ST ScI Preprint #1384

Charge Transfer Efficiency of the Wide Field and Planetary Camera 2

Observations of  Cen have been used to characterize the Charge Transfer Efficiency (CTE) of the Wide Field and Planetary Camera 2 (WFPC2) onboard the Hubble Space Telescope. A set of formulae has been developed to correct aperture photometry for CTE loss with dependencies on the X and Y positions, the background counts, the brightness of the star, and the time of the observation. The observations indicate that for very faint stars on a very faint background, the CTE loss from the top to the bottom of a chip has increased from about 3% shortly after the cool-down of WFPC2 (April 23, 1994) to roughly 40% in February 1999. In general, typical WFPC2 exposures are much longer than these short calibration images, resulting in higher background which significantly reduces the CTE loss and minimizes the CTE problem for most science exposures.

Status:

Appeared in: PASP

Affiliations:

Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218