U.S. military space leaders and outside experts both agree that the U.S. has a lot of work to do in order to protect military and civilian space-based assets. One uncontroversial step the U.S. can take is to increase and improve ground and space-based assets to identify and keep track of objects in orbit. Currently, the U.S. has a ground network of telescopes and radar sites to keep tabs on about 8,100 man-made objects in orbit ranging from a lost glove to empty satellite boosters, but it's not hard to sneak a few extra devices into orbit.
Small "microsatellites," weighing under 220 pounds and measuring under three feet in length, can be tucked away as secondary payloads on launches of larger satellites. Once in orbit, they are very difficult to spot and can have the capability to maneuver close to other spacecraft on their own. A microsat flying in formation with another satellite could use any number of ways to either temporarily disrupt or permanently damage optics, electronics, and communications links. The U.S. Air Force has looked into the possibility of temporarily "sliming" a spacecraft's optics with a substance that would dissipate over time in order to disrupt access to satellite imagery without causing permanent damage and has also officially deployed a capability to temporary disrupt satellite communications. The Counter Communications System was built with commercial off the shelf (COTS) equipment and is designed to be air transportable.
Satellites most vulnerable to attack are those in low-earth orbit around 200 to 400 kilometers up, including optical imaging, radar, and some signal intelligence platforms. The same features that require them to be in low-earth orbit make them more accessible to interference by either directed energy weapons, such as laser or microwave devices, or by interception by a ground-launched microsatellite. Complicating matters, the United States and Russia are now joined by Europe (through the European Space Agency), China, Japan, India, Israel, and Brazil in having the capability to put payloads into orbit; North Korea could also arguably be put onto the list. Europe, China, Japan, India, and Israel have all put imaging satellites into orbit. Doug Mohney
The U.S. military has an ongoing nightmare a call from the White House asking two questions: "What happened to our satellite? And what are you doing about it?" Today, with few exceptions, the answers would be "We don't know and there's not much we can do." Threats to space assets range from terrorist attacks on ground stations, communications jamming, lasers used to blind spacecraft optical systems, and nuclear detonations in space.