The Altitude-Latency Tradeoff

The primary constraint on satellite latency is the speed of light ($c \approx 300,000\,\text{km/s}$) and the altitude of the satellite.

Doppler Shift in Orbit

Unlike GEO satellites which appear stationary to a ground terminal, LEO satellites move at approximately $7.5\,\text{km/s}$ relative to the Earth's surface. This high relative velocity causes a significant Doppler Shift in the carrier frequency.

Propagation in Vacuum vs. Glass

Light travels $\sim 31\%$ faster in the vacuum of space than it does in optical fiber ($n \approx 1.46$). This means that for trans-continental distances, an LEO satellite network with Inter-Satellite Laser Links (ISLL) can actually provide lower latency than a direct subsea fiber optic cable.

The latency advantage of vacuum-speed propagation.

Slant Range Geometry

Latency is not constant for a given satellite. It depends on the elevation angle ($\epsilon$). As a satellite moves from the horizon to the zenith, the distance (slant range) decreases, and so does the latency.

Calculating the Slant Range ($d$) for Earth radius ($R_E$) and altitude ($h$).

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.