Astrometric signal profile fitting for Gaia

TL;DR

This paper presents a new basis function approach for fitting Gaia's one-dimensional astrometric signals, analyzing fit accuracy, instrument calibration, and spectral effects to improve micro-arcsecond level astrometric measurements.

Contribution

It introduces a basis function based on the ideal telescope response and derivatives, tailored for Gaia's astrometric signal fitting, with analysis of parameter requirements and calibration considerations.

Findings

11 parameters needed for micro-arcsecond accuracy

Analysis of pixel array position and spectral influence

Calibration strategies for instrument response

Abstract

A tool for representation of the one-dimensional astrometric signal of Gaia is described and investigated in terms of fit discrepancy and astrometric performance with respect to number of parameters required. The proposed basis function is based on the aberration free response of the ideal telescope and its derivatives, weighted by the source spectral distribution. The influence of relative position of the detector pixel array with respect to the optical image is analysed, as well as the variation induced by the source spectral emission. The number of parameters required for micro-arcsec level consistency of the reconstructed function with the detected signal is found to be 11. Some considerations are devoted to the issue of calibration of the instrument response representation, taking into account the relevant aspects of source spectrum and focal plane sampling. Additional investigations and other applications are also suggested.