Hubble Status Report - February 2004
On Friday 16 January, NASA announced that there would be no further Hubble servicing missions, with future Shuttle missions going exclusively to ISS (International Space Station). The decision was taken by Sean O'Keefe, the NASA administrator, and was principally for reasons of crew safety rather than budget. The next servicing mission, SM4, originally scheduled for 2004, was expected to occur in 2006 when Shuttle flights had resumed after the Columbia accident. In addition to installing two new scientific instruments (WFC3 and COS), the mission would have addressed issues concerned with gyros and battery lifetime. Without this attention to spacecraft health, Hubble capabilities are expected to degrade over the next 3-4 years with the loss of a full gyro complement forcing special operational strategies.
The fate of the two new instruments scheduled for installation during SM4 is currently uncertain. There is some discussion about the possibility of launching them as part of Explorer-class missions but it is too early to comment in detail.
HST observing in 2003 has included many very large survey programmes that build on the earlier successes of the Hubble Deep Fields (HDF). In addition to the GOODS Treasury programme carried out with the Advanced Camera for Surveys (ACS), the ACS is currently being used for an Ultra Deep Field (UDF) exposure within the GOODS area of the Chandra Deep Field - South. This is a direct successor to the HDF and the STScI director is devoting a large allocation of discretionary time (412 orbits) to a single pointing in order to go as deep as possible - up to 1.5 magnitudes fainter than the original WFPC2 HDF in some bands. As a supplement to the primary imaging observations being taken with the Wide Field mode of the ACS, several other HST instruments will be used in parallel to produce both additional images and slitless spectroscopic data. The UDF observations will be completed in January 2004 and a full public data release is expected in mid-February or soon thereafter.
An interesting aspect of the UDF parallels is a deep observation with the grism mode of the ACS high-resolution camera. This will be by far the deepest observation using this particular setup. All the data processing for this slitless spectroscopy will be carried out at the ST-ECF who are responsible for the HST grism software developments.