Microwave Radiometric Detection of Oil SlicksRadiometry and the Detection of Optical RadiationOptical Systems Design Detection EssentialsOptoelectronic Workshops 7: Advanced Technology for Radiometry and the Detection of Optical RadiationStudies of Radio Frequency Interference Detection Methods in Microwave RadiometryPassive Infrared DetectionAdvances in Radiometry ResearchDetection and Assessment of Dental CariesMicrowave and Millimeterwave Remote Sensing for Security ApplicationsNon-Imaging Microwave and Millimetre-Wave Sensors for Concealed Object DetectionIntroduction to Radiometry and Photometry, Second EditionOptical Radiation Measurements: Grum, F. C., Becherer, R. RadiometryMicrowave Radiometric Studies in Relation to Mine DetectionMicrowave Radiometry and Remote Sensing of the Earth's Surface and AtmosphereMILLIMETER WAVE RADIOMETRIC DETECTION OF TARGETS OBSCURED BY FOLIAGE.Applied Photometry, Radiometry, and Measurements of Optical LossesPassive Standoff Detection of Chemical Vapors by Differential FTIR RadiometryClinical Application of Microwave Radiometry Techniques in the Detection of CancerPhotometry, Radiometry, and Measurements of Optical LossesRadiometryIce/frost Detection Using Millimeter Wave RadiometryFeasibility Study of Radiometry for Airborne Detection of Aviation HazardsEM Detection of Concealed TargetsLaser Photothermal Radiometry for the Detection of Early Enamel DemineralizationRadio Frequency Radiometry for the Remote Airborne Detection of Small Forest FirDetection and Characterization of Nuclear CloudsAn Application of Pattern Recognition to Radiometric Target DetectionTheory of Broadband Autocorrrelation Radiometry for Spectral Line DetectionInfrared Detectors and SystemsRadiometry Detection of Acoustic SignalsDetection of Greenbug Infestation Using Ground-based RadiometryRadiometry and the Detection of Optical RadiationW-band Radiometry for the Non-invasive Investigation of MaterialsHuman Presence Detection Using Millimeter-wave RadiometryRadiometry for Low Target DetectionUse of Airborne Microwave Radiometry for the Detection and Investigation of Oil Slicks at SeaFeasibility Study of Radiometry for Airborne Detection of Aviation HazardsIntroduction to Radiometry and PhotometryRadio Frequency Interference Characterization and Detection in L-band Microwave RadiometryDetection of Abandoned Underground Coal Mines by Geophysical Methods

Radiometry and the Detection of Optical Radiation

The metrological fields of photometry and radiometry and their associated units are closely linked through the current definition of the base unit of luminous intensity—the candela. These fields are important to a wide range of applications requiring precise and accurate measurements of electromagnetic radiation and, in particular, the amount of radiant energy (light) that is perceived by the human eye. The candela has been one of the base units since the inception of the International System of Units (SI) and is the only base unit that quantifies a fundamental biological process—human vision. This photobiological process spans an enormous dynamic range of light levels from a few-photon interaction involved in triggering the vision mechanism to a level of more than 1015 photons per second that is accommodated by the visual response under bright daylight conditions. This position paper, prepared by members of the Task Group on the SI of the Consultative Committee for Photometry and Radiometry Strategic Planning Working Group (CCPR WG-SP), reviews the evolution of these fields of optical radiation measurements and their consequent impact on definitions and realization of the candela. Over the past several decades, there have been significant developments in sources, detectors, measuring instruments and techniques, that have improved the measurement of photometric and radiometric quantities for classical applications in lighting design, manufacturing and quality control processes involving optical sources, detectors and materials. These improved realizations largely underpin the present (1979) definition of the candela. There is no consensus on whether this radiant-based definition fully satisfies the current and projected needs of the optical radiation community. There is also no consensus on whether a reformulation of the definition of the candela in terms of photon flux will be applicable to the lighting community. However, there have been significant recent advances in radiometry in the development of single-photon sources and single-photon detectors and the growth of associated technologies, such as quantum computing and quantum cryptography. The international acceptance of these new quantum-based technologies requires improved traceability and reliability of measurements at the level of a few photons. This review of the evolution of the candela and the impact of its possible reformulation might lead, in the future, to a reformulation in terms of quantum units (photons). This discussion is timely since redefinitions of four of the other SI base units are being considered now in terms of fundamental constants to provide a more universally realizable quantum-based SI system. This paper also introduces for the first time a fundamental constant for photometry.

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Photometry, radiometry and 'the candela': evolution in the classical and quantum world

The measurement of precise absolute fluxes for stellar sources has been pursued with increased vigor since the discovery of dark energy and the realization that its detailed understanding requires accurate spectral energy distributions (SEDs) of redshifted Ia supernovae in the rest frame. The flux distributions of spectrophotometric standard stars were initially derived from the comparison of stars to laboratory sources of known flux but are now mostly based on calculated model atmospheres. For example, pure hydrogen white dwarf (WD) models provide the basis for the HST CALSPEC archive of flux standards. The basic equations for quantitative spectrophotometry and photometry are explained in detail. Several historical lab-based flux calibrations are reviewed; and the SEDs of stars in the major online astronomical databases are compared to the CALSPEC reference standard spectrophotometry. There is good evidence that relative fluxes from the visible to the near-IR wavelength of ~2.5 μm are currently accurate to 1% for the primary reference standards, and new comparisons with lab flux standards show promise for improving that precision.

https://iopscience.iop.org/article/10.1086/677655/pdf

Techniques and Review of Absolute Flux Calibration from the Ultraviolet to the Mid-Infrared

The measurement of precise absolute fluxes for stellar sources has been pursued with increased vigor since the discovery of the dark energy and the realization that its detailed understanding requires accurate spectral energy distributions (SEDs) of redshifted Ia supernovae in the rest frame. The flux distributions of spectrophotometric standard stars were initially derived from the comparison of stars to laboratory sources of known flux but are now mostly based on calculated model atmospheres. For example, pure hydrogen white dwarf (WD) models provide the basis for the HST CALSPEC archive of flux standards. The basic equations for quantitative spectrophotometry and photometry are explained in detail. Several historical lab based flux calibrations are reviewed; and the SEDs of stars in the major on-line astronomical databases are compared to the CALSPEC reference standard spectrophotometry. There is good evidence that relative fluxes from the visible to the near-IR wavelength of ~2.5 micron are currently accurate to 1% for the primary reference standards; and new comparisons with lab flux standards show promise for improving that precision.

The Spectral Irradiance Monitor (SIM) on board the NASA SORCE satellite (Solar Radiation and Climate Experiment) was launched on 25 January 2003 and has been making twice-daily measurements of solar variability in the 220 to 1630 nm range and daily measurements in the 1600 to 2400 nm range. This study presents preflight and postlaunch calibration activities of the SIM instrument and its flight spare components as well as in-flight comparisons with the ATLAS 3 composite spectrum (Atmospheric Laboratory for Applications and Science) in the ultraviolet (UV), visible, and near infrared (NIR) as well as comparisons with the SOLSTICE (Solar Stellar Irradiance Comparison Experiment) in the UV. In the 258 to 1350 nm range, the SIM agrees with ATLAS 3 with a fractional difference of −0.021±0.021 (k=1, estimated standard deviation) and with the additional corrections discussed herein the agreement improves to −0.008±0.021 (k=1). In the ultraviolet (220–307 nm) the agreement between all the instruments in this study is better than 5%, but fractional differences reveal other instrument- and calibration-related differences. In the 1350 to 2400 nm range the agreement between SIM and ATLAS 3 is about 8%, so these SIM data are corrected to agree with ATLAS 3 in this range.

/pdf/the-sorce-sim-solar-spectrum-comparison-with-recent-aylx6kf3lo.pdf

The SORCE SIM Solar Spectrum: Comparison with Recent Observations

The National Institute of Standards and Technology (NIST) operates the newly upgraded Synchrotron Ultraviolet Radiation Facility (SURF III) mainly as a light source for radiometry. SURF III provides continuum radiation from the far-infrared to the soft X-ray spectral range and has its peak output in the extreme ultraviolet. SURF III is a circular-orbit, weak-focusing (single dipole magnet) storage ring, a feature which is advantageous if the synchrotron radiation output is calculated. We report the improvements achieved during a recent upgrade from SURF II to SURF III and our strategy to accurately determine the magnetic flux density, radio frequency (RF), beam current, and beam size, which are the parameters necessary to characterize the source completely.

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R Friedman

Papers

SURF III - An Improved Storage Ring for Radiometry