Charging and arcing experiment

In the last decade the power level of geostationary satellites has increased dramatically to nearly 10 kW or even higher to load more transponders into one satellite.

To manage the large amount of power efficiently, nowadays many European and American commercial telecommunication satellites employ solar arrays that generate electricity at 100V. In Japan, an ETS-VIII that employed Japan's first 100V bus power supply voltage as a geostationary satellite was launched in 2006.

As the voltage of solar arrays increase, continuous satellite accidents due to power supply system failure including solar array trouble has been reported. Power supply system failure accounts for nearly half of the insurance claims in the world for commercial satellites.

The Advanced Earth Observing Satellite II (ADEOS-II) experienced an anomaly on 25th October 2003. ADEOS-II operation was halted in less than one year due to sudden power generation reduction over 80%. In addition to this, the failure of the Japanese H-IIA rocket and the first Mars explorer Planet-B led to collapse of the credit of Japanese space development.

The ADEOS-II failure investigation revealed that charging of multi-layer insulator film by energetic auroral electrons led to a sustained arc between primary power cables. After this failure,the spacecraft charging problem has been recognized as a serious hazard inside JAXA and space companies.

Spacecraft operate in a plasma environment.

When the plasma environment changes greatly (e.g. substorm of aurora), the potential difference on the satellite surface exceeds 1kV, and electrical discharge may occurr.

Discharge tends to occur at the so-called triple junction, where vacuum, conductor and insulator meet which corresponds to the solar cell edge.

Repeated discharges degrade the electrical performance of solar cells, tarnish MLI surface and causes electromagnetic interference. If discharge occurs on the electrical power components, it way lead to loss of satellite function due to the short-circuit accident of the electric power system.

Our laboratory has the world's leading ground test facilities for simulating spacecraft charging by space plasma environment to evaluate spacecraft insulation strength. We have carried out ESD ground tests on solar array and other components that were loaded onto domestic satellites since 1999. (Link:Results of the experiments)

Using these facilities effectively, we test the conventional satellite apparatus, and develop the technology to endure space plasma environment to make next-generation space industry a reality, such as a space factory, a space hotel, a space solar power system (SSPS) and electro-dynamic tethers. Our laboratory leads the collaboration research between national and international experts.

Our laboratory leads the collaboration research between national and international experts. Furthermore, we promote further the collaboration and domestic investigation, aiming at the establishment of ISO standard on ESD test of satellite components within a few years.