AO-73 / FUNcube-1 spin period and illumination

AO73 / FUNcube-1 Spin Period

AO-73 / FUNcube-1 Spin Period

The attitude of AO-73 / FUNcube-1 is passively stabilised using the traditional magnet and two hysteresis rods. Since the launch over four years ago we have been intrigued with the resultant actual spin rate/period which seems to vary over time for reasons that have not yet been properly explained.

This graphic, which has been developed from telemetry received and maintained by Colin, VK3IH, and his team, shows the variations in some detail. Explanations would be gratefully received.

Mike, DK3WN’s, illum.exe software showing predicted duration of the first period

Mike, DK3WN’s, illum.exe software showing predicted duration of the first period

As it is expected that illumination levels may be having an influence, the next few months and years will prove interesting. The spacecraft will be entering periods of continuous sunlight. Initially this will be for a six-week period but then for periods of up to nine months!

AO-73 / FUNcube-1 celebrates its 4th birthday https://amsat-uk.org/2017/11/21/funcube-1-celebrates-4th-birthday/

FUNcube Website https://amsat-uk.org/funcube/

FUNcube Yahoo Group https://amsat-uk.org/funcube/yahoo-group/

FUNcube Forum https://amsat-uk.org/funcube/funcube-forum/

FUNcube-1 celebrates its 4th birthday

Final gluing of FUNcube-1 bolt by Wouter Weggelaar PA3WEG – Image credit Gerard Aalbers

Final gluing of FUNcube-1 bolt by Wouter Weggelaar PA3WEG – Image credit Gerard Aalbers

Today, November 21st 2017, marks the fourth birthday for FUNcube-1 (AO-73) in orbit.

FUNcube-1 was launched at 07:10 UTC on November 21st 2013 and its first signals were received immediately after deployment over the Indian Ocean by amateurs in South Africa. Since then it has been operating continuously in either its education mode or, with the transponder active, in amateur mode when in eclipse and at weekends.

AMSAT-UK FUNcube Mission Patch Rev4 20100609

AMSAT-UK FUNcube Mission Patch

The spacecraft has spent the four years in space orbiting the earth at between 640 and 580 km and has now traveled around the earth more than 20,000 times. That represents a distance traveled of approaching 500 million miles.

Up to now, each of the orbits has been spilt approximately 65% in sunlight and 35% in eclipse. This has resulted in the temperatures inside the small spacecraft varying by about 25° C during each orbit.

During the recent AMSAT-UK Colloquium, Wouter Weggelaar, PA3WEG, in his presentation about the FUNcube project mentioned that the power available from the solar panels has been slowly increasing since launch. This observation led the team to do some further investigations as to the cause.

Although the launch was into a nominally Sun Synchronous orbit, over time this has drifted and the spacecraft is now entering a period when it will be in the sun for longer periods during each orbit. The exact details are still being determined, but it seems likely that, starting from January 2018, there will be periods when the spacecraft will be in the sun for all, or almost all, of its orbits.

FUNcube-1 temperature rise

FUNcube-1 temperature rise

This means that the on-board temperatures will be much higher than we have previously experienced in flight, although we have some test records from pre-flight thermal air testing that were undertaken after integration.

The key will be to discover what the equilibrium temperature will be internally. For comparison, AO85 has already “enjoyed” periods of full sun and its internal temperatures have reached up to around 55° C.

So the next few months will be quite an exciting time for the team! We remain extremely grateful to everyone is using the spacecraft for both its educational and amateur missions. Of course we are also very very grateful to those who are downloading the telemetry and uploading the data to the Data Warehouse. It continues to provide a unique record of “life on board” a 1U CubeSat in space.

Watch the FUNcube presentation by Wouter Weggelaar PA3WEG

Get your 73 on 73 Award, details at https://amsat-uk.org/funcube/73-on-73-award/

AO-73 (FUNcube-1) website https://amsat-uk.org/funcube/funcube-website/

FUNcube Yahoo Group https://amsat-uk.org/funcube/yahoo-group/

ZACUBE-1, FUNcube-1 and HiNCube in the deployment pod - Image credit Wouter Weggelaar PA3WEG

ZACUBE-1, FUNcube-1 and HiNCube in the deployment pod – Image credit Wouter Weggelaar PA3WEG