Hiroaki Kusawake

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.

First flight demonstration of glass-type space solar sheet

The electrical performance of a glass-type space solar sheet (G-SSS) was demonstrated in space. G-SSS comprises InGaP/GaAs dual-junction and InGaP/GaAs/InGaAs triple-junction solar cells. It is lightweight solar generation sheet, less than 0.5mm thick. It is mounted on the “HISAKI” (SPRINT-A) small scientific satellite, which was launched on September 14, 2013. The initial flight data were successfully acquired and this flight demonstration was a world-first experiment for G-SSS using III-V multi-junction thin-film solar cells. The cells demonstrated superior performance and the electrical outputs matched the flight prediction.

Influence of electron irradiation on electroluminescence of Cu(In,Ga)Se2 solar cells

Cu(In,Ga)Se2 (CIGS) solar cells were irradiated with 250 keV electrons, which can create only Cu-related defects in the cells, to reveal created radiation defects. The electron irradiation increased electroluminescence (EL) emission intensity from the CIGS cells with similar behavior to light soaking. A hundred keV electrons also increased the EL intensity without producing displacement defects. Both the 100 and 250 keV electrons increased the effective acceptor density and improved cell performance. Since these phenomena have been reported as a light-soaking effect for CIGS solar cells, electron radiation effects with less than 250 keV for CIGS solar cells are thought to be equivalent to the light-soaking effect.

Degradation mechanisms of InGaP solar cells by irradiation with less than 100 keV electrons

InGaP solar cells with high radiation resistivity are not expected to be degraded by irradiation with less than 100 keV electron-beams. Recently, it was observed that the InGaP solar cells were degraded by irradiation with 60 keV electron-beams. However, a mechanism of this degradation is unclear. In this study, we use deep-level transient spectroscopy (DLTS) to investigate a carrier trap levels in InGaPsolar cells irradiated with less than 100 keV electron-beams. The result of DLTS indicates that non-ionizing energy loss (NIEL) may not explain the degradation caused by low-energy electron beams well. Additionally, we propose displacement threshold energy (Ed) of phosphorus in InGaP by calculating introduction rate of irradiation-induce defect.

Study of decentralized collaboration power control for spacecraft

Spacecraft have many components required for existence in orbit, e.g. subsystems for electrical power, thermal control, communication & data handling and attitude control, which are known as “BUS systems”. To increase the ratio of mission payloads in spacecraft, a compact and lightweight BUS system is demanded, in response to which JAXA has been studying the establishment of decentralized and collaboration power control. In this paper, we describe an algorithm of decentralized and collaboration power control and a test of an experimental model.

Aurora Charging of Large Solar Panel of a Polar Orbit Satellite

Advanced Land Observing Satellite (ALOS) that will be launched by Japanese Aerospace Exploration Agency in 2005 will carry a large solar paddle of 22mx3m in polar orbit. The wake side of solar paddle can be charged to a highly negative value. Laboratory experiments are carried out to investigate charging and arcing phenomena on the backside of the solar paddle that has exposed bypath diode boards and Silver- Teflon® thermal coating. We irradiate solar panel coupons with an electron beam to simulate charging situation near the North Pole. Surface flashover is observed once the insulator potential exceeds -7kV. Possibility of sustained arc and surge voltage between hot and return ends of power circuit have been investigated.