Comparison of microwave black-body target radiometric measurements

Walker, D. A.; Gu, Dazhen; MacReynolds, K.; Direen, Randal H.; Randa, J.; Cox, A.E.; Houtz, Derek; Billinger, R.L.

doi:10.1109/igarss.2010.5652481

Cited by 2 publications

(1 citation statement)

References 3 publications

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“…The previous work is summarized in [1]. Currently, the principal goal [2] is to develop a standard radiometer, traceable to fundamental primary noise standards, but we are also taking steps toward characterizing standard targets. An early step in the characterization of calibration targets is to measure their reflectivity, and this paper reports initial measurement results for the monostatic reflection coefficient in normal incidence.…”

Section: Introductionmentioning

confidence: 99%

Reflectivity studies of passive microwave calibration targets and absorptive materials

Cox

Houtz

et al. 2010

2010 IEEE International Geoscience and Remote Sensing Symposium

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We report on the characterization of blackbody reflections as a part of the recent progress on the development of brightness standards for microwave remote sensing at National Institute of Standards and Technology (NIST). Three blackbody targets at variable temperatures used for airborne and/or satellite systems along with an aluminum plate were measured in terms of their reflection coefficients by horn antennas in connection with a vector network analyzer (VNA) in the WR-42 waveguide band. Precision measurements of reflection are needed for blackbody emissivity computation to check against the brightness temperature measurement of blackbody targets. All experiments were conducted in two distance ranges by free-space methods in an anechoic chamber. Preliminary results show negligible reflections from the calibration targets, indicating near ideal blackbody characteristics in the measured frequency range.

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Section: Introductionmentioning

confidence: 99%

Reflectivity studies of passive microwave calibration targets and absorptive materials

Cox

Houtz

et al. 2010

2010 IEEE International Geoscience and Remote Sensing Symposium

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Extraction of Illumination Efficiency by Solely Radiometric Measurements for Improved Brightness-Temperature Characterization of Microwave Blackbody Target

Houtz

Randa

et al. 2012

IEEE Trans. Geosci. Remote Sensing

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We report our recent progress toward the development of microwave brightness-temperature (BT) standards. As one of the crucial parameters, the target illumination efficiency (IE) was traditionally determined from the relative antenna pattern. We propose a measurement technique to extract the target IE solely by the use of passive radiometric measurements for characterizing the BT of the blackbody radiator. Such a technique allows us to skip the complexities that are often encountered during the measurement and calculation of the antenna pattern. Taking advantage of the variable heating capability available on most blackbody targets, we varied the temperature of a heated blackbody target and ran a series of radiometric measurements when the target was separated at different distances away from the the antenna with the radiometer operating at a few frequencies.Our experimental results show excellent measurement accuracy on the IE, with uncertainty of about 1% at close separation distance between the antenna and the target. We further measured and computed the BT of the blackbody target at the locations where we had measured the extracted IE. The BT was slightly lower than the physical temperature of the target and exhibited 0.7 K to about 1 K uncertainty when the target was located no more than 1 m away from the antenna. A measurement uncertainty of 1 K already meets the accuracy requirements of some climate variables, and such results reflect a significant step toward the establishment of BT standards at microwave frequencies.Index Terms-Blackbody target, brightness temperature (BT), illumination efficiency (IE), microwave radiometer, uncertainty analysis.

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Comparison of microwave black-body target radiometric measurements

Cited by 2 publications

References 3 publications

Reflectivity studies of passive microwave calibration targets and absorptive materials

Reflectivity studies of passive microwave calibration targets and absorptive materials

Extraction of Illumination Efficiency by Solely Radiometric Measurements for Improved Brightness-Temperature Characterization of Microwave Blackbody Target

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