• Spectral radiance scale realization
• Spectral irradiance scale realization
• Spectroradiometric source calibration services
• Calibration uncertainties
• How to request spectroradiometric source calibration services
• Groups supported by this calibration service
• References

Spectral Irradiance Measurements

1. A gold freezing point blackbody (reference standard) and the Planck radiation law are used to realize and disseminate the 1990 NIST Scales of Spectral Radiance and Spectral Irradiance.
   
   The Planck equation:
   
       (1)
   
       (2)

   where  =	wavelength in air [cm]
   =	Spectral emissivity = 1 for ideal blackbody
   c1L  =	first radiation constant in radiance form = c1 / = 1.191 043 x 10-12 [W · cm2]
   c2  =	second radiation constant = 1.4388 [cm · K]
   n  =	refractive index of air at 15 °C and 76 cm Hg using the Cauchy formula ( in Å)
   	1 + {2726.43 + [12.288 / (2 x 10-8)] + [0.3555 / (4 x 10-16)]} x 10-7
   =	1.000 28 for = 6553 Å

2. The radiance temperature of the gold-point transfer standard (GPTS) is determined by comparison to the gold point blackbody. A high stability vacuum lamp operated at approximately 1337.33 K is the gold-point transfer standard.
   
   
3. The radiance temperature of the working standard (WS) is determined by comparison to the gold-point transfer standard. A high stability vacuum lamp operated at approximately 1528 K is the working standard.
   
   
4. The FASCAL spectroradiometer is the transfer device used to compare the sources.
   
   
5. The transfer device is a CARY 14 spectroradiometer which uses a prism/grating double monochromator to select the bandpass. A photomultiplier tube with a quartz window and a S-20 spectral response is used in the DC mode for measurements from 200 nm to 900 nm. A lead sulfide photodiode is used the AC mode for measurements from 800 nm to 2400 nm. The spectral radiance spot size is a 0.6 mm by 0.8 mm rectangle.
   
   
6. The radiance temperature of the variable-temperature blackbody (VTBB), transfer standard, is determined by comparison to the working standard. The spectral radiance of the VTBB is calculated using Eq. (1). The blackbody operates between 900 K and 2700 K with a 2-mm diameter opening and an estimated emissivity of 0.999.
   
   
7. The spectral radiance of the test source from 225 nm to 2400 nm is determined by comparison to the variable-temperature blackbody.
   

1. An integrating sphere is used as the spectroradiometer input optics for spectral irradiance measurements. A barium sulfate (BaSO₄) coated sphere is used for the deuterium arc lamp measurements and a polytetrafluoroethylene (PTFE) coated sphere is used for the tungsten lamp measurements.
   
2. The spectral irradiance of the ISS is calculated by multiplying the spectral radiance of the ISS by a geometrical factor.
   
3. The spectral irradiance of the primary working standards (PWS) is determined by comparison to the ISS. A group of 1000-watt quartz-halogen lamps are the primary working standards.
   
4. For the spectral range from 250 nm to 2400 nm, the spectral irradiance of the test source is compared to the PWS.
   
5. The relative spectral irradiance of the deuterium working standards (D2WS) is determined by comparison to an argon mini-arc. A group of 30-watt deuterium arc lamps are the deuterium working standards.
   
6. For the spectral range from 200 nm to 240 nm, the spectral irradiance of the test source is compared to the D2WS.
   

NIST calibrates and issues a type 30A/T24/13 ribbon filament lamp with a mogul bi-post base.

Test No.	Measurement Description
39010C	Spectral Radiance Standard, Ribbon Filament Lamp (225 nm to 2400 nm)
39020C	Spectral Radiance Standard, Ribbon Filament Lamp (225 nm to 800 nm)
39030C	Spectral Radiance Standard, Ribbon Filament Lamp (650 nm to 2400 nm)

• NIST Calibration Services Users Guide and Fee Schedule

The expanded uncertainty (coverage factor k = 2) is a two standard deviation estimate.

Standard	Wavelength (nm)	Typical values	Relative Expanded Uncertainty
Ribbon filament lamp	225  250  350  655  900 1600 2400	5.5 W cm-3 sr-1 1.3 x 105 4.0 x 104	1.5 1.3 1.0 0.6 0.6 0.5 0.4
Quartz halogen lamp	250  350  655  900 1600 2400	0.2 W cm-3 170 40	1.8 1.1 0.9 1.1 1.4 4.4
Deuterium arc lamp	200 250 400	0.5 W cm-3 0.3 0.05	5.0 3.2 3.2

• Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results

1. Prepare a purchase order with the following:
• Company name and address
• Contact person's name and phone number.
• Billing address
• Service ID number requested (include range and points)
• Test fee
• Address to ship test item
• Return shipping instructions (prepay and add, COD, charge to account with shipper)
• the test fee does not include shipping costs
• customers are responsible for all shipping costs
• If no instructions are given, NIST will return the test item by common carrier, collect, and uninsured.


2. Send the purchase order to:

National Institute of Standards and Technology

Calibration Program

Building 820, Room 232

Gaithersburg, MD 20899-0001

 

Tel.: (301) 975-2002

FAX: (301) 869-3548

E-mail: calibrations@enh.nist.gov.



3. Send the test item(s) to:

   Charles Gibson

   NIST

   Building 221 / Room B208

   Gaithersburg, MD 20899-0001

    

   Tel.: (301) 975-2329

   FAX: (301) 869-5700

   E-mail: cgibson@nist.gov.

• Aerospace industry
• Lighting manufacturers
• Measurement equipment and other instrumentation manufacturers
• NASA
• National standards laboratories
• Photographic equipment manufacturers
• Research universities
• Solar UV monitoring community
• US military service calibration laboratories

Spectroradiometric Determination of the Freezing Temperature of Gold, K. D. Mielenz, R. D. Saunders and J. Shumaker, J. Res. Natl. Inst. Stand. Technol., Vol. 95 (Jan-Feb. 1990).

The International Temperature Scale of 1990 (ITS-90), H. Preston-Thomas, Metrologia 27, 2-310 (1990).

NBS Measurement Services: The NBS Photodetector Spectral Response Calibration Transfer Program,E. F. Zalewski, Natl. Bur. Stand. (U.S.), Spec. Publ. 250-17 (1988).

NBS Measurement Services: Spectral Irradiance Calibrations, J. H. Walker, R. D. Saunders, J. K. Jackson, and D. A. McSparron, Natl. Bur. Stand. (U.S.), Spec. Publ. 250-20 (Sept. 1987).

NBS Measurement Services: Spectral Radiance Calibrations, J. H. Walker, R. D. Saunders, and A. T. Hattenburg, Natl. Bur. Stand. (U.S.), Spec. Publ. 250-1 (Jan. 1987).

Spectral Response Self-Calibration and Interpolation of Silicon Photodiodes, J. Geist, E. F. Zalewski, and A. R. Schaefer, Appl. Opt. 20, 3795 (1980).

Spectral Irradiance Standard for the Ultraviolet: The Deuterium Lamp, R. D. Saunders, W. R. Ott, and J. M. Bridges, Appl. Opt. 17, 593 (1978).

The 1973 NBS Scale of Spectral Irradiance, R. D. Saunders and J. B. Shumaker, Natl. Bur. Stand. (U.S.), Tech. Note 594-13 (1977).

Spectral Radiometry: A New Approach Based on Electro-Optics, J. Geist, M. A. Lind, A. R. Schaefer, and E. F. Zalewski, Natl. Bur. Stand. (U.S.), Tech. Note 954 (1977).

Fundamental Principles of Absolute Radiometry and the Philosophy of This NBS Program (1968 to 1971), J. Geist, Natl. Bur. Stand. (U.S.), Tech. Note 594-1 (1972).

High-Accuracy Spectral Radiance Calibration of Tungsten-Strip Lamps, H. J. Kostkowski, D. E. Erminy, and A. T. Hattenburg, Adv. Geophys. 14, 111 (1970).