WF/PC Instrument Science Report 91-08:
Exposure Times for G200L Images of AGK+81D266 During UV Flood
Keith Horne and John MacKenty
November 5, 1991
Abstract excerpted from the report:
During the UV Flood procedure executed 25-29 Dec 1990, UV grism (G200L) exposures of AGK+81D266 (a hot circumpolar subdwarf O star and UV (not optical) flux standard) were taken on all 8 WF/PC chips. The purpose of these grism exposures was to verify the presence of UV sensitivity (i.e. absence of contamination) following high-temperature decontaminations and the UV flood. The relevant grism images extracted from the DMF show that the 5s (WF) and the 23s (PC) exposures slightly saturate the order 0 image, and weakly expose (20-40DN/pixel) the order -1, +1, and +2 spectra of the target.
In the new UV flood procedure, which will become available in early 1992, the JPL exposure times of 40s (WF) and 160s (PC) will nicely increase the exposure level of the dispersed spectra, but will over-saturate the order 0 image causing charge to bleed down the columns. On most chips this bleeding will not seriously interfere with the order -1 and +1 spectra, from which the UV sensitivity is most easily gauged. However, on WF1 and WF3 the grism dispersion is roughly parallel to the columns. We therefore recommend using the JPL exposure times for all chips except WF1 and WF3, for which 10s exposures should be used to prevent bleeding.
For a copy of this report, please contact help@stsci.edu.