EO79 FUNcube-3 transponder commences regular operation

EO79 (QB50p1) FUNcube-3 Transponder Passband - Credit David Bowman G0MRF

EO79 (QB50p1) FUNcube-3 Transponder Passband – Credit David Bowman G0MRF

AMSAT-UK and AMSAT-NL working with ISIS BV are delighted to announce that the FUNcube 435/145 MHz SSB/CW transponder, on the 2U CubeSat QB50p1 (EO79), has now been activated with a regular schedule.

EO79 (QB50p1) CubeSat - Credit ISIS

EO79 (QB50p1) CubeSat – Credit ISIS

Due to power budget constraints the transponder cannot be operational 24/7 and an orbit specific schedule has been developed. The transponder will commence operation 27 minutes after the spacecraft enters sunlight and will stay on for a period of 25 minutes. This schedule may be modified over the forthcoming weeks as a result of experience.

The transponder nominal frequencies are:
Uplink: 435.047-435.077 MHz LSB
Downlink: 145.935-145.965 MHz USB
The output power is approximately 400mW.

David Bowman G0MRF has been attempting to characterize the actual operating frequencies of the EO79 Transponder and suggests that the operational bandwidth of the transponder might be considered to be 25 kHz rather than 30 kHz. His report is available here. On the AMSAT Bulletin Board he writes:

From observations, there seems to be no downlink below 145.946 MHz. By taking readings at Time of Closest Approach (TCA) on low elevation passes, which for me is about 20 minutes into the 25 minute schedule. The transponder appears as follows:

Lower limit is quite well defined at 145.946.
Upper limit roles off slowly above 970. But 145.971 seems a reasonable limit. Very strong signals are visible to 973 but are heavily attenuated.

Upper limit (for 145.946) = 435.0723
Lower limit (for 145.971) = 435.0473

This suggests the transponder has a nominal bandwidth of 25 kHz. My best guess at a translation frequency is 581.0183MHz

Qb50p1 (EO79) was launched in June 2014, as a collaborative effort led by the von Karman Institute and ISIS-BV, into a sun synchronous 620×600 km polar orbit as a precursor spacecraft for the QB50 mission. The primary function of the satellite was to test a number of the systems and science payloads. This phase has now been completed and we are grateful to VKI and ISIS BV for carrying this transponder into space and, again, to ISIS, for developing and uploading the new, required, flight code.

We hope you have lots of fun using EO79!

Another EO-79 Transponder Activation

EO-79 Passband - Credit Jan van Gils PE0SAT

EO-79 Passband – Credit Jan van Gils PE0SAT

The EO-79 CubeSat SSB/CW transponder will be active from Monday, December 28 until Thursday, December 31.

The first activation has shown the transponder uplink is about 12 kHz higher than expected. The suggested frequencies to try are now:
Uplink: 435.047-435.077 MHz LSB
Downlink: 145.935-145.965 MHz USB

EO-79 and EO-80 - Image Credit ISIS

EO-79 and EO-80 – Image Credit ISIS

The team has seen that activating the transponder makes the satellite power negative, meaning the solar arrays cannot generate enough power to keep the transponder running permanently. This is not unexpected as the satellite is operating in a different mode than originally anticipated during the design phase.

The team are discussing various ways to solve this, including multiple ways of scheduling the transponder operations. With these discussions ongoing we would still like to try the second activation and obtain some more data about the system. The team aim to activate the transponder for as much time as the power budget allows, but please be aware that you may find the transponder to be off while the batteries recharge.

EO-79 has been set to only beacon the normal AX.25 beacon every 30 seconds instead of 10 seconds. The beacon frequency is 145.815 MHz and consists of AX.25 frames on BPSK. More details about the downlink can be found on the ISIS Ham Radio page at http://isispace.nl/HAM/qb50p.html

We kindly request you to share your experiences with the AMSAT Bulletin Board so everyone can benefit from operating tips and tricks, as well as being up-to-date on the status.

We would also welcome any observation related to the transponder behaviour when the AX.25 beacon comes on.

Just like FUNcube-1, the crystal oscillator circuits exhibit drift with temperature. This means manual tuning will probably work best.

Graham Shirville G3VZV says that due to platform sharing considerations the FUNcube transponder on EO-79 uses 1/4 wave monopole antennas rather than the full dipoles used on AO-73. The actual effects of this difference in practice may be interesting to observe.

AMSAT keps name: EO-79
Celestrak keps name: QB50P1
Celestrak file: cubesat.txt
NORAD #  40025
COSPAR designator: 2014-033-R

SatPC32 tracking software Doppler SQF information used by Peter VK4NBL:

PE0SAT http://www.pe0sat.vgnet.nl/

Real-time track of EO-79 (QB50p1) http://www.n2yo.com/?s=40025&df=1

Satellite Tracking https://amsat-uk.org/beginners/satellite-tracking/

AMSAT Bulletin Board (AMSAT-BB) http://www.amsat.org/mailman/listinfo/amsat-bb

EO-79 CubeSat Update

QB50p1 and QB50p2 - Image Credit ISIS

QB50p1 and QB50p2 – Image Credit ISIS

Wouter Weggelaar PA3WEG has provided this update on the status and plans for QB50p1 – EO-79.

Earlier testing campaigns indicate that the AMSAT-UK/AMSAT-NL transponder on board of this spacecraft is in good health. We have activated the transponder on various occasions for testing purposes.

At the moment we believe the power system is capable of sustaining transponder operations indefinitely. ISIS (the satellite designer and operator) still needs to write and apply a software patch that would keep the transponder running. The current logic in the satellite will switch off the transponder if a reset occurs of the On Board Computer or power system.

Efforts are being made to allow usage of the transponder in the mean time and also allow select command stations to take the satellite out of safe mode if it does reset. ISIS will continue to monitor all telemetry and the satellites health.

QB50p1 EO-79 FUNcube-3 Transponder - Credit Mike Rupprecht DK3WN

QB50p1 EO-79 FUNcube-3 Transponder – Credit Mike Rupprecht DK3WN

The precursor satellites have gathered valuable data about the sensor payloads, and the lessons learnt are being implemented in the flight units for the QB50 main mission.

We will still have to wait until procedures are in place and the activation is cleared by the operator and owners of the satellite, but we are nearly ready for the activation of another transponder!

Transponder activations will be announced on the AMSAT Bulletin Board.

On behalf of AMSAT-NL and the ISIS operations team I would like to thank the community for supporting our mission and thank you for your patience.

Wouter Weggelaar PA3WEG

EO-79 (FUNcube-3) Transponder Test May 4