The Telemetry from Thybolt satellites Thybolt-1 and Thybolt-2 are encoded in CCSDS frame format. Upon demodulating the 2-FSK signal at 4800 BaudRate, operators will be able to view the sync word ‘PDOT’ followed by the CCSDS frame.
Telemetry packet is divided into two parts, Sync Word/Preamble and CCSDS frame
| PDOT Preamble Detector Block | Online Decoder | ||
|---|---|---|---|
| Sync Word <AAAAAAAAAAAAAAAA> | Preamble <D42D50444F54> | CCSDS Frames 510 Bytes | |
Amateur Radio Operators can use below mentioned gr-thybolt block to extract ccsds packet and upload it in online decoder software mentioned below to view decoded telemetry packet
PDOT preamble detector block is developed so users can use GNU Radio 3.8.0 with any supported SDR to detect the syncword, preamble and automatically retreive the required encoded packet in Message Debug Block.
The Encoded packet will further have to be uploaded in the online decoding tool to view Telemetry data.
Currently the block is developed and tested for Ubuntu 18.04.6 LTS and GNU Radio 3.8.0 and will soon be available in GNU Radio versions 3.9 and 3.10
Block Details :
- Parent : gr-thybolt
- Name : PDOT preamble detector
- Input : Bytes
- Output : PDU print
- Default Packet Length : 510 (Thybolts' satellite telemetry packet length)
The above image is available in assests folder
Instructions to install :
- mkdir build
- cd build/
- cmake ../
- make
- sudo make install
- sudo ldconfig
Link : thyboltmission.web.app
After fetching 510 bytes in Message Debug Block, upload the plain hex data in the website's text-feild to see decoded telemetry data
Detailed instructions with example are available on website.
Total Packet Size after demodulation : 522 Bytes
Header : Sync Word(AAAAAAAAAAAAAAAA) + Preamble(D42D50444F54) -> 12 Bytes
CCSDS Frame : Convoluted Coding(1/2,7) -> 255 Bytes
Reed-Solomon(255,223) -> 32 Bytes
Data Link Layer -> 8 Bytes
Space Packet Protocol -> 6 Bytes
Telemetry Data -> 186 to 209 Bytes