ALOS Data Users Handbook

ALOS Data Users Handbook3.3.5 Satellite Structure (STR)With high resolution observing sensors, ALOS's performance of observation will be changed for the worse bythermal distortion of the structure of spacecraft. To avoid this thermal distortion, the main truss structure ofALOS was made from carbon fiver reinforced plastics (CFRP) and aluminum joints connect those truss. Thermalexpansion of aluminum joints are designed to be cancelled by CFRP truss, and each CFRP truss in the busstructure are covered by silver thermal insulators to minimize those distortion. In addition, PRISM's wholesystems are covered by black polyimide insulators to keep and control its thermal range within 0.5 degree inorbit. In launch condition, maximum acceleration is three times as much as the land surface, so the satellite mustbe designed to endure those heavy loads.3.3.6 Thermal Control Subsystem (TCS)ALOS control its thermal condition by two ways to keep its component within proper thermal range. The one ispassive control installing proper insulators or radiators on the surface of the satellite to control its thermalcondition by their optical properties. The other is active control switching heaters, moving louvers and so onaccording to the satellite's thermal condition.Sheets covering the satellite, silver, gold and black, are thermal blankets and almost all satellites use thoseblankets to keep their thermal condition. Some thermal elements like heaters and heat pipes are integrated insidethis model. TTM thermal vacuum test was conducted to confirm their function and satellite's design for thermalcontrol.To trash the waste heat out, radiators are used to radiate the heat to deep space. Thermal insulators (Multi LayerInsulation: MLI) are used to protect direct solar radiation or inappropriate heat loss from inside the satellite.ALOS is designed to control some thermal-sensitive components and sensors actively using heaters, heat pipes,and some thermal elements.Some heaters are switched by thermostats, and others are controlled by the Heater Control Electronics (HCE) bytemperature data measured by thermometers. PRISM, the most thermal-sensitive sensor on ALOS, is designed tobe controlled within the range of 0.5 °C at any satellite thermal conditions.3-27