Abstract. A well-known technique for
measuring the total reflectivity, transmissivity, and coherent intensity transmittance
of dry snow samples is developed for use
under room
conditions. The main distinction from the known technique is that new algorithms
for measuring and calculating the coefficients listed above allow correctly to
take into account the difference in the thermodynamic temperatures of the snow
and the room.
The measurement algorithm is
complemented by the operation of fixing the level of the output signal of
radiometers corresponding to the intensity of the thermal radiation of a black
body whose thermodynamic temperature is equal to the thermodynamic temperature
of the snow sample of being examined. In calibration operations, in addition to
this black body, three more black bodies are used, two of which are cooled by liquid nitrogen, and
the thermodynamic temperature of the third is equal to the thermodynamic
temperature of the room. Black bodies are made of a mixture of wood shavings
and soot. The density of this mixture increases from the front to the back.
The method is implemented
using a measuring system, the main component of which is a camera with
artificial "cold" thermal illumination of snow samples. The intensity level of the
illumination is determined by means of a metal reflector with a wide scattering
indicatrix. The radiometer antenna is a Teflon lens 0.2 m in diameter with a
focal length of 0.4 m. The snow samples are placed in metal cylindrical containers
with an outer lateral thermal insulation shell.
It is shown that the proposed method
is based on relative measurements, i.e. without the traditional need to measure
the absolute values of the radio brightness temperatures of calibration bodies
and samples.
Key words: microwave thermal radiation,
dry snow cover, measurement technique, reflectivity, transmissivity, coherent
intensity.
References
1. Golunov V.A., Korotkov V.A., Sukhonin
Ye.V. Effektyi rasseyaniya pri izluchenii millimetrovyih voln atmosferoy i
snezhnyim pokrovom. [Scattering effects under the millimeter wave emission from
atmosphere and snow cover]. Moscow, VINITI Publ. Itogi Nauki i Tekhn. Radiotekhnika, Vol. 41, 1990, pp. 68-136.
(In Russian).
2. Wiesmann A., Mätzler C. Weise T.
Radiometric and structural measurements of snow samples. Radio Sci.,
1998, Vol. 33. No.2, pp. 273-279.
3. Golunov V.A. Method for measuring the
emissivity of natural coverings. Avtorskoe svidetelstvo ¹ 1417593. Priority
06.05.86. (In Russian)
4. Shvetsov A.A., Korotaev D.V.,
Fedoseev L.I. Remote sensing of terrestrial cover near the 2.5 mm oxygen line. Radiophysics
and Quantum Electronics, 2005, Vol. 48. No. 10-11. pp. 807-816.
5. Rytov S.M., Kravtsov Yu.A., Tatarskii
V.I. Principles of statistical radiophysics. Publication Info. Berlin;
New York: Springer-Verlag, 1989. Vol.2. 463p.
6. Hallikainen M. T., Ulaby F. T. and
Deventer T. E. V. Extinction behavior of dry snow in the 18-to-90 GHz range. IEEE
Trans. Geosci. Remote Sens., 1987, Vol. GE-25. No.6. pp.737-745.
7. Golunov V. A., Barabanenkov Yu. N.
Radiometric methods of measurement of the total reflectivity, the total
transmissivity and the coherent transmissivity of a weakly absorbing random
discrete medium layer in the millimeter wavelengths range. Proc. Progress in
Electromagnetics Research Symp. Moscow, Russia, August 19-23, 2012.
Electromagn. Acad., Cambridge, 2012, pp.1415-1418.
8. Born M., Wolf E. Principles of
Optics. Pergamon Press. Oxford. 720p. 1964.
9. Landsberg G.S. Optika [Optics].
Moscow, Nauka Publ. 1976. 928p. (In Russian).
10. Golunov
V. A., Kuz’min A. V., Skulachev D. P., and Khokhlov G. I. Experimental results
on the frequency dependence of attenuation, scattering, and absorption of
millimeter waves in a dry snow cover. J. of Communications Technology and
Electronics, 2017, Vol. 62. No. 9. pp. 951–959. DOI 10.1134/S106422691709008X
11. Golunov
V.A., Khokhlov G.I. The exponent of the frequency dependence of microwave
backscattering from dry snow and artificial snow-like media. Zhurnal
Radioelectroniki - Journal of Radio Electronics, 2017, No. 9.
Available at
http://jre.cplire.ru/jre/sep17/6/text.pdf
(In Russian)
12. Golunov
V. A., Marechek S. V., Kchokchlov G. I. Features of the microwave radiation scattering
in dry fluffy snow. Zhurnal Radioelectroniki - Journal of Radio
Electronics, 2018. No. 6. Available at
http://jre.cplire.ru/jre/jun18/2/text.pdf
(In Russian).