AO73/FUNcube-1 is entering a further period of full sunlight

AO-73 Spin PeriodAO73/FUNcube-1 has been in space for almost five years and the original Sun Synchronous Orbit has now changed slightly such that the spacecraft will no longer be in eclipse for 35 mins every orbit.

The eclipse period has already reduced and will again become zero on September 8, 2018. This means that our usual autonomous switching between transponder on in eclipse and high-power telemetry when in sunlight will no longer be effective!

This schedule was originally planned to provide a very strong telemetry signal for schools to use during daylight hours and for amateur operation at night (and also at weekends and over holidays).

We have already experienced a short period of full sunlight but this time it looks like the spacecraft will be in this situation for more than eight months until sometime in April next year.

In addition to the additional thermal effect that will occur during this period, we also expect that the spin rate will increase. The reason for this effect is not yet fully understood but may be related to the amount of current flowing from the solar panels to the spacecraft bus being sufficient to cause a torque effect with the earth’s magnetic field.

We have therefore decided to have AO73/FUNcube-1 initially operate for alternate periods of one week in either safe or educational modes. This should enable us to evaluate whether the currents do affect the spin rate. Safe mode provides low power telemetry and education mode the usual high power telemetry. It will also enable an analysis to see whether the satellite becomes hotter or cooler in each mode.

This schedule may be changed in light of experience and we will update everyone on such changes via the AMSAT-BB in the usual way

The new schedule will be put into effect on Friday, August 31, 2018.

This will be a new experience for the spacecraft so the capture of the largest possible amount of telemetry remains an important tool for the team to have. We are very grateful to everyone who continues to upload the telemetry they have received to the Data Warehouse. It is invaluable.

In addition to AO73/FUNcube-1, the FUNcube-2 transponder on UKube-1 remains operational and EO88/Nayif-1 continues to operate autonomously with the transponder on when in eclipse and high- power telemetry in sunlight.