Hi,
Polarcube is a 3U CubeSat by the Colorado Space Grant Consortium. For more info on the satellite you can see the NASA brief in the ELaNa 20 fact sheet.
Operations for the satellite will be done out of CU Boulder where we have a ground station but would love to hear beacons from around the world, particularly in the bus commissioning phases so I am reaching out here to see if we can get it integrated into the system for people to use.
Launch is currently projected some time in January 2021. It has been delayed many many times but I am hopeful it will finally be going to space.
A few important details about the beacons. The frequency/modulation/format is very nonstandard. We are at 401.365MHz. The radio was designed around a SPIRIT1 transceiver which is configured to do 2-FSK at 4800 baud with a +/-2.4kHz deviation. It uses an [0x88 0x88 0x88 0x88] sync to indicated start of packet followed by an length byte, payload and CRC. The length+payload is data whitened with the built in function of the SPIRIT1 which is a rather odd LSFR implementation described in the linked documentation.
I am working to create a Kaitai decoder for the beacons as well as to figure out what the best way to integrate the GNU radio blocks into the SatNOGs framework is. Right now we use a custom block from an OOT module to detect the sync, dewhiten the packet, and check the CRC. All of the FSK demod and filtering is done with standard blocks.
We have an updated launch date of January 13th, 2021.
I have created an issue for added Polarcube to the database.
Can FSK4800 be decoded from the baseband audio recordings? Launch is very soon and I imagine it will take a bit to get new blocks integrated so would be useful to download audio to extract telemetry until the decoder is ready.
I have setup a SatNOGS system to start testing gnuradio block decoder:
Working on integrating in a block for decoding polarcube into gr-satnogs.
Kaitai Struct for downlink beacons still in progress.
I’ve used them to schedule ~40-50 observations for each satellite for the first 8h. Have in mind that these TLE may not be accurate so avoid to schedule observation with them in the far future. Waiting for TLE set from the satellite teams for more accurate orbit.
Given that we have received satellites with this TLE set, either something is wrong with the data or the calculations. Unfortunately I’m not familiar and I can not help.
I saw the transmitter frequency got changed to 401.35MHz, that was a typo in my first post. I double checked when I created the issue for the satellite it is at 401.365MHz.
Hi all, Patrick Walton from the BYU PICs team here. I noticed we’re out of your typical frequencies, but we should have a beacon transmitting automatically every 30 seconds on the 903.65-903.95 MHz band (PIC-A) and the 903.25-903.55 MHz band (PIC-B). So if any of you want to try and listen for the beacon, please let us know.
Also, are there any other communities that we might reach out to that might be interested in helping us make first contact?
Those frequencies are right in the middle of a 3G band (UTRA band 8) in Europe, Africa, and Australia. In fact, that frequency is right in the middle of an uplink to a Optus (phone provider) tower near my house.
How were you assigned those frequencies? They seem to be a terrible choice, and I’m surprised it would be legal transmit on them if you are not over North America at the time.
Certainly pretty much all stations outside of the US will have great troubles trying to receive anything on those bands due to interference from cell towers.
