NASA’s New Horizons spacecraft reached Pluto five years ago for an unexpected encounter that exceeded even astronomers’ wildest imagination. It showed geologically active dwarf planet replete with glaciers of nitrogen ice, possible ice volcanoes, tall mountain ranges carved out of water ice and frozen methane dunes fields – far beyond anything anticipated at that time by scientists.
Orbiter
NASA’s New Horizons spacecraft completed an astonishing flyby of Pluto and its moons in 2015, inspiring scientists to consider returning with an orbiter mission for further investigation of questions that were left unanswered by New Horizons, such as studying its changing surface and atmosphere.
This spacecraft would carry cameras, radars and spectrometers. As its power requirements exceed those used by New Horizons’ single plutonium generator, additional launch vehicle support will likely be required for it.
SwRI scientists have designed a flight system using the existing Space Launch System (SLS), equipped with an enhanced upper stage called Centaur, to launch a Pluto orbiter. Additionally, it could also be modified to carry satellites for visiting dwarf planets or Kuiper Belt Objects (KBOs). Powered by 12 rocket engines, its total mass would surpass New Horizons fivefold.
Lander
After the success of Voyager missions, planetary scientists looked towards Pluto as their next destination. After passing by Jupiter to increase its speed, New Horizons spacecraft reached Pluto on 14 July 2015.
The spacecraft was equipped with various instruments designed to measure fields and particles as well as create images. Much like digital cameras, this data is stored on a solid-state recorder that operates much like flash memory cards before being compressed, encoded, and sent back down through its 2.1 meter antenna back home.
New Horizons was initially created with the goal of studying Pluto and its moons as well as objects in the Kuiper Belt that remain from whence came our solar system. Since 2015, however, New Horizons has been diverted toward studying Kuiper Belt objects from 2014 MU69 (Arrokoth) instead. Mission scientists will use observations made during this flyby to gain further insights into how our Solar System was formed.
Cameras
The New Horizons spacecraft will carry two cameras and several instruments designed to study Pluto’s surface and atmosphere, drawing on the expertise of scientists such as Buie who worked on Hubble Space Telescope missions before. He had developed skills for extracting information from small images received back from space.
Ball Aerospace-built Ralph will capture images of Pluto and Charon with resolutions of about 800 feet per pixel in visible light, returning color images. Furthermore, this camera can detect methane gas signatures believed to be present in Pluto’s atmosphere.
PEPSSI will measure nitrogen, carbon monoxide, frozen methane and water in Pluto’s atmosphere using two techniques to track their source. SWAP will detect interactions between Pluto and solar wind (a fast stream of charged particles that transports solar energy towards Kuiper Belt), providing insights into interactions between Pluto and solar winds and Pluto.
Thermal Imaging
As New Horizons approached Pluto, scientists used its onboard cameras to study both it and its system of moons. MVIC or Ralph was used for visible-light imaging which provided football-field size images revealing previously unseen details of Pluto’s surface.
Scientists used these images to detect clouds and hazes in Pluto’s atmosphere, search for rings and additional moons, determine surface topography and refine radii/orbit calculations for Pluto and its moons.
LEISA and PEPSSI multiband spectrometers detected traces of nitrogen, methane, carbon monoxide, and frozen water on Pluto’s sunlit surfaces. LEISA mapped surface temperatures while PEPSSI counted microscopic dust particles to estimate collision rates among asteroids, comets, Kuiper Belt Objects (KBOs), Pluto’s moons, asteroids and comets. It also analyzed neutral gases that escape Pluto’s weak gravity, becoming electrically charged by solar UV radiation before streaming away as pickup ions allowing scientists to measure gas loss rates on Pluto.