STIS Instrument Handbook for Cycle 24

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17.8	Cycle 11 Calibration

The Cycle 11 calibration plan closely follows the plans for previous Cycles. Supported modes continue to be monitored for sensitivity changes, flat-field evolution, dispersion solutions, and the evolution of charge transfer efficiency of the CCD detector. Existing monitor programs have been expanded to include routine sensitivity measurements at the E1 aperture positions, to include an annual NUV-PRISM flux monitor observation, and to more thoroughly check the adopted STIS dispersion solutions. The frequency of some other monitors has been decreased, as our improved understanding of STIS allows us to predict future trends with greater confidence.

In addition to monitoring instrument health and safety and maintaining the overall calibration of STIS supported modes at the accuracies established during Cycles 7 through 10, a few special calibration programs have been added for Cycle 11, with the following goals:

1:	To improve the calibration of detector sensitivity, aperture throughputs, and the PSF at the E1 positions that were defined to mitigate CTE effects;

2:	To better test the effects of the monthly MSM offsetting on echelle sensitivity;

3:	To verify models of the PSF for first order G750L and G750M observations that are critical for many programs targeted at determining rotation curves of galaxies and black hole masses;

4:	To re-measure, with improved accuracy, the ratio between CCDGAIN=1 and CCDGAIN=4 observations;

5:	To define additional faint spectroscopic flux standards to support calibration of ACS (especially the ACS Sloan filters), and COS.