The STIS stopped science operations on 2004-Aug-03, due to the failure of a power supply within the Side 2 electronics. Since then, STIS has been in
safe mode: the instrument and its on-board computer are switched off but the heaters are on to ensure a healthy and stable thermal environment.
The failed unit delivered power to all the mechanisms within STIS, including the aperture wheel, the Mode Select Mechanism, and the CCD shutter. At the time of the failure, the STIS was in
idle mode, in which the light path is completely blocked (a precaution to prevent over-illumination of the MAMA detectors). In the absence of a working power supply, the mechanisms cannot be moved from their current positions. STIS has therefore remained inoperable since 2004-Aug-03.
As this Handbook is being prepared for release, the current plan for SM4 (the next servicing mission to
HST) includes time for an attempt to repair STIS (see
http://sm4.gsfc.nasa.gov/technology/instruments.php#stis for details). Any updates on this situation will be reported on the STIS Web site, and also distributed within the STScI Analysis Newsletters (STANs).
