Telemetry framing & protocols

Also known as AX.25, CSP, CCSDS, Kaitai Struct

AX.25, CubeSat Space Protocol (CSP), CCSDS reed-solomon/convolutional coding, Morse CW beacons and Kaitai Struct decoders for small-satellite downlinks.

Document
SQ-SS-012
Updated
21 Oct 2026
Reading time
1 min
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Why uncoded AX.25 loses marginal passes#

Amateur-band CubeSats historically transmitted uncoded UI frames with HDLC bit-stuffing and a 16-bit CRC[1]. Because HDLC aborts the entire frame if a single bit flips inside an flag sequence—and because uncoded 2- requires for [2]—uncoded AX.25 wastes low-elevation passes. Adding a Reed–Solomon outer code (correcting up to byte errors per block) or a rate-, constraint-length- convolutional inner code provides of coding gain.

References

  1. [1]nadir lab. (2026). PocketQube picosatellites: A review of standards, mission trends and miniaturization constraints, with lessons learned from Grizu-263A, Türkiye’s first PocketQube [Preprint]. nadir lab.Read on nadir lab.
  2. [2]Proakis, J. G., & Salehi, M. (2008). Digital Communications (5th ed.). McGraw-Hill.
  3. [3]Estévez, D. (n.d.). gr-satellites: a GNU Radio out-of-tree module with decoders for amateur satellites.github.com(accessed 20 October 2026)
  4. [4]Kaitai Project. (n.d.). Kaitai Struct: a declarative language for describing binary data structures.kaitai.io(accessed 20 October 2026)

Cite this SatWiki entry

@misc{nadirlab2026telemetry,
  author       = {{nadir lab.}},
  title        = {{Telemetry framing \& protocols}},
  year         = {2026},
  month        = oct,
  howpublished = {nadir lab. SatWiki SQ-SS-012 (Rev. 1)},
  url          = {https://nadirlab.space/en/wiki/telemetry-protocols/}
}