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GASPACS CubeSat Communications Information

GASPACS is a 1U CubeSat designed, developed, and completed by undergraduate students on the Get Away Special team at Utah State University.

GASPACS stands for Get Away Special Passive Attitude Control Satellite. The satellite is a technology demonstration for an inflatable boom structure that will double as a passive attitude stabilization device due to the aerodynamic drag in Low Earth Orbit (LEO).

GASPACS was launched on 12/21/2021 on SpaceX CRS-24. GASPACS is currently aboard the International Space Station (ISS), with deployment into orbit via the NanoRacks CubeSat Deployer (NRCSD) scheduled for the week of 1/24/2022. This page will be updated after deployment with information on tracking GASPACS and ongoing mission operations.

UPDATE: 1/28/2022!!

GASPACS is in orbit and fully operational!! Several images, and telemetry data have been received. For updates and copies of the pictures, see:


Note: this has only been tested to work on Windows 10. It should work on linux as well, but it is not tested.

  1. GASPACS only transmits images and telemetry by command. The GAS team can schedule downlinks over other ground stations. If you would like us to attempt a downlink over your ground station, email
  2. Record a GASPACS observation containing image or telemetry downlink (or find a recording)
  3. Download the soundmodem made by UZ7HO:
    • Note: gr-satellites has also been able to demodulate GASPACS packets, however the output format of the packets has not been tested to work with the GASPACS decoding script.
  4. Route your computer’s audio output into its audio input, so you can have the recorded audio as an input for the soundmodem program.
  5. Run the soundmodem program. Under Settings, click “Open monitor log file”. Save the log file somewhere you’ll remember (make sure the log file is a .txt file).
  6. Play the audio recording, and watch as packets are decoded in the soundmodem program.
  7. Download the GASPACS decoder software:
  8. Install the GAS team fork of SSDV:
  9. Edit line 329 of to point to the full PATH/FILENAME of your SSDV executable
  10. Test the decoder software by moving the file “Example-W7KKE-soundmodem-ouput.txt” into the “new” folder, and run the script.
    • If all goes well, you should see a lot of packets printed to the console, and there will now be a “0” folder in the “Pictures” folder, which will contain a .bin file, and the decoded .jpeg! The Example .txt file will be moved into the “old” folder. To decode it again, simply move the .txt file back into the “new” folder.
  11. To demodulate and decode your own recording: simply move your soundmodem log .txt file into the “new” folder, and run
    • This program will work with images, TTNC data, Attitude Data, and Deployment Data from GASPACS. Images are placed in the “Pictures” folder under their appropriate image ID, and data is stored in the “allData.csv” file.
    • This program can handle missing image packets, out of order packets, and images received over multiple different transmissions. It will automatically combine picture packets from multiple .txt files, so if you receive half of the picture in one transmission, and the other half in another, it will put them together into a final .jpeg!

RF Specifications:

CubeSat Communications Hardware:

Packet Structure:

All packets transmitted by GASPACS utilize the Endurosat radio packet structure, containing a preamble, sync word, payload, and CRC16: Screenshot 2022-01-11 025351.jpg Screenshot 2022-01-11 025456.jpg

AX.25 Packet Structure:

Every 120 seconds, an AX.25 beacon is broadcasted:

Audio Beacon Information:

Every 500 seconds, an audio beacon is broadcasted:

Telemetry Packet Structure:

All telemetry and image packets fit inside of the Data Field 2 “Payload” portion of the Endurosat packet structure.

GASPACS has three types of telemetry packets: Attitude, Deployment, and TT&C

Attitude Data:

Deployment Data:

TTNC Data:

Image Packet Structure:

GAS Team Ground Station: