The Comet Nucleus Tour, or CONTOUR, mission launched from Cape Canaveral on July 3, 2002. CONTOUR’s objective was to study two very different comets, Encke and Schwassmann-Wachmann-3, as they made their periodic visits to the inner solar system.

At each comet flyby, the spacecraft was to get as close as 60 miles to the comet nucleus to capture high resolution pictures, perform detailed compositional analyses of gas and dust, and determine the comet's precise orbit. This information would have dramatically improved our knowledge of comet nuclei and their diversity.

Unfortunately, six weeks after launch, on August 15, contact with the spacecraft was lost after a planned maneuver that was intended to propel it out of Earth orbit and into its comet-chasing solar orbit. Limited ground-based evidence at the time suggested the spacecraft split into several pieces.

Attempts to contact CONTOUR were made through December 20, 2002, when NASA and The Johns Hopkins University Applied Physics Laboratory concluded the spacecraft was lost.

NASA convened a CONTOUR Mishap Investigation Board with Theron Bradley Jr., NASA Chief Engineer, as chair. The purpose of the Board was to examine the processes, data and actions surrounding the events of August 15; to search for proximate and root causes; and develop recommendations that may be applicable to future missions.

After an extensive investigation, the board identified four possible causes for the failure but concluded the probable proximate cause was structural failure of the spacecraft due to plume heating during the embedded solid-rocket motor burn. Read the Board's Full Report.