The operational response to temporal changes in the gain of the ACIS instrument on the Chandra X-ray Observatory

The gain of the Advanced CCD Imaging Spectrometer (ACIS) instrument has changed over time since the Chandra X-ray Observatory launch in July 1999. The calibration and data analysis teams have addressed this issue, but it has only been recently that the operations team has examined how the commanding of the instrument could be altered to partially compensate for these changes. This paper will address the changes in the gain, the impact on science data and the changes the operations team has considered to improve the science return. We also discuss the restrictions imposed by the commanding software on our response.