The SWAS Acousto Optical Spectrometer
M. Klumb, J. Frerick, R. Schieder, and G. Winnewisser
I. Physics Institute, University of Cologne
V. Tolls
Smithsonian Astrophysical Observatory, Cambridge, Ma
SPIE Proceedings of "Infrared Spaceborne Remote Sensing II", Vol. 2268, 1994
Abstract:
The first fully space qualified acousto-optical spectrometer (AOS) is described. It
is built for the Submillimeter Wave Astronomy Satellite (SWAS) to be launched in July
1995. It has a very large bandwidth from 1400 to 2800 MHz covered by 1356 channels.
This corresponds to a nearly 1 MHz channel spacing. The design is optimized for
very high stability, which is demonstrated by means of Allan variance stability
test. The Allan plot minimum time was found well above 800 seconds. The AOS can
operate within a temperature range from -5 to +30 ° C (+5 to +25 ° C nominal) and
with temperature variations of up to 2 ° C/h. The performance was verified also
after environmental testing such as random vibration (10.2 G rms) and thermal
cycling of -30 to +50 ° C. The lightweight mechanical design resulted in a total
weight of 7.2 kg including electronics. A detailed optical design study was
performed in order to achieve diffraction limited channel resolution, high
efficiency and low sensitivity to mechanical distortion. The RF input power
needed for full scale is 11 mW. The power consumption is 5.4 Watts (including
data pre-averaging and DC-DC converter losses). The development has shown that
AOSs are well suited for spaceborne applications.