After 30 years and 135 missions, it's curtains for NASA's Space Shuttle. The Shuttle Atlantis blasted off on Friday for one last rendezvous with the International Space Station, bringing to an end the current era of impressive -- but pricey and dangerous -- manned spaceflight. But never fear! America's space arsenal might be down four giant Shuttles, but there's still plenty of U.S. government hardware orbiting the Earth, much of it top secret.

Counting commercial satellites with government missions, Washington has access to around 400 spacecraft -- four times as many as the number-two space power, Moscow. U.S. spacecraft include communications satellites, orbital cameras and other sensors, craft designed to eavesdrop on radio traffic and at least one secretive, robotic space plane similar to in shape to the retiring Shuttle.

Here's a sampling of some of the "blackest" of America's secret space fleet.

Spotting missile launches from space is old hat -- the Air Force's Defense Support Program infrared-sensing satellites have been detecting missiles' heat blooms since the 1960s. But when the Pentagon began seriously trying to shoot down ballistic missiles in the 1990s, it realized it needed faster, more accurate space detection -- and that meant flying lower. Enter the Space Tracking and Surveillance System, built by Northrop Grumman and Raytheon on behalf of the Missile Defense Agency and the Air Force and launched beginning in 2009.

STSS orbits just 100 miles high, compared to 22,000 miles for the geosynchronous DSP. Northrop happily discusses the accomplishments of the two newest STSS sats, but there's a third bird whose exact mission was classified. The Missile Defense Agency is now trying to coax STSS into automatically providing targeting data to the Navy missile-killing Aegis warships.

Photo: Northrop Grumman