Satellite Coverage Calculator
How much of the Earth one satellite sees from a given altitude — the footprint radius and area, the share of the globe, the minimum satellites for continuous coverage, and the orbital period.
A satellite at altitude h sees the ground out to the horizon, but a ground station needs the satellite some way above its own horizon — ten degrees is a common minimum — which shrinks the footprint.
How the satellite coverage calculator works
A satellite at altitude h sees the ground out to the horizon, but a ground station needs the satellite some way above its own horizon — ten degrees is a common minimum — which shrinks the footprint. The geometry is one triangle: Earth's centre, the satellite, and the edge of coverage.
Higher is bigger: a geostationary satellite sees 42% of the planet; one at 550 km sees under 1%, which is why low-orbit constellations need hundreds of satellites and geostationary systems need three.
Formula: β = arccos(R cos ε / (R + h)) − ε; fraction = (1 − cos β) / 2
Worked examples
| Inputs | Share of Earth's surface covered | Note |
|---|---|---|
| Low orbit at 550 km | 1.6964% | under 1% each |
| Geostationary | 42.4437% | 42% of the planet |
| A stricter ground station | 0.5439% | a much smaller footprint |
FAQFrequently asked questions
How much of the Earth can a satellite see?
It depends on altitude: 0.5% from 550 km with a 10° elevation mask, 42% from geostationary orbit. No single satellite sees more than half.
What is minimum elevation?
How high above a ground station's horizon the satellite must be to give a usable link. Ten degrees clears trees and buildings; 25 is typical for phone antennas.
Why do constellations need so many satellites?
Because each low-orbit footprint is tiny and the satellites move at 7.6 km/s, so continuous coverage needs one always overhead. The no-overlap minimum here is the floor; real designs add half again.
Why three for geostationary?
Three satellites 120° apart each see 42% of the Earth, together covering everything except the poles. That was Arthur C. Clarke's 1945 proposal.
What is slant range?
The straight-line distance from ground station to satellite at the coverage edge — what sets signal delay and the transmitter power needed.
Where these figures come from
- NIST — CODATA 2018 fundamental physical constants — G and the speed of light
- IAU 2015 Resolution B3 — nominal solar and planetary conversion constants — the astronomical unit, solar mass and planetary radii
- CSIRO Space and Astronomy — Australia's national science agency
Last checked: September 2026. Constants are CODATA 2018 (G, c) and IAU 2015 nominal values (solar and planetary parameters).