The Space Telescope Imaging Spectrograph (STIS) was successfully repaired during SM4 and has resumed science operations with all channels. Most aspects of instrument performance are similar to what had been anticipated. In particular, the time-dependent sensitivity and charge-transfer efficiency are close to what had been extrapolated from trends seen in 2004. The most notable anomaly is that the dark current for the NUV MAMA detector is substantially higher than had been expected.

The STIS NUV MAMA, while otherwise performing well, exhibits a dark current several times higher than expected. For the STIS Cycle 17 exposure time calculator, we had adopted a mean rate of 0.0013 counts/s/pixel. Currently, the measured mean value is about 0.011 counts/s/pixel. This excess dark current appears to be fading with an e-folding time of about 100 days. We will continue to track and report on its decay. If you believe that the higher NUV MAMA dark rate may adversely affect your Cycle 17 program, or if you have other questions about this issue, you should communicate with your Contact Scientist.

Further information about STIS instrument performance will be made available on the STIS web page and in a STAN in the near future. Processed data from the STIS Early Release Observations can be found at http://archive.stsci.edu/pub/sm4earlypublic/stis/11506/.