Tracking, TLEs & spacecraft identification

Also known as NORAD ID, COSPAR ID, TLE, OMM, 18 SDS

NORAD/COSPAR cataloguing by the 18th Space Defense Squadron, SGP4 orbital elements (TLE/OMM), radar cross-section of 5 cm cubes and Differential Doppler identification.

Document
SQ-OP-006
Updated
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How 5 cm picosatellites are tracked and catalogued

The US Space Force 18th Space Defense Squadron (18 SDS) maintains the public satellite catalogue (Space-Track / CelesTrak), assigning each tracked object a five-digit Catalog Number and an international COSPAR designator (e.g., 2022-002 for Falcon 9 Transporter-3)[1]. Orbits are distributed as Two-Line Elements () or CCSDS Orbit Mean-Elements Messages (OMM) designed for propagation with the analytical theory[2].

Approximate radar cross-section (RCS) across UHF (440 MHz), S-band (3.1 GHz), and X-band (10 GHz) space-surveillance regimes
Spacecraft configurationUHF 440 MHz (dBsm)S-band 3.1 GHz (dBsm)X-band 10 GHz (dBsm)S-band scattering regime
1P PocketQube (50 × 50 × 50 mm, bare bus)−43.0−24.5−16.4Mie
1P PocketQube + 34 cm UHF dipole−11.1−18.4−8.3Optical
3P PocketQube (50 × 50 × 178 mm)−22.5−13.8−3.6Optical
1U CubeSat (100 × 100 × 100 mm)−25.0−12.5−2.3Optical
1P PocketQube + mini X-band corner reflector−38.3−11.7−3.6Mie

Breaking the cluster ambiguity with Doppler curves

When a mission releases small satellites within a few minutes, differential separation velocities () separate adjacent spacecraft by only along-track per day[3]. During the first week, 18 SDS publishes unassigned tracks (OBJECT A, OBJECT B, …).

Operators identify which ID belongs to their spacecraft by comparing the measured Time of Closest Approach (TCA)—the inflection point where the UHF downlink crosses zero—against the TCA predicted by for every candidate in the deployment cluster across multiple passes[4].

References

  1. [1]nadir lab. (2026). PocketQube-class picosatellites: architecture, flight heritage, and a multi-method post-flight analysis of Grizu-263A [Preprint]. nadir lab. Research Monographs (SQ-R-001).Read on nadir lab.
  2. [2]Vallado, D. A. (2013). Fundamentals of Astrodynamics and Applications (4th ed.). Microcosm Press.
  3. [3]Libre Space Foundation community forum. (2022). SpaceX F9 Transporter-3, 2022-01-13 15:25 UTC (discussion thread).community.libre.space(accessed 20 October 2026)
  4. [4]Libre Space Foundation. (2026). SatNOGS DB — satellite and transmitter database.db.satnogs.org(accessed 20 October 2026)

Cite this SatWiki entry

@misc{nadirlab2026tracking,
  author       = {{nadir lab.}},
  title        = {{Tracking, TLEs \& spacecraft identification}},
  year         = {2026},
  month        = oct,
  howpublished = {nadir lab. SatWiki SQ-OP-006 (Rev. 1)},
  url          = {https://nadirlab.space/wiki/tracking-identification/}
}