CONTOUR

Artist impression ofCONTOUR approaching a comet.
Names	Comet Nucleus Tour
Mission type	Cometary flyby
Operator	NASA /APL
COSPAR ID	2002-034A
SATCATno.	27457
Website	science.nasa.gov
Mission duration	1 month, 12 days
Spacecraft properties
Manufacturer	Applied Physics Laboratory
Launch mass	398 kg (877 lb)
Dimensions	2.1 × 1.8 × 1.8 m (6.9 × 5.9 × 5.9 ft)
Power	670 watts
Start of mission
Launch date	3 July 2002, 06:47:41UTC
Rocket	Delta II 7425–9.5 D-292
Launch site	Cape CanaveralSLC-17
Contractor	Boeing
End of mission
Disposal	Destroyed
Last contact	15 August 2002
Instruments CIDA Comet Impact Dust Analyzer CRISP CONTOUR Remote Imager/Spectrograph CAI CONTOUR Aft Imager NGIMS Neutral Gas Ion Mass Spectrometer
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TheComet Nucleus Tour (CONTOUR) was aNASADiscovery-class space probe that failed shortly after its July 2002 launch. It was the only Discovery mission to fail.

The two comets scheduled to be visited wereEncke andSchwassmann-Wachmann-3, and the third target wasd'Arrest. It was hoped that a new comet would have been discovered in theinner Solar System between 2006 and 2008, in which case the spacecraft trajectory would have been changed if possible to rendezvous with the new comet. Scientific objectives included imaging the nuclei at resolutions of up to 4 meters (13 ft), performing spectral mapping of the nuclei at resolutions of up to 100 meters (330 ft), and obtaining detailedcompositional data on gas and dust in the near-nucleus environment, with the goal of improving knowledge of the characteristics of comet nuclei.

After thesolid rocket motor intended to inject the spacecraft intosolar orbit was ignited on August 15, 2002, contact with the probe could not be re-established. Ground-based telescopes later found three objects along the course of the satellite, leading to the speculation that it had disintegrated. Attempts to contact the probe were ended on December 20, 2002. The probe thus accomplished none of its primary scientific objectives, but did prove some spaceflight technologies, such as the APL-developed non-coherentDoppler tracking spacecraft navigation technique, which was later used on theNew Horizons spacecraft.^[1]

TheCONTOUR spacecraft was constructed in-house at theJohns Hopkins UniversityApplied Physics Laboratory.CONTOUR was shaped as anoctagonal 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 theStar 30booster it was attached to, during the launch phase of the mission.^[2] The spacecraft was fitted with a 25 cm (9.8 in)whipple shield, similar to the one used onStardust, on its leading face, designed with four layers of nextel fabric and seven layers ofkevlar.^[3][4] The shield was built to allow the spacecraft to withstand the respective 28.2 and 14 km/s velocity flybys of comets Encke and Schwassmann-Wachmann-3, where the spacecraft would be subjected to numerous particles ejecting from thenuclei of the comets.^[5] Although mission scientists predicted that the spacecraft would take no significant damage during the Encke and Schwassmann-Wachmann-3 encounters, the shield and itsprototypes were tested vigorously during the construction of the spacecraft, including one where a shield prototype was shot at with surrogatenylon particles from a two stagelight-gas gun. The results of the earlier tests allowed mission planners to determine a safe distance from which theCONTOUR would pass by comets targeted on the mission.^[5] Three of the fourscientific instruments aboard the spacecraft were embedded within this shield.^[3]

Power forCONTOUR derives fromsolar cells, which are mounted onto the spacecraft, decorating the sides and rear and generating up to 670watts of power. Anickel–cadmium battery designed to last up to nineampere hours was also installed aboard the spacecraft in the event that the solar cell system fails, or does not provide enough power for the spacecraft or its instruments to function.^[3]

Unlike many interplanetary missions, CONTOUR was not designed to be propelled beyond Earth orbit by the rocket that launched it, instead it exited Earth orbit using a STAR-30 solid rocket booster built into the spacecraft. This STAR-30 engine provided 1,922 meters per second of delta-v.^[5] The firing of this engine is the reason the CONTOUR spacecraft was destroyed. In addition, there were 16 hydrazine thrusters for normal propulsion and course corrections. These thrusters were divided into four clusters of four.^[5]

• CIDA

The Comet Impact Dust Analyzer (CIDA)

• CRISP

The CONTOUR Remote Imager/Spectrograph (CRISP)

• CAI

The CONTOUR Aft Imager (CAI), also known as the CONTOUR Forward Imager (CFI)

• NGIMS

Neutral Gas Ion Mass Spectrometer (NGIMS)

CONTOUR launched on a Delta 7425 (aDelta II Lite launch vehicle with four strap-on solid-rocket boosters and a Star 27 third stage) on July 3, 2002, at 6:47:41 UT (2:47:41 a.m. EDT) fromCape Canaveral Air Force Station. It was launched into a high-apogee Earth orbit with a period of 5.5 days. 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. During the August 2002 injection maneuver, the probe was lost.

Three more Earth flybys would have followed, on August 14, 2004, February 10, 2005, and February 10, 2006. On June 18, 2006, CONTOUR would have encountered comet Schwassmann-Wachmann-3 at 14 km/s, 0.95 AU from the Sun and 0.33 AU from Earth. Two more Earth flybys were scheduled in February 2007 and 2008, and a flyby of comet d'Arrest might have occurred on 16 August 2008 at a relative velocity of 11.8 km/s, 1.35 AU from the Sun and 0.36 AU from Earth. All flybys would have had a closest encounter distance of about 100 km and would have occurred near the period of maximum activity for each comet. After the comet Encke encounter, CONTOUR might have been retargeted towards a new comet if one was discovered with the desired characteristics (e.g. active, brighter thanabsolute magnitude 10, perihelion within 1.5 AU).

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."^[6][7][8]

After the loss of CONTOUR, a replacement spacecraft – CONTOUR 2 – was proposed, scheduled for launch in 2006. However, the replacement did not ultimately materialize.^{[citation needed]}

• List of missions to comets

• "CONTOUR".NASA Discovery Program. Archived fromthe original on April 25, 2010. RetrievedDecember 27, 2007.
• CONTOUR Mission Profile byNASA's Solar System Exploration

• Missions to comets
• NASA space probes
• Discovery Program
• Satellite launch failures
• Space probes launched in 2002
• Derelict satellites in heliocentric orbit
• Spacecraft launched by Delta II rockets
• Destroyed space probes
• Spacecraft launched in 2002
• Space accidents and incidents in the United States

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