Question

How far away is the orbit of the closest man made satellite?

Answer 1

Roughly 100 miles up.

Explanation:

Those satellites, however, have the shortest lifetime. Even though at 100 miles the satellite it considered 50 miles past the earth's atmosphere that is only partially true. The earth's atmosphere actually pulses between daylight and night, the ionosphere being created during the daytime. Other naturally occurring phenomena also extend the height of the atmosphere.
For a satellite to remain in orbit it needs two things, the least elliptical orbit plus a single orbit time greater than 90 minutes.