Metrological radiometric facilities for optoelectronic instruments calibration utilize in terms of standards as radiation detectors in a form of cryogenic radiometers (CR), so as radiation sources. However in practice, there are no CR working within IR spectral range. An alternative way of radiometric calibration in middle and far IR ranges is to develop a parametric series of standard radiation sources -blackbody (BB) models.The paper describes some of BBs developed at VNIIOFI for the last time [1] from cryogenic (80 K to 200 K), to low (about 200 K to 400 K) and medium (400 K to 700 K) temperature regions for calibration of the IR instruments under cryogenic-vacuum conditions. These BBs are presented by models of both types: variable-temperature and based on fixed points of Ga or In. BBs are characterized with high temperature uniformity and stability. Copper and aluminum alloys are used as the radiation cavity materials. The required value of emissivity epsilon(lambda) is achieved by using different black coatings. Low-temperature and cryogenic BBs are based on the principles of indirect multi-zone electric heating (with heat isolation from LN2 cooling loop, or by using an external liquid thermostat with circulating heat-transfer agent. The principles of operation, design and test results of BBs are described.

This article describes the vacuum variable medium-temperature blackbody (VMTBB) constructed to serve as a highly stable reference source with an aperture diameter of 20 mm in the temperature range from 150 °C to 430 °C under medium-vacuum conditions (10−3 Pa) and in a reduced background environment (liquid-nitrogen-cooled shroud). The VMTBB was realized for the calibration facility at the PTB in the field of reduced background radiation thermometry under vacuum. This facility is intended for performing radiometric and radiation thermometric measurements under vacuum conditions in the temperature range from −173 °C to 430 °C and spectral emissivity measurements in the temperature range from 0 °C to 600 °C without atmospheric interferences. It is difficult to realize a precision blackbody with high emissivity for temperatures above 400 °C. Cavities of such blackbodies are normally made of copper and coated by a paint with high emissivity. But any paint put on copper does not survive several cycles of heating to temperatures up to 450 °C. As a result of investigations at PTB, a special procedure of coating the surface of the cavity by paint with high emissivity has been developed. The cavity surface is coated by chemical nickel plating before covering it by a paint with high emissivity. The general concept and the design of the VMTBB are given. For realization of good temperature uniformity along the complete radiating cavity, a three module design is used consisting of a heat exchanger and two stages of temperature control of the cavity, based on two precision PID controllers. The temperature of the cavity is determined by 15 precision Pt resistance thermometers. Six of them are used for the VMTBB cavity and heat exchanger temperature control, and the others are used for the cavity temperature measurement and correction. A description of the temperature control and measurement system of the VMTBB is presented. Optical ray tracing with a Monte Carlo method (STEEP 3) indicated that the effective emissivity of this blackbody cavity is not worse than 0.9994. Tests of the VMTBB were carried out at the PTB facility, and the radiation of the VMTBB was measured in comparison to the vacuum variable low-temperature blackbody (VLTBB) in the temperature range from 150 °C to 170 °C with the vacuum infrared standard radiation thermometer (VIRST). The temperature uniformity of the blackbody from the bottom to the front of the cavity is better than ±100 mK in the whole temperature range. The stability of the temperature of the blackbody is within 50 mK in the whole temperature range.

The present state-of-the-art of precision radiometry based on the vacuum variable-low-temperature blackbody source VTBB100 developed for the low-background calibration facility at PTB is analyzed. This article describes the vacuum variable-low-temperature blackbody (VTBB) constructed to serve as a highly stable reference source for the calibration of blackbody sources in the temperature range from 100 K to 450 K under medium-vacuum conditions (10−3 Pa) in a medium-background environment (liquid-nitrogen-cooled shroud). The general concept and the design of the VTBB100 are given. The numerical investigation of the effective emissivity of the VTBB100 is performed. A description of the temperature control and measurement system of the VTBB100 is presented. Cooling of the VTBB100 is by liquid nitrogen. Heating of the VTBB100 is by a two-stage temperature control scheme. A thermal model of the radiator was developed. As a result of the analysis, it was shown that the system achieves an instability of the blackbody temperature of less than 20 mK. The characteristics of the blackbody operation—now at PTB—are described.

The international Global Earth Observation System of Systems is at its initial stage. We present some general information about the program and formulate the task of ensuring the uniformity of radiometric measurements to be conducted by all the participating national systems. Methods of solving the task are suggested on the basis of the wide application of standard sources that use phase transition of eutectic alloys and pure metals as well as with the help of improved ground calibration facilities.

The paper presents a detailed review of precision blackbodies that are low-, medium-, and high-temperature range sources developed at VNIIOFI during the past 30 years. Low-temperature blackbodies were developed for calibration facilities of spaceborne instruments. Medium-temperature blackbodies are used for radiance temperature and IR radiometric measurements. The high-temperature pyrolitic graphite blackbodies BB3200 and BB3500 were developed for world-leading metrology centers as NIST (USA), PTB (Germany), NPL (Great Britain), VNIIOFI (Russia), CNAM (France) and others for the realization and dissemination of radiometric and radiation temperature scales. The latest modification of the high-temperature blackbody BB3500MP, the large-aperture version (with an opening of up to 16 mm) of the famous BB3500, suitable for holding large fixed-point cells with high-temperature TiC-C and ZrC-C eutectics, is under development.

The VNIIOFI Spectroradiometer (VSR) has been developed for the Medium Background Facility which is intended for calibrations and comparisons of low-temperature sources in the temperature range from -60 degreesC up to +80 degreesC. The VSR is designed to measure the radiance temperature of the blackbody sources in the spectral range from 2.5 mum up to 14 mum in a cryogenic vacuum environment (liquid nitrogen cooled shroud). The VSR is based on the Circular Variable Filter (CVF) assembly with a slit aperture and an InSb-CdHgTe two color sandwich detector with an integral Stirling cooler. The Circular Variable Filter covers the 2.5 mum to 14.1 mum region in three segments. The width of the slit equal to 1.2 mm provides a spectral resolution from 80 nm to 360 mn for the spectral range from 2.5 mum to 14.1 mum accordingly. The Circular Variable Filter assembly is rotated by a stepper motor. The Cassegrain telescope is used as a foreoptic unit. Radiation passes through the CVF and is focused on the detector with help of the ellipsoidal mirror. Radiation from a low-temperature (77 K) blackbody is used as a reference level of radiation. The instrument has a field of view of 8.9 mrad with a distance to the object being equal to 2250 mm. The spectral and temporal characterizations of the spectroradiometer are reported. The facility for CVF calibration is described. Temperature resolutions for the calibrated sources are given for different temperatures and for different wavelengths. A brief description of the design, operation principles and specifications of the main parts of the spectroradiometer such as the Cassegrain telescope, CVF and detector assembly are presented. The measurement uncertainties of radiance temperature associated with spectral bandwidth are discussed.

The calibration of IR sensors, thermal imagers, instrumentation for remote earth sensing, signature recognition, and low background spacebome radiom-eters requires development of low- and near-ambient-temperature reference standard sources capable of operating in vacuum at low or medium background conditions. The paper contains the characteristics of blackbodies (BB), developed at the All-Russian Research Institute for Optical and Physical Measurements (VNIIOFI). A novel Medium Background Facility (MBF) intended for calibrating IR sources has been developed at VNIIOFI. The MBF used for the calibration under vacuum conditions (10-3 Pa) and medium background temperatures includes a Ga Fixed-Point Blackbody (29.76 °C), Variable Temperature Blackbody (-60 °C ~ +80 °C) and Filter Radiometer. A brief description of the operating principles and specifications of the MBF is presented. The results of a comparison of the Variable Temperature Blackbody and Ga Fixed Point Blackbody in the Medium Background Facility are given. The measurement uncertainties radiance temperature associated with spectral bandwidth are discussed.

A new Medium-Background Facility (MBF) for the calibration of infrared sources and sensors has been designed by specialists from the All-Russian Research Institute for Optophysical Measurements (VNIIOFI) under contract to the Xi'an Institute of Applied Optics (China). The facility consists of several detachable modules, the configuration of which can be changed to suit the requirements of a specific task. The modular design allows flexible and independent use of the main components and simplifies upgrading. The facility was designed to allow absolute radiometric calibration of black-body sources and IR sensors; to compare the radiometric scale with predictions for measured temperatures; to allow measurements over an extended temperature range (up to the indium point); and to serve as the IR spectral radiance standard. Intended for the calibration of IR sensors and sources under vacuum conditions (10−3 Pa) and a medium-background environment (liquid-nitrogen-cooled shroud), the MBF is briefly described with reference to its design, operating principles and measurement results.

The precision blackbody sources developed at the All-Russian Institute for Optical and Physical Measurements (Moscow, Russia) and their characteristics are analyzed. The precision high-temperature graphite blackbody BB22p, large-area high-temperature pyrolytic graphite blackbody BB3200pg, middle-temperature graphite blackbody BB2000, low-temperature blackbody BB300, and gallium fixed-point blackbody BB29gl and their characteristics are described.

A new stereo-spectral-imaging system, ARGUS, has been developed for the Mars 94/96 mission and consists of three videospectrometers with a wide field-of-view covering the spectral range 320 nm to 5200 nm. The on-board radiometric calibration is based on a diffusing target illuminated by the Sun's radiation. The provision for a common target for all the videospectrometers of the ARGUS system allows an intercomparison of instruments to be carried out in addition to individual calibration verification. The development and testing of the target for on-board radiometric calibration is described and techniques for preparing the target surface are given. A brief description of the setup for measurements of the spectral and angular response of the target reflectivity is presented, together with results of the spectral and angular response of the target reflectivity, for an angle of incidence of -70° (relative to the normal) and at viewing angles from 0° to +60° at 2° intervals. The bidirectional reflectance factor of the target is reported for the spectral range 320 nm to 5200 nm at an angle of incidence of -70° and at a viewing angle of +20°.

This work summarizes the progress in the development and testing of the telescope for a space imaging spectrometer 'OMEGA' of a new stereo-spectral-imaging system ARGUS developed in the frame of the International project for MARS 94/96 missions. The results of the telescope aberration calculation are given. Brief description of the facility for the main optical characteristics measurements are described. The telescope was tested at a special vacuum chamber at the temperature range from 180K to 300K. The results of the telescope investigation are given.

Absolute cryogenic electrical-substitution radiometers (ESRs) are widely used in many applications of absolute radiometry and are accepted today as being the most accurate instruments for radiant-power measurements. An absolute cryogenic electrical-substitution radiometer has been developed at the All-Russian Research Institute for Optophysical Measurements (VNIIOFI) as the radiometric standard of Russia. The design and characterization of the VNIIOFI absolute cryogenic radiometer currently used for the calibration of detectors in Russia is described. This radiometer uses laser radiation and a power level of 1,3 mW and achieves an uncertainty of 0,02%. The factors limiting the overall uncertainty of the VNIIOFI cryogenic radiometer are also analysed.

The method for on board calibration of the space imaging instruments using a diffusing target illuminated by the sun radiation is gaining acceptance. This raises a problem of measurements of the spectral and angular response of the target reflectivity in illumination conditions similar to the actual one on-board. This work summarizes the progress in the development and testing of the target for on-board radiometric calibration of the space video-spectrometers in stereo- spectral imaging system ARGUS. The spectral and angular response of the target reflectivity and the experimental procedure used for getting these characteristics are described. The target manufacturing technique is described. This target was tested for the spectral properties from 0.3 micrometers to 5.2 micrometers at angle of illumination -70 degree(s) (relative to the normal of the target) and angle of viewing +20 degree(s). The angular response was measured with three incident angles 70 degree(s), 75 degree(s) and 80 degree(s) (relative to the normal) for angles of viewing varying between 0 degree(s) and 60 degree(s) (relative to the normal). Brief description of the setup for measurements of the spectral and angular response of the target reflectivity are presented. The values of angular and spectral response of the reflectivity have been determined with the accuracy of 2 - 5% depending on the wavelength.

A new low-cost absolute cryogenic radiometer of the electrical substitution (ES) type optimized for performing black-body models calibration is described. Nitrogen is used as a cryogenic liquid for cooling of a radiometer receiving cavity up to temperature 80 K. This absolute ESR has been developed for measuring the irradiance in the range of 10-3 divided by 10-6 W/cm2 with the uncertainty of 0.1% for the upper level of irradiance range. The receiving cavity having 16 mm aperture, is fabricated from copper foil with thickness of 30 micrometers . A substitution winding of the receiving cavity is made of manganin wires. Measured heat conduction of the receiving cavity is 1.1 X 10-3 W/K. A single time constant of the receiving cavity is 80 sec. Brief description of the design, operating principles, and measurements results of the new cryogenic radiometer at nitrogen temperature are given.

A national standard of low background irradiance from 1 W/m2 to 10(-3) W/m2 has been created at the Research Institute for Optophysical Measurements (VNIIOFI, Moscow). The standard is based on a cryogenic radiometer and a low temperature black body (LTBB) variable in temperature from 80 K to 300 K.