New Delhi: NASA's Lucy Mission is the first space mission that will explore a diverse population of small bodies known as the Jupiter Trojan Asteroids. The asteroids are remnants of our early solar system, and are about as far away from the Earth as Jupiter. 


They are now trapped in stable orbits associated with Jupiter. 


The Trojan asteroids are now in two "swarms", one of which leads Jupiter and the other follows the gas giant, in its orbit around the Sun. There are numerous Trojan asteroids, just like the objects in the Main Asteroid Belt. 


Lucy will explore a record-breaking number of asteroids over its 12-year primary mission. The spacecraft will fly by one main belt asteroid and seven Trojan Asteroids. 


Also, Lucy will have three Earth flybys for gravity assists. This makes Lucy the first spacecraft ever to return to Earth from the vicinity of the Solar System. The Earth gravity assists will occur in October 2022, December 2024, and December 2030. 


Why has Lucy been named so?


A fossilised skeleton of an early hominin, which is a pre-human ancestor, was found in Ethiopia in 1974 and was named Lucy. Paleontologists got unique insights into human evolution from the fossil. Since the Lucy mission is believed to provide scientists with knowledge of planetary origins and the formation of the Solar System, the Lucy mission has been named after the fossil. 


What is the mission?


Lucy will be launched atop an Atlas V 401 rocket during a 21-day launch period which begins on October 16, from Kennedy Space Center at Cape Canaveral, Florida. In order to use the Earth's gravitational field which will provide assistance on its journey towards the asteroids, Lucy will fly by the Earth twice.


On April 20, 2025, Lucy will fly by the main asteroid belt (52246) Donald Johanson. Lucy's first target is Eurybates. The spacecraft will fly by the following bodies that are a part of the L4 Trojans — Eurybates and its satellite, Queta, on August 12, 2027; Polymele on September 15, 2027; Leucus on April 18, 2028; and Orus on November 1, 2028. The L4 Trojans are the leading swarm, and are located near the fourth Lagrange point. 


Then, Lucy will be brought back to the vicinity of Earth by the spacecraft's orbit for another gravity assist. After this, Lucy will once again move towards Jupiter. During this period, the Trojan asteroids will have changed their positions while orbiting the Sun, as a result of which Lucy will pass through Jupiter's trailing L5 swarm, which is located near the 5th Lagrange point. 


Lucy will fly by Patroclus and its near-twin binary companion Menoetius on March 2, 2033. The Trojan asteroid encounters will occur from 2027 to 2033.


Lucy is expected to remain on a stable orbit that will possibly enable the spacecraft to fly by the Trojan asteroids continuously, over millions of years, according to NASA.


Science Goals and Objectives of Lucy Mission


The Trojan asteroids are likely to be remnants of the same primordial material which formed Jupiter, Saturn, Uranus, and Neptune, the outer planets of the solar system, according to planet formation and evolution models. 


In this way, these asteroids can serve as time capsules from the birth of our solar system 4.5 billion years ago. The environments in which the solar system's planets formed and evolved, and the history of the solar system can be deciphered with the help of vital clues these primitive bodies hold. 


The surface composition of each Trojan asteroid is unique, indicating that they may have formed in different locations of the solar system, and were transported to their current orbits as a result of the planets' evolution. Also, these bodies can provide clues about organic materials that may have been supplied to Earth.


Lucy has a number of science objectives that will help us understand the history of our planetary system by deciphering the diversity of the Trojan asteroids. 


Lucy's objectives include determination of Surface Geology, Surface Colour and Composition, Interior and Bulk Properties, and look for Satellites and Rings.


For Surface Geology, Lucy will map the shape, albedo (proportion of incident light or radiation reflected by the surface of a planet), craters, and size-frequency distributions. Also, the nature of crystal structure and layering, and the relative ages of surface units will be determined.


For its objective of Surface Colour and Composition, Lucy will analyse the colour, composition and regolith properties of the surface, and determine the distribution of ices, organic species and minerals.


The Interior and Bulk Properties, which will be determined by Lucy, include masses and densities. The spacecraft will also study surface composition by excavating the craters, fractures (separations in geologic formations), ejecta blankets (asymmetric distribution of ejected material or debris around a crater rim), and exposed bedding (stratification which has been exposed). 


Lucy will also search for and study Satellites and Rings which may be orbiting the Trojan asteroids. 


Spacecraft Overview


The length of Lucy, from top to bottom, is more than 52 feet or 16 metres. Most of the area is covered by the two huge solar panels, which are more than seven metres in diameter. The solar panels will power Lucy's systems as it travels towards Jupiter. 


The much smaller spacecraft body harbours all the instruments, and the high gain antenna, 6.5 feet or two metres in length, is required to communicate with Earth. The spacecraft was built by Lockheed Martin Space at its facility near Denver, Colorado.


United Launch Alliance Atlas V 401 Configuration


United Launch Alliance's Atlas V 401 Rocket will launch Lucy. The spacecraft will be fitted into the four metre Payload Fairing of the rocket. It has no solid rocket boosters. The Centaur Stage in the rocket is the first rocket stage to use liquid hydrogen and liquid oxygen propellants. The rocket also has an RL10C-1 Engine, which burns cryogenic liquid hydrogen and liquid oxygen, and a RD-180 Engine, which is used for the first stage of the Atlas V Launch Vehicle, and is fuelled by RP-1 (refined petroleum 1) or Liquid Oxygen. 


What are the science payloads aboard Lucy?


Lucy will explore the Trojan asteroids with a suite of remote sensing instruments which include L'Ralph, L'LORRI, L'TES, T2CAMS, Solar Panels, and the High Gain Antenna.


L'Ralph is an instrument provided by NASA's Goddard Space Flight Center in Greenbelt, Maryland, which consists of two parts — L'Ralph Linear Etalon Imaging Spectral Array (LEISA) and L'Ralph Multi-spectral Visible Imaging Camera (MVIC). LEISA is an infrared spectrometer that will reveal the absorption lines which serve as fingerprints for different ices, organics and silicates that may be present on the surface of the Trojan asteroids. 


Colour images of the Trojans will be captured by MVIC to determine their composition, and interpret surface activity.


L'LORRI, which stands for Lucy LOng Range Reconnaissance Imager, is a high resolution, panchromatic (sensitive to light of all colours in the visible spectrum) visible camera, which will provide the most detailed images of the Trojan asteroids' surface. The instrument was fabricated by the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. 


L'TES, which stands for Lucy Thermal Emission Spectrometer, is an instrument that will observe the thermal infrared spectrum, and measure the surface temperature of the Trojan asteroids, in order to understand the physical properties of the top material. This was built by Arizona State University in Tempe, Arizona.


The Terminal Tracking Cameras, or T2CAMS, are navigation cameras which will help determine the shapes of the Trojan asteroids. T2CAM will also take wide-field images of the asteroids to understand their shapes better. In order to determine the density of the material inside, the scientists will combine the information about the shapes, with the radio measurement of mass.


The High Gain Antenna will let Lucy communicate with Earth. Scientists on Earth will use radio signals to measure the mass of each asteroid as Lucy fliess past it. A team from the University of Cologne in Germany will lead Lucy radio science.


Lucy also has two huge solar panels which will provide electrical power to the spacecraft during its journey.


Lucy will travel farther from the Sun than any previous solar powered mission.