The CONTOUR Discovery Mission - Objectives, Design, Operations, and Loss


Abstract:

The CONTOUR (COmet Nucleus TOUR) mission is part of NASA's Discovery Program of low-cost and moderate-risk interplanetary missions with focused but valuable objectives in planetary exploration. The responsibility for mission and spacecraft design as well as mission operations was delegated by NASA to Johns Hopkins University's Applied Physics Laboratory in Laurel, MD, USA.

The spacecraft was launched into an Earth-phasing orbit on July 3, 2002 and operated flawlessly for about 6 weeks. Unfortunately, the spacecraft was lost on August 15, 2002 during the injection (by means of a Solid Rocket Motor) into its trajectory on course to comet Encke.

The objective of the CONTOUR mission was to investigate comet nuclei and to assess their similarity and diversity by means of images, spectral maps, and dust and gas analyses. The mission would have extended our knowledge of comet nuclei (structure, composition, processes) far beyond the level realized by the Halley flybys. Over a six year period, CONTOUR would have flown within about 100 kilometers of three comet nuclei: Encke in 2003, Schwassmann-Wachmann-3 in 2006, and finally d'Arrest in 2008.

The CONTOUR mission and spacecraft design feature a number of innovative concepts in comparison to NASA's conventional Galileo and Cassini-type deep-space missions. These new approaches allow performing deep space missions at a relatively low-cost while maintaining acceptable risk levels. Of particular interest are the indirect launch strategy by means of Earth phasing orbits, the unique mission and spacecraft design involving 3-axis as well as spin-stabilized attitude control modes, and the unattended autonomous hibernation mode during the long cruise phases.