To reduce the level of stray light in a new-generation externally occulted space coronagraph, we consider new concepts for its external occulter and its associated diaphragm and report extended measurements of their light-rejection properties. The experimental setup, which includes an artificial Sun, uses both photometric and CCD imaging techniques and permits the study of the sensitivity to misalignement of the instrument’s performance. Conic occulters that have either a multithreaded or a polished surface are found to give performances superior to those of the classical three-disk system and further are highly tolerant to misalignement. Serrated diaphragms outperform circular ones, as the bulk of the diffracted light is diverted from the coronagraphic objective.
© 2000 Optical Society of America
(220.4830) Optical design and fabrication : Systems design
(220.4840) Optical design and fabrication : Testing
(290.5820) Scattering : Scattering measurements
(350.1270) Other areas of optics : Astronomy and astrophysics
(350.4600) Other areas of optics : Optical engineering
Maurice Bout, Philippe Lamy, André Maucherat, Claude Colin, and Antoine Llebaria, "Experimental Study of External Occulters for the Large Angle and Spectrometric Coronagraph 2: LASCO-C2," Appl. Opt. 39, 3955-3962 (2000)