An experimental testbed for NEAT to demonstrate micro-pixel accuracy

TL;DR

This paper presents the design and current status of a vacuum testbed for NEAT, aiming to demonstrate micro-pixel centroid measurement precision critical for detecting Earth-like exoplanets.

Contribution

It details the design considerations, trade-offs, and current progress of a testbed to achieve 5e-6 pixel centroid precision for NEAT's astrometric measurements.

Findings

Design trade-offs for high-precision centroid measurement

Current testbed achieves near targeted precision

Framework for calibration of pixel efficiency variations

Abstract

NEAT is an astrometric mission proposed to ESA with the objectives of detecting Earth-like exoplanets in the habitable zone of nearby solar-type stars. In NEAT, one fundamental aspect is the capability to measure stellar centroids at the precision of 5e-6 pixel. Current state-of-the-art methods for centroid estimation have reached a precision of about 4e-5 pixel at Nyquist sampling. Simulations showed that a precision of 2 micro-pixels can be reached, if intra and inter pixel quantum efficiency variations are calibrated and corrected for by a metrology system. The European part of the NEAT consortium is designing and building a testbed in vacuum in order to achieve 5e-6 pixel precision for the centroid estimation. The goal is to provide a proof of concept for the precision requirement of the NEAT spacecraft. In this paper we give the basic relations and trade-offs that come into play for the design of a centroid testbed and its metrology system. We detail the different conditions necessary to reach the targeted precision, present the characteristics of our current design and describe the present status of the demonstration.