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15 October 2004 Stray light estimates for the TPF formation flying interferometer
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A formation flying interferometer suffers a unique stray light problem: it is the only space astronomical instrument which looks at starlight in the presence of a bright object (the sunlit collector spacecraft) which is intentionally placed in the field of view. The combiner instrument is a collection of astronomical telescopes looking at stellar targets relayed by the collectors; but other parts of the collector spacecraft can scatter or emit substantial fluxes. Screening the glare while collecting the starlight is the challenge. The TPF formation-flying interferometer is especially vulnerable because the planets it seeks are so faint. We present a preliminary estimate of stray light from various sources appearing in the interferometer science detector. We assumed a pinhole field stop would be employed, but that two mirrors preceding that pinhole in the combiner optical system would scatter off-axis light into the pinhole. Sources include scattering of direct sunlight and thermal emission, both from the multi-layer thermal shades which permit passive cooling of the instruments to about 40K. We find that the estimated stray light fluxes are of order 104 times the planet flux. We conclude that the optics at the combiner entrance must be blocked from any direct view of the thermal shades.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Charley Noecker, Zongying Wei, and James Decino "Stray light estimates for the TPF formation flying interferometer", Proc. SPIE 5526, Optical Systems Degradation, Contamination, and Stray Light: Effects, Measurements, and Control, (15 October 2004);


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