Tomorrow morning at approximately 7:04 a.m. EDT, NASA’s Lucy spacecraft will skim the Earth’s atmosphere, passing only 220 miles above the planet’s surfance. According to the agency, the spacecraft will be slingshotting past its home to gain some of the orbital energy it needs to travel to a never-before-visited population of asteroids. Even more, this flyby is also a bit celebratory as Sunday is the first anniversary of Lucy’s launch into space.
At around 6:55 a.m. EDT, Lucy makes its debut with observers on the ground in Western Australia (where it will be 6:55 PM). The spacecraft will quickly pass overhead there and be visible without a telescope or binoculars before disappearing at 7:02 a.m. EDT, when it passes into the Earth’s shadow. Lucy will continue its journey across the Pacific Ocean and will emerge from Earth’s shadow at 7:26 AM EDT (a bright and early 4:26 AM PTD). Those in the western US could catch a glimpse of the spacecraft with binoculars around that time, as long as cloud cover is low.
“The last time we saw the spacecraft, it was being enclosed in the payload fairing in Florida,” said Hal Levison, Lucy principal investigator at the Southwest Research Institute (SwRI) Boulder, Colorado office, in a press release. “It is exciting that we will be able to stand here in Colorado and see the spacecraft again. And this time Lucy will be in the sky.”
After floating over the West Coast, Lucy will rapidly recede from the Earth’s vicinity. It will pass the moon to take few more calibration images before continuing into interplanetary space.
“I’m especially excited by the final few images that Lucy will take of the moon,” said John Spencer, acting deputy project scientist at SwRI, in a press release. “Counting craters to understand the collisional history of the Trojan asteroids is key to the science that Lucy will carry out, and this will be the first opportunity to calibrate Lucy’s ability to detect craters by comparing it to previous observations of the moon by other space missions.”
One year into a 12-year voyage, NASA’s Lucy mission is the first spacecraft launched to explore the Trojan asteroids. These are a group of primitive space rocks orbiting Jupiter. Sunday’s assist from Earth’s gravitational field will place Lucy on a new trajectory for an orbit that will last two years.
In 2024, it will return to Earth for a second gravity push that will give Lucy the energy needed to cross the solar system’s main asteroid belt. Once there, it will observe asteroid Donaldjohanson, and then travel into the leading Trojan asteroid swarm. After that, the spacecraft will fly past six Trojan asteroids: Eurybates and its satellite Queta, Polymele and its yet unnamed satellite, Leucus, and Orus. In 2030, Lucy will return to Earth for yet another bump that will gear it up for a rendezvous with the Patroclus-Menoetius binary asteroid pair in the trailing Trojan asteroid swarm.
Lucy’s current trajectory will bring the spacecraft even lower than the International Space Station. That means the probe will pass through a lot of Earth-orbiting satellites and debris. NASA has developed procedures to anticipate potential hazards, and can move Lucy out of the way if need be to avoid collision.