Instrument Science Report WFPC2 96-02:
Contamination Correction in SYNPHOT for WFPC2 and WF/PC-1
S. Baggett, W. Sparks, C. Ritchie, J. MacKenty
February 19, 1996
We have implemented a time-dependent photometric calibration of WFPC2 and WF/PC-1 within synphot based on the stellar photometric monitoring data. This provides an empirical correction for the build-up of uniform contaminants on the CCD faceplates of the WFPC2 and WF/PC-1. Although the contaminant issue is less severe for WFPC2, there is more UV science where the effect is still significant. We present the empirical models of the time-variable throughput decline in WFPC2 and WF/PC-1. To activate the correction within synphot, the keyword 'cont#' should be included in the obsmode with the Modified Julian Date as the parameter, e.g: "wfpc2,1,f555w,a2d7,cal,cont#49500.0" or "pc,6,f555w,cal,dn,cont#49219." Note that the automatic pipeline does not include the contamination correction in its computation of the photometric header keywords; the correction must be applied manually by, for example, executing the synphot "bandpar" or "calcphot" tasks off line with the cont# keyword in the obsmode.