Detector-based transfer standards for improved accuracy in spectral irradiance and radiance measurements

Abstract

This paper discusses the performance of a range of new detector-based transfer standards for the dissemination of source-based scales. The transfer standards presented include both detector-stabilized and -monitored sources of spectral irradiance and radiance as well as a more radical absolute transfer standard spectrometer. The primary aim in developing the new transfer standards is to improve traceability and accuracy to the International System of Units (SI) while at the same time reducing the cost. Some generic remote-sensing applications are considered as examples.

A Status Overview of Earth Observation Calibration/Validation for Terrestrial Applications

“…Recent developments in detector-based radiometers used in metrology as calibration transfer standards show excellent promise toward reducing the number of steps in the traceability chain and reducing calibration uncertainties (Fox et al, 1997;Slater et ai., 1996).…”

“…The anisotropy of surface reflectance as a function of illumination and viewing geometry (see, for example, Gauthier et al, 1991;Staenz et al, 1995) is best described in terms of the Bidirectional Reflectance Distribution Function (BRDF). In the analysis of remotely sensed data, BRDF effects should be taken into consideration, by correcting for them where necessary and/or by taking advantage of anisotropic behaviour to improve target discrimination.…”

Realization of a filter radiometer-based irradiance scale with high accuracy in the region from 286 nm to 901 nm

“…The scales for optical quantities can be realized by using detector-based and source-based methods with high accuracy [1,2]. The main elements of detector-based and sourcebased measurements are the electrical substitution-cryogenic radiometer (ESCR) and the high temperature blackbody, respectively [3][4][5][6]. On the other hand, a detector-based technique has two important advantages-a lower uncertainty and a reduced traceability chain to the ECPR.…”

The NPL detector-stabilized irradiance source

“…The ability to stabilize using any of the photodiodes provides added flexibility. Stabilization using the UV channel, for example, would provide the most stable transfer standard in the UV-blue region, and since the output of high-power tungsten-halogen lamps is approximately Planckian, much smaller current changes are required to maintain the output in this region than at longer wavelengths, leading to better overall maintenance of calibration [4,5].…”

“…The NPL-DSL is a development of our prototype described in [5] and is similar in concept to the OMTec TSS-1000 [4] used in the comparison described elsewhere in these proceedings [6]. Other than differences in the details of the detector arrangement, software, etc., the main difference between the NPL-DSL and the OMTec system is that the NPL-DSL is a fully enclosed system, which has the added benefit of drastically reducing the amount of stray light present within the laboratory, while providing the rigid geometry required for successful detector stabilization.…”