NASA Successfully Launches Lucy Spacecraft to Jupiter’s Trojan Asteroids
The early morning of October 16, 2021, witnessed the successful launch of the Lucy space probe at 5:34 AM EDT from Cape Canaveral Space Force Station in Florida, United States. The probe is set to explore different asteroids (one main-belt asteroid and seven Trojan asteroids orbiting Jupiter). As the probe embarks on its 12-year journey, it introduces us to several new regions and terminologies of the space. This article provides a brief overview of the mission design, its significance, and its objectives. Before starting, it is important to mention that this will be the first space mission to visit and explore the Trojan asteroids.
Mission Overview
On 4th January 2017, the mission was chosen as Discovery Mission 13 under NASA’s Discovery Missions Program. Lucy will be launched by a 401 variant of the United Launch Alliance Atlas V launching vehicle and will receive two gravity assistance from Earth, one in 2022 and the other in 2024. The mission will be jointly operated by NASA Goddard Space Flight Center (GSFC) and Southwest Research Institute (SWRI).
The spacecraft will visit two out of five Lagrange points (L4 and L5) of Jupiter and will gain two gravity assists from Earth to pass by the asteroid 52246 Donaldjohanson in the inner main belt in 2025. In 2027, it will fly past four Trojans, 3548 Eurybates with its satellite Queta, 15094 Polymele, 11351 Leucus, and 21900 Orus, in the L4 Trojan cloud (a Greek camp of asteroids orbiting about 60° ahead of Jupiter).
Lucy will return to Earth in 2031 for third gravity assist toward the L5 Trojan cloud (the Trojan camp roughly 60 degrees behind Jupiter), where it will visit the binary Trojan 617 Patroclus with its satellite Menoetius in 2033. The mission will come to an end with the Patroclus–Menoetius flyby. If the mission is not extended, Lucy will stay in a stable, 6-year orbit between the L4 and L5 clouds for thousands of years.
The Name ‘Lucy’
The mission and space probe is named after Lucy Hominini Fossil found in Ethiopia in 1974. It is estimated that the fossil is dated to about 3.2 million years ago. The discovery of this fossil was a breakthrough as it helped us connect the missing links of human evolution. The mission name and its purpose are an analogy of this fossil’s significance as the study of Trojans could reveal the missing links of how the planets and other bodies were formed.
Fun Fact: The fossil was named after a 1967 song “Lucy in the Sky with Diamonds” by the Beatles and Lucy itself carries a disc made of lab-grown diamonds with her L’TES instrument.
Mission Objective and Payload
On her 12 year journey, Lucy will fly by and carry out remote sensing operations on seven Trojan asteroids. These asteroids orbit the Sun with the same speed as Jupiter and are considered the time capsules from the formation of the solar system as they are believed to be formed in the same region as Jupiter and entered its orbit when the planet was forming. Their origin theories also suggest that these asteroids were some of the astronomical objects scattered during the formation of the solar system.
The remote sensing operations will address the following objectives:
- Surface Geology: Map the solar radiation, shape, craters, and size-frequency distribution of the asteroids. This will help in determining the nature of crystal structure and the relative age of surface units.
- Surface Color and Composition: Map the color and composition and regolith properties of the surface. This will determine the minerals, organic species, and ice distribution on the asteroids.
- Interiors and Bulk Properties: Study the sub-surface composition by excavating craters, fractures, ejecta blankets, and exposed bedding. Apart from this, Lucy will also explore the satellite rings of the Trojan asteroids.
The above objectives will be accomplished with the help of the following three science instruments mounted on the space probe:
- Lucy Thermal Emission Spectrometer (L’TES): This instrument measures the surface temperature of the Trojan asteroids by observing the thermal infrared spectrum. These readings can help in understanding the physical properties of the surface. It is built by Arizona State University (ASU), Tempe, Arizona.
- Lucy LOng Range Reconnaissance Imager (L’LORRI): A high-resolution panchromatic camera installed to provide high-detail images of Trojan asteroids. It is made by Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland.
- L’Ralph: An optical and near-infrared imaging spectrometer built by NASA Goddard Space Flight Center (GSFC). It consists of L’Ralph Linear Etalon Imaging Spectral Array (LEISA) and Multi-spectral Visible Imaging Camera (MVIC). LEISA is an infrared imaging spectrometer to observe the absorption lines. These lines serve as the fingerprints for different silicates, ices, and organics that may be on the surface of the Trojan asteroids. MVIC is a color imaging device that will take color images of the asteroids to help determine their composition.
Mission Timeline
- The mission is divided into six phases (Phase A — Phase F). Phase A began when the mission was selected by NASA as the 13th Discovery class mission. It progressed with the drafting and approval of the preliminary and critical design reviews under Phases B and C.
- After these phases, the instrument construction and testing began under Phase D. The launch was planned under the same phase and it was the last milestone for Phase D.
- Lucy will advance into Phase E with its first Earth flyby and gravity assist on 15th October 2022. This will transfer her into a two-year orbit followed by a second Earth flyby and gravity assist on 12th December 2024 which will finally send the probe out towards the Trojan asteroids. Lucy will encounter the main-belt asteroid (52246) Donaldjohansen on 20th April 2025. Phase E will end after Lucy encounters the binary pair (617) Patroclus and Menoetius on 3rd March 2033 after a third Earth flyby and gravity assist.
- Phase F will mark the end of the prime mission in 2033 and the spacecraft will keep orbiting the Sun for thousands of years.
