Northrop Advanced Technology Observation Platform (ATOP)
The ATOP was a concept for a manned or unmanned light reconnaissance, observation and air support aircraft as a replacement for the O-2. It was created as a USAF, NASA, Boeing, Lockheed and Northrop personnel off-duty “what if” project. Design goals included light weight and STOL capacity. There were three different concept models. The aircraft was approximately 25 feet long, 7 feet high and had a 32 feet wingspan. The eventual power plant was to be two PT-6 turboprops of 1,600 hp in total. First mockup was made in 1978 and the aircraft could have been used in the COIN role in the 1980s. First flight of the Joint Test Vehicle JTV-1 was made on 28 October 1990 dropped from the wing of a Cessna 150F (T-51).
It should be noted that the accuracy of the above description regarding ATOP has been questioned. One source claimed ATOP to be flying novel sensors on an existing platform.