The Comet Nucleus Tour (CONTOUR) was a NASA Discovery-class space probe that failed shortly after its July 2002 launch.

After the solid rocket motor intended to inject the spacecraft into solar orbit was ignited on August 15, 2002, contact with the probe could not be re-established.

CONTOUR was shaped as an octagonal prism, measuring at 2.1 metres (6.9 ft) tall and 1.8 metres (5.9 ft) long, had a total fueled mass of 398 kg (877 lb) at launch, not including the 377 kg (831 lb) mass of the Star 30 booster it was attached to, during the launch phase of the mission.

Following a series of phasing orbits, the Star 30 solid rocket motor was used to perform an injection maneuver on August 15, 2002, to put CONTOUR in the proper trajectory for an Earth flyby on August 15, 2003, followed by an encounter with comet Encke on November 12, 2003, at a distance of 100 to 160 km and a flyby speed of 28.2 km/s, 1.07 AU from the Sun and 0.27 AU from Earth.

According to NASA: "An investigation board concluded that the most likely cause of the mishap was structural failure of the spacecraft due to plume heating during the solid-rocket motor burn.

Alternate possible but less likely causes determined were catastrophic failure of the solid rocket motor, collision with space debris, and loss of dynamic control of the spacecraft.