Transcript Angelopoulos_Artemis_LRO_v01

ARTEMIS Contributions to Planetary
Exploration
THEMIS Extended Phase
=
THEMIS baseline + ARTEMIS
Vassilis Angelopoulos, and the ARTEMIS team
ARTEMIS from a Planetary Perspective
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September 9, 2008
Overview
• 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
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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 and
characterize source populations of particle radiation
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September 9, 2008
ARTEMIS payload, operations concept
Data volume: 100Mbits/day
Orbit periods at moon: ~1 day
EFIs
SCM
ESA
Products:
2hr latency
Relay: DSN
3hr daily
BGS
SST
Mission Ops
UCB
FGM
Tspin=3s
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)
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September 9, 2008
ARTEMIS mission phases
Insertion: FY10; Science: FY11,12
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September 9, 2008
ARTEMIS Heliophysics objectives
Insertion FY10; Science: FY11,12
Lunar Wake
Formation/Evolution
Magnetotail
Moon
X THEMIS
P1 P2
e?
k
a
w
lent field line
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b
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Tu
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s
o
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c
Las t
Geotail
P2
D P1
Sh
Ac iffus
Fo ock
re
ce i v
sh tang
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o c en
ra a
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tio rti
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FY10: Translunar injection
FY11-12: 6mo Lissajous + 18 mo Lunar
ARTEMIS from a Planetary Perspective
Solar Wind
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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
P2
P1
ARTEMIS from a Planetary Perspective
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September 9, 2008
Issues
•Removing 11Hz noise in magnetometer
Due to internal EMI from particle sectoring
Not a show stopper
•Need to change energy ranges to measure pickup ions
Best to have fine dE/E.
Not mission critical
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September 9, 2008
Heliophysics from the Moon
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In the Magnetosphere, study:
– Particle acceleration
– Reconnection: 3D character and
global effects
– Turbulence: Drivers and effects
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In the Solar Wind, study:
– Particle acceleration at shocks
– Nature and extent of reconnection
– Inertial range of turbulence
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First two-point measurements, at 1-10RE
Reveal 3D distant tail, dynamics
First two-point measurements;
from gyroradius to RE scales
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September 9, 2008
The Electrodynamic Environment
of the Moon: Lunar Wake
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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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September 9, 2008
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Dust Levitation in Electric Fields
LADEE
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Apollo observers saw dust
elevated above the lunar
surface to possibly high
altitudes.
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LADEE will probably have a
dust detector, but has no
capability of measuring the
solar wind electric and
magnetic fields.
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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.
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ARTEMIS plus LADEE will
enable us to determine the
response of charged lunar
dust to the lunar and solar
wind electric fields.
ARTEMIS-1
ARTEMIS-2
ARTEMIS from a Planetary Perspective
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September 9,10
2008
Lunar Exosphere
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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.
ARTEMIS mass spectrometry
of pickup ions assumed “protons”
V,y
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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.
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This observation needs confirmation. If true, there may be a source of
lunar volatiles at low latitudes, not just at the poles.
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ARTEMIS has an ion detector and measures the solar wind electric
field so it can test the SIDE hypothesis of an outgassing moon.
Exospheric
Pickup
Ion
H+
He+
V,x
H2O+ S+
Solar Wind
ARTEMIS-2
ARTEMIS-1
Hartle et al., 2005
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September 9, 2008
ARTEMIS and Lunar Surface
• Lunar Surface:
• Using first of kind:
– Study composition and distribution of sputtered ions
– Understand crustal magnetic fields, surface charging
– Remotely sense surface properties of lunar regolith
• Result:
– …two point measurements
of ions and electrons near the Moon,
with unprecedented energy coverage
and resolution; beyond LP electron
reflectometry capability
– Advance our understanding of fundamental plasma
interactions with planetary surfaces.
Secondary electrons
measured by Lunar
Prospector [Halekas et al. 2008]
Trace sputtered ions
back to lunar surface ARTEMIS
Secondary and photo-electrons
accelerated from charged lunar surface
reveal regolith surface properties
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September 9, 2008
Interior Structure of the Moon
P1
P2
Core?
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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.
ARTEMIS from a Planetary Perspective
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September 9,13
2008
ARTEMIS and Planetary
• 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
• 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
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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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September 9,15
2008