The present state of the art of temperature blackbody (HTBB) sources development at the All-Russian Institute for Optical and Physical Measurements (VNIIOFI, Russia) and their characteristics are analyzed. The precision graphite blackbody BB22p, operating now at NIST, PTB, NPL and VNIIOFI, large area blackbody BB2000 and super high temperature pyrolitic graphite blackbody BB3200pg are described. Results of their theoretical and experimental investigation are given.

An absolute radiation detector (a cryogenic radiometer) is being developed to replace the existing UK primary national standard cryogenic radiometer with an improved uncertainty. The cryogenic radiometer will be capable of measuring black body radiation and laser radiation with an uncertainty approaching 10 ppm. From these measurements it will be possible to determine the fundamental constant, the Stefan Boltzmann constant, confirming the radiometer as an absolute detector, and link this determination to the SI unit of luminous intensity, the candela. Thus detector and source based scales/standards will be tied to an invariant physical quantity ensuring their long-term stability.

Fifteen participants are due to take part in an international comparison of cryogenic radiometers to be organized by the BIPM. The comparison will be made using trap detectors as transfer instruments. The analysis of the performance of the trap detectors when used with cryogenic radiometers show that the comparison can be done at the highest accuracy, provided that certain experimental parameters are carefully controlled.

The paper describes the high-accuracy radiometric calibration of filter radiometers using both laser and Fourier transform spectrometer based methods to uncertainty levels < 0.1%. The paper also describes the development of detector-based transfer standards and their use for the spectral calibration of radiometric sources. It discusses how these techniques can improve the accuracy and reduce the cost of source calibration.

NPL, the UK National Standards laboratory, is currently engaged in a program of work to improve the accuracy of measurements in the infrared region of the spectrum (1 to 20 micrometers ) particularly in the atmospheric windows, with a target best uncertainty of around 0.1%. This work includes the identification of the most appropriate detector type on which to maintain and disseminate the new scale. Transfer standard detectors should ideally be large in area (up to 10 mm diameter), spatially uniform, linear, have high D* values over a wide spectral range and have good stability/ageing characteristics. A number of detector technologies have been investigated and the characteristics of these devices are described together with an assessment of their suitability as transfer standards.

In recent years, the consistency of ultraviolet solar spectral irradiance measurements has improved to the extent that broad band averages of solar irradiances agree to within a few percent over ranges of a few hundred nanometers. Over spectral ranges from tens to tenths of nanometers significantly larger disagreements in spectral irradiances are observed. Some well known factors which contribute to measurement uncertainties over smaller wavelength intervals are wavelength calibration errors, uncertainties in radiometric standards especially in the transition region from one standard to another, and differences and uncertainties in slit scattering function between instruments. Extensive pre-launch radiometric calibration of SBUV-2 ozone monitoring instruments in air and vacuum have indicated new sources of radiometric calibration uncertainties. These are effects of Woods anomalies in grating efficiency and wavelength dependent changes (sometimes with significant structure) in the reflectance of MgF₂ overcoated aluminum surfaces which seems to be associated with the absorption and desorption of water vapor by the MgF₂ thin film. These effects combine to produce wavelength dependent radiometric calibration differences between air and vacuum conditions of as much as 10 percent or more. These results indicate that one should not assume that an accurate radiometric calibration in air is valid in space for the wavelength region of 200 - 400 nm.

Recent efforts in Earth remote sensing have focused on accurately measuring to-of-atmosphere and surface-leaving radiances. When applying calibration coefficients to such scenes, one must account for the differences in polarization between the calibration target, used to determine the calibration coefficients, and the scene itself. Generally, this has not been done for measurements of infrared Earth scenes. This paper derives the impact of polarization on the radiometric calibration coefficients using the Stokes vector formalism, gives the result of the derivation using the Jones vector formalism, and accounts for the instrument polarization sensitivity, calibration target polarization, and scene polarization through normalization. The expected infrared polarization of Earth scenes is reviewed.

Improvements to solid rocket motor (SRM) nozzle designs and material performance is based on the ability to instrument motors during test firings to understand the internal combustion processes and the response of nozzle components to the severe heating environment. Measuring the desired parameters is very difficult because the environment inside of an SRM is extremely severe. Instrumentation can be quickly destroyed if exposed to the internal rocket motor environment. An optical method is under development to quantify the heating of the internal nozzle surface. A radiometric probe designed for measuring the thermal response and material surface recession within a nozzle while simultaneously confining the combustion products has been devised and demonstrated. As part of the probe design, optical fibers lead to calibrated detectors that measure the interior nozzle thermal response. This two color radiometric measurement can be used for a direct determination of the total heat flux impinging on interior nozzle surfaces. This measurement has been demonstrated using a high power CO₂ laser to simulate SRM nozzle heating conditions on carbon phenolic and graphite phenolic materials.

The standard equation for the radiometric emission factor as monitored by an infrared radiometer includes radiation emitted and reflected by the sample. The derivation of this equation assumes that the temperature variation of the band emittance is neglible which is only valid if the sample is gray within the band of observation. The radiometric emission factor obtained from the standard equation will therefore not agree with the true average emittance if the spectral emittance exhibits spectral structure. Ceramic beryllium oxide has one emittance edge rising with wavelength in the 3 - 5 micrometers atmospheric window and another edge falling with wavelength in the 8 - 13 micrometers window. Broadband radiometer measurements and model calculations are used to compare the temperature variation of the radiometric emission factors with that of the correct band emittance. Comparing the model calculations with experimental heat- camera data confirm the prediction that the band emittance and the radiometric emission factor decrease with temperature in the lower atmospheric window and increase in the upper atmospheric window. An approximation based on linearizing the temperature dependence of the radiometric data to obtain the correct band emittance is applied to these two cases. The agreement with the integrated results of spectral measurements is very satisfactory for the data from the 8 - 13 micrometers window, but less so for the 3 - 5 micrometers range. In the lower atmospheric window the material is partly transmitting and the atmosphere partly absorbing.

The Monte Carlo method was applied to statistical modeling of radiometric properties of integrating spheres. According to employed model of reflectance, specular and diffuse components are approximated by polynomial function of incident angle cosine. Developed software allows to simulate the irradiance distribution over internal surfaces of sphere with relative uncertainty of 0.1%. Sphere geometries with arbitrary number of apertures and baffles of circular shapes are admitted. To illustrate capabilities of software, an irradiance distribution over internal surfaces of the integrating sphere is plotted for several cases of practical importance.

Photons irradiated into biological materials show interactions with cells, molecules and molecule structures, the amount of interaction being dependent on wavelength, energy density, radiation duration and properties of biological materials. Soft tissue is known to have photons strongly forward scattered, because of the inhomogeneity of its cellular and subcellular structures. The geometric dimensions of the scattering centers are in the order of wavelengths (Mie-scattering). Investigations described in this paper will show the influence of photons on single, live standard cells and how the light transmission through a monolayer cell will change within a measuring time of up to one hour and in dependence on cell intensity. Experiments were carried out in vivo with monolayers of standard bovine kidney cells by means of optical spectroscopy in a range of wavelengths from 200 nm to 1.500 nm. Cell cultures as mono cell layers in chambers of glasses were developed by a nutrient solution within 3 days. The growth of the cell layers was microscopically controlled. Details are described in the paper. Spectrophotometric measurements in visual- and near infrared range were carried out with cells on chambers of glasses (in nutrient solutions). Various effects, such as color of the nutrient solution or dying of cell regions will influence the measuring results. The measurements allow conclusions as to the determination of optimal wavelengths for an optical inspection of tissue. A photon scattering is possible preferably at the boundaries (cell faces, nuclear membrane, alteration of refractive index).

Fluctuation for the laser beams of wavelengths on and off absorption lines were recorded, and the power spectral density function for each record was calculated, and the co- spectrum of the two records as well. A system with a 7 micrometers band lead-salt semiconductor laser that can be changed its wavelength were made up for examining the correlation between the fluctuation of the laser beam of 7859.50 nm and of 7860.27 nm. The former hit two absorption lines of water vapor located at 7859.49 nm and 7859.51 nm and the later were out of them. This experiment was carried out on the in- door corridor using a round-trip propagation path. Three electrical heaters and a humidity source set on the floor under the propagation path, which disturbed the temperature and humidity of the environment. In addition a fan agitated the air. As the results, the power spectral density function for the on-line data had a peak in the lower frequency region at which a contribution of the absorption is strong. The peak frequency agree with a predicted frequency by the integral length scale L₀. Moreover, the co-spectrum increased in the frequency region less than 0.1 Hz. On the contrary, it decreased dramatically in the frequency region higher than 10 Hz. The results tell us the lower frequency region reflects the transportation of water vapor in the air.

The design of filters with specific spectral characteristics is a requirement not only for the design of filter radiometers, but also for many applications in optical measurements. The most general type of absorptive filters are composite subtractive-additive filters and the general problem of filter radiometer spectral response optimization using such filters is formulated. The algorithm and software realization of constrained optimization for various objective functions with arbitrary weight functions are described. Successive random search and Hooke-Jeeves methods are employed in the optimization and several goodness-of-fit criteria are used for evaluation of the results. Illustrative numerical examples are presented.

The National Institute of Standards and Technology (NIST) has developed a low-level peak power and pulse energy radiometer (APD 900) transfer standard for collimated laser light at a wavelength of 1064 nm. The peak power irradiance measurement range is from 500 pW/cm² to 50 (mu) W/cm² for laser pulse widths of 10 -250 ns. The pulse energy measurement range is from 0.05 fJ/cm² to 50 pJ/cm². The instrument combines the functions of peak power and pulse energy measurement into one unit, and improves the responsivity by two orders of magnitude greater than previous NIST designs calibrated at 1064 nm. The radiometer is based on an infrared-enhanced silicon avalanche photodiode with 100 mm diameter full aperture collecting optics. Selectable aperture sizes and a neutral density filter extend the measurement range of the instrument to higher levels, especially with large diameter beams. The output is a voltage waveform that can be measured with an oscilloscope. Calibration uncertainty for the APD 900 radiometer is typically less than +/- 8%. Improvements in the NIST calibration system will potentially lower the uncertainty to approximately +/- 5%.

The Monte Carlo technique is applied to model the radiation transfer in a radiometric system, consisting of a cavity radiator, a stray radiation trap with two apertures, and a cavity radiometer. The algorithms for the statistical simulation of the non-isothermal black body, the cavity detector, and the radiation trap are described. The method is used for the numerical simulation of the radiative heat transfer in the radiometric system for the precise determination of the Stefan-Boltzmann constant.

We present the results of theoretical studies of optical system spatial-range selectivity and show that it is specified by the complex design parameter and the tuning distance. We perform the analytical calculations of the sky background radiation passing through the receiving optical system and consider the possibilities of spatial-range- resolvable control of atmospheric optical parameters and their range distribution reconstruction by passive optical measurements.

We are developing new detector-based radiometric scales in the near infrared to extend existing spectral radiant power calibrations to spectral irradiance and radiance calibrations. High accuracy irradiance and radiance meters have been developed to realize these new detector-based radiometric scales. Mechanical, optical, and radiometric design considerations of Ge and InGaAs radiometers are discussed. Calibration principles and design considerations of the calibration setup are also described. Several results of preliminary radiometric characterizations are reported.

The paper presents the method and the apparatus used in the characterization of photodiodes--type DFR 01--produced in Romania which are used in the spectral range of 0.38 divided by 1 micrometers . Thirty photodiodes were picked from a representative group. This process took into consideration two parameters: the shunt resistance and the dark current, both of them measured in a thermostat control enclosure, for a photoconductive mode. The photodiodes from the first third of the list were tested and measured from: the linearity of the answering signal and from the spatial uniformity of the signal on the receiving surface point of view. It was determined the relative spectral responsivity of the photodiodes with a good linearity, using the methods of substitution and comparison: the methods used a responsivity standard internationally certificated.