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American comet probe. Cancelled in the early 1990s. The CRAF spacecraft (Comet Rendezvous Asteroid Flyby) was to have rendezvoused with the Comet Kopff and flown alongside the comet for at least three years.

AKA: Comet Rendezvous Asteroid Flyby;Mariner Mark II. Status: Cancelled 1993. Payload: 290 kg (630 lb). Gross mass: 6,360 kg (14,020 lb). Unfuelled mass: 2,060 kg (4,540 lb).

It was cancelled in the early 1990's in order to free budget up for the Cassini mission to Saturn, which used the same Mariner Mark II bus.

CRAF would take a Mars-Earth-Earth gravity assist trajectory to reach Kopff. It would also have flown by asteroids: Thisbe, Fortuna and Tamariwa en route. On arrival at the comet, it would make a rocket burn to enter orbit around the comet. From this vantage point, it would monitor the comet's activity as it neared the sun, adjusting the orbit to move out into the comet's tail. Here it would collect dust, analyzing it with on-board spectrometers. At the end of the mission, the spacecraft would make a soft landing on the comet's surface.

It was to have been the first mission to use the next generation Mariner Mark II bus designed by JPL. Cassini was to have followed, and then Pluto flyby and Neptune orbiter flights. Instead the cost of the spacecraft led NASA to attempt "faster-cheaper-better" missions with less expensive designs, and Cassini was the only mission to use the Mariner Mark II design.

The Mariner Mark II spacecraft was 3-axis stabilized spacecraft, using fiber optics rotation sensors with no moving parts in place of conventional gyroscopes. For the CRAF mission it would have launched with a full load of 4300 kg of propellant. Power would have been from three radioisotope thermal generators. The European, German, and Italian space agencies would have cooperate in the mission.

The mission would have followed the following schedule:

  • 9 April 1997 - Launch by Titan 4/Centaur
  • 4 July 1998 - Mars Flyby
  • 18 July 2000 - First Earth Flyby
  • 7 June 2001 - Asteroid Thisbe Flyby
  • 5 May 2002 - Deep Space Maneuver
  • 25 October 2002 - Asteroid Fortuna Flyby
  • 18 July 2003 - Second Earth Flyby
  • 7 March 2004 - Asteroid Tamariwa Flyby
  • 12 April 2004 - Deep Space Maneuver
  • 26 January 2006 - Comet Kopff Rendezvous
  • 25 May 2009 - Comet Kopff Perihelion
  • 30 September - End of Mission / landing on Comet Kopff

Electric System: 170.00 average kW.

Country: USA. Launch Vehicles: Titan. Agency: JPL, NASA. Bibliography: 4469.

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