ALOS Data Users Handbook

Section 3 Outline of ALOS Satellite SystemFigure 3.3-1 Onboard EPS LocationFour sets of Shunt Dissipater (SHNT) are the silver pizza boxes in front on the photo, which convert theexcessive electrical power from PDL to heat and dissipate it into the space. They are placed outside the satellitebody on the PDL side open to the space. Other EPS components are installed inside.ALOS has five sets of NiCd type battery (BAT). BAT is manufactured, tested and then being kept in arefrigerator to avoid specific deterioration. They are installed at the satellite just before the launch operation.NiCd type battery comes not to be able to provide enough current more than a certain level, if discharging andcharging repeatedly at that same level (Memory effect). Reconditioning Load (RCL) is used to force batteriesdischarge more than normal level to avoid this memory effect.Power Control Unit (PCU) manages the efficient charge and discharge procedure between PDL and BAT, andprovides stable voltage of electric current to all ALOS's components. It sends control signals of shunt dissipationto SHNT and control signals of charging current to Battery Charge Control Unit (BCCU), by checking PDL'spower generation and BAT voltage.Battery Charge Control Unit (BCCU) is equipped with each BAT one by one. It actually charges BAT at thedayside orbit and discharge at the nightside orbit, according to the control of PCU. It also protects BAT bystopping charge at high temperature (33 °C) and by heating up BAT in low temperature (2 °C).ALOS's PDL, PALSAR antenna and DRC antenna are folded down at the top seat of rocket in launching. Theyhave to be deployed for working after ALOS's separation from the rocket in the space. Ordnance Controller(ODC) sends the electric current, at this time, from BAT to explosive materials to free them from holding bolts.3-24