Instrument Science Report 2002-02:

Updated WFPC2 Flatfield Reference Files for 1995 - 2001

A. M. Koekemoer, J. Biretta and J. Mack

March 01, 2002

Abstract:

We present updated flatfields for WFPC2 using on-orbit data from Earthflat exposures, covering dates ranging from September 1995 - May 2001. We divide the flatfields into epochs depending on the appearance of major new features, thereby substantially diminishing the effect of such features on the data by calibrating their variation with time. We also quantify their wavelength dependence by examining Earthflats from a wide range of filters, and measure the time dependence of large-scale flatfield features that may be caused by long-term changes in the camera geometry. In addition, we are able to measure pixel-to-pixel structure to levels below ~0.3% for the PC and ~0.2% for the WF chips. Here we describe the procedures for creating the new flats, which are now available in the standard CDBS processing pipeline as updated WFPC2 calibration reference files.

The Complete Paper (PDF 0.62 MB) is available.