The possibility of a collision such as that shown in the movie Gravity is real, although large objects are usually tracked with sufficient precision to enable the potential ‘target’ to take evasive action. The Department of Defense (DoD) maintains a highly accurate satellite catalog on objects in Earth orbit that are larger than a softball. DoD’s Space Surveillance Network tracks discrete objects as small as 2 inches (5 centimeters) in diameter in low Earth orbit and about 1 yard (1 meter) in geosynchronous orbit. 

A large number of the world’s spacecraft operators are members of the Space Data Association which was specifically set up to reduce the risk of collisions with space debris in earths orbit. At the present time operators are protecting operational spacecraft using avoidance maneuvers. NASA reports that it takes the threat of collisions with space debris seriously and has a long-standing set of guidelines on how to deal with each potential collision threat. These guidelines, part of a larger body of decision-making aids known as flight rules, specify when the expected proximity of a piece of debris increases the probability of a collision enough that evasive action or other precautions to ensure the safety of the crew are needed. 

NASA has a set of long-standing guidelines that are used to assess whether the threat of such a close pass is sufficient to warrant evasive action or other precautions to ensure the safety of the crew. These guidelines essentially draw an imaginary box, known as the “pizza box" because of its flat, rectangular shape, around the space vehicle. This box is about a mile deep by 30 miles across by 30 miles long (1.5 x 50 x 50 kilometers), with the vehicle in the center. When predictions indicate that the debris will pass close enough for concern and the quality of the tracking data is deemed sufficiently accurate, Mission Control centers in Houston and Moscow work together to develop a prudent course of action. 

The United Nations is promoting transparency and confidence building measures to remove suspicion about motives for tracking and removal of debris. Such measures could include General Assembly Resolutions, Treaties, Codes of Conduct and Forums to share information. Lessons learned from the evolution and deployment of the world’s air traffic control systems could also be applied to the creation of a space traffic control environment using transponders on spacecraft and mandatory reporting of maneuvers in orbit. In the longer term, concepts are being developed to remove rocket bodies and defunct spacecraft using devices such as harpoons, grappling mechanisms, and nets.