Astrometric effects of non-uniform telescope throughput

TL;DR

This paper investigates how non-uniform degradation of telescope throughput over time causes image profile variations and photo-centre displacements, potentially impacting high-precision astrometric measurements like Gaia, PRIMA, and SIM.

Contribution

It provides a numerical analysis of how non-uniform optical degradation affects astrometric accuracy and discusses mitigation strategies for future high-precision astrometry missions.

Findings

Degradation causes measurable photo-centre displacements.

Impact varies across different telescope configurations.

Calibration techniques can mitigate some effects.

Abstract

In real telescopes, the optical parameters evolve with time, and the degradation is often not uniform. This introduces variations in the image profile and therefore photo-centre displacements which, unless corrected, may result in astrometric errors. The effects induced on individual telescopes and interferometric arrays are derived by numerical implementation of a range of cases. The results are evaluated with respect to the potential impact on the most relevant experiments for high precision astrometry in the near future, i.e. Gaia, PRIMA and SIM, and to mitigation techniques applicable from design stage to calibrations.