Rumors started flying around yesterday morning (29-01-2007) that the Hubble Space Telescope had entered Safe Mode (i.e. it detected an operational anomaly and entered a mode of operation designed to prevent further harm or damage until engineers on the ground fix the problem), and worse still, that the flagship instrument on HST, the Advanced Camera for Surveys (ACS) was the instrument with the problem, possibly a big problem.
I didn't want to post anyhting about it until there was an official release of information, which occured some time last night. You can read about the problem yourself on the official ACS web pages. It sounds like ACS might be permanently broken.
The good news is that the other instrument on HST, the Wide Field and Planetary Camera 2 (WFPC2) is still working, and they expect to start normal observations with it later this week.
Unfortunately, this still means a major disruption. Ironically WFPC2 (an older instrument) does not have either the wide field of view or the sensitivity that ACS does, meaning that many scientific programs created with ACS in mind can not be performed using WFPC2.
HST entered inertial safe mode on Saturday January 27. Preliminary indications are that this event was associated with an ACS anomaly. GSFC and STScI engineers and scientists are still investigating the situation, but it appears unlikely that ACS CCD observations (both WFC and HRC) will be available in Cycle 16. Current indications are that ACS/SBC can be restored using operational workarounds, so observers should assume that the ACS/SBC configuration will be available in Cycle 16.
The formal Cycle 16 deadline was 8 pm EST on Friday Jan 26. We received a total of 747 proposals, including 498 to use ACS/WFC or ACS/HRC. The latter proposals are unlikely to be viable. In order to ensure that we accommodate the science areas covered by those programs, we are extending the HST Cycle 16 deadline.
Let's hope the engineers can fix ACS from the ground, as the proposed Shuttle-based servicing mission is toward the end of 2008.