NASAs Dawn Mission Journey to the Asteroid Frontier

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NASAs Dawn MissionJourney to the Asteroid
Frontier

• Lucy McFadden, Co-Investigator
• University of Maryland
• College Park, MD
• July 18, 2007
• Night Sky Network

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The Dawn Mission
9th mission in NASAs Discovery Program
http//discovery.nasa.gov
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Traveling Back In Time
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Dawn Explores the Earliest Epochs
Vesta and Ceres are intact survivors of the
earliest epoch of planetary formation.
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The Asteroid Belt
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Spacecraft
Dry mass 745 kg Wet mass 1240 kg Solar array
power (1 AU) 10.3 kW Solar array power (3 AU)
1.3 kW
Delta II 7925H-9.5
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Interplanetary Trajectory
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Ion Propulsion
Deep Space 1
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Ion Propulsion System
2.3 meters
Hydrazine tank 45 kg capacity
Xenon tank 450 kg capacity
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Ion thruster
Folded solar arrays
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Instruments
HGA High Gain Antenna LGA Low Gain
AntennaCSS Coarse Sun Sensors GRaND Gamma
Ray and Neutron Detector IPS Thrusters Ion
Propulsion ThrustersRCS Thrusters Reaction
Control System ThrustersVIR Visual and
Infrared Spectrometers FC Framing Camera
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Map the Gravity Field
Vesta Gravity from Shape Model
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Framing Camera
FC current design (left) FC EM (below)
Supports Imaging Science Navigation
Topography Gravity ScienceThese functions
are mission critical Two identical units to fly
for 100 redundancy

• 1024 x 1024 pixels
• frame-transfer CCD
• 14 µm pixel size
• F/8 system
• 5.5 x 5.5 FoV
• 93 µrad iFoV (1 pixel)
• 7 filters clear channel

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Mapping Global Topographic Maps
Framing Camera techniques have been proven on
many previous missions. The cameras most recent
heritage comes from Venus Express.
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Mapping Spectrometer VIR

• VIR experiment is a compact imaging spectrometer
  housing two data channels in the same optical
  head . It is made of 2 modules
• Optical head
• Electronics box

VIR will allow to perform spectroscopic
measurements of the Vesta and Ceres surface in
the range 0.35-5.01 um were most signatures of
rock-forming minerals are present
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GRaND
Cutaway view of GRaND

• Features
• Neutron spectroscopy using Li-loaded glass and
  boron-loaded plastic phoswich
• Gamma ray spectroscopy using Bismuth Germanate
  and Cadmium Zinc Telluride (new technology)
• Design enables measurement and suppression of
  background from the space environment
• Operating modes
• Standby
• Operating
• Anneal

25.7 cm
18.0 cm
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Map the Elemental Composition
Gamma ray and neutron detector (GRaND) techniques
have been proven on Lunar Prospector. GRaNDs
most recent heritage is from Mars Odyssey
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Exploring New Worlds

• Dawns Itinerary
• Launch September, 2007
• The Dawn Spacecraft will travel
• 6.3 billion kilometers (almost 4 billion miles)
• In eight years
• To the asteroids, 4 Vesta and 1 Ceres.

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Partners

• University of California, Los Angeles
• Scientific Leadership
• JPL Jet Propulsion Laboratory
• Management and Navigation
• Orbital Sciences Corporation
• Spacecraft design and build
• Los Alamos National Laboratory
• GRAND instrument
• DLR German Aerospace Center
• Framing Camera
• Max Planck Institute for Solar System Research
• Framing Camera
• ASI Italian Space Agency
• VIR
• New Roads School, University of Maryland, and
  McREL
• Education and Public Outreach

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Mission Timeline
Baseline mission shown in green Minimum mission
shown in blue
(1) Ceres arrival
(4) Vesta departure
(4) Vesta arrival
Mars gravity assist
End of mission
Aug 15
May 12
(1) Ceres arrival
(4) Vesta departure
Mar 09
Jan 16
Oct 11
Launch
Sep 15
Feb 12
Jun 07
Note There is a continuum of options between the
baseline and minimum, varying in scientific
return, cost, and technical robustness.
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Background of Ceres
First asteroid discovered in 1801 Biggest
asteroid with a diameter about 1000 km a2.77
AU, e0.079, i10.6??? Probably hydrated
(Lebofsky 1981, Feierberg 1981) or ammoniated
(King et al. 1992) Target of Dawn, scheduled to
orbit Ceres in 2015 for 11 months
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2007 Vesta apparition

• Vesta last made such a close approach to Earth in
  June, 1989.

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Hubble Space Telescope
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Vesta in May 2007

• Wide Field Planetary Camera 2 (WFPC2)
• Four Filters F439W, F673N, F953N, F1042M
• Same filters as previous observations in 1994,
  1996.
• Preliminary image deconvolution
• Maximum Entropy Method (MEM)
• Color composite images F439WF673N

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Hubble WFPC2 F439W image of asteroid Vesta in May
2007 raw
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Hubble WFPC2 F439W Vesta in May 2007 deconvolved
(MEM)
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Hubble WFPC2 F439W images of asteroid Vesta in
May 2007 raw
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Hubble WFPC2 F439W Vesta in May 2007 deconvolved
(MEM)
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Hubble WFPC2 Vesta May 2007 Color
Composite
To watch the Rotation of Vesta, click
here http//hubblesite.org/newscenter/archive/rel
eases/2007/27/video/a/
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500 km
500 km
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Ceres observations 2003-2004

• Map Ceres through one complete rotation in
  multiple filters.
• Improve knowledge of its size, shape and pole
  orientation.
• Search for satellites
• Extend knowledge
• Apply to sequence planning for Dawn

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Ceres 2003, 2004
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Hubble images of Ceres in January 2004

• Advanced Camera for Surveys (ACS) High Resolution
  Channel (HRC)
• Filters F220W, F330W, F555W
• Sub-sampled (dithered) images were drizzled to
  enhance resolution
• Color composite images F330WF555W
• Movies made from lower-resolution images (full
  phase coverage)

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Hubble images of Ceres reveal roundness, surface
features, and colors Three different faces
of Ceres
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Ceres Rotation
To see the video of Ceres rotation, go
to http//hubblesite.org/newscenter/archive/relea
ses/2005/27/video/b/
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Learn More!

• http//dawn.jpl.nasa.gov

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Unlocking the Mysteries

• Science on the Edge of Our Solar System

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