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 and characterize source populations of particle radiation Overview

ARTEMIS from a Planetary Perspective 3 September 9, 2008 ARTEMIS payload, operations concept BGS Mission Ops UCB Probe instruments: ESA: ElectroStatic Analyzer (i,e: 3eV-25keV; Carlson & McFadden) SST: Solid State Telescopes (i,e: keV; 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 T spin =3s DSN Products: 2hr latency Relay: 3hr daily Data volume: 100Mbits/day Orbit periods at moon: ~1 day

ARTEMIS from a Planetary Perspective 4 September 9, 2008 ARTEMIS mission phases Insertion: FY10; Science: FY11,12

ARTEMIS from a Planetary Perspective 5 September 9, 2008 ARTEMIS Heliophysics objectives Insertion FY10; Science: FY11,12 FY10: Translunar injection FY11-12: 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 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 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 R E scales In the Solar Wind, study: –Particle acceleration at shocks –Nature and extent of reconnection –Inertial range of turbulence First two-point measurements, at 1-10R E Heliophysics from the Moon

ARTEMIS from a Planetary Perspective 9 September 9, 2008 The Electrodynamic Environment of 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. 9

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-1 ARTEMIS-2 LADEE 10

ARTEMIS from a Planetary Perspective 11 September 9, 2008 Exospheric Pickup Ion ARTEMIS-1 ARTEMIS-2 H+H+ He + H2O+H2O+ S+S+ ARTEMIS mass spectrometry of 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 ions back to lunar surface Secondary and photo-electrons accelerated from charged lunar surface reveal regolith surface properties Secondary electrons measured by Lunar Prospector [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 13

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 15