Fully polarimetric microwave radiometer for remote sensing

The design, characteristics, and operation of the Helsinki University of Technology Fully Polarimetric Radiometer (FPoR) are described. The developed 36.5-GHz radiometer can be used for airborne remote sensing; however, ground-based and laboratory measurements are also possible. A direct cross-corre...

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Bibliographic Details
Published in:IEEE transactions on geoscience and remote sensing 2003-08, Vol.41 (8), p.1869-1878
Main Authors: Lahtinen, J., Pihlflyckt, J., Mononen, I., Tauriainen, S.J., Kemppinen, M., Hallikainen, M.T.
Format: Article
Language:English
Subjects:
Active control
Airborne sensing
Applied geophysics
Correlators
Earth sciences
Earth, ocean, space
Exact sciences and technology
Instruments
Internal geophysics
Laboratories
Mathematical models
Meteorology
Microwave radiometry
Radiometers
Remote sensing
Sea measurements
Stability
Stokes parameters
Temperature control
Testing
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Summary:The design, characteristics, and operation of the Helsinki University of Technology Fully Polarimetric Radiometer (FPoR) are described. The developed 36.5-GHz radiometer can be used for airborne remote sensing; however, ground-based and laboratory measurements are also possible. A direct cross-correlation technique with analog correlators, which measures all four Stokes parameters simultaneously, is applied. This paper is the first successful demonstration of an analog direct cross-correlation technique for polarimetric remote sensing radiometry. The radiometer was subjected to a variety of laboratory tests, and considerable attention is given to analysis of the characteristics of the instrument. Owing to the effective active temperature control system of the receiver, the radiometric stability of the instrument was found to be very high; test results showing stabilities below 10 mK and of 4-40 mK on time scales of 800 and 8000 s, respectively, are presented. Furthermore, the absolute accuracy of the system is analyzed to be at a sub-Kelvin level for most measurement conditions. A maritime wind vector experiment was carried out over the Gulf of Finland. The feasibility and performance of the applied correlation technique and the whole radiometer system were verified for fully polarimetric airborne measurements. The obtained brightness temperatures of the first three Stokes parameters show typical harmonic behavior with respect to the surface wind; the results suggest, however, that the model coefficients presented earlier for oceans may not be directly applicable for different conditions.
ISSN:0196-2892
1558-0644
DOI:10.1109/TGRS.2003.813847