DonaldJohanson – Behind The Black

First images from Lucy’s fly-by of asteroid Donaldjohanson

April 22, 2025 8:57 am Robert Zimmerman

Closest view of asteroid DonaldJohanson.
Click for movie.

The science team for the asteroid probe Lucy today released the pictures taken by the spacecraft as it approached the asteroid Donaldjohanson on April 20, 2025, compiled into a short movie.

The asteroid was previously observed to have large brightness variations over a 10-day period, so some of Lucy team members’ expectations were confirmed when the first images showed what appeared to be an elongated contact binary (an object formed when two smaller bodies collide). However, the team was surprised by the odd shape of the narrow neck connecting the two lobes, which looks like two nested ice cream cones.

…From a preliminary analysis of the first available images collected by the spacecraft’s L’LORRI imager, the asteroid appears to be larger than originally estimated, about 5 miles (8 km) long and 2 miles (3.5 km) wide at the widest point. In this first set of high-resolution images returned from the spacecraft, the full asteroid is not visible as the asteroid is larger than the imager’s field of view. It will take up to a week for the team to downlink the remainder of the encounter data from the spacecraft; this dataset will give a more complete picture of the asteroid’s overall shape.

Lucy is now on its way to the orbit of Jupiter, where it will get close-up views of five different Trojan asteroids in 2027, followed by a later visit to another group of Trojans in 2033.

2 comments

Lucy’s next asteroid fly-by on April 20, 2025

April 15, 2025 9:28 am Robert Zimmerman

Lucy’s route to the asteroids, with its first picture
of Donaldjohanson in lower right, taken in February.
Click for original blink animation.

The science team operating the probe Lucy are now preparing for the spacecraft’s second asteroid fly-by, set of April 20, 2025, and passing within 600 miles of the surface of asteroid Donaldjohanson.

Lucy’s closest approach to Donaldjohanson will occur at 1:51pm EDT on April 20, at a distance of 596 miles (960 km). About 30 minutes before closest approach, Lucy will orient itself to track the asteroid, during which its high-gain antenna will turn away from Earth, suspending communication. Guided by its terminal tracking system, Lucy will autonomously rotate to keep Donaldjohanson in view. As it does this, Lucy will carry out a more complicated observing sequence than was used at Dinkinesh [the first asteroid that Lucy saw up close in 2023]. All three science instruments – the high-resolution greyscale imager called L’LORRI, the color imager and infrared spectrometer called L’Ralph, and the far infrared spectrometer called L’TES – will carry out observation sequences very similar to the ones that will occur at the Trojan asteroids.

However, unlike with Dinkinesh, Lucy will stop tracking Donaldjohanson 40 seconds before the closest approach to protect its sensitive instruments from intense sunlight.

“If you were sitting on the asteroid watching the Lucy spacecraft approaching, you would have to shield your eyes staring at the Sun while waiting for Lucy to emerge from the glare. After Lucy passes the asteroid, the positions will be reversed, so we have to shield the instruments in the same way,” said encounter phase lead Michael Vincent of Southwest Research Institute (SwRI) in Boulder, Colorado. “These instruments are designed to photograph objects illuminated by sunlight 25 times dimmer than at Earth, so looking toward the Sun could damage our cameras.”

Unlike most of the Trojan asteroids Lucy will study, Donaldjohanson is a main belt asteroid. It is thought to be only 150 million years old, but its history would be expected to be very different than those Trojan asteroids.

Lucy takes first picture of its next target asteroid

February 26, 2025 9:12 am Robert Zimmerman

Lucy’s route to the asteroids. Click for original blink animation.

The asteroid probe Lucy, on its way to the orbit of Jupiter to study numerous Trojan asteroids, has taken its first picture of the the main asteroid belt asteroid Donaldjohanson, which it will pass within 600 miles on April 20, 2025.

The map to the right shows the spacecraft’s looping route to get to the Trojans, with that image of Donaldjohanson in the lower right. Though the asteroid is about two miles side, it will remain an unresolved point of light until the day of the fly-by. This image was taken from a distance of 45 million miles. As for the asteroid’s name:

Asteroid Donaldjohanson is named for anthropologist Donald Johanson, who discovered the fossilized skeleton — called “Lucy” — of a human ancestor. NASA’s Lucy mission is named for the fossil.

After this encounter, Lucy will head to the Trojans, where it will visit its first six asteroids (including two binaries) in 2027-2028.