The high sensitivity provided by SOFIA (Stratospheric Observatory For Infrared Astronomy) and the spectral resolution obtained with the CTS (Chirp Transform Spectrometer) combine in a unique tool in order to address a wide range of topics of modern astrophysics, from questions about comets, planetary atmospheres and the interstellar medium in the galaxy to investigations related to the early Universe. Thanks to high resolution spectroscopy we can obtain atmospheric information from the shape of a spectral line, and with this retrieve the altitude distribution of molecular species, for instance water vapor on Mars and HCl on Venus.
German REceiver for Astronomy at Terahertz
GREAT will receive the IR radiation through coherent detection, using a dual heterodyne process
Chirp Transform Spectrometer
The Chirp Transform Spectrometer is based on the velocity dispersion of sonic surface waves, which is controlled by micro-structures on the surfaces of defined crystals. These dispersion properties allow us to perform a real-time convolution. The time-frequency transformation is performed by a correct combination of the dispersion features of two SAW (Surface Acoustic Wave) filters, an expander and a compressor. One critical parameter is the matching between the SAW filters, the resolution and the dynamic range depends strongly on this parameter, that can optimized by using a digital phase accumulator to produce an expanded chirp waveform.