The detectors in both channels offer subarray readout capability; see Section 6.4.4 (UVIS) and
Section 7.4.4 (IR) for full details. The UVIS channel also allows 2×2 and 3×3 on-chip binning of full-frame images. Finally, a variety of dithering patterns can be requested using the Astronomer’s Proposal Tool (APT) software. Predefined patterns have been established to address common requirements, such as sub-pixel dithering to improve PSF sampling or dithering to achieve large areal coverage while also sampling the inter-chip gap (
Appendix C:Dithering and Mosaicking). The post-observation pipeline software (see
Appendix E:Reduction and Calibration of WFC3 Data, the
WFC3 Data Handbook, and the
AstroDrizzle documentation) carries out appropriate calibration of data taken in all of these configurations, and offers the option of reconstructing dithered images with a drizzling algorithm. A combination of software packages in
DrizzlePac can be used to optimize the drizzling of images. If the dither pattern incorporates non-integer pixel offsets, it can effectively improve the sampling of the point-spread function (PSF). The software can also handle mosaicked images according to a set of rules or associations, rectifying them onto a cartesian pixel coordinate system.
