Observation 6313699: Geoscan-Edelveis (99395)

geoscan · August 10, 2022, 5:03am

Regarding Observation 6313699 …
Looks like our beacon! It sends message every 30 seconds. What we see here. Might be a good observation but somehow shifted?

PE0SAT · August 10, 2022, 7:28am

If so, then the configured frequency is way of, it looks like it is 25kHz higher then configured.

Can you confirm the frequency that should be used.

fredy · August 10, 2022, 7:48am

You refer to signals around 330s and 360s right?

Given that we don’t have identified the satellite, this shift is caused due to inaccurate TLE. When we identify which object is it, then we can check if there is a shift on the frequency itself, until then is not safe to calculate it.

EDIT: here is more visible SatNOGS Network - Observation 6313702

geoscan · August 10, 2022, 8:21am

We got signal at 436.200 MHz + doppler shift. So frequency is right. On both observations there is some signal with shift around 25 kHz. What could it be?

fredy · August 10, 2022, 10:43am

Oh, this is another satellite, not sure if it is from the same or another launch. We need to investigate it more. The signal looks like the one we get from the other satellites of this launch but we don’t know any of them to transmit on this frequency.

Let’s watch it for the next hours/days and see if we can find anything.

PE0SAT · August 10, 2022, 11:30am

Looking at an IQ recorded file (SatNOGS Network - Observation 6313689), we also found 9k6 signal

I am only unable to decode the signal, what are you using as a transceiver, can you give more detail on the signal.

geoscan · August 10, 2022, 11:47am

Yes, this is ours! Thank you! We are using CC1125 Texas Instruments chip. Information about our signal given in this file.
Main signal details:
GRTP.pdf (339.9 KB)

The satellite uses a Texas Instruments CC1125 FSK transceiver chip
frequency — 436.200 MHz
2-GFSK 9k6 baud
Preamble — 0xAAAAAAAA
Syncword — 0x930B51DE (in big-endian notation)
CRC16-CCITT(0x1021). Initialized to 0xFFFF. The final XOR value is 0.
Fixed packet size — 74 bytes
PN9 scrambler
CC11xx packet format length and address fields are used for our header

Almost like AALTO-1 and Reaktor Hello World. Bot we have different Syncword. (see Decoding packets from AALTO-1 ( 42775))

PE0SAT · August 10, 2022, 2:11pm

Thank you for the information, we will try to decode the data.

I do hope to get a better reception with some more SNR, if you have a example recording, that would help a lot.

Jan

PE0SAT · August 11, 2022, 11:59am

Decoding GEOSCAN, are these frames valid?

* MESSAGE DEBUG PRINT PDU VERBOSE *
((transmitter . 8k FSK downlink))
pdu_length = 64
contents = 
0000: 01 00 26 04 20 84 8a 82 86 9e 9c 60 a4 a6 64 60 
0010: a6 40 60 03 f0 0c 00 e1 05 bd 05 1b 00 09 00 58 
0020: 9e c7 09 e6 eb 00 f1 01 00 00 00 00 00 00 00 00 
0030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
***********************************

PE0SAT · August 11, 2022, 12:16pm

After some further investigation, it seems my initial IQ replay could be wrong.
Based on a new AF recording I got the following:

* MESSAGE DEBUG PRINT PDU VERBOSE *
((transmitter . 9k6 FSK downlink))
pdu_length = 64
contents = 
0000: 01 00 29 02 20 ff ff ff ff ff ff ff ff ff ff ff 
0010: ff ff ff ff ff ff ff ff ff 58 14 ff 54 4b ed 0c 
0020: 05 0b 07 80 07 01 02 00 02 00 00 00 00 00 00 00 
0030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
***********************************

Some extra decoded frames:

* MESSAGE DEBUG PRINT PDU VERBOSE *
((transmitter . 9k6 FSK downlink))
pdu_length = 64
contents = 
0000: 01 00 26 04 20 84 8a 82 86 9e 9c 60 a4 a6 64 60 
0010: a6 40 60 03 f0 0c 00 e1 05 bd 05 1b 00 09 00 58 
0020: 9e c7 09 e6 eb 00 f8 01 00 00 00 00 00 00 00 00 
0030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
***********************************
gr::log :INFO: crc_check0 - CRC OK
* MESSAGE DEBUG PRINT PDU VERBOSE *
((transmitter . 9k6 FSK downlink))
pdu_length = 64
contents = 
0000: 01 00 26 04 20 84 8a 82 86 9e 9c 60 a4 a6 64 60 
0010: a6 40 60 03 f0 0c 00 e1 05 bd 05 1b 00 09 00 58 
0020: 9e c7 09 e6 eb 00 f8 01 00 00 00 00 00 00 00 00 
0030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
***********************************
gr::log :INFO: crc_check0 - CRC OK
* MESSAGE DEBUG PRINT PDU VERBOSE *
((transmitter . 9k6 FSK downlink))
pdu_length = 64
contents = 
0000: 01 00 26 04 20 84 8a 82 86 9e 9c 60 a4 a6 64 60 
0010: a6 40 60 03 f0 0c 00 e1 05 bd 05 1b 00 09 00 58 
0020: 9e c7 09 e7 ec 00 f8 01 00 00 00 00 00 00 00 00 
0030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
***********************************

geoscan · August 11, 2022, 3:00pm

PE0SAT, thank you very much! This is our frame. First five bytes here is our header generated for every message. They can be cut off. Here is message from our beacon. Starting from 0x84 is our payload message in AX.25 format.
Destination - BEACON with SSID 0:

84 8a 82 86 9e 9c 60

Source - RS20S with SSID 0:

a4 a6 64 60 a6 40 60

Control byte and PID:

 03 f0

And then data till 0’s, kaitai decoder for which we can integrate in Satnogs.

geoscan · August 16, 2022, 11:33am

PE0SAT, fredy, hello! Did someone figured out what second satellite on spectrum here is? It looks like it’s satellite from our launch and it’s frequency is close to 436.220-436.225 MHz. The signal looks like it’s from Sputnix satellites as it looks similar to the other satellites of this launch.

PE0SAT · August 16, 2022, 2:07pm

Hi,

No I have no idea, I am still not able to decode the transmission.
So all information is welcome.

PE0SAT · August 16, 2022, 7:52pm

I couldn’t resist and had another try, and yes, we found the satellite.

It is CYCLOPS, VOENMEH, SXC3-2110 RS29S on 436.050 MHz.

-> Packet from 2k4 FSK downlink
Container: 
    header = Container: 
        addresses = ListContainer: 
            Container: 
                callsign = u'R2ANF' (total 5)
                ssid = Container: 
                    ch = False
                    ssid = 0
                    extension = False
            Container: 
                callsign = u'RS29S' (total 5)
                ssid = Container: 
                    ch = False
                    ssid = 1
                    extension = True
        control = 0x00
        pid = 0xF0
    info = b'\x16B\x02\x00\x01\x00B\x00\x99\x14\xef\x15H\x14\x02\x00\x01\x005\x03\xba\x00\x00\x00\x1e\x00\x00\x00\x00\x00\x06\x00\x02\x00\x02\x00\x07\x00< \x00\x00\xc0\x1e\x0f\xcc\x02\x00G\xd2\xf4bL\x0c\x07\x06\xff\x80 \x08\xcb\x1eH\xd2\xf4b\x18\x15\x00\x00\x1e\x00\xf4\x1e' (total 74)

geoscan · August 17, 2022, 7:22am

Thank you very much! Now we all know!

73!

geoscan · August 17, 2022, 2:35pm

Is it possible to integrate demodulation for our signal in SatNOGS for data to appear after observations? I know that there is a flowgraph for Reaktor Hello World which is similiar to ours.

jebba · August 17, 2022, 2:47pm

Try to get it integrated into gr-satellites, then many ground stations will be able to decode it.

PE0SAT · August 17, 2022, 3:01pm

Look at the beginning of this post, this is already done.

cat GEOSCAN-EDELVEIS.yml

name: GEOSCAN-EDELVEIS
alternative_names:
   - RS20S
   - GEOSCAN
norad: 53385
data:
   &tlm Telemetry:
     unknown
transmitters:
   9k6 FSK downlink:
     frequency: 436.200e+6
     modulation: FSK
     baudrate: 9600
     framing: GEOSCAN
     data:
     - *tlm

fredy · August 17, 2022, 5:13pm

@geoscan We can try GFSK Rktr mode for some observations if you want to. Just let me know.

PE0SAT · August 17, 2022, 7:46pm

That will not work, the deframing isn’t compatible.
Daniel created a new version, called framing: GEOSCAN