Proc. SPIE 5901, 590118, 1−10, 2005
Solar Physics and Space Weather Instrumentation
S. Fineschi and R.A. Viereck (eds.)
© SPIE − The International Society for Optical Engineering
Space performance of the multistage labyrinthine SMEI baffle
A. Buffington, B.V. Jackson and P. Hick
Center for Astrophysics and Space Sciences, University of California San Diego
Abstract
The Solar Mass Ejection Imager (SMEI) was launched on 6 January 2003, and
shortly thereafter raised to a nearly circular orbit at 840 km. Three SMEI
CCD cameras on the zenith-nadir oriented CORIOLIS spacecraft cover most of
the sky beyond about 20° from the Sun, each 102-minute orbit. Data
from this instrument provide precision visible-light photometric sky maps.
Once starlight and other constant or slowly varying backgrounds are subtracted,
the residue is mostly sunlight that has been Thomson-scattered from
heliospheric electrons. These maps enable 3-dimensional tomographic
reconstruction of heliospheric density and velocity. This analysis requires
0.1% photometry and background-light reduction below one S10 (the brightness
equivalent of a 10th magnitude star per square degree). Thus
10-15 of
surface-brightness reduction is required relative to the solar disk. The
SMEI labyrinthine baffle provides roughly 10-10 of this reduction;
the subsequent optics system provides the remainder. We analyze data obtained
over two years in space, and evaluate the full systems stray-light
rejection performance.