High-Precision Calibration of the WFC3/UVIS Geometric Distortion
Abstract
The geometric distortion solution for WFC3/UVIS is known in most filters to better than 0.01 pixels from the analysis of pointed data. Astrometric data taken with spatial scans suggest that residuals from this solution have typical magitudes of 0.003-0.005 pixels, and correlate on scales of 50-100 pixels. These deviations also appear to be stable in time, and therefore can be calibrated using apropriate data. This proposal aims at improving the calibration of local deviations from astrometric solution via spatial scans. The observations target two regions with high density of bright stars at several different large-scale dithers to obtain a dense coverage of high S/N trails over the majority of the detector. The data will be used to obtain a static correction to the distortion solution that can be used to improve the geometric distortion solution. The open clusters M 67 and M 48 have been selected to provide the highest density of stars of the right brightness for F606W (M 67) and F621M and F673N (M 48); these are the recommended filters for optimal extraction of astrometric information, depending on the brightness of the target.
- Publication:
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HST Proposal
- Pub Date:
- October 2014
- Bibcode:
- 2014hst..prop13929R