Private companies are now offering "spy satellite photos" that, while not equal to the "golf-ball detecting" and "license-plate reading" capabilities of the best US military satellites, are still more than adequate to tell a potential adversary how many planes are located at a given base and their sortie-generation rates. The US was very concerned about one such company which might have sold photos of NATO bases during the Kosovo War, but its first spy satellite conveniently crashed into the Pacific a few minutes after liftoff on 27 April.--Stephen V Cole

The next generation of spy satellites will be designed to avoid or survive attacks. Defenses could include some hardening with aluminum foam, decoys, and detectors that give a satellite enough warning to evade an attack. Another solution is a satellite able to quickly and repeatedly change orbit to avoid allowing the enemy to gain a target solution, although the key to making this idea work is as-yet-undeveloped power sources or some kind of system able to refuel the satellites cheaply. Another option is to launch dozens of small spy satellites which combine to get the job done but individuals can be lost without compromising the network.--Stephen V Cole