Spectral Reflectivity of Epner Laser Gold

[caption id="attachment_372" align="alignleft" width="150" caption="Courtesy of Epner Technology, Inc."][/caption]

(CLICK ON GRAPH TO ENLARGE)
Almost everyone who attends the SPIE DSS Exposition and many other optical and optical engineering Conferences & Expos has received a gold-plated paper clip from Mr. David Epner, personally.

Well, the gold costing that Epner supplies to the optics industry has some interesting infrared reflectance (and emittance) properties.

Those properties, specifically the hemispherical spectral reflectance in the near, mid and far infrared is now available for all to view first hand on the Epner website.

A copy of the curve and the data related to it can be downloaded from the site, too.

Shown here, of course, is the Spectral Reflectance of "Laser Gold", which as most know is the complement of Spectral Emittance at each and every wavelength from the formula: e(lambda) = 1 - r(lambda) - t(lambda),

where, respectively:

e is the emittance,
r is the reflectance,
t is the transmittance and
lambda is the wavelength (on this graph shown in units of micrometers). (Note: the usual expressions for these terms are in the Greek letters, epsilon, rho, tau and lambda and have been modified for use on this webpage)

The assumption most often made is that the transmittance of solid gold is zero, or so nearly so that it can be neglected.

That can be an false assumption in some cases according to the degree of precision required in a specific measurement situation. For instance, a very thin film of gold may be partially transparent especially in the long wavelength regions of the infrared and the optical properties on the material under the gold layer may come into play.

Systematic Errors in the Measurement of Emissivity Caused by Directional Effects

In the Optics InfoBase, by the American Institute of Physics' Optical Society of America:
Authors: Abraham Kribus, Irna Vishnevetsky, Eyal Rotenberg, and Dan Yakir

---

Applied Optics, Vol. 42, Issue 10, pp. 1839-1846
Keywords (OCIS):
(120.0280) Instrumentation, measurement, and metrology : Remote sensing and sensors
(260.3060) Physical optics : Infrared
(300.2140) Spectroscopy : Emission
Abstract
Accurate knowledge of surface emissivity is essential for applications in remote sensing (remote temperature measurement), radiative transport, and modeling of environmental energy balances...  » View Full Text: PDF

Spectral Emittance of Ablation Chars, Carbon, and Zirconia to 3700 deg K

Hemispherical Spectral Emittance of Ablation Chars, Carbon, and Zirconia to 3700 deg K
Authors: R. G. Wilson; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CENTER

Abstract: The initial results of the application of special optical techniques to high-temperature emittance and reflectance studies of an ablation-material char and certain other refractory materials representative of those present in ablation residues formed during aerospace reentry operations are presented. Spectral hemispherical emittance and reflectance were determined with an image pyrometer integrated with an arc-imaging furnace for carbon, graphite, zirconia, and a phenolic-nylon ablation-material char at wavelengths from 0.37 micrometer to 0.72 micrometer for temperatures from 2100 deg K to 3700 deg K. The data obtained are compared with those of other investigations to the extent that the existence of comparable data permits. Surface-roughness properties of the materials studied were determined from measurements made with a light-section microscope. The dependence of the spectral hemispherical emittance of oxidized carbon at a wavelength of 0.65 micrometer on its surface-roughness properties was investigated experimentally and the emittance was found to be a linear function of the root-mean-square slope of the surface when the roughness is large compared with wavelength. p3

Limitations: APPROVED FOR PUBLIC RELEASE
Description: Technical note
Pages: 31
Report Date: MAR 65
Report Number: A107703

The InfraRed Sea Surface Emissivity (IRSSE) model

From Paul van Delst's Work Page at The Cooperative Institute for Meteorological Satellite Studies of the University of Wisconsin - Madison Space Science and Engineering Center.
The InfraRed Sea Surface Emissivity (IRSSE) model was developed for use in the Global Data Assimilation System (GDAS) at NCEP/EMC. Previously, the GDAS used an IRSSE model based on Masuda et al (1988). The Masuda model doesn't account for the effect of enhanced emission due to reflection from the sea surface (only an issue for larger view angles) and the implementation was based on coarse spectral resolution emissivity data making its application to high resolution instruments, such as AIRS, problematic.

The old IRSSE model has been upgraded to use sea surface emissivities derived via the Wu and Smith (1997) methodology as described in van Delst and Wu (2000). The emissivity spectra are computed assuming the infrared sensors are not polarised and using the data of Hale and Querry (1973) for the refractive index of water, Segelstein (1981) for the extinction coefficient, and Friedman (1969) for the salinitiy/chlorinity corrections.

Traceable emissivity measurements in RTP using room temperature reflectometry

By: Hunter, A.; Adams, B.; Ramanujam, R.
Advanced Thermal Processing of Semiconductors, 2003. RTP 2003. 11th IEEE International Conference on RTP
Volume , Issue , 23-26 Sept. 2003 Page(s): 85 - 88
Digital Object Identifier 10.1109/RTP.2003.1249127
Summary:

The design of an integrating reflectometer specific to the optical and spectral requirements of rapid thermal processing (RTP) is discussed. We report reflectance measurements of various materials. These measurements are correlated to in-situ emittance measurements recorded during rapid thermal processing. We also present the design of an optimized emissometer for an RTP chamber. We propose a means for correlating room temperature reflectance measurements to emittance standards for RTP.

View citation and abstract

Real Time Emissivity Measurement For IR Temp Measurements

This online page at The Pyrometer Instrument Company website, discusses the emissivity correction techniques employed in their products, the very narrow waveband devices called the Pyrolaser® (Shown here), the Pyrofiber® & the Optitherm® III Emissivity Technology.

(Notes: 1. The article speaks about "emissivity" but the spectral emissivity is implied due to the fact that these devices operate in very narrow wavebands at 865nm, 905nm or 1550nm, according to the model.
2. The article also provides a calculation and describes the radiant power of the laser as "energy".)

Here's an edited quote from the page:
"The emissivity is measured by firing a pulsed laser of monitored output energy to the target and measuring the reflected laser energy. Assuming that no energy is transmitted through the target (opaque material) the impinging energy must either be absorbed or reflected.

"The unknown absorbed energy can be calculated from the two measured quantities outgoing energy and reflected energy.

"Since absorptivity and emissivity are equal...the target emissivity (e) is known as soon as the absorptivity is known.

The temperature is measured by collecting the radiance in a narrow band (10-50nm) at the same wavelength (865nm, 905nm or 1550nm depending on the specific instrument) where emissivity is measured with the laser."

Normal Spectral Emittance Measurements (600–2000 nm) of Alumina

An online General Electric Company Downloadable Corporate R& D Technical Report (PDF Format - 308KB)
Report Title: Normal Spectral Emittance Measurements (600–2000 nm) of Polycrystalline Alumina (PCA) at High Temperatures


Author(s) L. Bigio, of the Component Ceramics Laboratory
GE Report Number: 99CRD128

Date: November 1999
Number of Pages: 8

Key Words: spectral emittance, 600-2000 nm, polycrystalline alumina, PCA, high temperatures, fiber optic radiance probe

"A novel method is shown for measuring the spectral emittance of polycrystalline alumina (PCA) in the temperature range ~1100-1400 C, from 600-2000 nm. The method utilizes a CO2 laser at 10.6 microns to heat a ~4 mm size spot on a small sample (~6x4 mm) from one side, while the temperature and emission are measured optically from the other side. A fiber optic radiance probe focuses on a 2 mm spot in the middle of the larger heated region, and directs the collected emission to a spectrometersystem. Radiance measurements are conducted relative to a blackbody at 1000 C. The temperature is measured at the same location viewed by the radiance probe using a thermal imaging pyrometer with a narrow bandpass at 10.6 microns. Since this is the same wavelength as the laser, care must be taken to avoid the scattered laser radiation that partially overfills the sample. An emittance at 10.6 microns of 0.97 is assumed for the temperature measurements. In this spectral region, the emittance is found to decrease with increasing wavelength and increase with increasing temperature. This method can be used on other ceramic materials as well."

SPECTRAL MEASUREMENTS FIELD GUIDE

This web site gives the executive summary and table of contents for the Field Guide.

Here's a summary of what the Field Guide is all about in the words of its authors:

EXECUTIVE SUMMARY

"Because of the rapid advance of airborne and satellite sensor technology in providing higher spectral resolution over progressively broader wavelength regions, there is a need for more (and more accurate) field measurements to complement overhead data. The purpose of this field guide is to facilitate such ground-based measurements, first through a review of the environmental factors affecting such measurements, second through an evaluation of the instrumentation involved, and third through a suggested approach to the measurement process.

"In evaluating environmental factors affecting spectral measurements in the field, the sources of radiance from a target are discussed in both the reflectance and emittance regions of the spectrum, as well as how those sources are modified by atmospheric attenuation and scattering, and the presence of clouds and wind.

"Another factor affecting all spectral measurements in the field is the computer typically used for instrument control and data storage. Computers tend to be the universal weak link in field spectrometers, because of their typical low tolerance for bright sunlight, temperature extremes, windblown dust, and rain. Various solutions to the computer problem are discussed, including the acquisition of hardened computers.

"The most commonly used field spectrometers are described, with advice on how to get the most out of each instrument. Then the pros and cons of each instrument are discussed with regard to different applications.

"Finally, how to approach field measurements is described, beginning with a thorough testing of a field instrument (and the field instrument user) in the laboratory. Approaches to data collection, record keeping, data reduction, and data analysis are discussed. A major conclusion is that much greater support for data analysis is necessary to reach the full potential of spectroscopic remote sensing for target identification".

Emissivity Spectra of Sulfates, Phosphate, and Chlorides

Emissivity Spectra of Sulfates, Phosphate, and Chlorides

The absorption features of sulfate (gypsum and anhydrite) and phosphate (apatite) result from vibrations of the S-O and P-O bonds in the sulfate and phosphate anions, respectively. The strong ionic bonding of the chlorides inhibits independent vibration between the individual diatomic pairs (e.g., Na and Cl) but rather requires the entire crystal lattice to vibrate as a whole.

This figure is from Lane, M.D. and P.R. Christensen, Thermal infrared emission spectroscopy of salt minerals predicted for Mars, Icarus, 135, 528-536, 1998.



CLICK ON IMAGE TO ENLARGE --SOURCE: Arizona State University website: www.mars.asu.edu/~lane/sulfphoschl.html

Infrared Sea Surface Emissivity

"The InfraRed Sea Surface Emissivity (IRSSE) model was developed for use in the Global Data Assimilation System (GDAS) at NCEP/EMC. Previously, the GDAS used an IRSSE model based on Masuda et al (1988).

"The Masuda model doesn't account for the effect of enhanced emission due to reflection from the sea surface (only an issue for larger view angles) and the implementation was based on coarse spectral resolution emissivity data making its application to high resolution instruments, such as AIRS, problematic.

"The old IRSSE model has been upgraded to use sea surface emissivities derived via the Wu and Smith (1997) methodology as described in van Delst and Wu (2000).

"The emissivity spectra are computed assuming the infrared sensors are not polarised and using the data of Hale for the refractive index of water, Segelstein (1981) for the extinction coefficient, and Friedman (1969) for the salinitiy/chlorinity corrections.

"Instrument spectral response functions (SRFs) are used to reduce the emissivity spectra to instrument resolution. These are the quantities predicted by the IRSSE model."

Emissivity Measurements on Metallic Surfaces with Various Degrees of Roughness:

A Comparison of Laser Polarimetry and Integrating Sphere Reflectometry: Proceedings of the Fifteenth Symposium on Thermophysical Properties, Part I

Authors: Seifter A.1; Boboridis K.2; Obst A.W.2

Source: International Journal of Thermophysics, Volume 25, Number 2, March 2004 , pp. 547-560(14)

Publisher: Springer

Abstract:

Both integrating sphere reflectometry (ISR) as well as laser polarimetry have their advantages and limitations in their ability to determine the normal spectral emissivity of metallic samples. Laser polarimetry has been used for years to obtain normal spectral emissivity measurements on pulse-heated materials. The method is based on the Fresnel equations, which describe reflection and refraction at an ideally smooth interface between two isotropic media. However, polarimetry is frequently used with surfaces that clearly deviate from this ideal condition. Questions arise with respect to the applicability of the simple Fresnel equations to non-specular surfaces. On the other hand, reflectometry utilizing integrating spheres provides a measurement of the hemispherical spectral reflectance, from which the normal spectral emissivity can be derived. ISR provides data on spectral-normal-hemispherical reflectance and, hence, normal spectral emissivity for a variety of surfaces. However, the resulting errors are minimal when both the sample and the reference have a similar bidirectional reflectance distribution function (BRDF). In an effort to explore the limits of polarimetry in terms of surface roughness, room temperature measurements on the same samples with various degrees of roughness were performed using both ISR and a laser polarimeter. In this paper the two methods are briefly described and the results of the comparison are discussed.

Keywords: emissivity; integrating sphere; laser polarimetry; reflectometry; rough surfaces; roughness

Document Type: Research article

Affiliations: 1: Los Alamos National Laboratory, Physics Division (P-23), MS H803, Los Alamos, New Mexico 87545, U.S.A., Email: seif@lanl.gov 2: Los Alamos National Laboratory, Physics Division (P-23), MS H803, Los Alamos, New Mexico 87545, U.S.A.

AZ Technology Optical Properties Instrumentation

AZ Technology is an industry leader in measuring the Optical Properties of materials.

All measurements are made with the finest instruments on the market. AZ Technology specializes in the measurement of solar absorption,emittance, reflectance, and transmittance.

Optical properties measurements are made with the following instruments:

SpectraFIRE

The SpectraFIRE measures near normal reflectance directly and the emittance is calculated from the reflectance measurements. SpectraFIRE has the following specification:

Wavelength:
32 wave numbers (cm-1); selectable down to 4 cm-1.

Reflectance Repeatability:
2.5 - 16um± 1%
16 - 25um± 1.5%
25 - 40um± 2%

Spectral Resolution:
2.5 to > 40um

LPSR 200IR
The LPSR 200IR measures total hemispherical spectral reflectance directly and solar absorption, transmittance, or emittance is calculated from the reflectance measurements.The LPSR 200IR has the following specification:

Wavelength:
250 to 2800nm

Spectral Resolution with Automatic Slit Control:
250-2500nm better than 5% of wavelength
2500-2800nm better than 8% of wavelength

Repeatability:
250 to 2500nm±1%
2500 to 2800nm - ±2%

AZ Technology Corporation
7047 Old Madison Pike, Suite 300
Huntsville, AL 35806 USA

Tel: +1 256.837.9877

FAX: +1 256.837.1155

ASTM E307-72(2002)

ASTM E307-72(2002):

Standard Test Method for Normal Spectral Emittance at Elevated Temperatures

Developed by Subcommittee: E21.04

Book of Standards Volume: 15.03
"1. Scope

"1.1 This test method describes a highly accurate technique for measuring the normal spectral emittance of electrically conducting materials or materials with electrically conducting substrates, in the temperature range from 600 to 1400 K, and at wavelengths from 1 to 35 ?m.

"1.2 The test method requires expensive equipment and rather elaborate precautions, but produces data that are accurate to within a few percent. It is suitable for research laboratories where the highest precision and accuracy are desired, but is not recommended for routine production or acceptance testing. However, because of its high accuracy this test method can be used as a referee method to be applied to production and acceptance testing in cases of dispute.

"1.3 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only.

"1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use."

STANDARDIZATION OF THERMAL EMITTANCE MEASUREMENTS. PART 5

Title: STANDARDIZATION OF THERMAL EMITTANCE MEASUREMENTS. PART 5. NORMAL SPECTRAL EMITTANCE, 800-1400 K (ABSTRACT BELOW)
DOWNLOAD FULL REPORT IN PDF FORMAT


Corporate Author : NATIONAL BUREAU OF STANDARDS GAITHERSBURG MD

Personal Author(s) : Harrison, William N. ; Richmond, Joseph C. ; Shorten, Frederick J. ; Joseph, Horace M.

Handle / proxy Url : http://handle.dtic.mil/100.2/AD426846

Report Date : NOV 1963

Pagination or Media Count : 99

Abstract: Equipment and procedures were developed to measure normal spectral emittance of specimens that can be heated by passing a current through them, at temperatures in the range of 800 to 1400 K, and over the wavelength range of 1 to 15 microns. A data-processing attachment for the normal spectral emittance equipment was designed to (1) automatically correct the measured emittance for '100% line' and 'zero line' errors on the basis of previously-recorded calibration tests; (2) record the corrected spectral emittance values and wavelengths at preselected wavelength intervals on punched paper tape in form suitable for direct entry into an electronic digital computer; and (3) to compute during a spectral emittance test on a specimen the total normal emittance, or absorptance for radiant energy of any known spectral distribution of flux, of the specimen. Working standards of normal spectral emittance having low, intermediate and high emittance values, respectively, were prepared and calibrated for use in other laboratories to check the operation of equipment and procedures used for measuring normal spectral emittance.

Spectral Emittance...Ash-Like Deposits

Spectral Emittance of Particulate Ash-Like Deposits: Theoretical Predictions Compared to Experimental Measurement, Journal of Heat Transfer -- April 2004 -- Volume 126, Issue 2, pp. 286-289

S. P. Bhattacharya

Cooperative Research Centre for Clean Power from Lignite, 8/677 Springvale Road, Mulgrave, Victoria 3170, Australia
(Received September 11, 2002; revised July 1, 2003)

From  the Abstract: "This note presents results of a theoretical and experimental investigation on the emittance of particulate deposits."

Source Abstract

Cool Roofing Samples (Emittance)

The Heat Island Group at Lawrence Berkeley National Laboratory, Berkeley, CA have measured solar reflectance of roofing samples with an UV-VIS-NIR Spectrometer with an integrating sphere and they measured the spectral emittance of the samples with a FTIR Spectral Emissometer. The following writeup and graphs are from their webpageat eetd.lbl.gov/HeatIsland/CoolRoofs/Samples.html


"Below are examples of complete reflectance and emittance data for several metal roofing samples made of cool roofing materials. These measurements show examples of complete laboratory information needed to determine radiative heat exchange by a roof which, in turn, can be used to estimate peak roof temperatures.

"The spectral solar reflectance is the total reflectance (diffuse and specular) as a function of wavelength, across the solar spectrum (wavelengths of 0.3 to 2.5 µm). It is used to compute the overall solar reflectance, using a standard solar spectrum as a weighting function. It also contains the information in the visual range (0.4 to 0.7 µm) which is sufficient to compute the color coordinates for color matching with other materials.

"The spectral thermal emittance (the graphs on the right) contains the information for computing the overall thermal emittance, using a blackbody curve as the weighting function. The spectral range is about 5 to 40 µm. If the spectral thermal emittance is approximately a horizontal line (a "gray" body), then the overall emittance is adequate for computing longwave radiative radiative exchange between the roof and the atmosphere. If the spectral thermal emittance deviates markedly from a horizonal line, then the details of the spectral emittance and the atmospheric emittance are necessary for a complete computation.

Note that the hunter green sample (middle graph) looks green to the eye because of the reflectance "bump" at 0.5 µm. The average solar reflectance, at 0.086, is almost as low as black (zero).""The burgundy sample (bottom graph) looks red due to the increase in reflectance near 0.7 µm. The visible reflectance is only about 0.1, but the relatively high reflectance in the near infrared (0.7 to 2.5 µm) yields an overall solar reflectance of 0.226."The emittance for all these samples is roughly 0.9, with an abrupt fall-off near 6 µm. Link to: Roof Heat Transfer > Emittance"

"

Galvalume (top graph), due to the inclusion of aluminum metal in the zinc anti-corrosion coating, is more reflective to sunlight than traditional galvanized steel which has a solar reflectance around 0.5.A further coating, with a clean acrylic material (low graph), can be used to raise the infrared emittance without significantly changing the solar reflectance.

Emissivity Tips at IRINFO.ORG

For your reference, there are several that deal with emittance that may be of interest to you.

For your convenience, they are on the IRINFO.org web pages at the following links:

www.irinfo.org/tip_of_week_2004.html#t02092004

www.irinfo.org/tip_of_week_2004.html#t04052004

www.irinfo.org/tip_of_week_2003.html#t09292003

www.irinfo.org/tip_of_week_2004.html#t08022004

www.irinfo.org/tip_of_week_2005.html#t09122005

www.irinfo.org/tip_of_week_2005.html#t09192005

www.irinfo.org/tip_of_week_2005.html#t09262005

<a href="http://www.irinfo.org/tip_of_week_2007.html#t05282007" title="http://www.irinfo.org/tip_of_week_2007.html" target="_blank">www.irinfo.org/tip_of_week_2007.html#t05282007

Enjoy!

Emissivity and Optical Properties of UO(2)

Emissivity and Optical Properties of UO₂

• Discussion of Data Assessment/Analysis


• References

Tabulated Values:

• Table 1: Normal Spectral Emissivity of Premelted UO₂ at a Wavelength of 630 nm


• Table 2: Normal Spectral Emissivity of Liquid UO₂ at a Wavelength of 630 nm

Graphs:

• Fig. 1: UO₂ Emissivity


• Fig. 2: Average Refractive Index of UO₂


• Fig. 3: Average Refractive Index of UO₂ from Measurements of Bober et al.


• Fig. 4: Average UO₂ Absorption coefficient from Measurements of Bober et al.

NASA Tech Reports Emittance Abstracts

A Search on the NASA website results in the following abstracts






DETERMINATION OF THE EMISSIVITY OF MATERIALS

Author(s): Askwyth, W. H.
Abstract: Space power systems - emissivity of candidate materials for snap-8 powerplant
NASA Center: NASA (non Center Specific)
Publication Year: 1962
Added to NTRS: 2006-11-06
Accession Number: 63N11697; Document ID: 19630001823; Report Number: PWA-2088





Determination of emissivity of materials quarterly progress report, 1 jul. - 30 sep. 1962

Author(s): Askwyth, W. H.; Hayes, R. J.
Abstract: No Abstract Available
NASA Center: NASA (non Center Specific)
Publication Year: 1962
Added to NTRS: 2006-11-06
Accession Number: 67N83465; Document ID: 19670084086; Report Number: NASA-CR-83756, PWA-2128





EMITTANCE OF MATERIALS SUITABLE FOR USE AS SPACECRAFT RADIATOR COATINGS

Author(s): Askwyth, W. H.; Hayes, R. J.; Mikk, G.
Abstract: Emittance measurements of materials suitable for spacecraft radiator coatings
NASA Center: NASA (non Center Specific)
Publication Year: 1963
Added to NTRS: 2006-11-06
Accession Number: 63A24987; Document ID: 19630028928





Measurement of spectral normal emittance of materials under simulated spacecraft powerplant operating conditions

Author(s): Askwyth, W. H.; House, R. D.; Lyons, G. J.
Abstract: Spectral normal emittance of materials under simulated space environment
NASA Center: NASA (non Center Specific)
Publication Year: 1963
Added to NTRS: 2006-11-06
Accession Number: 64N10959; Document ID: 19640001050





THE EMITTANCE OF MATERIALS SUITABLE FOR USE AS SPACECRAFT RADIATOR COATINGS

Author(s): Askwyth, W. H.; Hayes, R. J.; Mikk, G.
Abstract: Emittance of materials suitable for use as spacecraft radiator coatings
NASA Center: NASA (non Center Specific)
Publication Year: 1962
Added to NTRS: 2006-11-06
Accession Number: 63N10264; Document ID: 19630000390; Report Number: ARS PAPER-2538-62





THE EMITTANCE OF MATERIALS SUITABLE FOR USE AS SPACECRAFT RADIATOR COATINGS

Author(s): Askwyth, W. H.; Hayes, R. J.; Mikk, G.
Abstract: Measurements of total hemispherical emittance for materials suitable for high-temperature spacecraft radiation coatings
NASA Center: NASA (non Center Specific)
Publication Year: 1962
Added to NTRS: 2006-11-06
Accession Number: 63A11692; Document ID: 19630015633; Report Number: ARS PAPER 62-2538





A SIMPLE TECHNIQUE FOR DETERMINING TOTAL HEMISPHERICAL EMITTANCE BY COMPARING TEMPERATURE DROPS ALONG COATED FINS

Author(s): Askwyth, W. H.; Curry, R.; Lundberg, W. R.
Abstract: Determination of total hemispherical emittance by comparing temperature drops along coated fins
NASA Center: NASA (non Center Specific)
Publication Year: 1962
Added to NTRS: 2006-11-06
Accession Number: 62N17085; Document ID: 19620007085





Measurement of total hemispherical emittance of structural materials and coatings under simulated spacecraft conditions

Author(s): Askwyth, W. H.; Mikk, G.
Abstract: Hemispherical emittance of structural materials and amp coatings under simulated spacecraft conditions over wide temperature range
NASA Center: NASA (non Center Specific)
Publication Year: 1963
Added to NTRS: 2006-11-06
Accession Number: 64N10962; Document ID: 19640001053





Determination of the emissivity of materials

Author(s): Askwyth, W. H.; Hayes, R. J.; House, R. D.; Mikk, G.
Abstract: No Abstract Available
NASA Center: NASA (non Center Specific)
Publication Year: 1962
Added to NTRS: 2004-11-03
Accession Number: 76N78693; Document ID: 19760073652; Report Number: NASA-CR-148751, PWA-2206(VOL.1)





Determination of the emissivity of materials

Author(s): Askwyth, W. H.
Abstract: No Abstract Available
NASA Center: NASA (non Center Specific)
Publication Year: 1961
Added to NTRS: 2004-11-03
Accession Number: 82N70372; Document ID: 19820065104; Report Number: NASA-CR-164941, PWA-2043

Measurement of spectral emissivity of samples, coatings and infrared sources

A reference laboratory for calibration of infrared instruments was established at Risø, Denmark in 1996.

The following services are offered for customers:

• calibration service of infrared thermometers and calibration sources;


• calibration of FTIR spectrometers and advanced infrared instrumentation;


• measurement of spectral emissivity of samples, coatings and infrared sources;


• consultative service and information.

An introduction to non-contact measurement of temperature is given in the report "Measurement of Temperature by Means of Infrared Instruments", Risø-R-862(DA).

The report (in Danish) is available on request.

Risø National Laboratory
Technical University of Denmark – DTU
Frederiksborgvej 399 · P.O. 49 · DK-4000 Roskilde ·
Tel: +45 4677 4677
Fax: +45 4677 5688
Email: risoe@risoe.dk
EAN: 5798000416611 · CVR: DK42154113

Optical Properties Measurements, Data and 3D Models

Surface Optics Corporation (SOC) operates a world-class measurement facility equipped for the most demanding spectral measurement tasks for spectral directional and bidirectional reflectance measurements for modeling, simulation, special effects and more.

Spectral measurements can be made in wavelength regions from the ultraviolet to long wave infrared and include one or all of the following types of reflectance measurements:

Directional or hemispheric reflectance: the fraction of the light incident on a sample at a given angle that is reflected back into the hemisphere.

Bidirectional Reflectance Distribution Function (BRDF): the distribution of light, described as a function of two angles, reflected back into the hemisphere from light incident at a given angle on a sample.

Monostatic Bidirectional Reflectance(enhanced backscatter measurement): a small portion of the BRDF measured at the direct backscattered angle using a laser interferometric reflectometer.

SOC also develops and expands on its off-the-shelf library of optical properties data for a variety of materials. This library can be purchased in whole or in part at considerable savings over the cost of individual measurements.

For more information on our database and its contents contact SOC.

You can also download the Optical Properties Database brochure.

A list of FAQs regarding the database, and information on using the databases in 3D sensor simulation.

1. Spectral Reflectance Data for (52) rocks, (29) soils, (28) vegetation types, (41) construction materials, (38) paints, and (12) fabrics from 0.3 to 25 microns.


2. Hemispherical, Directional, Diffuse and Specular


3. Surface temperatures versus time-of-day, climate and orientation


4. Complete solution for visual and infrared radiance simulation.

3D Models for Sensor Simulation

SOC is constantly developing computationally efficient polygonal models for accurate sensor simulation.

Unlike visual simulation models, sensor models require an intimate understanding of the physical nature and physics responsible for the signature of an object.

SOC's extensive background in both Infrared and Radar sensor simulation and analysis is incorporated into all of our 3D models.

Evaluating Emittance in the Lab or Field

NASA Portable Infrared Reflectometer Designed and Manufactured

The optical properties of materials play a key role in spacecraft thermal control. In space, radiant heat transfer is the only mode of heat transfer that can reject heat from a spacecraft.

One of the key properties for defining radiant heat transfer is emittance, a measure of how efficiently a surface can reject heat in comparison to a perfect black body emitter.

Heat rejection occurs in the infrared region of the spectrum, nominally in the range of 2 to 25 micrometer.

To calculate emittance, one obtains the reflectance over this spectral range, calculates spectral absorptance by difference, and then uses Kirchhoff’s Law and the Stefan-Boltzmann equation to calculate emittance.

Portable infrared reflectometer for evaluating emittance. Photo from NASA

A portable infrared reflectometer, the SOC–400t, was designed and manufactured to evaluate the emittance of surfaces and coatings in the laboratory or in the field.

It was developed by Surface Optics Corporation under a contract with the NASA Glenn Research Center at Lewis Field to replace the Center’s aging Gier-Dunkle DB–100 infrared reflectometer.

The specifications for the new instrument include a wavelength range of 2 to 25 micrometer; reflectance repeatability of ±1 percent; self-calibrating, near-normal spectral reflectance measurements; a full scan measurement time of 3.5 min, a sample size of 1.27 cm (0.5 in.); a spectral resolution selectable from 4, 8, 16, or 32 cm^–1; and optical property characterization utilizing an automatic integration to calculate total emittance in a selectable temperature range.

The computer specified to drive the software is a laptop with a menu-driven operating system for setup and operation, a full data base manager, and a full data analysis capability through MIDAC Grams/32 software (MIDAC Corporation, Irvine, California).

Spectral scanning is achieved through the use of a Fourier Transform Infrared (FTIR) Michelson interferometer. In addition, the reflectometer’s size and weight make it conducive to portable operation.

Although most of the planned uses for the instrument are expected to be in the laboratory, some field operations are anticipated. The only requirement for field operation is a source of power (115 V alternating current).

NASA Glenn took delivery of this world-unique, portable infrared reflectometer in January 1999. It is a resounding success, and an evaluation of thermal control materials for NASA and aerospace customers is currently underway.

Find out more about this research.

Glenn contact: Dr. Donald A. Jaworske, (216) 433–2312, Donald.A.Jaworske@grc.nasa.gov

Author: Dr. Donald A. Jaworske

Headquarters program office: OSS (ATMS)

Programs/Projects: Space Power, ISS, Aerospace Industry

Journal of the Atmospheric Sciences

Article: pp. 1459–1472 | Abstract | PDF (1.02M)

Infrared Emittance of Water Clouds

Petr Chýlek^a, Peter Damiano^a, and Eric P. Shettle^b

a. Atmospheric Science Program, Department of Physics and Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada
b. Optical Sciences Division, Naval Research Laboratory, Washington, D.C.

Chýlek, P., P. Damiano, and E.P. Shettle, 1992: Infrared Emittance of Water Clouds. J. Atmos. Sci., 49, 1459–1472.

ABSTRACT

A simple approximation has been developed for the infrared emittance of clouds composed of water spheres based on the absorption approximation for the emittance and on the polynomial approximation to the Mie absorption efficiency. The expression for the IR emittance is obtained in a simple analytical form as a function of the liquid water content and two size distribution parameters, namely, the effective radius and effective variance. The approximation is suitable for numerical weather prediction, climate modeling, and radiative transfer calculations. The accuracy, when compared to the exact Mie calculation and integration over the size distribution, is within a few percent, while the required computer time is reduced by several orders of magnitude. In the limit of small droplet sizes, the derived IR emittance reduces to a term proportional to the liquid water content.

18 Emissivity FAQs at evitherm

Emissivity & other infrared-optical properties FAQs at the evitherm website,
evitherm is the European Virtual Institute for Thermal Metrology

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Click on the number below for an answer on the evitherm website...

C1. What is the emissivity of a surface?
C2. Why is emissivity important?
C3. How is emissivity used?
C4. Is it easy to measure emissivity?
C5. Is it possible to predict or calculate emissivity?
C6. What type of emissivity should I use for my application: total emissivity or spectral emissivity?
C7. What is the emissivity of painted metal surfaces and how does it depend on layer thickness?
C8. Which surfaces behave like a grey body?
C9. What is the emissivity of a layer of gas?
C10. Where can I find information on the emissivity of a given surface?
C11.How can I measure the emissivity of a surface using an IR-thermometer?
C12. What is the difference between emissivity and emittance?
C13. What is a radiant barrier?
C14. What is a low-e coating?
C15. What is low-e glass?
C16. What is a selective absorber?
C17. Is a knowledge of emissivity important for contactless temperature measurements?
C18. What is infrared thermography?

Furnace radiation modelling

Furnace radiation modeling

Location: Industrial Research Limited (IRL): Measurement Standards Laboratory of New Zealand
Their Client: New Zealand Refining Company
The Topic: Infrared radiation thermometry for furnace tube temperature measurement
Client benefit: High quality measurement leads to better plant control, reduced risk and increased profitability

Most of this article is from the writeup on the IRL website.

Industrial Research undertook furnace radiation modeling for the New Zealand Refining Company which operates several large furnaces in many stages of the production of gasoline (Also known around the world variously as "petrol" and "benzene").

Thermal infrared radiation thermometry, or IR Thermometry, is the only feasible method for obtaining temperature measurements of many furnaces and the process tubes within.

The technology is not new, it was known that the measurements suffer from errors stemming from several environmental factors such as reflection of background thermal radiation and absorption and emission of the emitted & reflected radiation (from the surfaces being measured, by furnace gases.

Variations in the spectral emissivity and reflectivity of the materials comprising the surfaces being measured also influence the resulting temperature measurements.

The New Zealand Refining Company used the knowledge and background offered by Industrial Research's Measurement Standards Laboratory in furnace radiation modelling to obtain more accurate measurements.

The service gave increased confidence that safe and efficient operating parameters were being maintained. As a result, the plant can operate more efficiently through the operators being able to better predict plant life and tube life.

Inconel, Inconel-X and Type 347 SS

Effects of Preoxidation Treatments on Spectral Normal and Total Normal Emittance of Inconel, Inconel-X and Type 347 Stainless Steel


Authors: Wayne S. Slemp; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CENTER


Abstract:

The spectral/normal-emittance values of several oxidized surfaces prepared by varying the preoxidation treatments or oxidation time for inconel, Inconel-X, and type 347 stainless steel were determined at temperatures of 900, 1,200, l,500, and 1,800 F over a wavelength range of 1 to l5 microns. Polishing, grit blasting, etching, or combinations of these preparations were used as preoxidation treatments. These values were compared for 900 and 1,800 F to determine the effects of these treatments on the spectral-normal-emittance values. Significant effects of preoxidation treatments and oxidation times on the spectral normal emittances of oxidized inconel, Inconel-X, and type 3k7 stainless steel are presented. In general, if a grit-blasted surface is etched before being oxidized, the final oxidized surface will have a lower emittance but will be more adherent and uniform. Of the two types of grit used in this study, the coarser grit provided the higher emittance. Polishing provided the lowest emittance of all specimens tested. In the one set of tests in which oxidation time was varied (on the inconel specimens), increasing oxidation time increased the emittance; however, increasing the time beyond 2 hours produced no further effect.

NIST IR Spectral Emittance Lab

The Optical Properties measurements laboratory at The USA National Institute of Standards & Technology (NIST), a part of the Optical Technology Division of the PHYSICS Laboratory has been developing a full spectral emissivity (emittance) measurement capability.

This facility enables the measurement of spectral emittance using the direct method of radiance comparison of the sample with a blackbody reference source. Spectral emissivity is a key physical property in the determination of radiation transfer and balance.

Numerous industrial and scientific applications, such as remote sensing and single- and multi-band pyrometry, require its accurate determination.

_{Layout of the NIST Setup for Direct and Indirect Infrared Spectral Emittance Measurements}

The sample emittance is determined through a series of measurement steps. The first step is a measurement of the sample’s hemispherical-directional reflectance at the measurement temperature and at a single wavelength matched to the filter radiometer. A diode laser or broadband source input to the integrating sphere, is selected based on the temperature and rough emittance value of the sample. The reflectance is obtained via comparison to a calibrated standard.

The second step is a relative radiance measurement of the sample to a blackbody at the same wavelength. The integrating sphere is removed for the second step. The temperature is then calculated from the results of these two steps. This procedure has the benefit of obtaining the temperature of the sample from the region on the sample identical to that for which the infrared spectral emittance is measured. It also makes use of the steep short wavelength edge of the Planck function for sensitive (and higher accuracy) temperature measurement.

Finally, the Fourier transform infrared spectrometer is used to compare the sample spectral radiance to that of the reference blackbody source as a ratio, and the sample emittance is obtained from the ratio and Planck’s Law using the sample and blackbody temperatures.

Alternatively, spectral directional emittance can be determined indirectly from reflectance and transmittance measurements described in Infrared Spectrophotometry. These capabilities have limits of temperature, measurement geometry and sample type.
Specifications / Capabilities:

The facility consists of a set of reference blackbody sources mounted on a motorized stage for selection; interchangeable sample heater/mounts on motorized translation and rotation stages; a removable visible/near-infrared integrating sphere for measuring the sample temperature above 500 K; low scatter interface optics to image the 3 mm to 5 mm central region of the sample or blackbody source onto a water cooled field stop; the field stop is re-imaged onto either a Fourier transform spectrophotometer equipped with beamsplitters and detectors to cover a spectral range from the visible through the far infrared or a set of filter radiometers mounted on a motorized translation stage for temperature scale transfer between the blackbody sources and for sample temperature determination (together with the integrating sphere); a sectored purge enclosure for the entire beam path; electrical supply, signal, purge gas (Ar, or N2), and cooling water subsystems; control of system elements and data processing via several PC computers using LabView software programs.

Each blackbody contains calibrated platinum resistance thermometer (PRT) or thermocouple (TC) temperature sensors. These are used to control and monitor changes in the blackbody temperature. For absolute temperature determination, two fixed point BB furnaces with interchangeable crucibles (containing Ag, Al, Zn, Sn and In) are used.

Filter radiometers (with filters at 650 nm, 900 nm, 1550 nm, and 2400 nm) are used to transfer the scale from the fixed points to 4 variable temperature blackbody’s covering a temperature range of 250 K to 1400 K. The spectral emissivities of the blackbodies have been calculated using a Monte Carlo ray tracing algorithm with input of the measured spectral reflectance of the cavity wall materials or coatings.

Associated Programs/Projects:

Infrared optical properties of materials and components
Fourier transform infrared spectrometer (FTIS) facility

Selected Publications

Infrared Spectral Emissivity Characterization Facility at NIST, L.M. Hanssen, S.N. Mekhontsev, and V.B. Khromchenko,Proc. SPIE 5405, 112 (2004).

Temperature-Resolved Infrared Spectral Normal Emissivity of SiC and Pt-10Rh for Temperatures up to 900 C

Use of a High Temperature Integrating Sphere Reflectometer for Surface Temperature Measurements, L.M. Hanssen, M. Noorma, A.V. Prokhorov, S.N. Mekhontsev, and C.P. Cagran, Intl. J. Thermophysical Prop.

Beginner's Guide to (Spectral) Emissivity

Introductory Guide to Emissivity

This is an introductory page on the National Physical Laboratory (NPL) website in the UK.

It has several such sketches as on the left showing the concept of the "radiometric method" of emissivity measurement and discusses both the concepts and measurement methods used to quantify spectral and total emissivity values.

The page also features links to other resource materials on the subject and a list of reference books.

Red, White & Blue Blackbodies?

It is not an oxymoron, nor a quote from Yogi Berra.

Real Blackbodies do not exist, at least on Earth. Only approximations or simulations are real. We use them to calibrate IR Thermometers, Radiation Pyrometers and Thermal Imagers.

Technically they should have a spectral emissivity very close to 1.0. How close, you might ask? Read on.
Max Planck needed the concept of a perfect absorber of electromagnetic, thermal radiation to develop his theory of Thermal Emission of Radiation in 1899. Fortunately, Gustav Kirchhoff had already develped the foundation for them forty years earlier.

A perfect blackbody is perfectly absorbing to all the thermal radiation incident upon it. For that reason it had, necessarily, to be opaque and non-reflecting.

By logical reasoning, it was also clear that the same device had to be a perfect emitter of thermal radiation related to its absolute temperature, that is, temperature on the Absolute or Kelvin Temperature Scale.

There are several radiation equations or "Laws" that have been developed to describe the physics of thermal emission properties. They are well explained in a number of texts and shown in some detail in the online Hyper Physics website.

In an online Java applet, one can see visually also the three main radiation laws in graphic action; the temperature on the screen is shown on a column in a thermometer on the right side, and you can change it by clicking and/or dragging on it with your mouse.

If someone asks about the color of a blackbody, you can always refer them to this great set of webpages by Mitchell Charity at MIT.
They show both the temperature from 1000 K to 29,800 K (of course below about 700 K blackbodies actually look black to the human eye) . As can be seen on this page, red, white and blue blackbodies are possible!

There aren't many 29,800 K blackbodies on Earth, but astronomers & AstroPhysicists see them all the time. How do you think they measure the temperatures of stars?

So, now you know, there can be both Red and Blue Blackbodies!

The devices used by calibration laboratories to calibrate and check the calibration of IR Thermometers, Radiation Thermometers and Infrared Thermal Imagers are not perfect (and seldom Blue, but often appearing Black, Red, Orange, Yellow and even White), but they can be very close to perfect.

The closer to perfection, the higher the cost of them also.

A blackbody having a spectral emissivity of 0.99 would have, at best, an error of about ± 1% in emitted thermal radiation or radiance, at a stable operating temperature and could be used to calibrate Infrared Thermometers.

The thermometers would be limited in their calibration uncertainty, since the radiance they emit would be uncertain to at least ± 1%.

Depending upon the radiance to temperature relationship for the temperature in question, that could mean a bigger or smaller effective temperature calibration uncertainty that could be assigned to a thermometer being calibrated.

That's another issue for another time, but , if you can't wait, one of the best explanations (and a lot more) that we have seen on that subject is in a 547 KB, downloadable PDF file from Land Instruments.

Effects of atmosphere, temperature and emittance on reflected and emitted energy

A NASA report by R. Kumar, dated Sep 1, 1977, available online and downloadable as a PDF document.

ABSTRACT:

The effects of temperature and emittance on the relative magnitude of reflected energy and emitter energy from a target including atmospheric effects was studied. From the calculations of energy reflected and emitted from a target including atmospheric effects using LOWTRAN 3 programs for midlatitude summer model, the following conclusions were obtained (1) At 3.5 micrometers q is considerably less than 1 except at high temperatures and for high emittance (2) at 4 micrometers q is of the order of magnitude equal to 1 for most targets and (3) at 4.6 micrometers, q is considerably greater than 1 at high temperatures and high emittance. In addition, incident atmospheric emission reflected from the target was found to be negligible except for targets having low temperature and low emittance.

New System for Spectral Emissivity Measurements & Spectral Emissivity of Metals at the University of Duisburg

On the 13-15 June, 2001, in Budapest, Hungary, the 12th International Conference on Thermal Measurements and Thermogrammery (THERMO) was held.

Among the papers were two by Prof. Dr.-Ing. W. Bauer, Dipl.-Phys., A. Moldenhauer, Dipl.-Phys. & M. Rink of the Gerhard Mercator Universität Duisburg, Germany

The first presentation was entitled:

"New System for Spectral Emissivity Measurements at the University of Duisburg"

(Click on the link to access the Abstract in PDF Format)

The second was:

"Spectral emissivities of metals dependent on heat-treating processes".

(Click on the link to access the Abstract in PDF Format)

Other papers by the members of the Duisburg Universitat have their abstracts listed on this Conference information page, also.

Contacts for more information are:

Prof. Dr. Ing. W. Bauer, Gerhard-Mercator-Universität, Duisburg, Germany

Fachbereich 8, Fachgebiet Energieeinsatz(Germany)
47048 Duisburg
Tel.: +49 203/379-3629
Fax.: +49 203/379-3464

Prof. Dr. Ing. W. Bauer

Email: bauer [at] ihg.uni-duisburg.de

and

Thomas Funke Dipl.-Ing.


Email: Thomas.Funke [at] uni-duisburg.de

Homepage: www.ihg.uni-duisburg.de/energieeinsatz/

Spectral and Total Emissivity Measurement Services at Near Ambient Temperatures

The National Physical Laboratory in The UK offers a title="Emissivity Measurement Service -PDF Downloadable Brochure" target="_blank">spectral emissivity measurment service (downloadable brochure - PDF 284kb) through its Infrared Optical Spectroscopy group to measure the spectral emissivity as needed by customers.

They also offer related calibration measurement services on their webpage as stated below:

"Optical Properties of Materials Measurement Service offers calibrations in the areas of Spectrophotmetry (reflectance and transmittance measurements, colorimetry, measurement of appearance) and Infrared Spectrometric Measurements (reflectance and transmittance measurement)"

On another webpage they repeat much of what's in the downloadable document above and provide both equations and an informative sketch to illustrate the various measurement parameters involved.

Additionally, they provide a list of related reference documents that support the technologies involved in the services. These are quoted below:

"CLARKE, F.J.J. Measurement of the radiometric properties of materials for building and aerospace applications. Proc. Soc. Photo-Opt. Instrum. Eng., 1980, 234, 40-47.

CLARKE, F J J, and LARKIN, J A. Measurement of total reflectance, transmittance and emissivity over the thermal IR spectrum. Infrared Physics, 1985, 25, 359-367.

CLARKE, F J J, and LARKIN, J A. Emissivity determined from hemispherical reflectance and transmittance throughout the thermal infrared spectrum. High Temp. - High Press., 1985, 17, 89-96.

CLARKE, F J J and LARKIN, J A. Improved techniques for the NPL hemispherical reflectometer. Proc. Soc. Photo-Opt. Instrum. Eng., 1988, 917, 7-14."

Modifying a Surface To a Known Emissivity for Temperature Measurement

One of the techniques to deal with emissivity problems taught to most beginning Infrared Thermographers and many using so-called spot radiation thermometers or IR Thermometers, is to modify the surface with unknown spectral emissivity to one with a known emissivity. While much of that information seems to get lost in "How-To" books and notes, the Infraspection Institute publishes Tips of the Week on their IR/INFO website, open and free to the public.

They have graciously given us permission to reprint some of their tips, especially those that deal with handling some of problems and solutions for dealing with emissivity. Here, verbatim, is their Tip of September 29, 2003 "Modifying a Surface for Temperature Measurement", with permission.

"Unknown emittance values are often the greatest error source when taking infrared temperature measurements. This error source can be eliminated by modifying a target with a material having a known E value.

"Some of the modifying materials that thermographers commonly use include flat-finish spray paint, PVC electrical tape, masking tape, and spray deodorants containing powder.

"Prior to modifying any surface:

• Make sure that it is safe to contact the subject equipment.


• Obtain permission to modify the surface from the end user.


• Ascertain that the selected modifying material will not melt, catch fire or emit toxic fumes when heated.

"Once you have determined it is safe to modify a surface, proceed as follows:

1. Place radiometer at desired location and distance from target. Aim and focus.

2. Measure and compensate for Reflected Temperature.

3. Apply a surface modifying material having a known E value on target making certain that material is in full contact with target and there are no air pockets. Modifying material should be larger than radiometer’s spot measurement size for the chosen distance from the target.

4. Enter E value of modifying material into radiometer’s E setting.

5. Measure temperature of modifying material once it has reached thermal equilibrium with target.

6. For greater accuracy, repeat measurement three times and average the results.

"For more information on the above technique, refer to the Infraspection Institute Guideline for Measuring and Compensating for Reflected Temperature, Emittance and Transmittance available from Infraspection Institute."

Measurements of the infrared emissivity of a wind-roughened sea surface

Measurements of the infrared emissivity of a wind-roughened sea surface, By Jennifer A. Hanafin and Peter J. Minnett, published in Applied Optics, Vol. 44, Issue 3, pp. 398-411, in 2005 is more properly cited as:

J. A. Hanafin and P. J. Minnett, "Measurements of the infrared emissivity of a wind-roughened sea surface," Appl. Opt. 44, 398-411 (2005)

And the abstract is available online also as: www.opticsinfobase.org/abstract.cfm?URI=ao-44-3-398

It shows that measurements in the 8-12µm waveband region of the sea surface at viewing angles of 55°, in typical at-sea conditions, could introduce introduce errors of up to 0.7 K in sea-surface temperature measurements.

To Quote:

"The emissivity was found to increase in magnitude with increasing wind speed, rather than decrease, as predicted by widely used parameterizations. Use of these parameterizations can cause significant bias in remote sensing of sea-surface temperature in noncalm conditions."

Measuring the spectral emissivity of rocks and the minerals that form them

Measuring the spectral emissivity of rocks and the minerals that form them, By Miroslav Danov, Dimitar Stoyanov, and Vitchko Tsanev.

It is an online paper at the SPIE news room website. The tagline for the paper reads:

"A new ground-based technique measures minerals in their natural conditions, a prerequisite for satellite data processing".

The paper discusses a new measurement technique that uses both a scanning FTIR spectrometer and a gold-plated hemispherical mirror and provides data from tests using limestone as the test subject material.

Several references are cited, as follows:

Jingmin Dai, Xinbei Wang, Guibin Yuan, Fourier transform spectrometer for spectral emissivity measurement in the temperature range between 60 and 1500°C, J. Phy. 13, pp. 63-66, 2005.

S. Fonti, Spectral emissivity as a tool for the interpretation of Martian data: A laboratory approach, 32nd Annual Lunar and Planetary Science Conference, no. 1279, pp. 12-16, 2001.

A. M. Baldridge, P. R. Christensen, A laboratory technique for thermal infrared measurement of hydrated samples, 38th Lunar and Planetary Science Conference, pp. 2407, 2007. Lunar and Planetary Science XXXVIII, held March 12-16, 2007 in League City, Texas. LPI Contribution No. 1338

Z. Wan, D. Ng, J. Dozier, Spectral emissivity measurements of land-surface materials and related radiative transfer simulations, Adv. Space Reg. 14, no. 3, pp. 91-94, 1994.

T. W. Stuhlinger, E. L. Dereniak, F. O. Bartell, Bidirectional reflectance distribution function of gold-plated sandpaper, Appl. Optics 20, no. 15/1, 1981.

ASU Thermal Emission Spectra of Silicate, Carbonate, Sulfate, Phosphate, Halide, and Oxide Minerals

The spectral library is hosted by the Mars Space Flight Facility at Arizona State University (ASU) consists of thermal infrared emission spectra (typically 2000 - 220 cm-1) of a variety of geologic materials.

It is open and free, but one needs to register with a valid email address and take the time to learn how to access the data and obtain plots. It is not a trivial task.

Each spectrum comes with descriptive information, sample quality, and a comments field that describes any appropriate, related information.

To quote from the introduction to the library about the sources of data:

"Emission spectra were acquired using a Nicolet Nexus 670 interferometric spectrometer equipped with a CsI beamsplitter and an uncooled deuterated triglycine sulfate (DTGS) detector; the spectral range of the instrument is from 2000 — 220 cm-1 (5 — ~45 microns). Both the spectrometer and the sample chamber/glovebox were continuously purged with nitrogen gas during sample analysis to minimize atmospheric H2O and CO2 which also have absorption features in the 2000-220 cm-1 region of the spectrum. The particulate samples were heated in an oven to 80°C to improve the signal to noise ratio during spectral analysis (this temperature is maintained during analysis by placement of the sample cup on a heater element). The samples were raised into a water-cooled sample chamber that closely approximates a blackbody cavity [Ruff et al., 1997]. A total of 270 scans at 2-cm-1 sampling were taken over ~7 minutes and averaged together by the spectrometer. In the case of a hand sample, active heating during measurement is not possible. Hand samples were taken directly from the oven and placed into the sample chamber and 180 scans were taken over a period of ~5 minutes to minimize the effects of sample cooling. The spectral calibration method is a variation of method 1 of Christensen and Harrison [1993] as described in detail by Ruff et al., [1997]."

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References cited above:

"Christensen, P.R., and S.T. Harrison, Thermal infrared emission spectroscopy of natural surfaces: Application to desert varnish coatings on rocks, J. Geophys. Res., 98 (B11), 19,819-19,834, 1993."Christensen, P.R., J.L. Bandfield, V.E. Hamilton, D.A. Howard, M.D. Lane, J.L. Piatek, S.W. Ruff, and W.L. Stefanov, A thermal emission spectral library of rock-forming minerals, J. Geophys. Res., 105,9735-9739, 2000. {ED NOTE: PDF DOWNLOAD}


"Feely, K.C. and P.R. Christensen, Quantitative compositional analysis using thermal emission spectroscopy: Application to igneous and metamorphic rocks, J. Geophys. Res., 104, 24195-24210, 1999.

"Lane, M.D. and P.R. Christensen, Thermal infrared emission spectroscopy of salt minerals predicted for Mars, Icarus, 135, 528-536, 1998.""Lane, M.D., Midinfrared emission spectroscopy of sulfate and sulfate-bearing minerals, American Mineralogist, in press, 2006.

"Ruff, S.W., P.R. Christensen, P.W. Barbera, and D.L. Anderson, Quantitative thermal emission spectroscopy of minerals: A laboratory technique for measurement and calibration, J. Geophys. Res., 102, 14,899-14,913, 1997."

Further reference publications related to the work at ASU may be viewed on the ASU website.

TES and Spectral Emissivity Curves: Quartz, Feldspar & Hornblende

This linked website discusses the background and flight of the instrument and also provides some interesting spectral emissivity curves for Quartz (SiO₂), Feldspar* and Hornblende** and an equal mixture of the two,

The TES instrument first flew aboard the Mars Observer spacecraft that was lost. The TES instrument was rebuilt and launched along with instruments aboard the new Mars Global Surveyor spacecraft.

The purpose of the TES device is to measure the spectral distribution of thermal infrared radiation emitted from Martian surfaces. The TES technique, can tell us much about the geology and atmosphere of Mars.

One can learn much about this method and the device by visiting the Arizona State University website pages that provide much more detail and background and reading through the TES News Archives.

[NOTE: The above curves actually exist on the Arizona State University website on their webpage address: http://tes.asu.edu/MARS_SURVEYOR/MGSTES/mixed_spec.gif]

The Thermal Emission Spectrometer is a scientific instrument and also Thermal Emission Spectroscopy is a measurement technique.

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* K-feldspar end member KAlSi₃O₈, Albite end member NaAlSi₃O₈ or Anorthite end member CaAl₂Si₂O according to the Wikipedia article on Feldspar.
** The general formula (for Hornblende) can be given as (Ca,Na)_2-3(Mg,Fe,Al)₅(Al,Si)₈O₂₂(OH,F)₂ , according to the Wikipedia article on Hornblende..

Radiometric Temperature: Concepts and Solutions

A downloadable (PDF Format) "Application Note" from the Santa Barbara Infrared website. It explains the relationship between emitted thermal radiation, reflected thermal radiation, emissivity and the wavelength region used by a measuring device. It provides several informative examples with figures and graphs.

It reads in part:

".. a 40°C blackbody in a 40°C room would require no correction. But a 40°C blackbody in a 25°C room would have a radiometric temperature of less than 40°C....
Note that this error will be wavelength dependent. ...the reflected energy will be a different fraction of the total flux in the 3-5? band than in the 8-12? band."

AFR's SPECTRAL EMISSOMETER MEASUREMENT SERVICE

Advanced Fuel Research, Inc. (AFR) offers a testing service using the SERIES 205 SPECTRAL EMISSOMETER at their Connecticut-based laboratories.The Series 205 Spectral Emissometer is an automated bench-top device that measures spectral emissivity over a broad spectral range while simultaneously determining the surface temperature at the measurement location.The bench top, FT-IR based instruments are designed specifically to facilitate simultaneous measurements of surface spectral emittance and temperature, radiance, directional-hemispherical reflection and transmission using optical techniques over the spectral range at temperatures ranging from 50° to 2000°C.

The systems provide measurements of over a wide spectral range from 12,500 to 500 cm-1 (0.8 to 20 microns) for the Model 205 WB, and from 6,000 to 500 cm-1 (1.7 to 20 microns) for the Model 205 NB.

If you have a need for Emissometer measurements, please contact them.

For More Information Contact:
James R. Markham, CEO
Advanced Fuel Research, Inc.
87 Church Street, East
Hartford, CT 06108 USA

Tel: +1 860-528-9806 ext.104
Fax: +1 860-528-0648

Modeling and Simulation of Emissivity of Silicon-Related Materials and Structures

by N.M. RAVINDRA,(1,5) KRSHNA RAVINDRA,(1,2) SUNDARESH MAHENDRA,(1,3) BHUSHAN SOPORI,(4) and ANTHONY T. FIORY(1)
1.—Department of Physics, New Jersey Institute of Technology, Newark, NJ 07102. 2.—Intern atNJIT from Union County Magnet High School, Scotch Plains, NJ 07076. 3.—Intern at NJIT fromMillburn High School, Millburn, NJ 07041. 4.—National Renewable Energy Laboratory, Golden, CO 80401. Journal of ELECTRONIC MATERIALS, Vol. 32, No. 10, 2003, (Downloadable PDF Format)

Abstract:

"A brief review of the models that have been proposed in the literature to simulate the emissivity of silicon-related materials and structures is presented. The models discussed in this paper include ray tracing, numerical, phenomenological, and semi-quantitative approaches. A semi-empirical model, known as Multi-Rad, based on the matrix method of multilayers is used to evaluate the reflectance, transmittance, and emittance for Si, SiO2/Si, Si3N4/SiO2/Si/SiO2/Si3N4(Hotliner), and separation by implantation of oxygen (SIMOX) wafers. The influence of doping concentration and dopant type as well as the effect of the angle of incidence on the radiative properties of silicon is examined. The results of these simulations lead to the following conclusions: (1) at least within the limitations of the Multi-Rad model, near the absorption edge, the radiative properties of Si are not affected significantly by the angle of incidence unless the angle is very steep; (2) at low temperatures, the emissivity of silicon shows complex structure as a function of wavelength; (3) for SiO2/Si, changes in emissivity are dominated by substrate effects; (4) Hotliner has peak transmittance at 1.25 ?m, and its emissivity is almost temperature independent; and (5) SIMOX exhibits significant changes in emissivity in the wavelength range of 1–20 um."

"SPECTRAL EMISSIVITY OF HIGHLY DOPED SILICON"

by Curt H. Liebert and Ralph D. Thomas, NASA Lewis Research Center (Downloadable PDF File), APRIL 1968.

SUMMARY
"Measurements were made at temperatures of 300°, 882', and 1074' K of the normal was doped with a r s e n i c spectral emissivity of opaque, highly doped silicon. The silicon and boron to electron carrier concentrations of 2. 2X101', 3. %lo1', and 8 . 5 ~ 1 0 ~ ' electrons per cubic centimeter and hole carrier concentrationsof 6. 2X101' and 1 . 4 ~ 1 0 holes per cubic centimeter. The 30 K emissivity data were obtained at wavelengths from 2.5 to 35 microns. The high temperature emissivities were measured from 3.5 to 1 4 . 8 microns. Carrier concentrations and direct-current resistivity of the silicon were also measured. The carrier concentrations were determined from Hall measurements made at 30 K. The direct-current resistivity was measured at temperatures from 30 to 1200' K. These quantities (among others) were used in analytical calculations of the emissivities. Agreement of the Hagan-Rubens theory with experiment was found at wavelengths greater than 12 microns and at 30 K. Good agreement of the free carrier absorption theory with experiment w a s achieved at all wavelengths and temperatures investigated. The free carrier absorption theory predicts the emissivity in terms of the index of of these quantities are presented. A refraction and the absorption index. The values comparison of the values of the absorption index obtained herein with those obtained from the literature showed good qualitative agreement."

Normal Spectral Emittance of Some Metals, Carbon and SiC

The "Emissivity" page on the FAR Associates website includes a discussion of their unique instrument along with graphs and some tables of spectral emissivity values are evidently all reproduced from the Thermophysical Properties of Matter, Vol. 7: Thermal Radiative Properties, Y.S. Touloukian and D.P. DeWitt, IFI/Plenum, New York, 1970.

These include curves for: Carbon (Graphite), Tungsten, Aluminum, Copper, Iridium, Iron, Molybdenum, Silicon Carbide, Stainless Steel and Titanium.

"Emissivity of silicon at elevated temperatures"

By P. J. Timans , Microelectronics Research Centre, Cavendish Laboratory, Cambridge University, Madingley Road, Cambridge CB3 0HE, United Kingdom Journal of Applied Physics -- November 15, 1993 -- Volume 74, Issue 10, pp. 6353-6364

The ASTER Spectral Library

The ASTER spectral library, is a compilation of almost 2000 spectra of natural and man made materials that is searchable by material. The search returns a list of materials that match your search criteria, you can see a scaled plot of the spectrum and the ancillary information information for the spectrum, you can also download the spectral data.

Data and (No. of samples) are: Minerals (1348), Rocks (244), Soils (58), Vegetation (4), Water, Snow & Ice (9), Man made materials (56), Lunar (17) and Meteorites (60)

Surface Spectral Emissivity Derived from MODIS Data

A downloadable PDF Format copy of a technical paper by Yan Chen, Sunny Sun-Mack, SAIC, Hampton, VA USA and Patrick Minnis, David F. Young, William L. Smith, Jr., Atmospheric Sciences, NASA Langley Research Center, Hampton, VA USA. A paper that was presented at SPIE's 3rd International Asia-Pacific Environmental Remote Sensing Symposium 2002: entitled Remote Sensing of the Atmosphere, Ocean, Environment, and Space, in Hangzhou, China, October 23-27, 2002.

ABSTRACT: "Surface emissivity is essential for many remote sensing applications including the retrieval of the surface skin temperature from satellite-based infrared measurements, determining thresholds for cloud detection and for estimating the emission of longwave radiation from the surface, an important component of the energy budget of the surface-atmosphere interface. In this paper, data from the Terra MODIS (MODerate-resolution Imaging Spectroradiometer) taken at 3.7, 8.5, 10.8, 12.0 ?m are used to simultaneously derive the skin temperature and the surface emissivities at the same wavelengths. The methodology uses separate measurements of the clear-sky temperatures that are determined by the CERES (Clouds and Earth's Radiant Energy System) scene classification in each channel during  the daytime and at night. The relationships between the various channels at night are used during the day when solar reflectance affects the 3.7-?m data. A set of simultaneous equations is then solved to derive the emissivities. Global results are derived from MODIS. Numerical weather analyses are used to provide soundings for correcting the observed radiances for atmospheric absorption. These results are verified and will be available for remote sensing applications."