The Lucy Mission is a NASA Discovery-class mission to send a spacecraft to investigate seven primitive bodies near the L4 and L5 Lagrange points of Jupiter. These planetesimals can give us insight into the formation of the early solar system.
The science goals are derived from the 2013 Planetary Decadal Survey and include determining surface composition, assessing geology, determining bulk properties, searching for satellites and rings.
It will visit objects with diameters ranging from roughly 1 km to 100 km. The payload suite consists of a colour camera and infrared imaging spectrometer, a high-resolution panchromatic imagery, and a thermal infrared spectrometer.
Additionally, two spacecraft subsystems will also contribute to the science investigations: the terminal tracking cameras will supplement imaging during closest approach and the telecommunication subsystem will be used to measure the mass of the Trojans.
Lucy's mission patch proudly revels in being the first mission to the Trojan asteroids. I’m personally very excited about the potential for resource utilization; however, this paper is focused on the scientific goals of the mission. The largest focus of the paper is on deepening the understanding of the early formation of the solar system.
The mission is named after the famous Homonim fossil and suggests a link between how much we have learned from that fossil and how much we will learn from this mission.
Models developed within the last 15 years suggest that the diversity amongst the planetesimals is due to the distance with which they were formed, around ∼15–30 au and were pulled into their current positions by orbital evolution. The paper references Morbidelli and Nesvornýs models that suggest that the early entities in these Lagrange points were replaced by farther out objects during the early consolidation of the giant planets.
At the least this mission will help to disentangle the multiple theories about the evolution of the early solar system. LUCY will be able to confirm if these models are accurate and create new hypotheses.
LUCY will target 7 trojans and one main belt asteroid; the mission will last 11.6 years and it will be launched on the 16th of October 2021. The spacecraft will use two reath gravity assists to reach Jupiters L4 Trojan swarm.
Using some clever orbital mechanics the paper shows how the spacecraft can visit both the L4 and L5 swarms on consecutive orbits. After the final L4 encounter Lucy will return towards earth for an earth gravity assist that sets up an encounter with the final Trojan targets, Patroclus and its binary companion I Menoetius.
The Lucy mission has 17 Level 1 science requirements this table specifies the Trojan targets of the mission and the science data to be collected
The science objectives break down into five areas: target diversity, surface composition, geology, bulk properties, and satellite search, each covered in a section below.
In this paper, they review the broad science objectives behind these requirements. I picked this paper since I'm very interested in objectives 2, 3 and 8 through 17. I really believe this will have a disproportionate effect on the terrestrial economy and future of humanity in space.
On its way to the trojans the spacecraft will intercept a man belt asteroid Donald Johanson which is named in honour of the discoverer of the Lucy fossil; this should happen on 20th of April 2025. This encounter is mentioned in the paper as being planned as an in-flight demonstration of the spacecraft's ability to reduce risk prior to trojan encounters. But Donald Johanson is also a scientific target due to its membership in the 100 to 130 million year old ‘Erigone’ collision family.
After this encounter, LUCY will target Eurybates and its satellite Queta in the L4 swarm in 2027. 34 days later it will meet Polymele then it will finish its exploration of the L4 swarm by meeting Leucus and Orus in 2028.
Lucy’s first Level 1 requirement, R-1, specifies its multiple targets and that the overall drive of the mission is to understand as much as possible about a diverse, never-before-visited group of asteroids. The paper shows that they want to get as many candidates as possible and create opportunities for follow up missions.
The paper highlights three key attributes for where they have targeted;: color, size, and collisional history.
The Size Frequency distribution of the targets suggest that there may be a common origin for the two groups of asteroids. LUCY'S targets have been chosen to observe trojan targets ranging over two orders of magnitude in the Size Frequency distribution slope thereby directly probing the physical basis of this phenomenon. LUCY will focus on the impactor population down to the 10m scale
The paper points out that the binary Patroclus–Menoetius could be a relatively pristine representative of the early solar system. They will also visit Eurybates, the largest member of the eponymous catastrophic collisional family and its small satellite, Queta, which may be a collision fragment still in orbit. Surveying these objects will produce highly valuable data for our understanding of the early solar system.
Previous exploration has shown that small solar bodies of all scales have complex and diverse internal structures as well as the topography of the surface.
Lucy will contribute its data from flybys of the objects to creating digital terrain models. These will have varying resolutions depending on how close the approach distance, phase angle and spin rate of the target are.
Panchromatic images from multiple angles will contribute to these models.
As Lucy flies past its targets it can use measurements of the brightness distribution on the surface of the target to establish a photometric model that can be used to examine the physical properties of the surface regolith.
The mission will use data from close flybys and farther out flybys to observe different angles and fill in each other's gaps.
The paper argues that the photometric model will create a platform for the analysis, interpretation, and comparison of the other targets. As well as establishing the thermal balance and assessing the thermal evolution of the objects.
Near Infrared Spectroscopy can also be used to prove the limits of the abundances of ices, crystalline silicates, and hydrated minerals
Thermal Infrared Observations are called out by the paper as being an important way to scope interesting surface process and temperature anomalies.
They also reference the work of Rozitis which shows that Observations in the thermal infrared, enable determination of thermal inertia, which then gives insight into the grain size and porosity of the regolith.
The main tool used for these measurements will be The Lucy Thermal Emission Spectrometer (TES)
The 1993 Galileo mission proved that the asteroid Ida has a satellite called Dactyl; this was the first detection of a satellite around a small body.
rings have been found around the TNO Haumea, a dwarf planet past neptune and the Centaur Chariklo
Two of the Lucy mission targets, Patroclus and Eurybates, are also known to have satellites
Measurements of light curvature suggest there should be more and LUCY will be able to confirm this.
This information will also help us to understand the features of outgassing and surface volatility.
I think LUCY will be one of the most important missions in hindsight, I think humans need to expand or they fight each other and this mission represents a giant leap in Human activity in the solar system
Lucy will derive the densities of its targets from radio science mass determination and volume measurements from imaging.
These densities will be compared with known densities in other small-body populations to identify affinities. The mission will also carry out detailed compositional investigations of the surfaces of the targets.
At the moment a total of eight main-belt asteroids have been visited by all planetary spacecraft missions flown to date. These investigations were a huge deal for our understanding of terrestrial planet formation; Lucy on its own will visit almost as many asteroids in one mission.
Also I think it's significant that man measures its environment, once we have intricate measurements of the asteroids they should feel closer.
Lucy Mission to the Trojan Asteroids: Science Goals