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[05/20/2010] Image Distortion Polynomials for WFC3 IR Filters (Alpha Release)

NOTE: As of October 11, 2010, this file has been superseded by a newer version available from CDBS. More details are available here.

The geometric distortion of WFC3 images in the IR channel is represented by a 4th order general polynomial, as described in WFC3 ISR-2009-34. For each filter, unique coefficient values are stored in the Image Distortion Correction Table (IDCTAB). However, the first release of the IDCTAB contains the same set of coefficient values for each filter that were determined from images in the F160W filter. Although the differences in filter-to-filter distortion are small, they are not negligible. Therefore, we present here an IDCTAB containing distinct, newly determined coefficient values for the following five IR filters: F098M, F110W, F125W, F139M, and F160W. The coefficients are derived from nine exposures of omega Cen in each filter, taken with a large dither pattern at two epochs (December 2009 and March 2010). The reference point in the IR V2V3 coordinate system is calibrated following the recent alignment measurements of the IR channel, which improved the alignment of UVIS and IR images. The coefficients for the other 10 IR filters remain those of the F160W filter.

This distribution (t20100519_ir_idc.fits) is an alpha release of the IR IDCTAB, which we intend to install in CDBS and the OPUS pipeline by mid-August, 2010. Please notify help@stsci.edu of any discrepancies in the application of this calibration data.

Created 5/20/2010 MJD
Modified 10/11/2010 MJD