[OnACoffeeBreak]

From the Introduction: "Each satellite may carry traffic for dozens of independent networks through an array of on-board transponders, each covering a diameter of thousands of kilometers (at most a third of Earth’s surface)".

Can someone help me understand the use of "diameter" in this sentence. I am guessing it refers to the satellite's signal coverage of the Earth's surface. If that's the case, wouldn't something like arc degrees be a better measure? I just can't figure out how "diameter" can be used to describe a coverage arc or area.

[jnovacho]

They mean the intersection between the cone produced by the satellite and "illuminated" surface. If the antenna beam is normal to the sphere, it will produce a disk which has an diameter.

[slow_typist]

This, and 1/3 of earth’s surface is the maximum you can see from geostationary orbit.

[alterom]

Yeah, diameter is ambiguous (is it the diameter of the disk in space, or in the geometry/topology of the Earth's surface?).

Either way, they point is, it's a lot of coverage.