FO-29 Power Status

The internal impedance of the battery in FO-29 (Fuji-3) is now rising due to the deterioration caused by almost 12 years in orbit.

According to the telemetry data a 25 minute eclipse duration is estimated as a limit as for the analog battery system use. Because the eclipse length of FO-29 (Fuji-3) is currently about 30% or almost 32 minutes, the power supply of the relay with the battery cannot serve a period of the eclipse.

A malfunction also occurs in part of the electricity control system. The malfunction is the UVC which is an automatic function for electricity management. When the satellite is in the eclipse, and the light of the sun is not the solar battery, the transmitter is turned OFF by the UVC.

It is designed so that later an analog system transmitter becomes ON automatically when the terminal voltages of the battery exceed a set value after the power is available from the solar battery. However, it appears likely that a malfunction occurs for this function, and the terminal voltage cannot turn on a transmitter even if it exceeds the set value unless commanded from the ground.

The length of eclipses for FO-29 (Fuji-3) will rise in future and rises to 34% in March 2008 and comes over a peak of the eclipse duration. When it goes over this peak, the eclipses will decrease slowly, and drop to 20% in August 2009. By February 2010 it is all sunshine with no eclipses
for about 8 months. It seems that we can apply the analog system relay consecutively for this period.

Mineo Wakita, JE9PEL