MESSIER: exploring the ultra-low surface brightness universe with a curved focal plane based satellite

The extremely low surface brightness sensitivity required to observe the ultra-low-surface brightness universe lead us to propose MESSIER, a space mission designed to drift-scan the entire sky in 6 filters covering the 200-1000 nm range and reaching unprecedented surface brightness levels of 34 and 37 mag arcsec2 in the optical and UV, respectively. Here, we present the ground-based MESSIER pathfinder aimed at testing several breakthrough technologies involved (e.g. curved detectors) and carrying out observations. We present here a detailed analysis of the optical quality achievable through photon Monte Carlo simulations of the system, including atmospheric effects.