Herschel Status Report - April 2010
The spacecraft is operating nominally.
Star tracker warm pixels
On 29 March 2010 the star tracker CCD temperature has been permanently lowered from +13 °C to -10 °C. Initial results, although preliminary, are highly encouraging: none of the scan maps executed after this event and analysed to date appears to have been affected by guide stars crossing "warm" pixels. In the past, the resulting inhomogeneous scan speed along some scan lines had adversely affected the astrometric accuracy of the majority of maps.
The tentatively detected spatial clustering of "warm" pixels may have a natural explanation: according to analyses performed on full CCD dumps which are taken every other week, these clusters correlate very well with stars of mv ≥ 8 in the Tycho catalogue.
Herschel still meets its pointing requirements (Absolute Pointing Error (APE) requirement is 3.7 arcseconds, predicted and hoped for was 2.05 arcseconds, the actual APE is ~2 arcseconds with a probability of p ≥ 0.68, corresponding to a 1σ value for a Gaussian distribution). If the absence of "speed bumps" in scan maps after the CCD temperature reduction were confirmed, this would allow reconstruction of scan maps to a similar spatial accuracy.
All three instruments, HIFI, PACS and SPIRE, continue to operate nominally. In April, Herschel was declared to be in Routine Science Phase Mode and all preceding phases (Commissioning Phase, Performance Verification Phase, and Science Demonstration Phase) were formally declared "completed". The last Science Demonstration Phase (SDP) observations which had not yet been performed, were restored to the list of normal (non-SDP) observations, and will be executed as part of the routine phase. Very occasionally, for example when a new instrument observing mode needs to be commissioned, a few hours of commissioning/performance-verification type activities will be inserted. This however will be handled within the allocation of "calibration observations" which are performed regularly for each instrument.
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).
- 14 May 2010: First anniversary of launch
- May 2010: Issuing of first in-flight Announcement of Opportunity (AO) for Open Time (OT1) observations