Some of the asteroids that Lucy will visit are still more than 530 million kilometers from the spacecraft, which is more than three times the average distance between Earth and the Sun. But despite the great distance and the sizes small of these asteroids, Lucy recently imaged four of them.
Lucy used her highest resolution camera to capture her first images of four Jupiterian Trojan asteroids: Eurybates, Polymele, Leucus, and Orus. Trojan asteroids, named after characters from Greek mythology, revolve around the Sun in two swarms. One of them precedes Jupiter in its orbital path. The other follows the planet from behind. Lucy will be the first spacecraft to visit such asteroids.
Although the photographs taken by Lucy of the four asteroids are on the same scale, the orientation for each astro is different, due to the different orientations of the camera when turning to capture each target.
Lucy observed the asteroids for different lengths of time depending on their rotation periods. The images of Eurybates she captured over the course of 6.5 hours. In the case of Polymele, it was about 2.5 hours. In Leucus, 2 hours. And in Orus, 10 hours.
These images are the first in a series of observations planned to measure how Trojan asteroids reflect light at angles greater than those observable from Earth. Although the asteroids are just points of light in these images, seen against a background of distant stars, the data will help the team choose exposure times to take more photos as Lucy gets closer to the asteroids that are his objectives.
The four asteroids photographed from interplanetary space by the Lucy space probe. (Photos: NASA Goddard/SwRI/JHU-APL)
Lucy will pass close to these asteroids in 2027 and 2028, when the space probe travels through the swarm of small asteroids that precede Jupiter in its orbit around the Sun. Lucy is just over a year into a 12-year journey. The mission includes taking a close look at nine of Jupiter’s Trojan asteroids and two main belt asteroids.