One of the most active periods during the operations of a satellite in Geosynchronous Earth Orbit is during eclipse seasons. These period are centered around the vernal and autumnal equinoxes. On equinox the satellite will pass through the longest period of the eclipse season having a duration of approximately 70 minutes.

Due to refraction of the light passing through the Earth’s atmosphere the sunlight gradually fades in intensity from full sunlight to total darkness over a period of approximately 2 minuets proceeding and following the eclipse. This is call the penumbra and is depicted in gray. The area of total darkness is called the umbra and is 70 minutes in length.

The satellite operations team will prepare each satellite for eclipse before entry into the penumbra, monitor it through the umbra and  either verify or configure the charging system to recharge the batteries after the completion of the eclipse.

Before the scheduled eclipse the charging system is commanded to charge the batteries to 100% state of charge (SOC) this is shown by the increase of the green bar on the indicator. This bar turns yellow as the solar array power decreases. When the solar arrays can no longer support the power requirements of the satellite the load transitions to the batteries and this is indicated by the change to red on the status bar. During the eclipse the SOC of the batteries will decrease as the stored power is removed. By design the batteries are selected for their capacity and the ability to support the total power requirement with no less than a 25 percent margin at worst case. The SOC decreases to 25 % on exit. As the satellites exits into the penumbra the load is transitioned back to solar array power as it becomes available, the bar turns yellow again. In the absences of sunlight the solar arrays will dramatically cool to ruffly -200 degrees and will be more efficient on entry into the sun. This is shown in a slight bounce in the status indicator on exit.  When back in full sunlight the charging system is enabled and the batteries are recharged at the high charge rate.

The demo only shows the return to a 50% state of charge at the end. With an eclipse of 70 minutes, it typically requires high charge of the batteries for approximately 8 to 10 hours. This varies based on the battery type, the power load of the satellite, the initial charge state of the battery and a number of other variables.

A higher resolution AVI of this demo can be obtained through Turbosquid.