Dawn Mission
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This article or section contains information regarding a future spaceflight. Due to the nature of the content, details may change dramatically as the launch date approaches and/or more information becomes available. |
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| Dawn | |
|---|---|
 Artist's concept of Dawn with Vesta (left) & Ceres (right) |
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| Organization: | NASA |
| Major Contractors: | Orbital Sciences, JPL, UCLA |
| Mission type: | Orbiter |
| Satellite of: | Vesta and Ceres |
| Launch Date: | June 20, 2007[1],[2] |
| Launch Vehicle: | Delta 7925H |
| Mission Duration: | 8 years |
| NSSDC ID: | DAWN |
| Webpage: | Dawn Home |
| Mass: | 1250 kg |
| Eccentricity: | ~ circular |
| Inclination: | Polar |
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The Dawn Mission is a NASA unmanned space mission currently under development to send an orbiting space probe to examine the two most massive members of the asteroid belt, the dwarf planet Ceres and the asteroid Vesta. In March 2006, it was announced that the mission was to be canceled, but a subsequent review resulted in the mission being reinstated.[3] Dawn will be the first mission to enter into orbit around two different planetary bodies other than the Earth and Moon, and the first to visit the largest asteroid. The IAU adopted a new definition of planet on August 24, 2006, and thus, if the IAU's definition stands and the spacecraft experiences no delays, Dawn will become the first mission to study a dwarf planet, arriving at Ceres five months prior to the arrival of New Horizons at Pluto.
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[edit] Mission
The mission's goal is to characterize the conditions and processes of the solar system's earliest epoch by investigating in detail two of the largest protoplanets remaining intact since their formation. Ceres and Vesta have many contrasting characteristics that are thought to have resulted from them forming in two different regions of the early solar system; Ceres is theorized to have experienced a "cool and wet" formation that may have left it with subsurface water, and Vesta is theorized to have experienced a "hot and dry" formation that resulted in a differentiated interior and surface vulcanism.
Dawn is to be launched on a Delta 7925H rocket. To cruise from Earth to its targets it will use three DS1 heritage Xenon ion thrusters (firing only one at a time) to take it in a long outward spiral. The current estimated chronology is as follows:[4]
- June 2007: launch
- March 2009: Mars gravity assist
- October 2011: Vesta arrival
- April 2012: Vesta departure
- February 2015: Ceres arrival
- July 2015: End of operations
An extended mission in which Dawn explores other asteroids after Ceres is also possible.
The Dawn mission team is led by UCLA space scientist Christopher T. Russell. By March 2006, Orbital Sciences Corporation has completed more than 90% of the spacecraft, and NASA's Jet Propulsion Laboratory is providing the Ion Propulsion System and management of the overall flight system development. The German Aerospace Center (DLR) and the Max Planck Institute for Solar System Research is providing the framing camera, the Italian Space Agency is providing the mapping spectrometer, and the DOE Los Alamos National Laboratory is providing the gamma ray and neutron spectrometer.[5]
[edit] Motivation
Dawn is intended to study two large asteroids in order to answer questions about the formation of the solar system.
Ceres and Vesta were chosen as two contrasting protoplanets, one apparently "wet" (that is, icy) and the other "dry" (or rocky), whose accretion was terminated by the formation of Jupiter. They provide a bridge in our understanding between the formation of rocky planets and the icy bodies of our solar system, and under what conditions a rocky planet can hold water.
Ceres is a dwarf planet whose mass encompasses about one-fourth of the total mass of the asteroids in the asteroid belt and whose spectral characteristics suggest a composition like (but not exactly) a water-rich carbonaceous chondrite. Smaller Vesta, a water-poor achondrite, has experienced significant heating and differentiation. It shows signs of a metallic core, a Mars-like density and lunar-like basaltic flows.
Both bodies formed very early in the history of the solar system, thereby retaining a record of events and processes from the time of the formation of the terrestrial planets. Radionuclide dating of pieces of meteorites thought to come from Vesta suggests that Vesta differentiated quickly, in only three million years. Thermal evolution studies suggest that Ceres must have formed a little later, more than three million years after the formation of CAIs (the oldest known objects of Solar System origin).
Moreover, Vesta is the source of many smaller objects in the solar system. Most (but not all) V-type near-Earth asteroids, and some outer main-belt asteroids have similar spectra to Vesta and are known as 'vestoids'. Five percent of the found meteoritic samples on Earth, the Howardite Eucrite Diogenite ("HED") meteorites, are thought to be the result of a collision or collisions with Vesta.
[edit] Mission status
The status of the Dawn mission has changed dramatically. In December, 2003, the project was first cancelled, and then reinstated in February, 2004. In October, 2005, work on Dawn was placed into "stand down" mode.
In January, 2006, Dawn's "stand down" was discussed in the press as "indefinitely postponed", even though NASA had announced no new decisions regarding the mission's status.[6] On March 2, 2006, Dawn was publicly, but not formally cancelled by NASA headquarters.[7] In an unusual step, the cancellation was placed under review,[8] and on 27 March 2006, it was announced that the mission would not be cancelled after all.[9]
In the last week of September 2006, the Dawn mission instrument payload integration reached a full functional status. Until Dawn's launch on (approximately) June 20, 2007, there will be necessary environmental and other tests, but a launch is no longer in doubt.
[edit] References and notes
- ^ NASA's Shuttle and Rocket Missions - Launch Schedule. NASA. Retrieved on November 16, 2006.
- ^ Dawn payload management information given to Dawn instrument teams July 2006 (launch date will necessarily float plus/minus a few days during the present Integration Phase)
- ^ Malik, Tariq (27 March, 2006). NASA Reinstates Cancelled Asteroid Mission. Space.com. Retrieved on 2006-03-27.
- ^ http://planetary.org/explore/topics/dawn/
- ^ Rayman M. D., Fraschetti T. C., Raymond C. A., Russell C. T. (2006). "Dawn: A mission in development for exploration of main belt asteroids Vesta and Ceres". Acta Astronautica 58 (11): 605-616. DOI:10.1016/j.actaastro.2006.01.014.
- ^ Chang, Alicia (2006). NASA Asteroid Mission Won't Launch This Year. Space.com. Retrieved on 2006-03-04.
- ^ Clark, Stephen (2006). Probe built to visit asteroids killed in budget snarl. Spaceflightnow.com. Retrieved on 2006-03-04.
- ^ NASA reviewing canceled mission. CNN.com (March 16, 2006). Retrieved on 2006-03-27.
- ^ Geveden, Rex (2006). Dawn Mission Reclama (PDF). Retrieved on 2006-03-27.
[edit] See also
[edit] External links
- Dawn Mission. JPL. Retrieved on April 20, 2006.
- Dawn Mission. UCLA Space Physics Center. Retrieved on April 20, 2006.
- Visual and Infrared Spectrometer Instrument. INAF (Istituto Nazionale di Astrofisica). Retrieved on April 20, 2006.
- Dawn Framing Camera. Max Planck Institute for Solar System Research. Retrieved on April 20, 2006.
- Prettyman, T.H.; Barraclough, B.L.; Feldman, W.C.; Baldonado, J.R.; Bernardin, J.D. ; Dingler, R.D.; Enemark, D.C.; Little, C.K.; Miller, E.A.; Patrick, D.E.; Pavri, B.; Raymond, C.A.; Russell, C.T.; Storms, S.A.; Sweet, M.R.; Williford, R.L.; Wong-Swanson B. (2006). Gamma Ray and Neutron Spectrometer for Dawn (PDF). 37th Lunar and Planetary Science Conference. Retrieved on April 20, 2006.
