A detector interferometric calibration experiment for high precision astrometry

TL;DR

This paper presents a novel interferometric calibration system for high-precision detector calibration in astrometry, achieving sub-micron accuracy to enable detection of low-mass exoplanets in the habitable zone.

Contribution

The study introduces an experimental setup combining an astrometric simulator with an interferometric calibration system, demonstrating calibration accuracy of 4e-4 pixel and astrometric precision of 6e-5 pixel.

Findings

Achieved pixel position calibration accuracy of 4e-4 pixel.

Obtained astrometric accuracy of 6e-5 pixel with PSF motion over five pixels.

Reached photon noise limited precision of 3e-5 pixel in static mode.

Abstract

Context: Exoplanet science has made staggering progress in the last two decades, due to the relentless exploration of new detection methods and refinement of existing ones. Yet astrometry offers a unique and untapped potential of discovery of habitable-zone low-mass planets around all the solar-like stars of the solar neighborhood. To fulfill this goal, astrometry must be paired with high precision calibration of the detector. Aims: We present a way to calibrate a detector for high accuracy astrometry. An experimental testbed combining an astrometric simulator and an interferometric calibration system is used to validate both the hardware needed for the calibration and the signal processing methods. The objective is an accuracy of 5e-6 pixel on the location of a Nyquist sampled polychromatic point spread function. Methods: The interferometric calibration system produced modulated Young fringes on the detector. The Young fringes were parametrized as products of time and space dependent functions, based on various pixel parameters. The minimization of func- tion parameters was done iteratively, until convergence was obtained, revealing the pixel information needed for the calibration of astrometric measurements. Results: The calibration system yielded the pixel positions to an accuracy estimated at 4e-4 pixel. After including the pixel position information, an astrometric accuracy of 6e-5 pixel was obtained, for a PSF motion over more than five pixels. In the static mode (small jitter motion of less than 1e-3 pixel), a photon noise limited precision of 3e-5 pixel was reached.