The Herschel telescope decontamination heating is underway. It has been decided to prevent the Herschel telescope from cooling down to below 170 K for as long as possible compatible with opening the cryocover at a temperature of 120 K, where the cryocover opening date is determined by the needs of the science instruments. The secondary mirror (M2) is more exposed and cools more rapidly than the primary mirror (M1). Thus, having been tested on 17 May, at 06:13 (UT) on 18 May the M2 decontamination heating was started, while later the same day the M1 heating was briefly functionally verified (at the time the M1 temperature was about 187 K). The M1 heating will commence in the early hours of 20 May. The telescope heating will be discontinued about 6 days before cryocover opening to allow telescope cooldown.
A second, smaller, course correction manoeuvre was successfully performed on 18 May, with a target delta-V of 0.99 m/s.
[G. Pilbratt from ESTEC, posted 19 May 2009]