Akihiro Miyasaka

Thermal design verification of a large deployable antenna for a communications satellite

A large deployable antenna for a communication satellite requires sophisticated thermal control to satisfy the temperature requirements for electrical characteristics, and its performance must be confirmed by a thermal balance test. The results of a tradeoff study of the thermal control method for an antenna conducted in an effort to meet temperature requirement demands indicate that the thermal design of an antenna system can be accomplished by using passive thermal control techniques and heaters in spite of the large and complicated structure. Antenna system thermal balance tests are limited by the volume of the space simulation chamber. To overcome this problem, we introduce a two-step thermal design verification method consisting of component level tests and a whole antenna system level test. This paper describes the thermal control method, the thermal design verification method, and the predicted antenna temperatures in a geostationary orbit obtained from the verified thermal analytical model.

Deployment mechanism for a large reflector - Thermal-design verification using flight data

The thermal design of the deployment mechanism of a 3.5-m-diam reflector was certified using flight temperatures. The flight temperatures were recorded from Engineering Test Satellite Six, which was launched on Aug. 28, 1994, using an H-II vehicle. The satellite reflectors were successfully deployed on the sixth day after liftoff. The temperatures of the deployment mechanism and the difference in temperatures between the inner and the outer ring of the bearing for the deployment mechanism fell within the allowable temperature range. The minimum heating rate for the deployment mechanism was determined by taking into consideration the minimum allowable bearing temperature. The temperatures were evaluated using a thermal mathematical model of an antenna and a detailed model of the deployment mechanism. The antenna model was used to obtain boundary temperatures in the detailed model. This detailed model included the thermal contact resistance between the inner and the outer rings of the bearings. The predicted temperatures agreed with the flight data within 6%. The correct boundary temperatures are important in determining the exact temperature for the deployment mechanism. The thermal contact resistance between the inner and the outer ring was evaluated, considering the elastic deformation of the bearing due to the temperature difference between them. The thermal resistance in the flight agreed well with the value estimated in the ground tests.

Thermal Design Evaluation of Large Reflector Deployment Mechanism by Using Flight Data.

On the deployment mechanism of a large deployable onboard antenna of ETS-VI (Engineering Test Satellite Type 6), flight data are compared with predicted one. The deployment mechanism is thermally suitably controlled by heaters and by MLI (Multi-Layer Insulation) blankets. Such thermal control permits of deploying the main reflector within allowable temperature limits. That mechanism has thermally been evaluated with a mathematical model including thermal resistances between the inner and outer bearing rings. A good accuracy of the proposed method has also been demonstrated from flight data.