The Dawn Mission
is a NASA robotic mission to explore two of the asteroid belt's
most intriguing and dissimilar occupants: asteroid Vesta and the
dwarf planet Ceres. Dawn is NASA's first purely scientific
mission to be powered by ion propulsion and is Orbital’s first
planetary mission. It was launched on 27 September, 2007
Cape Canaveral Air Force Station Launch Complex 17 on a Delta II
Dawn is a
planetary space science mission funded by NASA’s Discovery
Program. Orbital is partnered with Principal Investigator Chris
Russell of UCLA and the Jet Propulsion Laboratory (JPL). Dawn’s
primary scientific objective is advancing our understanding of
the origin and evolution of the solar system by studying two of
the largest asteroids,
Vesta and Ceres, which appear to have
remained intact since their formation 4.6 billion years ago.
Earth-based studies indicate that these two protoplanets have
very different and complementary compositions, which may provide
clues to the conditions and processes of planetary formation.
Powered by solar electric ion propulsion, the Dawn spacecraft
will cruise to the main asteroid belt between Mars and Jupiter
where it will rendezvous with and orbit Vesta for eight months.
While orbiting, the spacecraft will conduct remote sensing
observations using a suite of science instruments. The
spacecraft will then depart Vesta and travel to Ceres where it
will perform the same set of measurements.
Dawn Mission Timeline
* Launch: 27 September, 2007 (previous launch date was 30 June) from Cape Canaveral Air Force Station
Launch Complex 17.
* 10.09.07 NASA's Dawn spacecraft successfully completed the
first test of its ion propulsion system in early October 2007.
* Mars gravity assist March 2009
* Vesta arrival September 2011
* Vesta departure April 2012
* Ceres arrival February 2015
* End of primary mission July 2015
kg (2,668 lb.) at launch, 740 kg (1,631 lb.) dry
Propulsion: Solar-electric propulsion using three
gimballed NSTAR ion engines and monopropellant reaction control
Power: Gallium Arsenide triple junction solar arrays, 10
kW at Earth and 1.4 kW at Ceres
Communications: Deep Space Network – compatible with
science downlink rates of 41-128 kbps
Dimensions: 20 m (65 ft.) tip-to-tip, spacecraft body is
2 m (6 ft.) high from separation plane to instrument deck
Orbit Altitude: At target asteroids: As high as 4,500 km
and as low as 25 km
Mission Life:10 years
Reliability: Redundant and cross-strapped spacecraft bus
Heritage: GALEX, SORCE, Deep Space 1, STAR™ Bus
Infrared Mapping Spectrometer (ASI/INAF)
Gamma Ray and Neutron Detector (LANL)
About Dawn’s Ion
spacecraft will be NASA's first purely scientific mission
powered by solar electric ion propulsion, the world’s most
advanced and efficient space propulsion technology. Ion
propulsion will provide the additional velocity needed to reach
Vesta once the spacecraft separates from its Delta launch
vehicle. Ion propulsion will also be used during asteroid
proximity operations to raise and lower the orbit altitude.
Dawn’s ion propulsion system is based on the technology
successfully demonstrated by Deep Space 1.
Key Mission Partners
Investigator: Dr. Christopher Russell, UCLA
- Jet Propulsion Laboratory (JPL), Pasadena, CA (Project
management, system engineering, ion propulsion subsystem,
science operations and spacecraft flight operations)
- Orbital Sciences Corporation, Dulles, VA; Chandler, Arizona
- Max Planck Institute for Solar System Research/German Space
- Italian space agency/National Institute for Astrophysics,
- Kennedy Space Center, Cape Canaveral, Florida (Launch services via NASA
Launch Services Contract)
If the Dawn
Mission is successful, it will be the first time a spacecraft
will orbit two planetary bodies on a single voyage.
Did you know?
* Dawn will carry a silicon chip
containing the names of asteroid, space and other enthusiasts
from around the world. People submitted their names for this
historic one-way mission by visiting JPL's Dawn Web site in
* In the
mid 1980s a Multiple Asteroid and Comet Fly-By French Soviet Vesta Mission
was proposed for 1991. No approved.
Asteroids and Dwarf Planets and How to Observe Them
(Astronomers' Observing Guides)
by Roger Dymock
Threat of Comets and Asteroids
by Gerrit L. Verschuur
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