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The underlying principal of an acousto-optical spectrometer (AOS) is very simple: laser light is deflected by an acoustic wave traveling through a deflector
(or Bragg cell). Then, the deflected light is focussed onto an linear detector array. Each detector measures the intensity in a small frequency intervall like
a set of radios tuned to different radio stations. However, in reality such a spectrometer is more complicated since its optical design must be thought through
carefully to properly manipulate the light and to avoid creating too much stray light.
The image below shows the optical setup of the SWAS-AOS. The SWAS-AOS was in operation from 1993 until 2006. The first years of operation were in support of the
ground-testing of the SWAS satellite. The following years it was in almost continuous operation in-orbit. Actually, today the AOS is still partially operation.
Since the SWAS satellite was put into a sleeping mode, the laser diodes in the AOS were turned off. But, the remaining parts of the instrument are still in
operation.
 SWAS-AOS: View into the optical setup from the top.
 SWAS-AOS: Laser diode module.
 SWAS-AOS: Bragg cell and imaging optics.
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