Binar satellites mission

Satellites & Observations
21

Taking into consideration the successful transmit to Binar 3 last night, I have updated commands that can be sent by anyone who wishes to participate. The hex bytes below contain the preamble and framing - it can be transmitted exactly as below over a 437.850 MHz GFSK modulated signal, 9600 bps, mod index 1.

Ping:
aa aa aa aa aa aa aa aa aa aa d3 91 d3 91 0000: 3b 01 01 01 11 11 01 01 01 01 2d 31 08 48 6b 18 82 8a c6 0a f0 7d 87 7a c5 4b 29 45 67 38 9d 38 e2 f3 ec 6c e2 12 84 b1 fb 2c c0 dd 4e 1b b5 6f 4f b3 aa 7a 88 9e 5a 00 04 01 be ef 28 7e 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Satellite Response:
Ack packet within 5 seconds of transmission

Change to Application Mode:
aa aa aa aa d3 91 d3 91 3b 01 01 01 11 11 01 01 01 01 2d 39 45 ef 9a 9e ff cf 17 3e 06 50 6a 2f 65 bb 45 17 79 d8 c4 44 6b 2b fc d3 0b ae 20 26 fa 30 16 1d 07 a5 98 2d f1 5a e7 23 ce 6f b2 00 04 01 be ef a3 76 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Satellite Response:
Ack packet within 5 seconds. Decoding the satellite beacon using a hex to ASCII converter (or checking the ACSII data output in the SatNOGS pass Data column) will display the following text at the start of the beacon: “ID: Binar-3Op Mode: AMVK6BSP”. This will persist for approximately 1 hour.

Storage Mass Erase:
aa aa aa aa d3 91 d3 91 3b 01 01 01 11 11 01 01 01 01 2d 0f 76 29 42 63 56 65 42 a1 2b b8 88 e7 c5 9a c4 f5 13 97 0f 47 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Ack packet within 5 seconds.

The reason for mass erase on the storage is to bypass a small bug in the software - our file handling system detects that the file system is full approximately every hour and performs an automated file cleanup. Unfortunately, this action is CPU blocking and takes longer than the watchdog timer, thus the satellite reboots before completion. A manual erase command should bypass this issue and allow the satellite to remain in application mode for around a week.

Attached are IQ recordings of our transmissions sent across the lab, these have been captured at 192k sample rate. The recording has been taken with a -20k offset from transmit frequency to shift the LO interference generated by the LimeSDR. If these aren’t suitable let me know and we can obtain different recordings.

Tx_IQ_Recordings.zip

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22

I listened out for Binar-4 a couple of nights ago on a high pass over my QTH in Thailand. Sure enough, at the predicted time, a signal was visible on my SDR# waterfall, with the doppler shift controlled by Gpredict.

But the received frequency wasn’t 437.925 MHz (nominal). Instead, it was about 437.918 MHz!!

I track different satellites every day and update my TLEs every day. So I’m confused by this. Perhaps it wasn’t Binar-4? (The signal wasn’t strong enough for a decode).

If not Binar-4, then what bird could it have been?

23

We had noticed some slight shift in the beacon frequency for Binar-2 and Binar-3. It seems to be caused by instability in the frequency of the radio over temperature changes. We have seen a 3k shift within our TVAC chamber under vacuum at -20 degrees C while diagnosing the same issue. Do you have an IQ or WAV recording of the pass that we could investigate? We can get temperature data from the satellite beacon, if any pass CRC.

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24

Hi, unfortunately I don’t have a WAV file. I will listen out on the next high pass and record it :slight_smile:

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25

A large shift in the middle of the pass, at the beginning and end of the pass there is no shift. But I’m sure this is due to the rapidly obsolete Kepler data because the satellites are already low.

When I use fresh TLE, the shift is much less.

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26

BINAR-3 IQ file

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