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 5 × 10^-6 pixel.

Current state-of-the-art methods for centroid estimation have reached a precision of about 2 × 10^-5 pixel at two times Nyquist sampling, this was shown at the JPL by the VESTA experiment.1 A metrology system was used to calibrate intra and inter pixel quantum efficiency variations in order to correct pixelation errors.

The European part of the NEAT consortium is building a testbed in vacuum in order to achieve 5 × 10^-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 present the metrology and the pseudo stellar sources sub-systems, we present a performance model and an error budget of the experiment and finally we describe the present status of the demonstration.