The geometric distortion of WFC3 images in the IR channel is
represented by a 4th order general polynomial, as described in
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 email@example.com of any discrepancies in the application of this calibration data.
Modified 10/11/2010 MJD