SWAS-AOS: the first acousto-optical spectrometer in space
J. Frerick, M. Klumb, R. Schieder, V. Tolls, G. F. Winnewisser
Infrared Spaceborne Remote Sensing VII, M. Strojnik, B. Andresen, eds. Proc. of SPIEE Vol. 3759, 1999
Abstract:
On December 5, 1998, the Submillimeter Wave Astronomy
Satellite has been launched with a PEGASUS carrier
after more than 3 years delay. SWAS is observing
molecular line signals (H$-2$/O, $+13$/CO, Cl, O$-2$/
and H$-2$/ $+18$/O) from astronomical sources at
frequencies between 487 and 557 GHz. SWAS is the first
sub-millimeter heterodyne space mission, and, for the
spectral analysis of the received signals, it carries
the first acousto-optical spectrometer (AOS) in space.
The AOS has been built at University of Cologne, and it
covers 1.4 GHz bandwidth with approximately 1400
frequency channels. The total weight is 7.5 kg and the
power consumption is 5.5 Watts only. The very stable
temperature conditions on SWAS allow longtime
integrations at total observing times far above 100
hours still with radiometric performance. So far, the
AOS- spectra have not been degraded by particle hits,
particularly the CCD detector of the AOS does not
exhibit any visible effect due to cosmic rays. SWAS has
already observed many interstellar sources in our
galaxy. Emission of water is seen to be very abundant,
while signals of molecular oxygen seem to be too weak
to be observable.