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StoriesPlace: Orbit

Orbits as infrastructure

Low orbits are fast and crowded, high orbits slow and spacious. Every choice of altitude is a trade between delay, footprint and how long the satellite stays up; the arithmetic is two centuries old and the traffic rules are new12.

Systems
LEO, MEO and GEO, Ground stations, Space sustainability
Toward 2030
Non-terrestrial networks in the cellular standard
Figures
4, map story, data story, simulator, timeline to 2030

Go to the references

01Map story

Four orbits around one Earth.

A broadband shell at 550 km, a sun-synchronous imaging orbit near 700 km, a navigation orbit at 20,200 km and the geostationary ring at 35,786 km. Each period follows from the altitude alone1.

Figure as text: Four orbit classes and their ground tracks

A wireframe globe with four orbits in red and their ground tracks: two low orbits, a medium orbit and the geostationary ring.

  • Ground station (45.4° N, 75.7° W)

02Data story

Delay is geometry.

From user to satellite to gateway, the signal travels at the speed of light over two slant ranges. At the edge of coverage, that alone takes milliseconds in low orbit and roughly a quarter of a second in geostationary orbit. These values are computed, not measured, and exclude processing and terrestrial routing3.

Figure as text: Bent-pipe propagation delay by orbit, at a 25° elevation mask

A bar chart of one-way user-to-gateway propagation delay at a 25 degree mask for five altitudes, rising from a few milliseconds in low orbit to about a quarter of a second in geostationary orbit.

Bent-pipe propagation delay by orbit, at a 25° elevation mask (ms)
OrbitOne-way delay
LEO 550 km7.5
LEO 1,200 km14.7
MEO 8,063 km70.3
MEO 20,200 km155.1
GEO 35,786 km260.6

03Simulator

Choose an altitude.

Raise the orbit and each satellite serves a wider circle, but the delay grows and the link budget worsens. Lower it and the opposite holds, and atmospheric drag shortens the satellite’s life, which the five-year deorbit rule now bounds in the United States2.

Figure as text: Footprint, delay and period by altitude

A section through the Earth with a satellite above it on a log altitude scale and its footprint arc in red.

Footprint, delay and period by altitude, at the starting values
Altitude550 km
Elevation mask25 °
Footprint radius940.5 km
Slant range at the mask1,123.3 km
One-way delay, nadir1.83 ms
Bent-pipe delay, user to gateway7.49 ms
Orbital period96 min

04Timeline to 2030

Traffic rules for orbit.

The cellular standard added non-terrestrial access in 20224; the 2023 World Radiocommunication Conference updated the spectrum rules many constellations depend on5; the five-year rule sets a deadline for leaving low orbit after the mission ends2.

Figure as text: Rules and standards for the orbital commons

A timeline from 2020 to 2030 with the NTN study, the initial NTN release, the five-year rule and WRC-23.

  1. 2020 Non-terrestrial networks studied (3GPP TR 38.811). Channel models and deployment scenarios for satellite access to 5G.3
  2. 2022-06 First NTN release. Release 17 adds satellite access to the cellular standard.4
  3. 2022-09 Five-year deorbit rule. Satellites in low orbit to be removed within five years of mission end.2
  4. 2023-12 WRC-23 Final Acts. Updated international rules for satellite spectrum.5

Figure 1

Map story

Orbit 550 km, 53°
95.5 min
Orbit 700 km, 98.2°
98.6 min
Orbit 20,200 km, 55°
718.4 min
Orbit 35,786 km, 0°
1435.7 min

Figure 1. Four orbit classes and their ground tracks. A wireframe globe with four orbits in red and their ground tracks: two low orbits, a medium orbit and the geostationary ring.

References

  1. Fundamentals of Astrodynamics and Applications, 4th edition. Vallado, D. A., Microcosm Press, 2013.
  2. Space innovation; mitigation of orbital debris in the new space age, Second Report and Order (FCC 22-74): the five-year rule. United States Federal Communications Commission, 2022.
  3. 3GPP TR 38.811: Study on New Radio to support non-terrestrial networks. 3rd Generation Partnership Project, 2020.
  4. Releases: the timeline of 3GPP Releases 17 to 21. 3rd Generation Partnership Project, 2025.
  5. World Radiocommunication Conference 2023 (WRC-23): Final Acts. International Telecommunication Union, 2023.

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Where this applies

Space and satellite systemsConnectivityPositioning, navigation and timingEarth observation & GeoAITelecomGovernmentResearchField tour: orbit viewField tour: ground station