Question

What is a geosynchronous orbit? Roughly how far from the surface of the earth is a geosynchronous orbit? Why are spy satellites NOT placed there?

Answer 1

A geosynchronous orbit is a high Earth orbit that allows satellites to match Earth's rotation. Located at 22,236 miles (35,786 kilometers) above Earth's equator, this position is a valuable spot for monitoring weather, communications and surveillance.A geosynchronous orbit (sometimes abbreviated GSO) is an orbit around Earth of a satellite with an orbital period that matches Earth's rotation on its axis, which takes one sidereal day (23 hours, 56 minutes, and 4 seconds). The synchronization of rotation and orbital period means that, for an observer on Earth's surface, an object in geosynchronous orbit returns to exactly the same position in the sky after a period of one sidereal day.

Spy satellite or reconnaissance satellite are placed at lower orbits (400 km ) from the surface of earth for communication and seeing different regions at different times of day.A satellite in geosynchronous orbit can see one spot of the planet almost all of the time. The higher a satellite is above Earth the slower it moves. This is because of the effect of Earth's gravity; it pulls more strongly at satellites that are closer to its center than satellites that are farther away. In order to move from one place to other spy satellites need to be placed in lower or medium orbits but not in Geosynchronus orbit.