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High accuracy measurements of the earth’s gravitational field by satellites are affected by noise due to micro-vibrations caused by the environment and internal sources. In order to derive the best possible gravity field model the effects of non-gravitational accelerations have to be avoided and, where this is not possible, compensated or minimized. Among many other sources of those undesired disturbances are also classical thermal hardware items. This paper describes the development test programme established within the GOCE project to characterize the performance of MLI blankets, which were identified as potential micro-disturbance sources. The outcome of these tests is briefly discussed and the resulting selection of the flight thermal hardware is presented.

The XMM (X-ray Multi-Mirror) spacecraft is a space-borne observatory for soft X-ray astronomy. It is developed and built under an ESA contract by an industrial consortium led by Dornier Satellitensysteme GmbH. Due to the large dimensions of the whole spacecraft measuring more than 10 m in height and more than 4 m in diameter, it is split into an upper and a lower module for integration and testing. These modules were separately vacuum tested in the Large Space Simulator at ESTEC, allowing for different spacecraft attitudes with reference to the solar simulator beam. This paper reports on the thermal vacuum test of the XMM lower module (LM), which was conducted in January 1999. The successful completion of this test was a further decisive cornerstone in passing the XMM flight acceptance review in late 1999.

Multi-layer insulations consisting of stacks of reflecting foils reveal extremely low thermal conductances under vacuum conditions. Therefore, to improve the thermal performance of a pure foam and to reduce the area related mass, experimental and analytical investigations have been extended to a combined advanced multi-layer/foam insulation concept which consists of a stack of reflecting screens separated by thin foam layers. The predicted thermal performance of this improved insulation concept is compared with test results.

A key element of spacecraft thermal balance testing is the reliable determination of the final temperature values of the temperature equilibrium. At the end of a thermal balance test phase, temperature equilibrium is generally considered to be reached when nearly all thermocouples have fulfilled pre-defined temperature equilibrium criteria, e.g. in the form of a maximal allowed rate of temperature change. Test time can be reduced in the same manner as the equilibrium temperatures can be reliably extrapolated from the measured thermocouples temperatures, thus requiring only a less stringent equilibrium criterion to be fulfilled by the sensed temperatures. This paper concentrates on a mathematical theory for practical use in the extrapolation of equilibrium temperatures for spacecraft and units with essentially radiative couplings to their thermal environment.

Rosetta, the ESA-NASA Comet Nucleus Sample Return (CNSR) mission, which will bring cometary material to Earth could be the key to understanding the chemical and physical process that marked the beginning of the Solar System. A major mission requirement is to keep the material samples on the in-situ temperature level to prevent any phase changes or alteration of its chemical composition. Since the a-priori knowledge of the extraterrestrial cometary surface is not very detailed before the implementation of the mission, and the implications on the spacecraft design as well as onto the mission scenario itself are mandatory, an engineering database for the expected thermal environment has been established. For that purpose a simplified thermal comet model has been created, applying the ESATAN software package. The model comprises thirteen material and comet parameters governing die cometary superficial heat balance as well as the cometary shape and mechanics.