# Presentation: 478373

## NASA’s Dawn MissionJourney 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 NASA’s Discovery Program
-              http://discovery.nasa.gov

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## Traveling Back In Time

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**Notes:**
The Dawn mission will explore a new frontier, traveling back in time over 4.5 billion years to the beginning of our Solar System. How is this “time travel” possible? 

## Dawn Explores the Earliest Epochs

- Vesta and Ceres are intact survivors of the earliest epoch of planetary formation.

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**Notes:**
During the earliest epochs of our solar system, the nature of the materials in the solar nebula varied with their distance from the sun.  As distance from the sun increased, the temperature dropped, with terrestrial, rocky bodies forming closer to the sun, and icy bodies forming farther away.  Dawn will examine the dividing line between our solar system’s rocky and icy bodies. We believe this line may be between Vesta and Ceres, as Ceres  probably has water ice beneath its surface and Vesta is bone dry. 

## The Asteroid Belt

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**Notes:**
Many hundreds of thousands of small bodies orbit the Sun in the Main Asteroid Belt--the region between the orbits of Mars and Jupiter. They formed at the same time and in similar environments as the bodies that grew to be the rocky planets (Mercury, Venus, Earth, and Mars). Scientist theorize that these budding planets were never given the opportunity to grow due to massive Jupiter’s gravitational pull.  In some cases, their formation also may have been disrupted by collisions in the asteroid belt.  Sometimes called minor planets, asteroids contain clues that reveal the conditions and processes at work inside the orbit of Jupiter during the Solar System’s earliest epoch. 

## 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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**Notes:**
In this slide NASA’s Dawn Spacecraft is depicted atop the Boeing Delta 2 rocket at the Cape Canaveral Air Force Station in Florida. Launch is now scheduled for September of 2007 after failed attempts in June and July. There were a series of events that prevented the June and July launches, including late delivery of the second stage of the rocket, a broken crane, inadequate resources to visually observe the launch during from over the ocean and weather.

## Interplanetary Trajectory

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**Notes:**
Trajectory Launching from Cape Canaveral in the fall of  2007, the Dawn spacecraft will encounter Vesta four years later, then travel an additional three years to reach Ceres in 2015.  This trajectory will probably be modified due to the launch delay, but I don’t have the details at this time.
The Dawn mission marks the first time that a spacecraft will orbit not one but two main belt asteroids, enabling detailed and intensive studies. Because this mission orbits two asteroids that are both large and massive with contrasting properties (Vesta-Dry), (Ceres-Hydrated), Dawn has the potential for tremendous scientific return.

## Ion Propulsion

- Deep Space 1

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**Notes:**
Ion Propulsion System (IPS) : Dawn’s journey to the asteroid belt, spanning eight years from launch to completion of data return, is made possible by ion propulsion. 
While ion propulsion was initially tested and proven successful on NASA’s Deep Space 1 mission, the Dawn mission represents the first time this innovative technology has been  applied in the design and implementation of a dedicated scientific space flight.  Ion propulsion will allow Dawn to undertake a bold and important mission that would be unaffordable—or perhaps even impossible—with a more conventional propulsion system. Dawn will thrust with its IPS for about 50,000 hours. This is three times the longest powered flight by any spacecraft.

## Ion Propulsion System

- Hydrazine tank
- 45 kg capacity

- Xenon tank
- 450 kg capacity

- Folded solar arrays

- Ion thruster

- 2.3 meters

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**Notes:**
Dawn will pack only 425 kg (937 pounds) of Xenon fuel for this eight year journey!  The spacecraft itself has a mass of 745 kg and the whole propellant system fits into less than 2 cubic meters of space!  Dawn will use hydrazine thrusters (chemical propulsion) for trajectory correction maneuvers. 

In comparison, a trip just to Vesta without an ion propulsion system would require  2500 kg of propellants aboard the spacecraft.  So the Dawn mission, which includes a trip to Ceres, would not be possible without utilizing an ion propulsion system. 
The solar array panels, shown folded in this image, stretch approximately 19.7 meters (65 feet) from tip to tip, and help to harness power from the distant Sun to power the ion engines. The power then ionizes the onboard fuel, xenon, accelerating the ions, which in turn accelerate the spacecraft.

## 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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**Notes:**
HGA – High Gain Antenna LGA – Low Gain AntennaCSS – Coarse Sun Sensors GRaND – Gamma Ray and Neutron Detector (Mapping of elemental abundances)
IPS Thrusters – Ion Propulsion ThrustersRCS Thrusters – Reaction Control System ThrustersVIR – Visual and Infrared Spectrometers (High resolution mineralogical and thermal emissivity mapping)
FC – Framing Camera (Imaging science and Navigation)
Dawn will be the first spacecraft ever to orbit two targets after leaving Earth, thus allowing the same suite of instruments to be used to gather comparative data on Vesta and Ceres. Aboard the spacecraft, the science payload consists of two cameras, a visible and infrared mapping spectrometer to reveal the surface minerals, and a gamma ray and neutron spectrometer to determine the elements that make up the outer parts of the asteroids. The spacecraft also will be used to measure gravity fields, thereby revealing details of these asteroids’ interiors. With the data from these systems, scientists will study the complex and varied landscapes of these ancient worlds, thereby gaining valuable new insights into their external and internal structure.

## Map the Gravity Field

- Vesta Gravity from Shape Model

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**Notes:**
Dawn will determine the mass and gravitational field of the asteroids. It will measure the bulk density and, through its correlation with optical topography, deduce or infer the internal structure of the asteroids. 

## 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 camera’s most recent heritage comes from Venus Express****.**

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**Notes:**
The framing camera will:
 map the extent of volcanic and aqueous processes
 establish a cratering record
 establish a relative chronology of crustal units
 establish population of early impactors
 determine the shape and spin state of the bodies
 map the topography of Vesta
 search for dust and satellites
 be used for navigation

## 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

- 25.7 cm

- 18.0 cm

- 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

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## Map the Elemental Composition

**Gamma ray and neutron detector (GRaND) techniques have been proven on Lunar Prospector. GRaND’s most recent heritage is from Mars Odyssey**

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**Notes:**
The GRaND instrument will measure:
 major elemental composition of oxygen, silicon, iron, magnesium, titanium, aluminum, calcium, and hydrogen
 trace elements uranium, thorium, potassium, gadolinium, and sulfur

## Exploring New Worlds

**Dawn’s 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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**Notes:**
By investigating two very different asteroids, Ceres and Vesta, the Dawn mission hopes to unlock some of the mysteries of planetary formation, including the building blocks and the processes leading to the present state of these asteroids.

Why Vesta and Ceres? Two of the largest main belt asteroids, Vesta and Ceres, survived the cosmic tug of war between the Sun and Jupiter and have remained intact since their formation. Furthermore, the distinct characteristics of these asteroids demonstrate that each has followed a different evolutionary path. Vesta appears to be dry, evolved, and differentiated, with surface features ranging from basaltic lava flows to a deep crater in its southern hemisphere. Ceres, in contrast, has a primitive surface and evidence of water, with hydrated minerals on its surface, and perhaps even frosty polar caps. Vesta’s physical characteristics reflect those of the inner planets, whereas Ceres is thought to be more like the icy moons of Jupiter. By studying these contrasts and comparing these two minor planets, scientists hope to develop an understanding of the transition from the rocky inner to the icy outer regions of the Solar System.
Vesta and Ceres are unlike any asteroids that have been visited by spacecraft.
They are 2 of the most massive asteroids.
Vesta is believed to be the source of the HED (howardite, eucrite, and diogenite) achondrite meteorites.
• Ceres has no candidate meteorites found on Earth.
All of what we now know about Vesta and Ceres comes from ground-based and Earth-orbiting telescopes like NASA’s Hubble Space Telescope (HST) and numerous observatories around the world.  This information is revealed by sunlight reflected from the surface in the ultraviolet, visible and near-infrared, and by emitted radiation in the far-infrared and microwave regions.   
Vesta’s diameter extends about the length of the state of Arizona.  However,  from the Hubble Space Telescope, its appears to be about the size of a potato suspended from one goal post and viewed from the other end of the football field. Vesta rotates once every 5 hours, 20.5 minutes on it short axis.
Even though Ceres was the first asteroid to be discovered 200 years ago, its physical characteristics have remained a mystery.  It is about as big as Texas and is located farther from the Sun than is Vesta.  Recent measurements with Hubble Space Telescope have revealed Ceres’ shape, indicating that it has experienced global processing, resulting in  density differentiation.  Thus, it appears to have heavier material in the center, a less dense crust most likely composed of water ice,  and a thin crust of dust on top of that ice.

Dawn’s Itinerary
The Dawn Spacecraft will travel:
 6.3 billion kilometers
 For almost eight years
 To the asteroids,  4 Vesta and 1 Ceres.

## 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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**Notes:**
Dawn is the ninth Discovery mission in NASA’s Science Mission Directorate and is a collaborative partnership made up of the University of California, Los Angeles; Jet Propulsion Laboratory; Orbital Sciences Corporation; Los Alamos National Laboratory; German Aerospace Center; Max Planck Institute for Solar System Research; Italian Space Agency, and Italian National Institute of Astrophysics. Dawn outreach materials are developed under contract by Mid-continent Research for Education and Learning (McREL), Aurora, CO.
	University of California, Los Angeles
Principal investigator, science team lead, overall mission responsibility for the science requirements.
	Science Team: 
Science team members from: Brown University, University of Tennessee, University of Maryland, Los Alamos National Laboratory, Italian Space Agency (ASI)	
	JPL
Project and systems management, delivery of some portions of spacecraft, systems engineering, mission design, and mission operations 
	Orbital Sciences Corporation
Spacecraft development, integration, and test
	Max Planck Institute for Solar System Research
	DLR – German Aerospace Center
Framing camera, fabrication, integration, test, sequencing and analysis. Integrate mapping spectrometer provided by CNR/IAS
	Los Alamos National Laboratory
GRaND instrument design, build, test, integrate, sequence and analyze data 
	ASI – Italian Space Agency
Mapping spectrometer design, build, test, integrate, sequence and analyze data 
McREL, New Roads School, and University of Maryland, 
Education and Public Outreach

## Mission Timeline

- Launch

- Jun  ‘07

- (1) Ceres
- arrival

- Aug ‘15

- (4) Vesta
- arrival

- Oct ‘11

- (4) Vesta
- departure

- May ‘12

- Mars gravity assist

- Mar ‘09

- End of mission

- Jan ‘16

- (1) Ceres
- arrival

- Sep ‘15

- (4) Vesta
- departure

- Feb ‘12

- Note: There is a continuum of options between the baseline and minimum, varying in scientific return, cost, and technical robustness.

- Baseline mission shown in green
- Minimum mission shown in blue

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## Background of Ceres

- First asteroid discovered in 1801
- Biggest asteroid with a diameter about 1000 km
*a*=2.77 AU, *e*=0.079, *i*=10.6
- 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: F439W+F673N

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## Hubble WFPC2 F439W image of asteroid Vesta in May 2007: raw

**Hubble WFPC2 F439W image of asteroid Vesta in May 2007: raw**

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## Hubble WFPC2 F439W Vesta in May 2007: deconvolved (MEM)

**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/releases/2007/27/video/a/](http://hubblesite.org/newscenter/archive/releases/2007/27/video/a/)_

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## 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: F330W+F555W
- Movies made from lower-resolution images (full phase coverage)

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## Hubble images of Ceres reveal 

- 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/releases/2005/27/video/b/](http://hubblesite.org/newscenter/archive/releases/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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