NASA's Lucy spacecraft swings by Earth on its way to Trojan asteroids

NASA’s Lucy spacecraft is on its way to the Trojan asteroids to learn about the formation of the solar system, but it isn’t traveling in a straight line from Earth to the orbit of Jupiter. Instead, it is performing a series of slingshot maneuvers to help it on its journey, including a recent maneuver around Earth. This weekend, a few lucky observers were able to see Lucy as it performed an Earth flyby before heading back out into space.

Here's @LucyMission during today's Earth gravity assist. Screengrab from observations made by @plutoflag.
Tracking continues on https://t.co/u9JmKlOCQ3 pic.twitter.com/ZNBWjcYPhB

— Raphael Marschall (@SpaceMarschall) October 16, 2022

The spacecraft came closest to Earth at 7:04 a.m. ET on Sunday, October 16, when it passed within 220 miles of the Earth’s surface. Originally, it had been set to come event closer, but the Lucy team chose to keep a little more distance due to problems that Lucy has had with one of its solar arrays. Lucy has two round arrays, which deployed following launch, but one of them failed to deploy fully and did not latch into place. After months of careful tweaking, the second array is almost fully deployed, but still isn’t latched, so it was best to be cautious with the gravitational forces of a flyby.

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“In the original plan, Lucy was actually going to pass about 30 miles closer to the Earth,” says Rich Burns, Lucy project manager at NASA’s Goddard Space Flight Center, in a statement. “However, when it became clear that we might have to execute this flyby with one of the solar arrays unlatched, we chose to use a bit of our fuel reserves so that the spacecraft passes the Earth at a slightly higher altitude, reducing the disturbance from the atmospheric drag on the spacecraft’s solar arrays.”

Illustration of NASA’s Lucy spacecraft performing a flyby of Earth. NASA

As Lucy moveda way from Earth, it also passed by the moon. This gave the spacecraft the opportunity to take some images that will be used for calibration, as the moon is a helpful stand-in for the asteroids that Lucy will eventually investigate.

“I’m especially excited by the final few images that Lucy will take of the moon,” said John Spencer, acting deputy project scientist at the Southwest Research Institute, which leads the Lucy mission. “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.”