ARTEMIS from a Planetary Perspective 1 September 9, 2008 THEMIS Extended Phase = THEMIS baseline +...
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Transcript of 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
ARTEMIS from a Planetary Perspective 2 September 9, 2008
• 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 from a Planetary Perspective 3 September 9, 2008
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 from a Planetary Perspective 4 September 9, 2008
ARTEMIS mission phasesInsertion: FY10; Science: FY11,12
ARTEMIS from a Planetary Perspective 5 September 9, 2008
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
ARTEMIS from a Planetary Perspective 6 September 9, 2008
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
ARTEMIS from a Planetary Perspective 7 September 9, 2008
•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
ARTEMIS from a Planetary Perspective 8 September 9, 2008
• 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
ARTEMIS from a Planetary Perspective 9 September 9, 2008
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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ARTEMIS from a Planetary Perspective 10 September 9, 2008
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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ARTEMIS from a Planetary Perspective 11 September 9, 2008
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 from a Planetary Perspective 12 September 9, 2008
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
ARTEMIS from a Planetary Perspective 13 September 9, 2008
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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ARTEMIS from a Planetary Perspective 14 September 9, 2008
• 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
ARTEMIS from a Planetary Perspective 15 September 9, 2008
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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