Astrometric precision tests on TESS data

Abstract

Background. Astrometry at or below the micro-arcsec level with an imaging telescope assumes that the uncertainty on the location of an unresolved source can be an arbitrarily small fraction of the detector pixel, given a sufficient photon budget. Aim. This paper investigates the geometric limiting precision, in terms of CCD pixel fraction, achieved by a large set of star field images, selected among the publicly available science data of the TESS mission. Method. The statistics of the distance between selected bright stars ($G\simeq 5mag$), in pixel units, is evaluated, using the position estimate provided in the TESS light curve files. Results. The dispersion of coordinate differences appears to be affected by long term variation and noisy periods, at the level of $0.01$ pixel. The residuals with respect to low-pass filtered data (tracing the secular evolution), which are interpreted as the experimental astrometric noise, reach the level of a few milli-pixel or below, down to $1/5,900$ pixel. Saturated images are present, evidencing that the astrometric precision is mostly preserved across the CCD columns, whereas it features a graceful degradation in the along column direction. The cumulative performance of the image set is a few micro-pixel across columns, or a few 10 micro-pixel along columns. Conclusions. The idea of astrometric precision down to a small fraction of a CCD pixel, given sufficient signal to noise ratio, is confirmed by real data from an in-flight science instrument to the $10^{-6}$ pixel level. Implications for future high precision astrometry missions are briefly discussed.

13 pages, 8 figures

References in corpus (8)

• Array Programming with NumPy
• The Gaia mission
• The Transiting Exoplanet Survey Satellite
• The K2 Mission: Characterization and Early results
• A detector interferometric calibration experiment for high precision astrometry
• RAFTER: Ring Astrometric Field Telescope for Exo-planets and Relativity
• Analysis of the Cramer-Rao lower uncertainty bound in the joint estimation of astrometry and photometry
• The ASTRA project: a doorway to future astrometry

Cited by in corpus (1)

• The Effect of Light Deflection by Solar System Objects on High-Precision SKA Astrometry