New Horizons team designs a return mission to Pluto

The lead scientist behind NASA’s spectacularly successful New Horizons mission to Pluto, and his team, have come up with plans to return to the remote world.

A montage showing dwarf planet Pluto with its largest moon and companion in space, Charon. Image credit:  NASA/JHUAPL/SwRI

Principal Investigator Alan Stern and his colleagues at the Southwest Research Institute (SwRI), in Texas, have devised a way to put a probe into orbit around the dwarf planet.

Their breakthrough would allow the spacecraft to study Pluto and its five moons in detail for several years, boosting our knowledge of how they formed in the outer Solar System.

And as a major plus for the mission, the probe would later use the gravitational pull of Pluto’s largest moon Charon to catapult it away from Pluto to study other icy objects in the zone known as the Kuiper Belt.

The New Horizons probe shot straight past Pluto in July 2015 after a nine year, high-speed race across the Solar System to get there. Yet in a brief interval, it was able to gather a wealth of images and data about the Pluto system that show that it and Charon are fascinating worlds.

Related: Must-see photos of Pluto

New Horizons’ mission is not yet over because it is now on its way to examine a small body in the Kuiper Belt that has been named Ultima Thule. It is due to pass it in December.

Earlier this year, Skymania’s Paul Sutherland asked Dr Stern if he wanted to revisit Pluto, and his reply hinted at the research that has now been revealed.

He told us: “I very much would,and there is a growing momentum for that in the United States, to send an orbiter spacecraft, and we think we know how to do that with electric propulsion so that we get into orbit after a seven or nine year journey and then spend years and years studying Pluto and its system of satellites.”

You can hear the full interview on the Sound of Astronomy podcast produced by the Society for Popular Astronomy.

The SwRI team, led by Dr Stern, discovered that they could make an extensive study of Pluto and its moons, and then go on to explore the Kuiper Belt, while saving on fuel costs.

Using what they call “gravity assists” from Pluto’s main moon, Charon, rather than propellant, their probe will be able to change its orbit frequently in order to view Pluto from different angles and to fly close to individual satellites.

An annotated image of Pluto and its satellites taken by the Hubble Space Telescope in 2012, Credit: ESA/NASA and L. Frattare (STScI)

Then after years within the Pluto system, the yet unnamed probe would be again use Charon’s influence to slingshot it away into space to explore other dwarf planets and Kuiper Belt objects in the distant Solar System.

There it would once again rely on the electric propulsion system it originally used to go into orbit around Pluto. It might even be possible to go into orbit around another dwarf planet, in a similar way to how NASA’s Dawn spacecraft went into orbit around Ceres after previously circling asteroid Vesta.

The mission’s design team included spaceflight engineer Dr Mark Tapley, planetary scientist Dr Amanda Zangari, project manager John Scherrer and software lead Tiffany Finley, all from SwRI’s Space Science and Engineering Division.

Dr Stern commented in an SwRI release announcing the plans: “This is groundbreaking. Previously, NASA and the planetary science community thought the next step in Kuiper Belt exploration would be to choose between ‘going deep’ in the study of Pluto and its moons or ‘going broad’ by examining smaller Kuiper Belt objects and another dwarf planet for comparison to Pluto. The planetary science community debated which was the right next step. Our studies show you can do both in a single mission: it’s a game changer.

“Who would have thought that a single mission using already available electric propulsion engines could do all this?

He added: “Now that our team has shown that the planetary science community doesn’t have to choose between a Pluto orbiter or flybys of other bodies in the Kuiper Belt, but can have both, I call this combined mission the ‘gold standard’ for future Pluto and Kuiper Belt exploration.”

The mission plan is an independent study by SwRI and will need to be accepted by NASA before it goes ahead. The team present their proposals this week at a workshop on future Pluto and Kuiper Belt exploration at the American Astronomical Society’s Division for Planetary Sciences meeting in Knoxville, Tennessee.


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