The Comet Nucleus Tour (CONTOUR) Mission
We are sorry to report that after a successful launch into Earth orbit, contact was lost with the CONTOUR spacecraft following its solid rocket burn on August 15, 2002.
Comets are the most pristine, primitive bodies in the solar system, and it is expected that they retain more evidence of the processes that took place when the solar system formed than do subsequently-evolved larger bodies. The complex organic molecules present in comet nuclei may have been the original source of organics on Earth from which life formed, and examination of comet nuclei would yield information on how these molecules were produced. The Comet Nucleus Tour, or CONTOUR, is a mission intended to greatly expand what is known of comet nuclei and to assess their diversity.
CONTOUR launched in July 2002 on a Delta-7425 launch vehicle. Then, over the course of five years, the CONTOUR spacecraft will perform close flybys of multiple comets: first Encke, and then possibly Schwassmann-Wachmann-3, or d'Arrest. However, after the Encke flyby, the spacecraft may be retargeted to a bright "new" comet, if such a suitable target is discovered, allowing observations to be made of a range of very different comets, from an evolved comet such as Encke to a new comet such as Hale-Bopp. The data obtained will extend the applicability of data obtained by the NASA comet mission Stardust as well as the ESA mission Rosetta by studying the uniqueness of several different comets. The goal of the mission is to assess the diversity among comet nuclei, and in this way to understand to what degree the differences between comets result from their origins or from subsequent evolutionary processes.
Comet Encke has been observed at more apparitions--57--than any other comet including Halley. It is a very old, very evolved comet, with a continuing and unexplained high level of activity. The encounter with Encke will occur in late 2003.
Comet Schwassmann-Wachmann-3, or SW3, was first discovered in 1930 and until recently its activity was very predictable. However, in late 1995 the comet split into three pieces. The arrival of CONTOUR in 2006 will allow observations to be made of the internal structure and materials of the broken comet.
Comet d'Arrest was discovered in 1851, and the observations made since that time suggest that the rotation rate and surface outgassing of the comet is stable. It displays more activity than Encke, with a less evolved surface. CONTOUR could be directed to encounter d'Arrest in 2008.
CONTOUR will perform imaging of the comet nuclei at resolutions of 4m, as well as perform spectral mapping of the nuclei at resolutions of 100-200 m. These observations will be linked with imaging, spectroscopic, and thermal data obtained from Earth-based or Earth-orbital telescopes, as the encounters occur at times ideal for remote sensing observations from Earth. In addition, detailed compositional data on both gas and dust in the near-nucleus environment will be performed. The Atmospheric Experiments Laboratory will contribute the Neutral Gas and Ion Mass Spectrometer (NGIMS) to perform the compositional analysis of the gases emitted from the comet nuclei.
A detailed description of the CONTOUR mission can be found at the CONTOUR web site.
