Persephone: A Pluto-system Orbiter and Kuiper Belt Explorer

Abstract

Persephone is a NASA concept mission study that addresses key questions raised by New Horizons’ encounters with Kuiper Belt objects (KBOs), with arguably the most important being, “Does Pluto have a subsurface ocean?” More broadly, Persephone would answer four significant science questions: (1) What are the internal structures of Pluto and Charon? (2) How have the surfaces and atmospheres in the Pluto system evolved? (3) How has the KBO population evolved? (4) What are the particles and magnetic field environments of the Kuiper Belt? To answer these questions, Persephone has a comprehensive payload, and it would both orbit within the Pluto system and encounter other KBOs. The nominal mission is 30.7 yr long, with launch in 2031 on a Space Launch System Block 2 rocket with a Centaur kick stage, followed by a 27.6 yr cruise powered by existing radioisotope electric propulsion and a Jupiter gravity assist to reach Pluto in 2058. En route to Pluto, Persephone would have one 50–100 km class KBO encounter before starting a 3.1-Earth-year orbital campaign of the Pluto system. The mission also includes the potential for an 8 yr extended mission, which would enable the exploration of another KBO in the 100–150 km size class. The mission payload includes 11 instruments: Panchromatic and Color High-Resolution Imager, Low-Light Camera, Ultra-Violet Spectrometer, Near-Infrared (IR) Spectrometer, Thermal IR Camera, Radio Frequency Spectrometer, Mass Spectrometer, Altimeter, Sounding Radar, Magnetometer, and Plasma Spectrometer. The nominal cost of this mission is $3.0 billion, making it a large strategic science mission.

The Geophysical Environment of (486958) Arrokoth—A Small Kuiper Belt Object Explored by New Horizons

“…New Horizons can also contribute to this by continuing to observe KBOs from within the Kuiper Belt during its extended mission. Future missions to small KBOs (like the Persephone mission concept to return to Pluto and explore the Kuiper Belt; Howett et al., 2021) could also address question, especially if the mass and density of targets can be directly measured with gravity science investigations. Similar investigations of the small irregular satellites of the gas giants may also be informative, since these populations are likely captured KBOs.…”

The Case for a New Frontiers–Class Uranus Orbiter: System Science at an Underexplored and Unique World with a Mid-scale Mission

“…Another primary design driver for a New Frontiers-class Uranus orbiter mission will be limitations on the total mission duration resulting from the nominal 14 yr flight design life of currently available RPSs (Lee & Bairstow 2015); however, future RPS designs are targeting on longer lifetimes, which have been used as baselines for recent predecadal mission studies designs (e.g., Howett et al 2021;Rymer et al 2021). The preliminary design is a 2 yr baseline mission in orbit at Uranus with a system tour that enables sufficient surface mapping of the large satellites, as well as imaging coverage of the planet, its rings, and the small moons.…”

The Dark Side of Pluto

“…At present, the Sun is still moving north, and it will still be three decades before it illuminates terrain further south than the limit at the time of the encounter. The ability to map terrain illuminated by Charon-light or Plutonian twilight will still be important for missions returning to Pluto for most of the century remaining (Howett et al 2021).…”

“…Figure 9 shows that for the next several decades Charon-light and Plutonian-twilight imaging will still be required for imaging the southern latitudes not in sunlight at the time of the New Horizons encounter. These considerations, for example, are reflected in the design of the Persephone Pluto orbiter concept, which includes a low-light-level camera, and reaction wheel pointing control, allowing for long integrations (Howett et al 2021). An orbiting spacecraft will also have excellent control of the imaging geometry, being able to avoid the scattered-sunlight and bright haze ring that affected the present imaging.…”