Calculate the delay in a relay

The Egyptian launch account identifies TIBA’s intended orbital longitude as 35.5 degrees east. A geostationary satellite circles above the equator at Earth’s rotational rate, so an observer sees it in approximately the same direction. The ideal orbit is circular and equatorial. Practical station keeping maintains the required position.

NASA’s orbit guide places this region roughly 36,000 kilometres above Earth’s surface. A ground antenna can therefore remain aimed toward a relatively fixed direction, but signals still cross a long distance. Longitude names the location around Earth; it is not an altitude and cannot by itself determine a terminal’s slant range.

Use an intentionally simplified relay: each space-to-ground leg is 36,000 kilometres, and radio waves travel at about 300,000 kilometres per second. One leg takes 0.12 seconds. A request from terminal to satellite to gateway crosses two legs, taking 0.24 seconds in propagation. A reply returning through the satellite adds two more, for 0.48 seconds round trip.

This is a teaching calculation, not a measured TIBA latency. Real endpoints usually have longer slant paths than the idealized vertical distance, and terrestrial routing, processing and queues add time. Do not count only one leg when describing a request and its reply.

Count all four space legs

Throughput is a rate of delivered data; latency is a delay. In a fictional link, transmitting a 12-megabit file at a sustained 6 megabits per second takes two seconds, before the modeled propagation and other delays. Doubling that data rate halves the serialization time for the file, but does not make the radio waves travel twice as fast.

A live conversation is sensitive to turn-taking delay. A scheduled file download may tolerate a longer wait if it delivers enough data by its deadline. These are different application needs. Evaluate the task with both timing and rate, rather than declaring one connection universally better because its advertised rate is larger.