The COR1 telescope on STEREO is based on the classic design by Bernard Lyot, adapted for spaceflight by engineers at NASA Goddard Space Flight Center and Swales Aerospace. COR1 is an internally-occulted coronagraph of length ~1.2m and is one of the STEREO SECCHI suite of remote sensing telescopes.
The COR1’s field of view is from 1.3 to 4 solar radii. A linear polarizer is used to suppress scattered light, and to extract the polarized brightness signal from the solar corona. The optical scattering performance of the coronagraph was first modeled using both the ASAP and APART numerical modeling codes, and then tested at the Vacuum Tunnel Facility at the National Center for Atmospheric Research in Boulder, Colorado. A detailed review of the COR1 instrument is described in the paper of William T. Thompson et al. 2003, titled “COR1 inner coronagraph for STEREO-SECCHI” (click to open) (Innovative Telescopes and Instrumentation for Solar Astrophysics, SPIE, Volume 4853 Pages 1-11, 2003).