All-sky imaging at high angular resolution: An overview using lossy compression

CERGA, UMR 6527, CNRS, Observatoire de la Côte d'Azur, BP 4229, Le Mont-Gros, 06304 Nice Cedex 4, France e-mail: dollet@obs-nice.fr

Received: 5 February 2004
Accepted: 30 June 2004

Abstract

We examine a possible extension of the Gaia mission in the form of a high-spatial resolution all-sky survey in the visible based on a scanning satellite and show that the main limitation is the amount of collected data to be transmitted. We then investigate the kind of image compression that would make it possible to carry out a complete cartography at a resolution of , which would constitute a major advance in sky mapping. The most significant information is projected into wavelet space after the subtraction of the brighter objects that are mapped independently with the instrument point spread function and transmitted separately. The study is based on a Gaia-like instrument using a rectangular pupil and one-dimensional high resolution along scan. The difference of resolution across- and along-scan is compensated by the combination of all the observations at the end of the mission in Fourier space. A gain of 2–3 mag compared with the magnitude limit of the on-board detection could be achieved with the features of the Astro Sky Mapper of the Gaia mission.