TOP.07 // ASTRODYNAMICS
Orbital Mechanics, Thermospheric Drag & Lifetime
King-Hele orbital contraction, Kennewell–Voigt F10.7 solar-cycle thermospheric density, ballistic coefficients, and Solar Cycle 25 LEO orbital decay reconstructions.
1. SatWiki Encyclopedia Specifications (3)
- SQ-EN-002
Space environment
What low Earth orbit does to a small satellite: a thermosphere whose density follows the Sun, atomic oxygen, trapped and solar radiation, a dipole-like magnetic field, strong thermal forcing and debris. PocketQubes feel each effect more strongly per kilogram.
- SQ-OP-003
Regulation and debris mitigation
Spectrum coordination, licensing and the end-of-life rules that decide where a small satellite may fly. The FCC five-year rule and the older 25-year guideline translate directly into altitude ceilings for spacecraft without propulsion.
- SQ-OP-006
Tracking, TLEs & spacecraft identification
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.
2. Interactive Lab Calculators & Workbenches (3)
3. Technical Notes (3)
- NL-TN-2026-016
Tracking a 5 cm satellite
A bare 50 mm cube sits deep in the Rayleigh scattering regime for UHF space-surveillance radars, yielding a radar cross-section near −43 dBsm. Once its 437 MHz tape-spring monopole or dipole deploys, resonant wire scattering boosts RCS by 25–30 dB. We examine radar cross-section across UHF, S-band and X-band and explain how Differential Doppler resolves rideshare TLE lotteries.
- NL-TN-2026-006
Meeting the five-year rule without propulsion
Satellites launched after 29 September 2024 under FCC authorization must re-enter within five years of the end of their mission. For a spacecraft without propulsion the rule becomes an altitude ceiling that depends on its ballistic parameter and on the Sun. With the lifetime model of the PocketQube review, a fully loaded 1P stays within five years below 559 km at moderate activity, between 493 and 627 km from low to high activity, while 1U, 3U and 12U CubeSats are limited to 525, 513 and 494 km. Above the ceiling, a tumbling drag sail of 80 cm² brings a 1P down from 600 km at moderate activity, but about eight times more at low activity, and a perigee-lowering burn costs 70–150 m/s, a seventh of a 1P’s mass in cold gas at 600 km. For PocketQubes the release orbit is the compliance strategy.
- NL-TN-2026-001
Orbital decay and lifetime of PocketQubes and CubeSats
We derive the drag-driven decay of a circular low Earth orbit from the energy equation, evaluate it with the single-scale-height density model of Kennewell driven by F10.7 and Ap, and produce lifetime tables for PocketQube and CubeSat form factors from 300 to 650 km. From 500 km at moderate activity a fully loaded 1P lives 1.7 years and a 1U 3.1 years; solar activity alone moves the 1P between 0.7 and 5.8 years. Checked against the re-entries of Grizu-263A and Delfi-PQ, both released from Transporter-3, the model overestimates lifetime at constant flux, as expected from a single scale height and the fast rise of Solar Cycle 25. We close with how lifetimes should be reported.