31 Aug 2011 09:49

Spacecraft

The spacecraft continues to be in good health and is operating nominally.

A correction for the star tracker focal length was uplinked to the spacecraft during the previous reporting period (see also the link from the right-hand menu). It actually translates into a star tracker plate scale correction, biasing the absolute pointing when the selected guide stars have a non-circular distribution around the centre of the star tracker's FOV.

While the pointing performance of the Herschel observatory has always been well within specification before this correction, the star tracker plate scale correction appears to have resulted in an improvement of the observatory's Absolute Pointing Error (APE) from 2 arcsec to around 1.5 arcsec.

Payload

Operations for all three instruments, PACS, SPIRE and HIFI, have been nominal during the reporting period.

Now more than two years into Herschel operations, the few recurring instrument anomalies are well understood, and handled routinely. Operationally, they account for the loss of less than 4% of the available observing time, which is more than made up for through efficient scheduling: on average, the observatory efficiency (hours spent per day to execute requested observations) continues to exceed the pre-launch expectations. The net effect - time lost to anomalies versus time gained through efficient use of the observatory - remains decidedly positive.

Ground Segment

Ground segment operations have been nominal and 100% of the data continues to be recovered. As of end July 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, in-flight Announcement of Opportunity (AO2) process is ongoing. Like the previous AOs there are two parts to this AO: a Call for Guaranteed Time Programmes (GT2) and a Call for Open Time Programmes (OT2).

The first part, the GT2 AO, was issued already on 7 April and closed on 12 May 2011. A total of 32 Guaranteed Time Programmes were proposed and accepted.

The second part, the OT2 AO, was issued on 9 June, and will close on 15 September 2011. After the conclusion of the evaluation process the approved proposals for the OT2 programmes will be announced in late November 2011. There will be no further AOs for Herschel observing time.

Mission Operations
During the reporting period, mission operations have been conducted with the support of ESA's New Norcia and Cebreros ground stations. Observational data stored on-board Herschel was received on ground during daily communication passes, each lasting approximately three hours.

Without impact on Herschel operations, two dummy passes have been executed with the New Norcia ground station to validate new ground station software.

A routine station-keeping manoeuvre, or orbit correction manoeuvre, was performed in the week of Monday 18 July. These routine manoeuvres ensure the spacecraft maintains its correct orbit about L2.

Archiving
The ground segment is operating nominally. Data products are generated routinely and ingested into the Herschel Science Archive (HSA).

Future Milestones

• 15 September 2011: Closing date of the OT2 AO.
• Late November 2011: Announcement of approved OT2 proposals.

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Legal disclaimer
This report is based on the Herschel mission manager's report dated 25 August 2011. Please see the copyright section of the legal disclaimer (linked from the home page http://sci.esa.int) for terms of use.