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The MUSES-B spacecraft will be launched in 1996 by the Institute of Space and Astronautical Science (ISAS). Its primary mission is experiments on space Very Long Baseline Interferometry (VLBI) for radio astronomy using a large deployable antenna. A challenging thermal design must be compatible with a wide range of sun angle and an 86 minute eclipse. The thermal design and verification has been performed separately for the major modules of the spacecraft; a main structure, a deployable antenna and Reaction Control System (RCS). Special attention is paid to the exposed RCS whose solar input varies significantly depending on the sun angle. This paper describes the thermal design concept for MUSES-B and verification results of its thermal model test focusing on the main structure and the RCS.

The Advanced Land Observing Satellite “DAICHI” (ALOS) is the latest Japanese 4-ton class earth observing platform launched on January 24, 2006. The primary mission of DAICHI is obtaining enormous amount of data for global topographic maps and emergency disaster observation. It is equipped with three remote sensing instruments; the stereo mapping panchromatic imager, the multi-spectral radiometer and the L-band synthetic aperture radar. The thermal control of the DAICHI employed new technologies enabling highly accurate earth observation and gigabit per second mission data handling. A combination of passive and active control techniques stabilizes orbital temperature variation of the truss structure and a large optical bench for observing instruments within less than a couple of degree C. The bus structure is entirely made of low CTE and high thermal conductive pitch-based CFRP instead of conventional aluminum alloy.

Japanese X-ray astronomy satellite ASTRO-E2 named “SUZAKU“ was successfully launched on July 10, 2005. SUZAKU is the fifth Japanese X-ray astronomy satellite to observe X-ray coming from hot and active regions in the universe in collaboration with NASA GSFC, MIT and University of Wisconsin. “SUZAKU” has achieved the high sensitivity wide energy band X-ray spectroscopy than ever before. It is equipped with X -ray telescopes (XRT) and three kinds of focal plane instruments, X-Ray Imaging Spectrometer (XIS), X-Ray Spectrometer (XRS) and Hard X-Ray Detector (HXD). A radiation-cooling system, connected to XIS and HXD with heat pipes, is provided to cool them below −30 C and −20 C respectively. Furthermore, a side panel has a large cut out to expose XRS cryogenic Dewar for direct cooling. Flight temperatures indicate that the three sensors are kept below their cooling-requirement temperature.

Variable emittance radiator, called SRD, is a thin and light ceramic tile whose infrared emissivity is varied proportionally by its own temperature. Bonded only to the external surface of spacecrafts, it controls the heat radiated to deep space without electrical or mechanical parts such as the thermal louver. By applying this new device for thermal control of spacecrafts, considerable weight and cost reductions can be achieved easily. In this paper, the new design and the new manufacturing process of the SRD and its optical properties, such as the total hemispherical emittance and the solar absorptance, are described. By introducing this new design and manufacturing process, the weight of the SRD is easily decreased, keeping its strength and the optical properties.

The Smart Radiation Device (SRD) decreases the temperature variation by changing its emissivity depending on the temperature. The first generation of the SRD has been demonstrated on the MUSES-C ‘HAYABUSA’ spacecraft launched on May 9th 2003. This new thermal control device reduces the energy consumption of the on-board heater, and decreases the weight and the cost of the thermal control system. With the opportunity to validate the SRD in space, lightweight and low cost thermal control devices offer a possibility for flexible thermal control on interplanetary spacecraft.

The ISAS's space VLBI satellite HALCA was successfully launched in February 1997. The spacecraft HALCA consists of a box shaped main structure and a large deployable mesh antenna with 8 m effective diameter. The integrated spacecraft with the mesh structure antenna is so large and complex that the thermal design and tests had been performed separately for the main structure and the large antenna. No thermal vacuum test had been conducted in the fully integrated spacecraft configuration. The complex heat exchange between the antenna and the main structure had been taken into account in the numerical thermal analysis. Good correlation between in-orbit temperature and flight prediction has proved validity of the design and the verification method where no integrated spacecraft thermal vacuum test was performed.

The Smart Radiation Device (SRD) is a new thermal control material that decreases the temperature variation by changing the emissivity without using electrical instruments or mechanical parts. The emissivity of the SRD changes physically depending on its temperatures. Bonded only to the external surface of the spacecrafts, the SRD controls the temperature. The drawback of the SRD is the high solar absorptance. The multi-layer film for SRD was designed in order to decrease the solar absorptance from 0.81 to less than 0.2 by putting multi-layer film on it and the optical performance of the Smart Radiation Device with Multi-layer film (SRDM) was evaluated.

The Smart Radiation Device (SRD) which is made from a ceramic material is a thin and light tile. The material undergoes a metal-insulator transition at around 290K and this allows the infrared emissivity of the device to change from low to high as the temperature is increased from 175K to 375K. This is beneficial for thermal control applications on spacecraft. For example, bonded only to the external surface of the spacecraft's instruments, SRD controls the heat radiated to deep space without electrical instruments or mechanical parts used for changing emissivity. It reduces the energy consumption of the electrical heater for thermal control, and decreases the weight and the cost of the thermal control system. In this paper, the design of the new material for SRD and the ground test results such as the radiation tests of electrons and UV will be described.