The giant, externally-occulted-coronagraph ASPIICS for the PROBA-3 formation flying mission

Formation flying opens new perspectives in solar physics, and allow to conceive giant, externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at a distance of hundred meters. ASPIICS (Association de Satellites Pour l'Imagerie et l'Interferometrie de la Couronne Solaire) is a mission proposed to ESA in the framework of its PROBA-3 demonstration program of formation flying which is presently in phase A. ASPIICS is a single coronagraph which will perform both high spatial resolution imaging of the solar corona as well as 2-dimensional spectroscopy of several emission lines from the coronal base out to 3 R-circle dot using an etalon Fabry-Perot interferometer. The selected lines will allow to address different coronal regions: the forbidden line of FeXIV at 530.285 nm (hot coronal matter), Fe IX/X at 637.4 nm (coronal holes), HeI at 587.6 nrn (cold matter). An additional broad spectral channel will image the white light corona so as to derive electron densities. The classical design of an externally-occulted coronagraph is adapted to the formation flying configuration allowing the detection of the very inner corona as close as 0.01 R-circle dot from the solar limb.