FUNcube-1 (AO-73) Marks 6 Weeks in Space
The FUNcube-1 (AO-73) spacecraft has now been in orbit and fully operational for about 6 weeks. A Russian Dnepr rocket carried the AMSAT-UK cubesat and 18 other satellites into orbit on November 21. The FUNcube-1 team has expressed its gratitude to all radio amateurs who have uploaded telemetry data to the satellite’s “data warehouse.” The telemetry downlink frequency is 145.935 MHz (BPSK). The team’s Dave Johnson, G4DPZ, reported that he has been refining the warehouse operation and promises more features soon, along with updates to the “dashboard” software. Version 814 of the dashboard software is available for download.
“We intend to keep the present operating schedule in place for the time being, whilst various onboard parameters continue to be characterized by the team,” the FUNcube-1 team said. “The present low internal temperatures being experienced by the spacecraft, at least in the Northern Hemisphere, are causing some frequency shifting to take place — especially on the uplink frequencies.”
Still uncertain is whether FUNcube-1 is “Object 2013-066AE” for tracking purposes, but, the team, said that object appears to be “the most likely candidate.” The latest Keplerian element data that seem to be the best fit for now are from NORAD/Celestrak, which refers to “DNEPR OBJECT AE.” The FUNcube-1 website has posted updated the two-line element (TLE) information.
AO-73 carries an inverting SSB/CW transponder, with an uplink passband at 435.150 to 435.130 MHz LSB, and a downlink passband at 145.950 to 145.970 MHz USB. The AO-73 team requests that users run no more than 5 W to a 7 dBi gain antenna. When it’s in sunlight, the satellite’s beacon runs 300 mW. In eclipse it runs just 30 mW.
A facility to view the latest FUNcube-1 high-resolution data uploaded to the data warehouse now is available. The FUNcube-1 team plans to make the high-resolution data downloadable as .csv files, as it already does for whole orbit data (WOD).
The FUNcube-1 team has made some changes to the service that receives, processes, and stores telemetry data. “The first change is to introduce an acceptance time window for packets uploaded from the dashboard,” it said. “This restricts packets to those whose sequence numbers are within ±48 hours of the latest sequence number stored in the data warehouse.”
The FUNcube-1’s Johnson said it’s doing this for two reasons. “We have received erroneous packets whose sequence numbers are significantly different to the latest value. To reduce the chance of double scoring of points when we release stored data back to the user community,” he explained. The second change was made to improve scoring. “We currently process packets immediately as they arrive at the server,” Johnson said. “Under load, this can cause us to lose a few packet scores because of contention in the database. To alleviate this problem, we are going to change the processing slightly to process packets through a buffer. This buffer will be processed every 5 seconds, so there will be a slight delay before packets are acknowledged on the ranking.”
Satellite enthusiast Patrick Stoddard, WD9EWK, has posted video of his AO-73 operation from Arizona on YouTube. “AO-73 hears very well, as long as you’re careful to match the polarization of the satellite’s antennas,” he said. “High power is not necessary to be heard through the transponder.” — Thanks to AMSAT News Service, FUNcube-1, Southgate Amateur Radio News