period. There have been no single event upsets (SEU) causing loss of science observation time.
Ground segment operations have been nominal and 100% of the data continues to be recovered. As of 1 February 2013, the approximate completion of the different programme parts was:
|KPGT||Key Programme Guaranteed Time||:||>99%|
|KPOT||Key Programme Open Time||:||>99%|
|GT1||First in-flight Guaranteed Time||:||>99%|
|OT1p1||First in-flight Open Time, priority 1||:||>99%|
|GT2||Second in-flight Guaranteed Time||:||>99%|
|OT2p1||Second in-flight Open Time, priority 1||:||>99%|
|OT1p2 + OT2p2||First and Second in-flight Open Time, priority 2, top||:||58%|
|First and Second in-flight Open Time, priority 2, middle||:||6.4%|
|First and Second in-flight Open Time, priority 2, bottom||:||0.5%|
For more details of the different programme parts, see the "overview of Herschel observing" linked from the right-hand menu.
During the first weeks in the reporting period mission operations were conducted with the support of ESA's New Norcia ground station. Due to problems affecting both the prime and backup uplink chains at New Norcia, Herschel communications were switched to ESA's Cebreros ground station in mid-January to allow for repairs. Throughout the reporting period, observational data stored on-board Herschel was received on ground during daily communication passes, each lasting approximately three hours.
Two routine station-keeping manoeuvres, or orbit correction manoeuvres, have been successfully performed on 7 December 2012 and 25 January 2013. These routine manoeuvres ensure the Herschel spacecraft maintains its correct operational orbit about L2.
The ground segment is operating nominally. Data products are generated routinely and ingested into the Herschel Science Archive (HSA).
A bulk reprocessing of all the science data in the HSA, using the then-latest release of the data processing software (version 9), was started in November 2012 and is nearing completion. Meanwhile, version 10 of the software was released on 22 January 2013, which in turn will be used for a bulk reprocessing of the science data.
- March 2013: Predicted end of operational lifetime for scientific observations (exhaustion of the liquid helium for the spacecraft's active cooling system)
- 1 July 2013: Start of Post-Operations Phase