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Space Telescope Imaging Spectrograph
NUV-MAMA Geometric Distortion Solution

New Geometric-Distortion Solution for the STIS NUV-MAMA

As of 2003-Oct-31, a new geometric-distortion solution for the STIS NUV-MAMA has been obtained using two fields in NGC 4214 and NGC 604, which were imaged using three filters (CN182, CN270, SrF2) for GO program 9096, using as a reference (WF)PC2 images of the same objects in F170W and F336W. Different polynomial degrees and weighting mechanisms for the geometric distortion were tested until an adequate solution was obtained. Typical median errors between the predicted and the real positions were found to be in the range of 0.28 to 0.53 MAMA pixels (7-13 mas). As a comparison, the older geometric distortion table produced median errors of a few MAMA pixels.

A new geometric distortion table incorporating these results has been delivered for use in the HST OTFR pipeline. Over the next few months we plan to also derive improved geometric-distortion solutions for the STIS-FUV MAMA and the STIS-CCD.