artemis from a planetary perspective 1 september 9, 2008 themis extended phase = themis baseline +...

ARTEMIS from a Planetary Perspective 1 September 9, 2008

THEMIS Extended Phase=

THEMIS baseline + ARTEMIS

Vassilis Angelopoulos, and the ARTEMIS team

ARTEMIS Contributions to Planetary Exploration


• THEMIS Extended Phase (FY10, FY11, FY12)– Extended THEMIS Baseline (3 probes) + ARTEMIS (2 probes)

– ARTEMIS = Acceleration Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (Heliospheric Objectives, as accepted)

• The magnetosphere

• The solar wind

• The lunar wake

– ARTEMIS Planetary Capabilities • Surface composition and weathering

• Exospheric composition, structure, and dynamics

• Electric fields and dust

• Interior structure

• Support for other planetary missions (LRO, LADEE, GRAIL, etc.)as solar wind monitor, provide low energy particle spectrum andcharacterize source populations of particle radiation

Overview


ARTEMIS payload, operations concept

BGS

Mission OpsUCB

Probe instruments:ESA: ElectroStatic Analyzer (i,e: 3eV-25keV; Carlson & McFadden)SST: Solid State Telescopes (i,e: 25-1000keV; Larson)FGM: FluxGate Magnetometer (0-128Hz; Glassmeier, Auster & Baumjohann)SCM: SearchCoil Magnetometer (1Hz-4kHz; Roux & LeContel)EFI: Electric Field Instrument (0-8kHz; Bonnell & Mozer)

SST

ESA

EFIa

EFIs

FGM

SCM

Tspin=3s

DSNProducts:

2hr latency

Relay:3hr daily

Data volume: 100Mbits/dayOrbit periods at moon: ~1 day


ARTEMIS mission phasesInsertion: FY10; Science: FY11,12


Lunar WakeFormation/Evolution

Diffusive Particle

Acceleration

Shock tangent

Foreshock waves

Turbulent wake?

Last closed field lineGeotail

THEMISMoon

P1P2

P1 P2Solar Wind

X

Magnetotail

ARTEMIS Heliophysics objectivesInsertion FY10; Science: FY11,12

FY10: Translunar injectionFY11-12: 6mo Lissajous + 18 mo Lunar


For purposes of addressing planetary objectives:Periselene of P1 can be lowered to 100km (P2 remains high)Orbit stable for >3years; longer with little fuel

P1 P2


•Removing 11Hz noise in magnetometerDue to internal EMI from particle sectoringNot a show stopper

•Need to change energy ranges to measure pickup ionsBest to have fine dE/E.Not mission critical

Issues


• In the Magnetosphere, study:– Particle acceleration– Reconnection: 3D character and

global effects– Turbulence: Drivers and effects

• Reveal 3D distant tail, dynamics• First two-point measurements;

from gyroradius to RE scales

• In the Solar Wind, study:– Particle acceleration at shocks – Nature and extent of reconnection– Inertial range of turbulence

• First two-point measurements, at 1-10RE

Heliophysics from the Moon


The Electrodynamic Environmentof the Moon: Lunar Wake

• The Moon is an ideal plasma laboratory for studying magnetized plasmas.• The simple geometry of the Moon and its absorbing boundary produces a

system that can be readily modeled with computers.• This allows the codes to be tested and the physics to be understood.• ARTEMIS measurements are particularly useful for such tests.

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Dust Levitation in Electric Fields• Apollo observers saw dust

elevated above the lunar surface to possibly high altitudes.

• LADEE will probably have a dust detector, but has no capability of measuring the solar wind electric and magnetic fields.

• ARTEMIS measures the solar wind velocity, the interplanetary magnetic field and hence the solar wind electric field. It also can measure surface potentials with electron reflectometry.

• ARTEMIS plus LADEE will enable us to determine the response of charged lunar dust to the lunar and solar wind electric fields.

ARTEMIS-1ARTEMIS-1

ARTEMIS-2ARTEMIS-2

LADEE

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ExosphericPickupIon

ARTEMIS-1

ARTEMIS-2

H+

He+H2O+ S+

ARTEMIS mass spectrometryof pickup ions assumed “protons”

V,x

V,y

Solar Wind

• Apollo’s ALSEP package contained a suprathermal ion detector (SIDE) that detected ions accelerated by electric field toward lunar surface.WIND observations confirmed presence of heavy ions around moon.

• Temporal history of ion fluxes on SIDE suggested that the moon might be episodically outgassing. Alpha particle observations of localized concentrations of radon also support this viewpoint.

• This observation needs confirmation. If true, there may be a source of lunar volatiles at low latitudes, not just at the poles.

• ARTEMIS has an ion detector and measures the solar wind electric field so it can test the SIDE hypothesis of an outgassing moon.

Lunar Exosphere

Hartle et al., 2005


ARTEMIS and Lunar Surface

• Lunar Surface:– Study composition and distribution of sputtered ions– Understand crustal magnetic fields, surface charging– Remotely sense surface properties of lunar regolith

• Result:– Advance our understanding of fundamental plasma

interactions with planetary surfaces.

• Using first of kind:– …two point measurements

of ions and electrons near the Moon, with unprecedented energy coverage and resolution; beyond LP electron reflectometry capability

Trace sputtered ionsback to lunar surface

Secondary and photo-electronsaccelerated from charged lunar surfacereveal regolith surface properties

Secondary electronsmeasured by LunarProspector [Halekas et al. 2008]

ARTEMIS


Interior Structure of the Moon

• Apollo orbital measurements provided evidence of an iron core of about 400 km radius.• Lunar Prospector made similar (single instrument) measurements and confirmed the

Apollo subsatellite result.• Two-point measurements are needed to go beyond the current two-layer model of the

interior electrical conductivity.• ARTEMIS will provide measurements of both the “exciting” field and the resulting induced

magnetic field at about 100 km over a range of frequencies and sound the electrical conductivity profile above the core.

Core?

P2P1

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• In support of LRO:– ARTEMIS can provide comprehensive monitoring of Lunar Space Environment– Complements LRO/CRATER providing measurements below 6MeV• Note: ARTEMIS has been already supporting LRO via White Sands G/N testing

• Supports NAS’s Scientific Content of Exploration of the Moon to:– Understand the lunar atmosphere

ARTEMIS and Planetary

• In support of all missions– ARTEMIS provides comprehensive

monitoring of plasma conditions and lunar surface electric fields

– Allows study of the response of the lunar exosphere and dust to external drivers

– ARTEMIS provides solar wind monitoring


Summary

• ARTEMIS consists of two well-instrumented spacecraft measuring the Moon’s plasma and magnetic environment.

• ARTEMIS can determine

– How dust is levitated

– The interior electrical conductivity of the Moon

– Whether the Moon has significant outgassing episodes

– The effect of the exploration program on the lunar exosphere

– The fundamental physical processes at work in a magnetized plasma

• ARTEMIS is effectively a new mission with high science return at low cost

– Can provide high value science return to the community

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artemis from a planetary perspective 1 september 9, 2008 themis extended phase = themis baseline +...

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