A high-precision absolute radiometer with a thermally stabilized cavity as the receiving element was designed in 1984 at the All-Union Research Institute for Optical and Physical Measurements (VNIIOFI) and used to derive the USSR National Special Standard of the solar irradiance unit. Since that time, the radiometer has been developed further. The absolute radiometer has taken part in the comparisons with the Å 212 pyrheliometer and other absolute radiometers and standards of COMECON countries. This work has made possible the development of a combined radiometric standard based on the absolute radiometer and black-body radiators.

A high-precision absolute radiometer with a thermally stabilized cavity as receiving element has been designed for use in solar irradiance measurements. The State Special Standard of the Solar Irradiance Unit has been built on the basis of the developed absolute radiometer. The Standard also includes the sun tracking system and the system for automatic thermal stabilization and information processing, comprising a built-in microcalculator which calculates the irradiance according to the input program. During metrological certification of the Standard, main error sources have been analysed and the non-excluded systematic and accidental errors of the irradiance-unit realization have been determined. The total error of the Standard does not exceed 0.3%. Beginning in 1984 the Standard has been taking part in a comparison with the Å 212 pyrheliometer and other Soviet and foreign standards. In 1986 it took part in the international comparison of absolute radiometers and standard pyrheliometers of socialist countries. The results of the comparisons proved the high metrological quality of this Standard based on an absolute radiometer.

The All-Russian Research Institute for Optical and Physical Measurements is currently carrying out a project on developing an integrated system for measurement assurance of Earth observations. The system should provide ground calibration of instruments and their control during space-borne observations. Such tasks require appropriate measurement facilities as well as regulatory documentation. In this paper we discuss the newly created radiometric facility, traceable to SI standard, for precise calibration of instruments for Earth observations, the project on precise monitoring of the stability of the instrument's in-flight performance and the development of national regulatory documentation in harmony with the international document ‘Quality Assurance Framework for Earth Observation—QA4EO’.

Soviet and Australian photometric and radiometric standards have been intercompared. Luminous intensity and luminous flux values were compared using lamps, and illuminance, irradiance and spectral responsivity using detectors. Agreement at the 1 O/O level or better was found for these values as determined by the two national laboratories.

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