A document describes solutions to problems of astrometry at the microarc-second (picoradian) level using a simple staring telescope. The problems include field-dependent beam-walk on the telescope’s mirrors, pixel position irregularity and distortion over time, non-flat intra-pixel quantum efficiency, and systematic errors inherent in the most common image centroiding algorithms (imperfect knowledge of the point spread function).

The problems are solved by using an architecture that is free of field-dependent beamwalk, using heterodyne (traveling) metrology fringes to calibrate the focal plane array’s inter-pixel distances and intra-pixel quantum efficiencies at the micro-pixel level, and using a low-error algorithm for determining image positions and displacements.

Precision astrometry is the most promising method of detecting Earth-like planets in the habitable zones of nearby stars. Precision photometry needed for weak-lensing-based investigations of dark energy is also helped by this technology.

This work was done by Michael Shao, Chengxing Zhai, Bijan Nemati, and Renaud Goullioud of Caltech for NASA’s Jet Propulsion Laboratory. NPO-48313


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Picoradian Staring Astrometry Using a Simple Staring Telescope

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This article first appeared in the August, 2014 issue of NASA Tech Briefs Magazine.

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