Comparison of Full-Aperture Interferometry to Sub-Aperture Stitched Interferometry for a Large Diameter Fast Mirror

摘要

The Herschel Space Observatory (formerly known as FIRST) consists of a 3.5 m space telescope. Stitching sub aperture interferograms may offer considerable cost savings during testing of the flight telescope as compared to other techniques. A comparative demonstration is presented of interferogram stitching techniques that enable a composite map of a 3-D surface to be assembled from a sequence of sub-aperture measurements. This paper describes the fundamental procedures for stitching together component data sets and demonstrates such techniques with real data sets. A set of 14 sub-aperture measurements was made of a 2 m diameter all-composite mirror developed as part of the Herschel Space Observatory program and two different stitching software packages were employed to stitch together the sub-aperture surface maps. The software packages differ fundamentally in the way the sub-aperture maps are three-dimensionally stitched, one employing a local technique and the other using a global technique. The processed results from both algorithms are compared with each other and with a full-aperture reference measurement made of the same test optic. A ummary of the results is presented and potential modifications and enhancements to the stitching techniques are dscussed.