Spectral Emissivity & Emittance

A Temperature and Emissivity Separation Algorithm for Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Images

by: Alan Gillespie, Shuichi Rokugawa, Tsuneo Matsunaga, J. Steven Cothern, Simon Hook, and Anne Kahle
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Manuscript received October 31, 1997. This work was a collaborative effort of the U.S. and Japanese EOS/ASTER instrument teams, sponsored by the NASA EOS Project and ERSDAC.

A. Gillespie and J.S. Cothern are with the Department of Geological Sciences, University of Washington, Seattle, Washington 98195-1310, USA.

S. Rokugawa is with The University of Tokyo, Faculty of Engineering, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, JAPAN.

T. Matsunaga is with the Geological Survey of Japan, 1-1-3 Higashi, Tsukuba, Ibaraki 305, JAPAN.

S. Hook and A. Kahle are with the Jet Propulsion Laboratory 183-501, Pasadena, California 91109, USA

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Abstract:
The ASTER scanner on NASA’s EOS-AM1 satellite (launch: June, 1998) will collect five channels of TIR data with an NE DT of <0.3 K to estimate surface temperatures and emissivity spectra, especially over land, where emissivities are not known in advance. Temperature/emissivity separation (TES) is difficult because there are five measurements but six unknowns. Various approaches have been used to constrain the extra degree of freedom. ASTER’s TES algorithm hybridizes three established algorithms, first estimating the normalized emissivities, and then calculating emissivity band ratios. An empirical relationship predicts the minimum emissivity from the spectral contrast of the ratioed values, permitting recovery of the emissivity spectrum. TES uses an iterative approach to remove reflected sky irradiance. Based on numerical simulation, TES should be able to recover temperatures within about 1.5K, and emissivities within about 0.015. Validation using airborne simulator images taken over playas and ponds in central Nevada demonstrates that, with proper atmospheric compensation, it is possible to meet the theoretical expectations. The main sources of uncertainty in the output temperature and emissivity images are the empirical relationship between emissivity values and spectral contrast, compensation for reflected sky irradiance, and ASTER’s precision, calibration, and atmospheric correction.

NORMAL SPECTRAL EMITTANCE, 800-1400 K, Authors: Harrison, W.N. ; Richmond, J.C. ; Skramstad, H.K.

From the Energy Citations Database, OSTI IdentifierOSTI ID: 4830164

Technical Report, WADC-TR-59-510(Pt.III), National Bureau of Standards, Washington, D.C.,1961 Sep 01

ABSTRACT:

The equipment for direct measurement of normal spectral emittance was extensively modified by incorporation of a new external optical system that increased the amount of radiant energy available for measurement by a factor of about 10, and other associated changes. The test procedure was modified by incorporation of a zero line” correction. The equipment was calibrated by means of sector-disk attenuators which passed known fractions of the radiant flux from a blackbody furnace. Working standards of normal spectral emittance were prepared, calibrated, and shipped. An equation relating the normal spectral emissivity of a metal to five other parameters of the metal, each of which makes a non-linear contribution to the emissivity, was solved for one set of data by long hand” methods. Some progress was made in setting up a program for solution of the equation by use of an electronic computer. Equipment for the automatic recording of spectral emittance data in a form suitable for direct entry into an electronic computer, and on-line computation from spectral emittance data of total emittance or solar absorptance, was designed. Specifications for the equipment were prepared and bids received preparatory to placing an order for its procurement. (auth)

Modern emissivity measuring facility for industry-orientated calibrations developed at PTB

This news release is available in German.
CAPTION: Local variation of the directed spectral emissivity of a car paint sample at a wavelength of 4 µm, measured using a thermography camera. (IMAGE COURTESY PTB)
Industry and research are increasingly relying on non-contact temperature measurements with the aid of heat radiation, for example, for the reliable and reproducible drying of car paint.

In order to attain exact and reliable results, the emissivity of the measured surface has to be known. It can only be determined precisely in complex measuring facilities.

The Physikalisch-Technische Bundesanstalt (PTB) has developed a modern emissivity measuring facility for industry-oriented calibrations.
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Infrared Spectral Emittance and Optical Properties of Yttrium Vanadate
Phys. Rev. 169, 705 - 709 (1968)

by: H. E. Rast, H. H. Caspers, and S. A. Miller *
Infrared Division, Research Department, Naval Weapons Center Corona Laboratories Corona, California 91720

Received 13 November 1967
“ABSTRACT: The infrared spectral emittance E of single crystals of YVO₄ has been examined near 4.2 and 77°K in the wavelength range 4-125 micrometers…”
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* Formerly Naval Ordnance Laboratory, Corona, Calif.

DIRECTIONAL SPECTRAL EMITTANCE OF A PACKED BED WITH COUPLED CONDUCTION-RADIATION HEAT TRANSFER

Dominique Baillis
Centre de Thermique de Lyon (CETHIL), UMR CNRS 5008, Institut National des Sciences Appliquées de Lyon, France

Jean-Francois Sacadura
Centre de Thermique de Lyon (CETHIL), UMR CNRS 5008, Institut National des Sciences Appliquées de Lyon, France

ABSTRACT

Recently a new experimental set up for measuring the directional spectral emittance has been developed. The both sides of packed bed sample are simultaneously heated with identical power laser beams (4kw, CO² 10.6 um) and the isothermal condition in the medium is assumed. In this paper, the coupled conduction-radiation equations are considered to investigate the effect of the temperature non-uniformity on the calculated value of the emittance and to verify if the isothermal assumption is valid. It is shown that the gradient temperature in the medium can be non negligible depending on the thickness and on the sample extinction coefficient.

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