The MESSENGER Mission to Mercury

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Nori LasloNori LasloJohns Hopkins University Johns Hopkins University

Applied Physics LaboratoryApplied Physics Laboratory

A NASA Discovery Mission

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•Why Mercury?

•MESSENGER – a NASA Discovery Mission

•MESSENGER Mission Objectives

•Mission Challenges

•Mission Timeline

•MESSENGER Payload

•Mercury Dual Imaging System

•MESSENGER Load Building Process

•MESSENGER data

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Why Mercury?Why Mercury?

• Highest orbital eccentricity in the solar system

• Only planet with 3:2 spin orbit resonance

• Smallest axial tilt: 0.01 degrees

• Widest daily temperature range: 1100°F from day to night! (-300°F to 800°F)

• Highest uncompressed density in the solar system

• Largest ratio of core to size of planet: core is approximately 75% of Mercury’s radius, 42% of volume

• Most inclined orbit: 7 degrees off of the ecliptic

• Difficult to study with Earth-based telescopes: limited by proximity to Sun

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• Some ground-based data: Arecibo, VLA, Goldstone

Arecibo radar image of north polar deposits [Harmon et al., 2001].

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• Mariner 10: 1974-1975

• First spacecraft to make use of “gravitational slingshot”

• Mapped 45% of planet’s surface

Mariner 10 image of Discovery Rupes

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MESSENGER: A NASA Discovery MissionMESSENGER: A NASA Discovery Mission

• NASA Discovery Program– Program began in 1994– Goal is to launch low-cost, scientifically focused

missions– Mission proposals, each led by a Principal

Investigator, undergo rigorous scientific and technical reviews

– MESSENGER is the seventh mission chosen by NASA Discovery Program

• Near Earth Asteroid Rendezvous (NEAR)

• Mars Pathfinder

• Lunar Prospector

• Stardust

• Genesis

• Comet Nucleus Tour (CONTOUR)

• MESSENGER

• Deep Impact

• Dawn

• KeplerDeep

Impact

Mars Pathfinder

Stardust

NEAR Lunar Prospector

Genesis

MESSENGER

CONTOUR

Dawn Kepler

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Mission ObjectivesMission Objectives

• MESSENGER – MErcury Surface Space ENvironment GEochemistry and Ranging

• Six fundamental science questions to answer regarding the formation and evolution of Mercury (Solomon et al. 2001)1. What planetary formational processes led to the planet’s high

metal-to-silicate ratio?

2. What is Mercury’s geological history?

3. What are the nature and origin of Mercury’s magnetic field?

4. What are the structure and state of Mercury’s core?

5. What are the radar-reflective materials at Mercury’s poles?

6. What are the important volatile species and their sources and sinks on and near Mercury?

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Mission Challenges: MassMission Challenges: Mass

• Mass– Delta II 7925-H launch vehicle, largest available to a

Discovery-class mission, limited total spacecraft mass to 1,107 kg

– Much of the mass had to be fuel: 54% of total mass– Minimized dry mass: used lightweight titanium fuel

tanks, carbon composite main structure, miniaturized instruments, integrated propulsion system into spacecraft structure

– Minimized fuel required by selecting a complex trajectory utilizing gravity assists: maneuvers that use tug of a planet’s gravity to adjust speed or shape of spacecraft’s trajectory

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Mission TimelineMission Timeline

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Mission Timeline: Orbital PhaseMission Timeline: Orbital Phase

• Orbit Insertion: March 18th, 2011

• Requires ~33% of propellant

• One orbit = 12 hours

• Orbit is highly elliptical: periapsis altitude is 200km (124 mi), apoapsis altitude is 15,200 km (~9,420 mi)

• Solar gravity slowly changes spacecraft’s orbit; corrective maneuvers required every 88 days

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Mission Challenges: Proximity to SunMission Challenges: Proximity to Sun

• At such a small distance, actually falling toward the Sun; increased spacecraft speed means we actually need to break for orbital insertion

• Solar radiation at Mercury 7-10 times that on Earth

• Key component of thermal design: unique ceramic-cloth sunshade to protect instruments from harsh solar environment

• Allowed for mostly standard electronics, components, and thermal blanketing materials

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Thermal DesignThermal Design

Thermal DesignThermal Design

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PayloadPayload

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Mercury Dual Imaging SystemMercury Dual Imaging System

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• Narrow-Angle Camera (NAC):– 1.5° Field of View– 1024x1024 pixels– Focal length = 550mm– 700-800 nm spectral range– Off-axis reflector:

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• Wide-Angle Camera (WAC):– 10.5° Field of View– 1024x1024 pixels– Focal length = 78 mm– Four-element refractor:

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• WAC also includes 12-color filter wheel; 395-1040 nm spectral range

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Load Building ProcessLoad Building Process

Mission Operations Team provides

Initials: initial state, track times etc.

Instruments/subsystems each

build a sequence of commands

All commanding is merged by payload manager; checked

for conflicts

Instruments/subsystems each

submit final sequence

Mission Operations Team builds load and runs through

simulator

Simulator output is reviewed and errors fixed if necessary

Load uplinked to spacecraft

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MESSENGER DataMESSENGER Data

The results are in.....

Courtesy NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

January 9, 2008

Distance: 1.7 million miles

Narrow-Angle Camera

Resolution: 70 km/pixel


January 13, 2008

Distance: 470,000 miles

Narrow-Angle Camera

Resolution: 20 km/pixel


January 14, 2008


Wide-Angle Camera

Filter: 750 nm


January 14, 2008


Narrow-Angle Camera


January 14, 2008

Narrow-Angle Camera


January 14, 2008


Wide-Angle Camera

Filters: 1000, 700, 430 nm

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For more information…For more information…

• Please visit:

http://messenger.jhuapl.edu

to see more data and animations (including the Earth and Venus flybys!), and for more information

on the MESSENGER team and project. Questions? Email Nori at [email protected].

The MESSENGER Mission to Mercury

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