The resulting two-year tour of the Pluto system begins with a Charon gravity assist and a braking maneuver to complete the Pluto orbit injection. Then, using orbits that are typically just a couple of weeks long, the craft will explore each of Pluto’s small moons half a dozen times in close flybys — and Charon itself with more than 30 close flybys. It also will make both polar and equatorial flybys of Pluto and dip into Pluto’s upper atmosphere for sampling multiple times. And it will fly over Pluto’s poles many times, as well as out into its distant “magnetospheric tail” for specialized studies. The tour could continue much longer, but after two years, the spacecraft will have met all of the scientific objectives we set for it.

The spacecraft





Most of the capabilities needed for the orbiter spacecraft are similar to those for New Horizons. But the resulting flight system, which features twice the payload mass of New Horizons, fully redundant spacecraft systems, and electric and chemical propulsion systems, has a mass of 5,156 pounds (2,339 kilograms). That’s the current estimate. However, the launch vehicle we chose will be able to lift 30 percent more than that into space, in case the payload changes. That weight is nearly five times more than New Horizons, but that’s the nature of an orbiter mission because it must carry so much fuel to brake into Pluto orbit.





There are three primary differences between the proposed orbiter and New Horizons. The first is the need for either more onboard fuel or spacecraft reaction wheels to perform the thousands of pointing maneuvers during the two-year tour. The second is the need for larger onboard data storage than the 16 gigabytes that New Horizons carried. But the biggest single change is the need for a more capable communications system.