TELIS: TErahertz and subMMW LImb Sounder – Project summary after first successful flight

Abstract

The TELIS instrument is a balloon-borne cryogenic three-channel heterodyne spectrometer for limb sounding of stratospheric trace gases. The instrument is flown together with the MIPAS-B Fourier-transform spectrometer of the IMK, Karlsruhe. TELIS was developed by a European consortium involving research institutions, universities, and industrial partners. Thermal emission radiation is coupled in by a 26x13 cm dual offset Cassegrain telescope controlled to maintain constant tangent height during measurement. Radiometric calibration is achieved by a blackbody and deep space view. The radiation is divided into three channels by means of a polarizer and a dichroic. Within a special lightweight cryostat three complete heterodyne receivers are kept at liquid helium temperature: THZ channel, 1750-1890 GHz, hot electron bolometer mixer, DLR; SIR channel, 450-650 GHz, integrated receiver, SIS mixer, SRON (see poster ‘TELIS instrument performance analysis’); subMMW channel, 499-503 GHz, SIS mixer, RAL. A digital autocorrelator spectrometer with 4 GHz bandwidth and ca. 2 MHz resolution serves as backend shared among the channels. The first successful flight was in March 2009 in Kiruna, Sweden. Calibrated spectra are so far only available as quicklook data. Sideband ratios have been characterized recently. The radiometric accuracy of the autocorrelator is under investigation (see poster ‘Characterisation of the TELIS autocorrelator spectrometer’). The present paper will present the instrument as well as first results from the flight.