their aircraft navigation systems' latest Jeppesen database revision with the ICAO airport identifier code of KXTA and listed as "Homey Airport". The probably inadvertent release of the airport data led to advice by the Aircraft Owners and Pilots Association (AOPA) that student pilots should be explicitly warned about KXTA, not to consider it as a waypoint or destination for any flight even though it now appears in public navigation databases. Security The perimeter of the base is marked out by orange posts and patrolled by guards in white pickup trucks and camouflage fatigues. The guards are popularly referred to as "cammo dudes" by enthusiasts. The guards will not answer questions about their employers; however, according to the New York Daily News, there are indications they are employed through a contractor such as AECOM. Signage around the base perimeter advises that deadly force is authorized against trespassers. Technology is also heavily used to maintain the border of the base; this includes surveillance cameras and motion detectors. Some of these motion detectors are placed some distance away from the base on public land to notify guards of people approaching. 1974 Skylab photography Dwayne A. Day published "Astronauts and Area 51: the Skylab Incident" in The Space Review in January 2006. It was based on a memo written in 1974 to CIA director William Colby by an unknown CIA official. The memo reported that astronauts on board Skylab had inadvertently photographed a certain location: The name of the location was obscured, but the context led Day to believe that the subject was Groom Lake. Day wrote that "the CIA considered no other spot on Earth to be as sensitive as Groom Lake". Even within the agency's National Photographic Interpretation Center that handled classified reconnaissance satellite photographs, images of the site were removed from film rolls and stored separately as not all photo interpreters had security clearance for the information. The memo details debate between federal agencies regarding whether the images should be classified, with Department of Defense agencies arguing that it should and NASA and the State Department arguing that it should not be classified. The memo itself questions the legality of retroactively classifying unclassified images. The memo includes handwritten remarks, apparently by Director of Central Intelligence Colby: The declassified documents do not disclose the outcome of discussions regarding the Skylab imagery. The debate proved moot, as the photograph appeared in the Federal