FRESNEL FORMATION FLYING: HIGH RESOLUTION IMAGER FOR OPTICAL ASTROPHYSICS

摘要

The scope of this paper is to present the capabilities of arnvery innovative concept: a distributed spatial imager forrnastrophysics, and the potential technical solutions.rnThe instrument uses a binary Fresnel zone plate, basedrnon the diffraction focusing principle. This implies longrnfocal lengths, hence a formation flying approach on thernbasis of some tens of kilometers.rnThe major interest of this particular approach torndiffractive focusing is that it has the same resolution asrna classical lens or mirror of equivalent size, but there isrnno optical material involved in the focusing process:rnjust vacuum, holes punched into a thin opaquernmembrane, and a very light supporting structure.rnAnother interesting feature, specific to the particularrngrid-like pattern of the primary focusing zone plate, isrnthe high dynamic range achieved in the images. Theserntwo elements make it possible to launch a very largernFresnel array allowing resolutions and dynamic rangesrnnever reached before, leading to new sciencernobjectives.rnOf course a lot of technical challenges have to bernovercome. This is the reason why critical domains havernbeen identified, then addressed by R&T activities and,rnmoreover, the performance limits explored withrnastrophysicists, in order to define the science needs thatrncould be fulfilled with such capabilities.rnThis paper presents some technical responses, and howrna lot of domains in astrophysics canrntake advantage of such missions.