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This paper describes a concept of a formation flyer for ASPICS (Association de Satellites Pour l'Imagerie Coronagraphique Solaire, see [1]), a giant 100 m base, externally occulted coronagraph aimed at observing the inner corona (and the solar disk) in the visible and ultra-violet. The two-satellite formation approach, based on existing space systems, is composed of a Myriade micro-satellite supporting the occulter and a Proteus platform as the main system carrying the coronagraph and the disk-imager scientific instruments. The two spacecrafts are launched as a single composite and deployed once in orbit, preferably a 3-day orbit, or at the L1 Lagrange point. The coronagraph satellite acts as the "master" and provides the main functions of the mission (data handling, communication, propulsion, guidance navigation and control) while the occulter satellite acts as the "slave". The control of the formation is performed in two steps: i) RF metrology for deployment and preliminary pointing, ii) classical optical attitude sensors and metrology based on diverging laser beams. This solution will satisfy the nominal requirement of a lateral positioning with an accuracy of 1 mm and a longitudinal positioning with an accuracy of 500 mm.

Abstract. The space mission PEGASE, proposed to the CNES (Centre National d'Etudes Spatiales = French Space Agency) in the framework of its call for scientific proposals : "formation flying missions", is a 2-aperture interferometer, composed by 3 free flying satellites (2 siderostats and 1 beam combiner), allowing baselines from 50 to 500 m in both nulling and visibility modes. With an angular resolution of a few mas and a spectral resolution of several tens in the spectral range 2.5-5 microns, PEGASE has several goals: -science : spectroscopy of hot jupiters (Pegasides) and brown dwarves, exploration of the inner part of protoplanetary disks -technology : validation in real space conditions of formation flying, nulling and visibility interferometry concepts. PEGASE has been studied at a 0-level. In this paper, we summarize the scientific program and associated technological and mission trade-off coming from this 0-level study. We also discuss how PEGASE can be considered as a TPF/DARWIN pathfinder in an international roadmap towards more complex space interferometry missions such as DARWIN/TPF.

Until recently, focusing of gamma-radiation was regarded as an impracticable task. Today, gamma-ray lenses have become feasible and present promising perspectives for future instrumentation. For the first time in high energy astronomy the signal/noise ratio will be dramatically improved as gamma-rays are collected on the large area of a lens from where they are focused onto a small detector. Besides an unprecedented sensitivity, MAX will feature very high angular and energy resolution. The conjunction of this new technique of Gamma Ray focusing and the new possibilities brought by the developping formation flying technology will allow a great step for Gamma Astronomy. This paper will describe after a short recall of the scientific objectives of MAX, the design of the MAX formation flying concept and the associated main design drivers and constraint.

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