Multispectral images of the basaltic surface of Venus obtained by Venera 13 were processed to remove the effects of orange-colored incident radiation resulting from interactions with the thick Venusian atmosphere. At visible wavelengths the surface of Venus appears dark and without significant color. High-temperature laboratory reflectance spectra of basaltic materials indicate that these results are consistent with mineral assemblages bearing either ferric or ferrous iron. A high reflectance in the near-infrared region observed at neighboring Venera 9 and 10 sites, however, suggests that the basaltic surface material contains ferric minerals and thus may be relatively oxidized.

Melting/freezing curves are studied for the single-component Ga and bimetallic eutectic alloys Ga–In, Ga–Sn, Ga–Zn and Ga–Al in small-size cells. These phase-transition studies were conducted at VNIIOFI and SDL in order to design small-size fixed-point devices for metrological monitoring of temperature sensors on autonomous platforms. Our prime objective is to develop technology to improve the long-term performance of in-flight blackbody calibration sources of space-borne radiometers. The repeatability of the melting temperature of Ga and the eutectic melting temperatures of Ga–In, Ga–Sn and Ga–Zn fixed points were studied. Our results show that small cells containing Ga and some Ga-based eutectic alloys can be used as melting fixed-point standards.

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.

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A necessary condition for accumulating fundamental climate data records is the use of observation instruments whose stability and accuracy are sufficiently high for climate monitoring purposes; the number of instruments and their distribution in space should be sufficient for measurements with no spatial or temporal gaps. The continuous acquirement of data over time intervals of several decades can only be possible under the condition of simultaneous application of instruments produced by different manufacturers and installed on different platforms belonging to one or several countries.The design of standard sources for pre-flight calibrations and in-flight monitoring of instruments has to meet the most stringent requirements for the accuracy of absolute radiometric measurements and stability of all instruments. This means that the radiometric scales should be stable, accurate, and uniform.Current technologies cannot ensure the high requirements for stability and compatibility of radiometric scales: 0.1% per decade within the 0.3 -3 µm band and 0.01 K per decade within the 3 -25 µm band.It is suggested that this task can be aided through the use of the pure metals or eutectic alloy phase transition phenomenon that always occur at the same temperature. Such devices can be used for pre-flight calibrations and for on-board monitoring of the stability of radiometric instruments. Results of previous studies of blackbody models that incorporate phase transition phenomenon are quite promising. A study of the phase transition of some materials in small cells was conducted for future application in onboard monitoring devices and its results are positive and allow us to begin preparations for similar experiments in space.

Melting/freezing temperature curves are studied for the single-component Ga and bimetallic eutectic alloys Ga-In, Ga-Sn, Ga-Zn, and Ga-Al in small-size cells. These phase-transition studies were conducted at VNIIOFI in order to design small-size fixed-point devices for metrological monitoring of temperature sensors on autonomous (e.g., space borne) platforms. The results show that Ga and some Ga-based eutectic alloys in small cells can be used as melting fixed points. The repeatability of melting temperatures of Ga, Ga-In, Ga-Sn, and Ga-Zn fixed points is studied. The effects of the concentration of the second element of Ga-based eutectic alloys and the thermal history on the melting plateau's shape and the melting temperature are studied.

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’.