Hironori Maejima

Investigation of Power System Failure of a LEO Satellite

The Solar Array Paddle generation power of ADEOS-II satellite dropped suddenly. We have investigated the cause of the anomaly. The telemetry indicated the generation power dropped by 2 A-step. This corresponded in the generation power of each array circuit. No anomalous telemetry was found except for attitude when the anomaly occurred. FTA was carried out and the possible locations for the anomaly were identified; Solar Array Paddle or Solar Array Paddle Harness. The laboratory tests showed the possibility that sustained arcs occurred between harnesses and the heat produced by arcs destroyed the bundled harnesses.

Sustained Arc Between Primary Power Cables of a Satellite

We investigated the power loss due to the sustained arc between primary satellite power cables. If the multi layer insulator (MLI) film on a satellite is electrically floating, energetic electrons in space will charge this film. We carried out an ESD test on cables with cracks and wrapped with this film. When the negative voltage on the MLI exceeded 600 V, a trigger arc discharge occurred between the MLI and the cables. Subsequently, a secondary arc electric discharge occurred between the cables themselves. After several discharges, this secondary arc caused sustained arc which burned out the cables. The heat caused by arc tracking between the hot and return cables made them burn out. If this phenomenon had occurred in space, the satellite would have suffered great damage.

Behavior of silicon bypass diodes in proton and high temperature environments for Mercury probe MMO

The behavior of silicon bypass diodes for space solar cells was experimentally investigated at high temperatures up to 250°C for the design of Japans Mercury probe BepiColombo MMO. Though the reverse current increased to nearly 10 mA at 250°C, the operation at such high temperatures did not permanently damaged the diodes. When the diodes were irradiated with protons and then kept at high temperatures, the output power recovered by annealing. The recovery was faster if the diodes were forward biased, presumably because of minority-carrier-injection-enhanced-annealing.

Uplink Radio Frequency Signal Fluctuations

KAGUYA was a Japanese large lunar explorer that orbited and observed the moon from 2007 to 2009. During in-orbit operation, unexpected fluctuations and lock-offs of KAGUYA’s uplink radio frequency telecommand signal were sometimes observed. To investigate the cause of the fluctuations, archived telemetry data were surveyed, and the telemetry data that showed the fluctuation were extracted. According to fault tree analysis of the telemetry data, multipath interference from the lunar surface and the spacecraft structure was deemed the most probable cause. This finding was verified by geometrical analysis of multipath interference. On the basis of the analysis results, the fluctuation map for a lunar polar orbiter was presented for the first time. This map was used to avoid the telecommand operation failure of KAGUYA. This lesson can be generally applied to operations of planet and lunar orbiters.