To conduct the UVSQ-SAT mission on the best way, the ham radio community is involved in many major project activities. To formalize this partnership, an agreement protocol has been signed on 1st October 2019 between LATMOS, F6KRK, and AMSAT-Francophone.
The Saint-Quentin-en-Yvelines Radio-Club (F6KRK) works jointly with the LATMOS on the project ground station preparation and commissioning.
As part of the ham radio mission, the UVSQ-SAT one-unit CubeSat embeds a radio transponder which will be accessible to the community in parallel of the other scientific objectives according to the power budget. The UVSQ-SAT team will provide an availability of the transponder up to 20% (schedule 7 to 15 days in advance with a distribution via the project's website and / or tweeter account, transponder activation/deactivation dates, satellite status information's (battery level, ...), constraints (ex: eclipses), ...).
UVSQ-Sat has been coordinated by IARU to use the radioamateur spectrum : IARU
Help us to spot UVSQ-SAT!
UVSQ-SAT is planned to be launch end of 2020. Like many CubeSat spacecraft, it will take time before having confirmed TLE for orbit prediction. The more people who can help us spot UVSQ-SAT, the sooner our operations phase can officially begin! If you would like to help listen for UVSQ-SAT, you can do so with the information below.
When the time comes, it will be possible to upload received telemetry on SatNOGS database or on AMSAT-Francophone database.
Alternatively, it will be possible to complete a Google form (with your contact information, lat/long location, TLE used, waterfall (if obtained), and any raw data that you have received from the spacecraft (screenshot or text file). If you haven’t Google account, please email this information to email@example.com
UVSQ-SAT transceiver characteristics
Hardware model: ISIS UHF downlink Full Duplex Transceiver
Operating frequency: 437,020 MHz
Beacon baud rate: 1200 bps and 9600 bps
Beacon interval: 30 seconds
Bandwidth: 20 kHz
Modulation type: BPSK
Protocol: AX-25 framing
Encoding: NRZI encoding and G3RUH scrambling
Spacecraft Callsign: LATMOS-01
Note for conventional ground station transceiver users
It should be noted that conventional transceivers could have a limited bandwidth that could create a limitation on the usable data rate of the Link. An example is that, due to the limitation of the IF filter bandwidth of the ICOM IC-910 radio the data rate cannot go higher than 1200 bps. 2400 bps may be possible, but with some degradation of the performance.
Another issue when using a conventional radio is the locking procedure. Because the TRXVU uses data scrambling, the audio output of a conventional transceiver is difficult to use as an indication for correct frequency setting by ear. This is due to the fact that the randomized data sounds like noise and is therefore very difficult to recognize. It is recommended to observe a waterfall plot or spectrum plot to ensure correct downlink frequency setting.
Recommended telemetry data flow for your ground station
The recommended telemetry data flow of the ground segment is depicted in the figure below.
Receiver filter: To limit the bandwidth of the received spectrum the ground segment demodulation chain could have an input receiver bandpass filter.
BPSK demodulation: The implementation of the BPSK demodulator could be based on a software defined implementation.
NRZ-I decode: The NRZ-I decoding takes care of decoding the differentially encoded data, it decodes a bit transition into a logic “0”, and no bit transition into a logic “1”.
Descrambling (derandomiser): After NRZ-I decoding, the data should be passed through a descrambler, where the original data is recovered. It is identical to the scrambling system used in G3RUH FSK AX.25 systems. The descrambling polynomial is 1 + X^12 + X^17.
AX.25 deframing: The AX.25 deframing block should deframe the AX.25 block and extract the frame contents (addresses, info field, FCS checking, …). More details about AX.25 could be found here: http://www.ax25.net/AX25.2.2-Jul%2098-2.pdf
LATMOS ground station
The LATMOS ground station is SDR based. It has been successfully used to decode several inflight CubeSat.
UVSQ-SAT transmits a health beacon every 30 seconds. This health beacon contains the most vital housekeeping telemetry on the spacecraft to allow mission operators to quickly assess the overall status of the spacecraft.
If you capture a message that looks similar to the following format, it means that you’ve heard our spacecraft!
Transmission will begin approximately 30 minutes after deployment when the spacecraft systems are initiated. (To be confirmed)