Io Volcano Observer (IVO) Discovery Mission Concept Fact Sheet, February 2009

Left: Io and Tvashtar plume (top) from New Horizons. Right: Tupan Patera from Galileo.

Introduction: In 2008-9 NASA supported studies of Discovery/Scout class missions enabled by Government- furnished Advanced Stirling Radioisotope Generators (ASRGs) for power. IVO provides a long-term flight test of the ASRGs, essential to future exploration of the outer Solar System. The ASRGs enable IVO by facilitating a high data rate and pointing flexibility at large sun-probe distances.

Mission Overview: $450 M cost cap including launch vehicle (but not ASRGs). Launch in 2015 on Atlas V 401. VEEGA trajectory and Jupiter Orbit Insertion (JOI) in 2021. Io flyby before JOI, then 6-month capture orbit about Jupiter inclined ~49º. 6 additional Io flybys over 10 months, each with similar Impact and Relevance: illumination for change detection. IVO provides a long-term flight test of the ASRGs and Closest approach to Io from 1000 to 200 km, closer in extended experience in the Jupiter radiation environment (important for mission and fly through active plumes. future exploration of Europa). The mission studies the most Collect up to 20 Gb science data near Io (100x total data from dynamic solid world in the Solar System and returns New Galileo on each flyby), playback near apoapsis. Frontiers class science. The 2002 Decadal Survey identified Nearly polar approach to and departure from Io to map global four broad themes: (1) The first billion years of Solar System (especially polar) heat flow patterns. history; (2) Volatiles and organics; (3) The origin and evolution Extended mission option with Io flybys to pump orbit apoapse of habitable worlds, and (4) Processes: How planets work. out to 1-year period for extended ASRG life test; possible Hyperactive Io is an ideal target for studying how planets work. flyby of outer irregular satellite (potential captured KBO). The tidal heating that drives Io’s activity controls the habitable zone in the Jovian system and perhaps extrasolar planetary Spacecraft (S/C) Concept: systems. IVO will provide insight into the first billion years of Solar System history since ancient voluminous and high- Block redundant S/C design, new technologies limited to ASRG temperature volcanic and interior processes on the Earth, Moon, power source and science instruments. Mercury, and Mars are active on Io today. Discerning how Io Radiation tolerance from parts selection and shielding of became devoid of water (and carbon?) but retained sulfur is sensitive electronics. fundamental to understanding the evolution of volatiles. Core structure places avionics and instruments on opposite sides of a common deck that incorporates a vault for radiation shielding. 3-m high-gain antenna and redundant 40-watt TWTAs provide 50 kb/s to 34-m DSN. Mono-propellant hydrazine and redundant engines used for all maneuvers and attitude control. No deployments and only moving parts are ASRG pistons and thruster valves. Lithium Ion batteries (18 year life) store power collected from ASRGs to be used during high-power activities. Heat Pipe system uses excess ASRG heat. 1077 kg dry mass (30% margin), including 200 kg for radiation shielding, 2360 kg wet mass (12% launch vehicle margin). Io presents a rich array of interconnected orbital, geophysical, atmospheric, and plasma phenomena, and is an exciting new target for Discovery. Io Volcano Observer

Science Payload: Science Goals and Methods: Radiation-hard Narrow-Angle Camera (RCam): 10 A1. Understand the eruption mechanisms for Io’s lavas and µrad/pixel CMOS detector with 2 e- read noise, color plumes and their implications for volcanic processes on imaging (pushbroom mode with digital time delay Earth and the other terrestrial planets. High-resolution integration) in 15 bandpasses from 200-1100 nm, framing repeat imaging at UV to thermal-IR wavelengths (RCam, images (clear-filter) for movies and optical navigation. ThM) and monitoring of escaping species (INMS). Thermal Mapper (ThM): 125 µrad/pixel, ten bandpasses for A2. Determine Io’s interior structure, especially the melt fraction thermal mapping and silicate compositions. Instrument of the mantle. Measure peak lava temperatures to estimate derived from Mars Odyssey THEMIS but with an improved the temperature of the mantle and measure microbolometer detector. electromagnetic induction signal to test for a magma Ion and Neutral Mass Spectrometer (INMS): Mass range 1- ocean (RCam, FGM). 1000 amu/q, M/!M ranges from 300 to 1000 (increasing A3. Determine the properties and mechanisms of Io’s tidal with mass). Contributed by the University of Bern and the heating and implications for the coupled orbital-thermal Swedish Institute of Space Physics. evolution of Io and Europa. Map and monitor global heat Fluxgate Magnetometers (FGM): One sensor will be mounted flow (during eclipses), especially polar regions (ThM). on a bracket ~1m long and the other on the S/C; sensitivity B1. Investigate the processes that form Io’s mountains and the of 0.01 nT. Contributed by IGEP, Braunschweig. implications for tectonics under high-heat-flow conditions Payload Enhancement Options: (1) Second INMS for better that may have existed early in the history of other planets. coverage, (2) Wide-angle camera for more stereo mapping, Image and measure topography of key tectonic structures (3) Contributed near-IR imaging spectrometer, (4) Student- (RCam). built dust detector. B2. Understand Io’s atmosphere and ionosphere, the dominant mechanisms of mass loss, and the connection to Io’s volcanism. Determine composition and temporal and spatial variability of escaping species (INMS, RCam, FGM). Directly sample a volcanic plume in extended mission. B3. Determine whether Io has a magnetic field and implications for the state of Io’s large core. Measure magnetic signatures (FGM). B4. Understand Io’s surface chemistry, including volatiles and Changes in Plume Deposits silicates, and implications for crustal differentiation and Typical Dataset from 1 Orbit: mass loss. Image at UV to near-IR wavelengths (RCam), Monitoring of Jupiter system. measure spectral thermal emission (ThM), and determine Imaging of entire illuminated hemisphere of Io at <1 km/pixel in composition of escaping species (INMS). 8 colors and key features at 10-100 m/pixel in 4 colors. B5. Improve our understanding of Jupiter system science, Imaging of high-temperature activity on night side in 4 colors at including meteorology and auroral phenomena on Jupiter, <100 m/pixel to measure liquid lava temperatures. composition and temporal variability of Europa’s Regional thermal mapping at 0.1-100 km/pixel. exosphere, Jovian magnetospheric processes, and small Two stereo image pairs and two movies of active plumes. inner moons and rings of Jupiter. Observations by full Imaging of Io eclipses for global heat flow mapping at <200 payload when outside Io encounter periods. km/pixel and emissions from 200-1100 nm at <16 km/pixel. Continuous FGM measurements. INMS data (~200 spectra) near Io closest approach and segments away from Io.

Study Team: PI: Alfred McEwen (U. Arizona) Scientists: Laszlo Keszthelyi (USGS), John Spencer (SwRI), Nick Thomas (U. Bern), Phil Christensen (ASU), Torrence Johnson (JPL), Karl-Heinz Glassmeier (IGEP), Elizabeth Turtle (APL), Krishan Khurana (UCLA), Julie Moses (LPI) Mission and S/C Design: Tim Girard (Sierra Nevada Corp.), Roberto Furfaro (U. Arizona), Chris Shinohara (U. Arizona), Tohil Mons towers 9 km above neighboring Radegast patera Dan Cheeseman (RMS), Tom Gardner (RMS), and from JPL: Education and Public Outreach: Jan Ludwinski, Richard Beatty, Theresa Kowalkowski, Chen- IVO is committed to sharing the excitement of exploration and Wan Yen, Robin Evans, Insoo Jun, others in Team X. discovery with students and the public. The active phenomena are captivating, making Io and the Jupiter system ideal places to learn about chemistry and physics and to appreciate science.