Physics – Optics
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004aas...20518007h&link_type=abstract
American Astronomical Society Meeting 205, #180.07; Bulletin of the American Astronomical Society, Vol. 37, p.385
Physics
Optics
Scientific paper
We have examined the possibility of applying difractive Fresnel optical concepts developed at Lawrence Livermore National Laboratory for a possible O/NIR space telescope to the much more relaxed tolerance regimes of the far-IR and sub-millimetre. We conclude that the approach is indeed applicable and that a powerful FIR-submm observatory (GISMO) could be built around a 30m primary lens of ultra-high molecular weight polyethylene (UHMW-PE) 2.3mm thick.This would be the main component of a "Lens" Spacecraft (LSC) which would be located 3 km from a second "Instrument" spacecraft (ISC) carrying field optics, a Fresnel corrector lens, re-imaging optics and focal plane instruments.
In its Sun-Earth L2 halo orbit, the Lens would cool by radiation to 10K; the ISC optics would be actively cooled to a few K and would resemble a simplified version of current plans for SAFIR, the Single-Aperture Far-IR mission under study by NASA. GISMO could be a good deal cheaper to build than the current 10m, 4K SAFIR concept. Relative positioning of the two spaceraft needs to be accurate to a few millimetres laterally and a tens of centimetres in separation (focus). We highlight some technical uncertainties.
For most observations at wavelengths between 20 and 600 microns GISMO should be between 3 and 10 times more sensitive than the 10m, 4K SAFIR concept. The possible exception is spectroscopy betwen 250 and 450 microns, where its sensitivity should be about the same. GISMO's 30m aperture would of course offer a three-fold improvement in spatial resolution at all wavelengths. As a result GISMO is expected to achieve almost complete resolution of the FIR background, reaching sources below 100 micro-Jansky in seconds, and would be an immensely powerful facility throughout its wavelength range of operation.
Cliffe M. R.
Hawarden Tim G.
Henry David M.
Stevens Jason A.
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