English: This pencil sketch of the Comet Kohoutek made by Skylab-4 astronaut Edward Gibson illustrates the crew's collective impressions of the comet's appearance on December 29, 1973. An early discovery of a large comet in an orbit that would reach close to the Sun at the end of 1973 prompted NASA to initiate Operation Kohoutek, a program to coordinate widespread observations of the comet from ground observatories, aircraft, balloons, rockets, unmarned satellites, and Skylab.