Exploring Jupiter’s Volcanic Moon Io on Just $615,000 a Day


Bypassing Chance for Double the Dollars, PI Pushes Io Volcano Observer for NASA Discovery Program

WASHINGTON — The principal investigator behind a proposal to explore Jupiter’s moon Io is in such a hurry to get there that he is content to develop the robotic mission for about half the money the planetary science community said NASA should spend to explore the volcano-laden Jovian satellite.

“My thinking now is Discovery is the best bet,” Alfred McEwen, professor of planetary geology at the University of Arizona and principal investigator for the Io Volcano Observer (IVO), told SpaceNews in a recent interview.

Alfred McEwen
Alfred McEwen, principal investigator for the Io Volcano Observer. Credit: University of Arizona

Discovery is the smaller of NASA’s two competitively selected planetary mission lines, with costs capped at $450 million not including launch. New Frontier missions, which launch less frequently, are capped at $1 billion.

Io missions have the planetary community’s blessing to compete for New Frontiers money: The moon is one of the seven priority destinations for the New Frontiers program in the decade spanning 2013-2022. However, the National Research Council panel that produced that 10-year roadmap, or decadal survey, rated Io a second-tier destination. Missions to a comet, the moon and Saturn all rated higher.

That means “unless NASA decides to open up the next New Frontiers competition, Io will not be one of the destinations” for a New Frontiers solicitation that could hit be released as soon as October, McEwen said.

Jim Green, NASA’s director of Planetary Science, said in February the agency will adhere strictly to the tier list from the 2011 decadal, “Visions and Voyages for Planetary Science in the Decade 2013-2022.” The decadal advised NASA to conduct two New Frontiers competitions in that period.

Io Volcano Observer at a glance

Nominal Launch: 2021

Orbital Insertion: 2026

Primary Mission: 9 Io flybys from Jupiter orbit over two years

Closest Approach: 200 kilometers

Principal Investigator: Alfred McEwen, University of Arizona

Builder: Johns Hopkins University Applied Physics Laboratory

Spacecraft Mass: 1.5 metric tons wet/715 kilograms dry

Fits in 4-meter fairing: Yes

So IVO faces a potentially long road for New Frontiers funding. The earliest the mission could enter the fray is around 2020, when the competition after the next is scheduled to begin. After that, Io’s decadal priority expires, unless scientists again anoint it as a favored destination.

A 1979 photo of Jupiter, Europa (right), and Io (left), taken from Voyager 1. Credit: NASA/JPL
A 1979 photo of Jupiter, Europa (right), and Io (left), taken from Voyager 1. Credit: NASA/JPL

There is some precedent for that, since Io was also a preferred destination in the 2003 planetary decadal that laid out community priorities for the 10-year period that ended in 2012.

But McEwen decided not to risk the wait and put together an IVO proposal for the Discovery competition now under way. The first round of cuts will take place in June ahead of an expected award in September. The winner must be ready to launch in May 2021.

The Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, would build IVO and operate it after launch.

Like the New Horizons Pluto probe on its way to a close encounter with that dwarf planet and the Mercury MESSENGER probe that cratered at the end of its mission on April 30, “the IVO spacecraft is too specialized for industry,” McEwen said.

Assuming a 2021 liftoff, IVO could reach the Jupiter system in 2026, McEwen said. The probe would insert itself into a highly elliptical Jovian orbit that would provide nine Io flybys over a two-year primary mission. With its six instruments, including a mostly visible-spectrum camera with some sensitivity in infrared and ultraviolet wavelengths, IVO will take Io’s temperature, study the composition of its surface and atmosphere, and examine how Jupiter’s gravity flexes the largest of its moons to produce the tidal heating that drives the satellite’s extreme volcanism.

A compilation of photos from NASA’s New Horizons mission that captures the giant plume from Io’s Tvashtar volcano. Credit: NASA

After the primary mission ends, and given some added funding, a healthy spacecraft, and NASA’s blessing, McEwen thinks IVO could alter its orbit to get nine more flybys over the course of a five-year extended mission.

As a Discovery mission, IVO would lose some capabilities it could afford with a New Frontiers budget. In a New Frontiers scenario, with more than double the development dollars, IVO could include instruments such as a gimbaled high-gain antenna “for a little gravity science,” and more powerful infrared and ultraviolet sensors, McEwen said.

McEwen tried to get IVO funded once before, in the Discovery competition that began in 2010 and concluded in 2012 with the selection of the Mars lander InSight: A proposal from the Jet Propulsion Laboratory in Pasadena, California, based heavily on NASA’s Mars Phoenix lander. InSight is now under construction at Lockheed Martin Space Systems (which also built Phoenix) near Denver.

Although IVO did not make it into the finals of the last Discovery competition, the mission was well reviewed at NASA, McEwen said.

“But not quite well enough,” he added.

Part of IVO’s problem in 2010, McEwen speculated, was the mission’s plan to use an Advanced Stirling Radioisotope (ASRG) power supply, a next-generation nuclear battery, instead of solar panels.

The ASRG was still in development during the last Discovery competition and NASA invited proposers to include the unit on their spacecraft as government furnished equipment. Ultimately, NASA went with the solar-powered Insight and canceled ASRG development altogether about a year later.

Solar power is mandatory for the 2015 Discovery competition, so IVO shifted power supplies. The mission would also carry an experimental optical communications payload NASA has incentivized Discovery competitors to test by offering to cover the estimated $30 million needed to install the hardware.

Now, McEwen said, IVO “is in much better shape than it was in 2010.”