The Lucy probe will make an Earth flyby on October 16. It will be as close as 220 miles (350 kilometers) above Earth’s surface.
This is close enough that skywatchers in northwestern Australia, Timor-Leste and parts of Indonesia could see it with the naked eye. It will briefly reflect sunlight, making it brighter.
It will make its closest approach between 6:55 p.m. and 7:02 p.m. local time in western Australia. At its closest approach, it will pass through the terminator line (the dividing line between night and day) and eventually pass into Earth’s shadow.
When it emerges from Earth’s shadow, it will be about 4,300 miles (7,000 kilometers) away from Earth, but observers can still see it with a telescope or binoculars with a wide field of view. Observers interested in seeing Lucy can track its coordinates using NASA’s Horizons System.
A team from Desert Fireball Network, which works with Curtin University’s Space Science and Technology Centre, will travel to western Australia to capture footage of Lucy as it reaches its closest point to Earth. It will share the footage with NASA’s Lucy control team. The Desert Fireball Network is a series of 52 autonomous stations located throughout Australia that normally tracks meteorites and predicts where they will land.
Lucy is using the Earth flyby to make a “slingshot” maneuver to pick up speed as it heads out toward its target: a group of Trojan asteroids that share an orbit with Jupiter. It launched in October 2021 to make a 12-year journey to the asteroids.
The Lucy probe will make close flybys of an asteroid in the main asteroid belt between Mars and Jupiter and seven Trojan asteroids. Science goals include studies of the asteroids’ surface geology, surface color and composition, interiors and bulk properties, and a search for any rings or satellites among the Trojan asteroids.
The Trojan asteroids could provide clues about the early solar system. Scientists believe they are “leftovers” from the formation of the planets more than four billion years ago. They might even find organic compounds, which typically contain carbon. (They may consider it likely that they’ll find diamonds, which consist of carbon compounds that crystallized under pressure.)
Lucy’s October 16 flyby will be the first of two Earth flybys meant to help it pick up speed before it reaches the Trojan asteroids. These flybys use Earth’s gravity to “slingshot” the probe and help it pick up speed. The second flyby will occur in 2024. The Lucy probe will reach its first target, the Donaldjohanson asteroid in the asteroid belt between Mars and Jupiter, in 2025.