Effects of stray light

摘要

A previous analysis of stray light in the SOFIA telescope has identified a potential problem. The primary and tertiary mirrors are partially illuminated by the bright Earth and partially shaded by the lower edge of the aperture door when the telescope is pointed at a low elevation angle. As the aircraft rolls during flight, the edge of the shadow of the lower edge of the aperture door moves across the mirror, causing a variable background to appear at the focal plane. This will contribute to the noise seen by a focal plane instrument. This note assesses the practical effect of this background variation taking into account the expected roll rates and the normal chopping methods used in IR astronomy.