CONTOUR (Discovery 6)

Launch data: Designation  27457 / 02034A Launch date  03 Jul 2002 - 06:47:41 UT Launch site  CC, SLC-17A Launch vehicle  Delta 7425-9.5 (#D292) Mission  Venus-flyby, Comet-Orbiter Operator   Heliocentric orbit Perihelion / Aphelion   Incl. to ecliptic   ° Period   min

An engineer inspects the CONTOUR spacecraft before it is loaded for launch.

Description:

• The CONTOUR spacecraft has a total fueled mass of 775 kg, including a Star 30 SRM booster with a mass of 377 kg and 70 kg of hydrazine fuel. Power is provided by a body-mounted solar array designed for operation at distances between 0.75 and 1.5 AU from the Sun. It is three-axis stabilized for encounters and spin-stabilized during cruise mode between encounters. Communications are through a fixed 0.45 m diameter high-gain antenna which will support data rates greater than 100 kbit/sec at encounters. Data and images are stored on two 3.3 Gbit solid-state recorders with a capacity of 600 images. The spacecraft is equipped with four primary science instruments, the Contour Remote Imager/Spectrograph (CRISP), the Contour Aft Imager (CAI), the Dust Analyzer (CIDA), and the Neutral Gas Ion Mass Spectrometer (NGIMS).

Mission details:

• The CONTOUR (Comet Nucleus Tour) probe, built and operated by the Johns Hopkins University's Applied Physics Laboratory (APL), launch on a Boeing Delta 7425 (a Delta II Lite launch vehicle with four strap-on solid-rocket boosters and a Star 30 third stage) on 3 July 2002 at 6:47:41 UT (2:47:41 a.m. EDT) into a high-apogee Earth orbit with a period of 5.5 days from Cape Canaveral Air Force Station.
• First burn of the second stage completed at 0659 UTC putting the spacecraft in a 185 x 197 km x 29.7 deg parking orbit. At 0746 UTC the second stage restarted for a short 4s burn to 185 x 309 km x 29.7 deg, and then separated once the PAM-D (ATK Star 48B) solid third stage was spun up. The 1.5 minute burn of the third stage motor at 0748 UTC put it and CONTOUR in a 90 x 106689 km x 30.5 deg phasing orbit. This is a little lower perigee than the planned 200 km, and may have been either a tracking error or something that was fixed at first apogee; by Jul 8 CONTOUR's orbit was 214 x 106686 km x 29.8 deg.
• The Contour probe fired its ATK/Thiokol Star 30BP solid motor at 0849 UTC on Aug 15, 2002. The burn was meant to insert the probe into solar orbit. No signals have been received from the probe since the motor firing, and the Spacewatch telescopes imaged three objects along the trajectory, so it looks like Contour has broken up. The Thiokol Star 30 motor has been launched 90 times and fired 86 times (4 no tests due to launch failures); the 30BP model has had 28 flights.
• Tracking of the three fragments of the Contour space probe suggests they will return to the Earth around 2003 Aug 16, a year after the apparently fatal motor firing. Fragments A and B will pass well beyond the Earth-Moon system's gravitational sphere of influence, with a closest approach of 5 to 7 million km. Fragment C's orbit is much more uncertain but it seems it will pass much closer to Earth, with the best fit value according to JPL's navigation team of 736000 km, but an uncertainty of over 1.2 million km. The C flyby will occur on 2003 Aug 15 between 0400 and 2300 UTC. The three objects are in an 0.876 x 1.131 AU orbit around the Sun inclined at 8.7 deg to the ecliptic plane and left the 1 million km nominal range of Earth's sphere of influence on Aug 17.
• The firing would have put CONTOUR in the proper trajectory for an Earth fly-by in August 2003 followed by an encounter with comet Encke on 12 November 2003 at a distance of 100 to 160 km and a fly-by speed of 28.2 km/sec, 1.07 AU from the Sun and 0.27 AU from Earth. Three more Earth fly-bys were to follow, in August 2004, February 2005, and February 2006. On 18 June 2006 CONTOUR would encounter comet Schwassmann-Wachmann-3 at 14 km/sec, 0.95 AU from the Sun and 0.33 AU from Earth. Two more Earth fly-bys were scheduled in February of 2007 and 2008, and a fly-by of comet d'Arrest was possible on 16 August 2008 at a relative velocity of 11.8 km/sec, 1.35 AU from the Sun and 0.36 AU from Earth. All fly-bys had a planned 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 could have been retargeted towards a new comet if one was discovered with the desired characteristics (e.g. active, brighter than absolute magnitude 10, perihelion within 1.5 AU)
• A mishap investigation board determined that overheating during the engine burn caused the spacecraft to break apart.
• Contour was planned to flyby comet 2P/Encke, 73P/Schwassmann-Wachmann 3 and 6P/d′Arrest.