Comet Nucleus TOUR: A Mission to Study the Diversity of Comet Nuclei
CONTOUR
COmet Nucleus TOUR: A Mission to Study the Diversity of Comet Nuclei
Encounter Date Sun Distance Earth Distance Phase Angle Flyby Speed
(AU) (AU) (degrees) (km/sec)
Encke, Nov 12, 2003 1.07 0.27 12 28.2
SW3, June 18, 2006 0.95 0.33 100 14.0
d'Arrest, Aug 16, 2008 1.35 0.36 68 11.8
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Science Objectives
CONTOUR's goals are to dramatically improve of comet nuclei and to assess their diversity. The targets span the range from evolved comet (Encke) to a future on the exploratory results from the Halley flybys, and will extend the of data obtained by NASA's Stardust and ESA's Rosetta understanding of comets. Key measurements include:
- Imaging nuclei at resolutions of 4 m (25 times better than Giotto).
- Spectral mapping of nuclei at resolutions of 100-200 m.
- Detailed compositional data on both gas and dust in the at precisions comparable to those of Giotto or better.
Science Payload
Instrument Mass Power Supplier
(kg) (watts)
Contour Remote
Imager/Spectrograph (CRISP) 8.6 29.1 JHU/APL
Contour Aft Imager (CAI) 1.8 2.5 JHU/APL
Dust Analyzer (CIDA) 11.0 13.0 von Hoerner
& Sulger,GMBH
Neutral Gas Ion
Mass Spectrometer (NGIMS) 9.3 23.3 GSFC
Mission Overview
- Target Selection: Emphasis on diversity and unique objects.
- Baseline Mission: Perform close flybys (d 100 km) of three comets--Encke, Schwassmann-Wachmann-3, d'Arrest.
- Launch Dates: July 4 - 28, 2002 (25-day window).
- Backup Launch Opportunity: July 2003 (25-day window).
- Launch Vehicle: Delta-7325 (Med-Lite).
- Launch Concept: Spacecraft placed into high-apogee Earth orbit (period 5. 5 days). Phasing orbits used to achieve proper conditions for injection maneuver on August 13, 2002 [performed with STAR-27 solid rocket motor (SRM)].
- Comet Encounters:
- Near maximum comet activity
- Very small Earth distances (0.27, 0.33, and 0.36 AU)
- Excellent viewing geometry for Earth-based observations
- Mission Flexibility: Use of Earth gravity-assist maneuvers to retarget spacecraft. Capability exists to retarget to bright "new" comet after Encke flyby.
- Minimal Operations and DSN Support: Spacecraft in spin-stabilized hibernation mode 85% of the time.
Cost
($M, FY 97) ($M, RY) Phase A/B 5.1 5.5 Phase C/D 51.3 60.2 Phase E (Mission Ops, Sci. Team) 11.3 15.4 Phase E (DSN Support) 4.9 6.7 Launch Vehicle (Delta-7325) 41.1 47.1 Total Mission Cost 113.7 134.9
The CONTOUR Comets
Encke: A unique object. Comet Encke has been observed at more apparitions (56) than any other comet including Halley. It is one of the most evolved comets that still remains active. In its present orbit, Encke returns to perihelion (dist. ~ 0.34 AU) every 3.3 years. Because Encke has been in this orbit for thousands of years. its continued high level of activity is rather puzzling.
SW3: First discovered in 1930, the activity pattern of SW3 is usually very predictable. However, in late 1995, this comet displayed dramatic variability, and split into at least three pieces. When CONTOUR arrives in 2006, it is likely that relatively unmantled materials will be visible in the cleaved areas, and that evidence of internal structures will remain exposed.
d'Arrest: Since this comet's discovery in 1851, the repeatability of its visual light curve from apparition to apparition suggests that the rotation state is stable, and that its surface outgassing vents change very little with time.
Typical Encounter Scenario
.E - 30 to E -10 days: Determine spacecraft orbit. Spacecraft and instrument checkout. TCM-1 @ E - 20 days.
E -10 to E - 0.5 days: Imaging and spectral obs. of coma, OpNav observations (once per day from E - 10 to E - 5 days, twice per day thereafter). TCM-2 @ E - 1 day.
E +/- 0.5 days: Encounter mode, all instruments turned on. Sequence designecl to fill data recorders.
E + 0.5 to E + 12 days: Data playback. TCM-3 at E + 5 days. Determine spacecraft orbit.
(TCM = Trajectory Correction Maneuver)
Encounter with "New" Comet
- Candidate target should be active and bright (absolute magnitude ' less than or equal to10). Perihelion distance should be less than or equal to1.5 AU. An average of 10 new comets per year satisfy these criteria.
- With CONTOUR's proposed search program, new comets satisfying the aforementioned conditions should be discovered at least 1 year before they reach perihelion.
- Any of the Earth gravity-assist maneuvers following the Encke flyby could be used to alter CONTOUR's trajectory so that it would return to the vicinity of the Earth at 6-month intervals (in Feb. and Aug.).
- Statistical Monte Carlo studies (Alan Friedlander et al., 1996) have shown that Earth gravity-assist opportunities for a spacecraft mission like CONTOUR, with Earth approach velocities of 6.3 km/sec (C3 ~ 40 km2/sec2), can be very effective in retargeting to a new comet.The probability of successfully retargeting CONTOUR to a suitable new comet sometime during the time interval between 2004 and 2008 is greater than 98%.
- If CONTOUR had been in its high-energy, 6-month, Earth-return trajectory in 1995-96, it would have been able to achieve an encounter with the very bright first-apparition comet Hale-Bopp on May 6, 1997.
Development Schedule
- Phase A: 9 months (Jan. 1998 - Sept. 1998)
- Phase B: 12 months (Oct. 1998 - Sept. 1999)
- Phase C/D: 34 months (Oct. 1999 - July 2002) (includes 3 months reserve)
- Launch Dates: July 4 - 28, 2002 (25-day window)
Education and Public Outreach
Conducted by the Office of Public Outreach of the Space Telescope Science Institute
Led by two CONTOUR Science Team Members
-R. Brown, Space Telescope Science Institute
-D. Yeomans, Jet Propulsion Laboratory
Five complementary, interlocking activities:
"CONTOUR Comet Watch" modeled after the highly successful International Halley Watch, coordinates global ground-based observations of the CONTOUR comets for both educational benefit and scientific purposes.
"CONTOUR Open Door" posts mission information, distributes curriculum modules, and receives and responds to e-mail inquiries on CONTOUR via the Intemet.
"Dateline CONTOUR" prepares and distributes press releases and photo releases, and produces a Space Science Update program.
"CONTOUR Amazing Space" is a workshop activity where teachers develop classroom resources based on the mission while obtaining professional development credits.
"CONTOUR Flight Deck" is a competitive opportunity for students to participate in spacecraft investigations by targeting the spacecraft cameras during an Earth-Moon encounter.
Mission Management
- Principal Investigator: J. Veverka, Cornell Univ.
- 16 Co-lnvestigators: Universities, industry, government
- Project Management and Technical Implementation: JHU/APL
- Mission Operations: JHU/APL
- Navigation, DSN Support: Jet Propulsion Lab
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