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Synergistic Sciencewith an

Thomas R. Spilker, SSSEMark D. Hofstadter, JPL

Neil Murphy, JPL

2013 June 19

10th International Planetary Probe WorkshopSan Jose, CA, USA

Entry Probe and

Carrier Vehicle

at Uranus

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TopicsTopics

Why is Uranus important?Why is Uranus important?

High-priority science objectives at UranusHigh-priority science objectives at Uranus

Studying the interiors of stars & planetsStudying the interiors of stars & planets

Giant planet normal mode seismologyGiant planet normal mode seismology

Combining Doppler imaging and atmospheric entry probesCombining Doppler imaging and atmospheric entry probes

SummarySummary

Uranus and Neptune represent a distinct class of planet, commonly referred to as “Ice Giants.”

Definitions• Gas: H2 and He.

• Ice: Things which could be solid or gas in the solar nebula, such as H2O, CH4, NH3. (We do not believe these species are present as solid ice in Uranus and Neptune today.)

• Rock (or metal): Things that were solid almost everywhere in the solar nebula.

Clues to solar system formation: materials, processes, time scales

Approximate Composition as a Percentage of Mass

Planet Gas Ice Rock Total Mass (MEarth)

Earth 0% 0% 100% 1

Jupiter/Saturn 95% 4% 1% ~200

Uranus/Neptune 10% 65% 25% ~15

Why is Uranus Important?Why is Uranus Important?

As of February 2011

Why Uranus? – The Concise AnswerWhy Uranus? – The Concise Answer

I) The Ice Giants are a distinct and important type of planet about which very little is known.

II) Ice Giants may be the most abundant type of planet in our galaxy.

III) Uranus is the most accessible ice giant, and is also the most challenging to our understanding of planetary interiors, energy balance, formation, and evolution.

Follow the water?

Why Uranus? – The Concise AnswerWhy Uranus? – The Concise Answer

I) The Ice Giants are a distinct and important type of planet about which very little is known.

II) Ice Giants may be the most abundant type of planet in our galaxy.

III) Uranus is the most accessible ice giant, and is also the most challenging to our understanding of planetary interiors, energy balance, formation, and evolution.

Follow the water? -- Oh, there it is!

Why Uranus? – The Concise AnswerWhy Uranus? – The Concise Answer

I) The Ice Giants are a distinct and important type of planet about which very little is known.

II) Ice Giants may be the most abundant type of planet in our galaxy.

III) Uranus is the most accessible ice giant, and is also the most challenging to our understanding of planetary interiors, energy balance, formation, and evolution.

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High-Priority Uranus Science ObjectivesHigh-Priority Uranus Science Objectives

Understand Ice Giant formation, evolution, and their current Understand Ice Giant formation, evolution, and their current state in our solar system, and implications for exoplanetsstate in our solar system, and implications for exoplanets

Understand the materials, processes, and time scales Understand the materials, processes, and time scales involved in formation of our solar systeminvolved in formation of our solar system

GOALS GOALS

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High-Priority Uranus Science ObjectivesHigh-Priority Uranus Science Objectives

Highest PriorityHighest Priority Determine the internal structure: bulk composition and density profile Determine the noble gas abundances Determine the isotopic ratios of H, C, N, and O

SecondarySecondary Determine atmospheric zonal winds and dynamics Determine atmospheric composition and structure Understand the structure of the magnetosphere & internal dynamo Determine the planet’s heat budget (absorbed solar vs. emitted IR) Determine atmospheric thermal emission, structure, and variability Measure the magnetic field, plasma, & currents to determine how the

tilted/offset/rotating magnetosphere interacts with the solar wind and upper atmos

Determine the geology, geophysics, composition, and interior structure of of large satelliteslarge satellites

Based on the PSDS and Reviews Since its Release Based on the PSDS and Reviews Since its Release

Studying the Interiors of Stars and PlanetsStudying the Interiors of Stars and Planets

Gravity field measurementsGravity field measurements Distribution of mass in the planet

Acoustic (seismic) wave propagationAcoustic (seismic) wave propagation Propagation constants of the media traversed

Magnetic field structure and variabilityMagnetic field structure and variability Structure and dynamics at the dynamo generation boundary Small-scale structure in a crust

Neutrino flux measurementsNeutrino flux measurements Useful for nearby stars (we have one)

Representation of standing acoustic waves in the atmosphere of Jupiter, with blue indicating regions of rarefaction, and red areas of compression. Note the differing radial, zonal, and meridional wavelengths. (Courtesy P. Gaulme)

Schematic of standing waves forming within a celestial body. Low-order waves (purple) sample the entire body, while higher-order waves (red) probe shallower levels.

A k-omega plot. It shows the power spectrum (reds having the most power, blue the least) as a function of oscillation frequency in time (omega, on the y-axis) versus spatial frequency (horizontal wavenumber, k, along the x-axis). The object’s natural resonances form curving patterns. Different interior structures yield different patterns. (Courtesy F.-X. Schmider)

Studying the Interiors of Stars and PlanetsStudying the Interiors of Stars and Planets

Studying the Interiors of PlanetsStudying the Interiors of Planets

Giant Planet normal mode seismologyGiant Planet normal mode seismology Emerging field – so far, observed only at Jupiter

Doppler Imager (DI) instrument and techniqueDoppler Imager (DI) instrument and technique Measures atmospheric motions using Doppler shifts of reflected visible-Measures atmospheric motions using Doppler shifts of reflected visible-

wavelength solar lineswavelength solar lines Data can be acquired at any distance allowing full-disk images of the planetData can be acquired at any distance allowing full-disk images of the planet Can also measure atmospheric winds and other dynamicsCan also measure atmospheric winds and other dynamics

Existing Doppler instrument operated at South Pole

Simulated DI images for Uranus

A DI instrument addresses two of the highest-priority goals of the Decadal Survey’s Uranus Flagship mission

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Combined DI and Entry Probe at UranusCombined DI and Entry Probe at Uranus

Addresses many high-priority science objectivesAddresses many high-priority science objectives ALL the highest-priority objectives

Interior structure, noble gas abundances, isotopic ratios Several of the secondary objectives, including the first two

Zonal winds and dynamics, atmospheric composition and structure

Synergistic measurementsSynergistic measurements Probe:

Measures depth of reflecting layers Shallow measurements of T, profiles In situ turbulence, dynamics measurements

DI: Imaging for probe entry site context Global view of atmospheric dynamics

A Powerful Combination A Powerful Combination

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Combined DI and Entry Probe at UranusCombined DI and Entry Probe at Uranus

Entry probe and DI data need not be taken simultaneouslyEntry probe and DI data need not be taken simultaneously DI data best taken some distance from the planet for full-disk images

Acquired long before closest approach

No DI constraints on near-close-approach trajectory or No DI constraints on near-close-approach trajectory or pointingpointing Orbit insertion not needed (nor proscribed) for either investigation Flyby spacecraft could optimize trajectory and pointing for probe data relay

Clean interfaces allow practical partnering optionsClean interfaces allow practical partnering options Examples: contributed probe or descent module Potential for ANY planetary mission class

NASA planetary programs: Discovery, New Frontiers, Flagships Would require GFE RPS (2) and Atlas-class launch vehicle

Naturally Compatible Naturally Compatible

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Uranus is an important destination for planetary scienceUranus is an important destination for planetary science

The DI technique can provide critical interior structure The DI technique can provide critical interior structure information without orbiting the subject planetinformation without orbiting the subject planet

A mission combining DI and an atmospheric entry probe A mission combining DI and an atmospheric entry probe could address could address allall the top-priority Uranus science objectives the top-priority Uranus science objectives

There is potential to fly such a mission in There is potential to fly such a mission in anyany planetary planetary mission classmission class Clean interfaces support practical partnering optionsClean interfaces support practical partnering options

SummarySummary

Questions?Questions?