STIS Cycle 30 Calibration Programs

Abstract

We discuss the suite of STIS calibration programs executed during HST Cycle 30, covering the period 2022 Nov 07 through 2023 Nov 05. For each of the 19 current regular calibration programs, we provide brief descriptions of the objectives, observations, analysis procedures, and results - with comparisons to the results from previous cycles and to desired accuracies, as well as references to more detailed analyses of the calibration data. Many of these calibration programs produce routine reference file deliveries or demonstrate the continuing applicability of existing reference files for processing STIS observations. This ISR provides a brief snapshot of the current instrument performance, similar to those given in annual reports for Cycles 7-10 and 17-21. Two Appendices briefly discuss the state of the onboard calibration lamps and the ongoing major effort to revise the flux calibration for the many STIS spectroscopic and imaging modes.

Figures (19)

• Figure 1: Charge transfer inefficiency (CTI = 1 - CTE) for the STIS CCD. The two panels show the general increases in the serial and parallel CTI, for the 0.3s (orange) and 3.6s (blue) exposures at gain=4, since SM4.
• Figure 2: Spurious charge in the reference superbiases, for gain=1 (top) and gain=4 (bottom). The values at pseudo-aperture E1 (orange) are somewhat lower than those at the center of the CCD (blue).
• Figure 3: CCD dark count rates for short (60-sec; top) and long (1100-sec; bottom) exposures. During Cycle 30, the dark rates remained relatively stable, with an average around 0.13 cts/s/pix.
• Figure 4: CCD read noise for gain=1 (top) and gain=4 (bottom). The read noise is consistent with the recent slow increases at both gains. The right-most red point is the most recent measurement.
• Figure 5: ( left) Comparison of the number of hot pixels ($>$ 0.1 e$^-$/s) in STIS CCD superdarks before (red) and after (black) annealing. ( right) Histogram of the difference in the number of hot pixels -- after anneal minus before anneal -- for post-SM4 anneals. While there appear to be many persistent hot pixels, the anneals do yield some reduction in the number, on average.