Orbital Mechanics & Latency
The Physics of Non-Terrestrial Routing
The Altitude-Latency Tradeoff
The primary constraint on satellite latency is the speed of light () and the altitude of the satellite.
| Orbit | Altitude | One-Way Delay | RTT (Minimum) |
|---|---|---|---|
| GEO | 35,786 km | ~120 ms | ~480-600 ms |
| MEO | 2,000 - 35,000 km | ~15-100 ms | ~100-250 ms |
| LEO | 500 - 1,200 km | ~2-4 ms | ~20-40 ms |
Operational Zone
leo Constellation
RTT LATENCY
3-10 ms
Orbital Mechanics
The physics of satellite networking is a function of signal propagation delay (c = 299,792 \text{ km/s}). Higher altitudes equate to larger propagation paths and increased round-trip times (RTT).
Ultra-low latency. Ideal for real-time cloud gaming, high-frequency trading (HFT), and VoIP.
Keplerian Elements: The Geometry of a Path
To calculate where a satellite is (and thus its latency), we use the six Keplerian Elements. These define the size, shape, and orientation of the orbit in 3D space.
The Orbital Fingerprint
- Semi-Major Axis (): The average distance from the Earth's center. This determines the orbital period .
- Eccentricity (): The 'roundness' of the orbit. Most LEO satellites target for consistent low latency.
- Inclination (): The angle relative to the equator. Polar orbits () provide global coverage but require more complex routing over the poles.
- Argument of Perigee (): The orientation of the orbit's 'closest point' to Earth.
Doppler Shift & The Relativistic Tax
LEO satellites move at . This high velocity introduces two types of frequency shift:
ISL: Inter-Satellite Laser Links
The 'Holy Grail' of satellite networking is the Inter-Satellite Link (ISL). Instead of bouncing signals back to a ground station (Bent Pipe), satellites communicate directly using 1550nm lasers.
This makes LEO-ISL networks faster than subsea cables for long-haul routes (e.g., London to Singapore), even with the added distance of going up and down to orbit.
Ionospheric Delay & TEC
The Ionosphere is a shell of ionized electrons that refracts radio waves. This introduces an additional delay () proportional to the Total Electron Content (TEC).
Because the delay is inversely proportional to the square of the frequency , higher frequency bands like Ka-band are much less affected by ionospheric jitter than lower L-band signals.
Slant Range Geometry
Latency is not constant; it depends on the elevation angle ($\epsilon$). A satellite at the horizon (low $\epsilon$) has a much longer path through the atmosphere (slant range) than one directly overhead (Zenith).
Conclusion
Orbital mechanics dictates the physics of future global connectivity. By moving the backbone of the internet into LEO, we are bypassing the refractive index of glass and the slow mechanics of GEO orbits, bringing us closer to the light-speed limit of communication.