arXiv subjects

Sébastien Soler

Publications and source records attributed to Sébastien Soler.

3 recordsLinked to original sources

arXiv2026

Pixel-Level Calibration for Space-Based High Precision Astrometry Using Young's Fringes

The detection of Earth-like exoplanets via astrometry necessitates centroiding precision at the 0.3 microarcsec level, thereby imposing stringent constraints on the focal plane geometry of space telescopes. The AGATE focal plane instrument, a proposed component of the NASA Habitable Worlds Observatory (HWO), aims to achieve this objective through the calibration of the intra-pixel response function of CMOS detectors to an accuracy of 50 micropixel (220 nm The present paper proposes a Young's fringes-based calibration method, derived from those employed by JPL and IPAG, for the purpose of mapping the pixel response barycenter offsets across the detector. Using a Pyxalis GIGAPYX-4600 CMOS sensor, we demonstrate via simulations and laboratory measurements that (1) a precision of 500 micropixel is achievable with 10,000 frames (current setup); (2) inter-pixel capacitance crosstalk and fringe hyperbolicity are dominating the errors at small and large scales, respectively; and, (3) an iterative inverse problem approach with a hyperbolic fringe model is proposed to overcome paraxial approximation limits for 1 Gpix focal planes. These results pave the way for on-board calibration of HWO's astrometric instrument, ensuring the sub-microarcsec precision required for exo-Earth detection.

astro-ph.IM↗

arXiv2025

Experimental tests of the calibration of high precision differential astrometry for HWO

Many different scientific applications require sub-micro arcsecond precision astrometry, including researching rocky exoplanets in the vicinity of the Sun and studying dark matter. The Habitable Worlds Observatory (HWO) is a promising candidate to carry an astrometric instrument because it provides a stable, space-based telescope with a large aperture, which allows faint sources and small displacements to be observed. This paper presents the characterization of an appropriate detector for an astrometric instrument: the 46Mpx Gigapyx from Pyxalis. Moreover it explains the implementation of a testbed enabling interferometric characterization of pixel positions. Finally, the paper introduces a method for calibrating the telescope's optical distortion. This method was implemented in simulation and tested thanks to an optical bench developed at IPAG in France.

astro-ph.IM↗

arXiv2024

Experimental tests of the calibration of high precision differential astrometry for exoplanets

High precision differential Astrometry is the branch of astronomy that evaluates the relative position, distance and motion of celestial objects with respect to the stars present in the field of view. A mission called Theia has been submitted in 2022 for ESA's M7 call for missions, using a diffraction-limited telescope about 1m in diameter and with a field of view of 0.5 degrees, capable of achieving sub-micro-arcsecond angular accuracy, corresponding to 1e-5 pixel on the detector. Such precision makes it possible to study the nature of dark matter in our galaxy and to reveal the architecture of exoplanetary systems close to the Sun, down to the mass of the Earth. The aim of the experimental tests presented in this poster is to improve the TRL of 2 specific aspects: the calibration of new CMOS detectors with very large number of pixels and the calibration of the telescope aberrations.First, a key element of such a space telescope is the focal plane, which must be calibrated spatially with an extreme precision down to the 1e-5 pixel level. Previous work has shown that this is possible with small detector matrices (80x80 px) [1]. The goal is now to check the performances and validate this method with the new very large detectors. Pyxalis, a company based near Grenoble, is developing very large detectors (8000x5000 px) that have a low noise level and high sensitivity. The aim is to characterize and validate this type of detectors in a laboratory demonstration (see poster Pancher et al.), to ensure that the performance achieved meets the required specifications. We present the results of these characterization in this contribution.The telescope stability is also a sensitive issue. Recent work [2] has shown that the reference stars in the field of the telescope can be used as actual metrology sources in order to compute the field distortion function. Our simulations allow to model the optical aberrations with bivariate polynoms. The effects on the calibration accuracy of the degrees of the polynoms, the number of reference stars and the tilt perturbation of the M2 mirror are investigated. This poster will present the latest results obtained on a test bed developed to experimentally study the performances of this new field calibration method.

astro-ph.IM↗