The Upper Atmosphere Research Satellite microwave limb sounder instrument
Article first published online: 21 SEP 2012
Copyright 1993 by the American Geophysical Union.
Journal of Geophysical Research: Atmospheres (1984–2012)
Volume 98, Issue D6, pages 10751–10762, 20 June 1993
How to Cite
1993), The Upper Atmosphere Research Satellite microwave limb sounder instrument, J. Geophys. Res., 98(D6), 10751–10762, doi:10.1029/93JD00798., et al. (
- Issue published online: 21 SEP 2012
- Article first published online: 21 SEP 2012
- Manuscript Accepted: 25 JAN 1993
- Manuscript Received: 23 JUN 1992
The microwave limb sounder (MLS) on the Upper Atmosphere Research Satellite (UARS) is the first satellite experiment using limb sounding techniques at microwave frequencies. Primary measurement objectives are stratospheric ClO, O3, H2O, temperature, and pressure. Measurements are of thermal emission: all are performed simultaneously and continuously and are not degraded by ice clouds or volcanic aerosols. The instrument has a 1.6-m mechanically scanning antenna system and contains heterodyne radiometers in spectral bands centered near 63, 183, and 205 GHz. The radiometers operate at ambient temperature and use Schottky-diode mixers with local oscillators derived from phase-locked Gunn oscillators. Frequency tripling by varactor multipliers generates the 183- and 205-GHz local oscillators, and quasi-optical techniques inject these into the mixers. Six 15-channel filter banks spectrally resolve stratospheric thermal emission lines and produce an output spectrum every 2 s. Thermal stability is sufficient for “total power” measurements which do not require fast chopping. Radiometric calibration, consisting of measurements of cold space and an internal target, is performed every 65-s limb scan. Instrument in-orbit performance has been excellent, and all objectives are being met.