Lucy (spacecraft)

Lucy is a proposed mission concept by NASA to tour five Jupiter trojans, which orbit along the planet's path either ahead of or behind Jupiter. Starting in late 2015, the team has one year and 3 million USD to produce more in-depth concept design studies and analyses.

The mission is named after the iconic 'Lucy' hominin skeleton, because studying the trojans could reveal the "fossils of planet formation" or materials that clumped together in the early history of the Solar System to form planets and other bodies.

Overview
Lucy was selected on 30 September 2015 as one of five semifinalists for the Mission #13 of the Discovery Program. Each of the five semifinalist missions received $3 million for a one-year study. The winner will be chosen in September 2016, and must be ready to launch by the end of 2021.

Lucy would launch in 2021 and arrive in 2027 to visit three asteroids with a final encounter in 2032. After those flybys, Lucy would return to the vicinity of Jupiter's orbit to visit the last two asteroids, which orbit each other as a binary. Some possible reported targets would be 3548 Eurybates, 21900 Orus, 11351 Leucus, the binary (617) Patroclus-Menoetius, and the belt asteroid 52246 Donaldjohanson, which is named for the discoverer of the Lucy hominin fossil.

Three instruments comprise the proposed payload: a high-resolution visible imager, an optical and near-infrared imaging spectrometer and a thermal infrared spectrometer.

Harold F. Levison of the Southwest Research Institute in Boulder, Colorado is the Principal Investigator with Catherine Olkin of Southwest Research Institute as the mission's Deputy Principal Investigator. NASA's Goddard Space Flight Center would manage the project.

Exploration of Jupiter trojans was one of the goals outlined in the Planetary Science Decadal Survey of this era, and considerable attention has been paid to this goal such as mission study by Mike Brown (discoverer of Eris) and studies on hardware architecture. Of particular interest is the use of solar electric propulsion (solar panels and ion drive) for a probe at the distance of Jupiter to accomplish this task. Previous mission to Jupiter have been heavily dependent on radioisotopes for power (e.g. Pioneer, Voyager, and Galileo) or in the case of Juno, which uses solar panels, still used chemical rockets for maneuvers including Jupiter orbit injection (see also Dawn (spacecraft)).

Jupiter trojans have been identified by the Wide-field Infrared Survey Explorer (WISE infrared space telescope) as being "uniformly dark with a hint of burgundy color, and have matte surfaces that reflect little sunlight" Jupiter is 5.2 AU, about five times the Earth-Sun distance from the Sun (1 AU = 149 million kilometers = 93 million miles). The Jupiter Trojans are at a similar distance but can be somewhat farther are closer to the Sun depending. There may be as many Jupiter Trojans as there are asteroids in the asteroid belt.

Science payload
Possible instrumentation could include:
 * color imaging and infrared mapping spectrometer
 * high-resolution visible imager
 * thermal infrared spectrometer.
 * Radio science experiment (uses radio telecommunications hardware)

Targets
Potential targets may include:
 * 52246 Donaldjohanson, main-belt asteroid—flyby April 2025
 * 3548 Eurybates C-type Trojan—flyby August 2027 (L4 Jupiter trojan)
 * 21900 Orus D-type Trojan—October 2028 (L4 Jupiter trojan)
 * 617 Patroclus (aka: (617) Patroclus-Menoetius), P-type trojan binary—March 2032 (L5 Jupiter trojan)
 * 11351 Leucus SEO April 2028, has long rotation period