Possible optical design for ASPICS, a formation-flyer solar coronagraph for close-limb visible and Lyman-? imaging of the corona

The recent possibility of deploying clusters of satellites in flight formation allows the development of a new generation of space instruments, and among them, of externally occulted solar coronagraphs. This can be implemented by introducing a large occulter on a first satellite, and all the remaining optical system on a second satellite, located in the shadow of the occulter. Since the capability of looking close to the solar limb is directly related to the distance between the external occulter and the coronagraphic objective, formation flyers offer the capability of a major improvement in observing the lower corona from space. In this paper, we describe a possible optical design for ASPICS, a formation flyer solar coronagraph composed of two satellites separated by about 100 m. The proposed dual channel design will allow for the first time to simultaneously observe the lower and intermediate corona in both visible and ultraviolet (HI Lyman-? line) spectral regions at a 6 arcsec/pixel scale factor with a single instrument.