Search Results

KOBE (Komplexe Bestrahlungseinrichtung), a test facility for the complex simulation of solar and particle radiation in high vacuum and space heat sink environment, is just now available in the DLR-Institute for Space Sensor Technology. The evaluation of degradation effects for material properties as a consequence of its interaction with solar and particle radiation in the free space is a very important requirement particularly for long term space missions. The essential point of our investigations concerning to degradation effects is the change of optical and thermooptical properties for several materials. These effects are to evaluate necessarily under the expected environmental conditions. That's why the availability of suitable test facilities is a requirement. The most important material defects in the free space are originated particularly from the solar radiation, especially in the wavelength range below 200 nm, as well as the particle radiation by protons and electrons.

Micro Satellites are one of promising instruments for near earth space research programs. The strong restrictions to mass and power budget of satellite subsystems and payload lead to choice of mainly passive Thermal Control Systems (TCS), often with heat pipe (HP) integration. New tendencies in micro satellite thermal requirements as multi temperature level payload instruments, thermal stability of mounting structures for precision optical devices cause the corresponding adequate modifications in thermal concept and in hardware realisation. Intended aim of this paper is to present the experience collected by authors during thermal design and preflight thermal tests of Micro Satellite BIRD, developed under the German small satellite program.

For the determination of the solar absorptance αs and the thermal emittance ε preferably optical methods are utilized. To these methods belong spectral reflectance αs and ε measurements and / or emission measurements (only ε), whereby for αs must be measured in the common range 0,3 μm to 2,5 μm and ε in the range 5 μm to 35 μm with an essentially better resolution than 10 nm. Besides so-called integrated reflectance measurements are known, for which special detectors are used, in the above indicated spectral ranges. These optical measuring procedures are relatively exact. They deliver also information about a perhaps spectral selective behavior of surfaces, however, special measuring equipment is required.

For the determination of the solar absorptance αs and the thermal emittance ε optical methods are preferred. These optical measuring procedures are relatively exact. They also deliver information about any potential spectral selective behaviour of surfaces. However, special measuring equipment is required. Particularly if space simulation facilities are already available, the method presented in [1] appears as a suitable enrichment of the measurement methods for the determination of the thermooptical properties αs and ε. It is possible with slight technical expense to expand the usage potential of such facilities. For this paper the same test rig as in [1] is used. In a common space simulation chamber (vacuum; cryogenic shroud; solar simulator) a test item (target) is arranged. In different measuring phases the target is heated up by an integrated electrical heater or by solar irradiation. The arrangement (target / shroud) is regarded as a two node model.