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Temperature/pressure and water vapor sounding with microwave spectroscopyTwo intense microwave spectra lines exist in the martian atmosphere that allow unique sounding capabilities: water vapor at 183 GHz and the (2-1) rotational line of CO at 230 GHz. Microwave spectra line sounding is a well-developed technique for the Earth's atmosphere for sounding from above from spacecraft and airplanes, and from below from fixed surface sites. Two simple instruments for temperature sounding on Mars (the CO line) and water vapor measurements are described. The surface sounder proposed for the MESUR sites is designed to study the boundary layer water vapor distribution and the temperature/pressure profiles with vertical resolution of 0.25 km up to 1 km with reduced resolution above approaching a scale height. The water channel will be sensitive to a few tenths of a micrometer of water and the temperature profile will be retrieved to an accuracy between 1 and 2 K. The latter is routinely done on the Earth using oxygen lines near 60 GHz. The measurements are done with a single-channel heterodyne receiver looking into a 10-cm mirror that is canned through a range of elevation angles plus a target load. The frequency of the receiver is sweep across the water and CO lines generating the two spectra at about 1-hr intervals throughout the mission. The mass and power for the proposed instrument are 2 kg and 5-8 W continuously. The measurements are completely immune to the atmospheric dust and ice particle loads. It was felt that these measurements are the ultimate ones to properly study the martian boundary layer from the surface to a few kilometers. Sounding from above requires an orbiting spacecraft with multichannel microwave spectrometers such as the instrument proposed for MO by a subset of the authors, a putative MESUR orbiter, and a proposed Discovery mission called MOES. Such an instrument can be built with less than 10 kg and use less than 15 W. The obvious advantage of this approach is that the entire atmosphere can be sounded for temperature and water vapor in a few hours with somewhat better than a scale height resolution. If a bigger mirror is used (greater than 30 cm) limb sounding geometry can be employed and half scale height resolution achieved to altitudes up to at least 60 km. Again, the measurements are immune to dust and ice loads. Water vapor sensitivity of 0.1 micrometer can be achieved (even with a nadir instrument) and temperature profiles retrieved to an accuracy of better than 2 K from the surface to about 60 km. Winds can be measured from the doppler shifts of CO lines in the limb sounding mode.
Document ID
Acquisition Source
Legacy CDMS
Document Type
Muhleman, D. O.
(California Inst. of Tech. Pasadena., United States)
Janssen, M. A.
(Jet Propulsion Lab. California Inst. of Tech., Pasadena., United States)
Clancy, R. T.
(Washington Univ. Saint Louis, MO., United States)
Gulkis, S.
(Jet Propulsion Lab. California Inst. of Tech., Pasadena., United States)
Mccleese, D. J.
(Jet Propulsion Lab. California Inst. of Tech., Pasadena., United States)
Zurek, R.
(Jet Propulsion Lab. California Inst. of Tech., Pasadena., United States)
Haberle, R. M.
(NASA Ames Research Center Moffett Field, CA, United States)
Frerking, M.
(Jet Propulsion Lab. California Inst. of Tech., Pasadena., United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1992
Publication Information
Publication: Lunar and Planetary Inst., MSATT Workshop on Innovative Instrumentation for the In Situ Study of Atmosphere-Surface Interactions on Mars
Subject Category
Instrumentation And Photography
Accession Number
Distribution Limits
Work of the US Gov. Public Use Permitted.

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