17.6 Cycle 9 Calibration

The STIS Cycle 9 calibration plan was modeled closely on the Cycle 8 calibration plan. Supported modes were monitored for items such as sensitivity changes, flat-field evolution, and dispersion solutions.
In addition to monitoring instrument health and safety and maintaining the overall calibration of STIS supported modes at the accuracies as established during Cycles 7 and 8, a few special calibration programs were added for Cycle 9, with the following goals:

  1. To improve the Charge Transfer Efficiency (CTE) characterization for the CCD, i.e., its dependences on time, source intensity, source nature (point source vs. extended source), and sky background;
  2. To quantify the remanence intensity level after over-illumination of the CCD as a function of time after saturation and of number of readouts after saturation. The remanence level may well have increased since STIS was installed on HST due to the degraded CTE;

  3. To improve PSF characterization for the CCD in imaging mode, coronagraphic mode, and spectroscopic mode as a function of source color;

  4. To improve the dispersion solutions for the reddest settings of the G750M grating;

  5. To model the ghosts (which are caused by multiple reflections in the CCD window) in the G750M grating mode.

The results of all the Cycle 9 calibration programs are presented in the close-out report STIS ISR 2003-02.