The person with the answers is U.S. Space Command spokesman Air Force Maj. That would be clear if there was a definite line between atmosphere and space, but that's not the case. The atmosphere fades to space. For example, astronaut wings are awarded when an individual is on a flight that reaches 50 miles in altitude or higher. All communications and missile-warning satellites are in geosynchronous orbit about 22,300 miles up.
Geosynchronous orbit allows the uplink and downlink of satellite signals over great distances.
Missile warning satellites can monitor over 90 percent of the Earth's surface. One of the more popular satellite systems in use today is the Global Positioning System. GPS satellites are in semi-synchronous orbit, about 11,200 miles in space. GPS is absolutely critical to U.S. military operations. GPS is a global navigational aid to deployed U.S. forces and our allies.