Research Note

High-resolution observations of Martian non-thermal CO₂ emission near 10 m with a new tuneable heterodyne receiver

¹ NASA Goddard Space Flight Center, Greenbelt, MD, USA e-mail: gsonnabend@lepvax.gsfc.nasa.gov
² Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany e-mail: [wirtz;vetterle;schieder]@ph1.uni-koeln.de

Received: 18 November 2004
Accepted: 21 February 2005

Abstract

We present first observations with the Tuneable Heterodyne Infrared Spectrometer (THIS). This instrument developed at University of Cologne has the potential to cover the mid-infrared from 7 to 19 μm. By using heterodyne techniques and an acousto optical spectrometer (AOS) as a back-end the frequency resolution achieved is better than 10⁷ at 10 μm. A tuneable quantum-cascade laser (QCL) is used as a local-oscillator (LO) and the instantaneous bandwidth supplied by the mercury-cadmium-telluride (MCT) detector and the AOS is 1.4 GHz. The system operates within a factor of two of the quantum limit. During December 2003 THIS was installed at the 1.5 m McMath-Pierce solar telescope on Kitt Peak/Arizona. Observations of molecular line features from the atmosphere of Mars were carried out. We present measurements of narrow non-LTE CO₂ emission from the Martian atmosphere observed with a never before achieved frequency resolution of 1 MHz. The first analysis suggests zonal winds in the mesosphere of Mars in good agreement with model predictions.