Heterodyne spectroscopy of astronomical and laboratory sources at 8.5 μm using diode laser local oscillators |
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Authors: | M. Mumma T. Kostiuk S. Cohen D. Bühl P. C. Von Thuna |
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Affiliation: | (1) Present address: Astrochemistry Branch, Laboratory for Extraterrestrial Physics, NASA/Goddard Space Flight Center, 20771 Greenbelt, Md., USA;(2) Laser Technology Branch, NASA/Goddard Space Flight Center, 20771 Greenbelt, Md., USA;(3) National Radio Astronomy Observatory, Greenbank, W. Va., USA;(4) Arthur D. Little, Inc., Cambridge, Mass., USA |
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Abstract: | The first 8.5m infrared heterodyne spectrometer has been constructed using tuneable semiconductor (PbSe) diode lasers and was used to measure absorption line profiles of N2O in the laboratory and black body emission from the Moon and from Mars. Spectral information was recorded over a 200 MHz bandwidth using an 8-channel filter bank. The resolution was 25 MHz (6 × 10–6m) and the minimum detectable (black-body) power was 1 × 10–16 W for 8 min of integration. The results demonstrate the usefulness of heterodyne spectroscopy for the study of remote and local sources in the infrared.We wish to thank Dr Jack Butler and Craig Simpson (Arthur D. Little, Inc.) for their continuing (and successful) efforts to grow better diode lasers during the course of this experiment. We thank the National Radio Astronomy Observatory for the loan of a 40-channel filter bank and associated mini-computer.We thank en masse the dozens of people who loaned equipment to us for the duration of this experiment, and the commercial firms (especially Harshaw, Inc.) which expedited orders for crucial equipment. We thank Dr Bertram Donn, Dr Norman Ness, and Dr George Pieper for administrative, scientific, and financial support; and we thank Mr James Faris for technical assistance and Dr Sol Glicker for preparation of sample gas cells. We thank Dr Thomas Clark for providing the Kohoutek ephemeris, sighting printout, and predicted molecular line positions and for advice and the loan of some equipment. Finally, we wish to acknowledge the strong support accorded us by our wives and families who scarcely saw us during this period. |
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