Lucy snaps its first pictures of four of the Trojan asteroids it will visit

Lucy's first look at four Trojan asteroid targets
Click for original movie.

Lucy's route through the solar system
Lucy’s route through the solar system

Though still many millions of miles away and really nothing more than tiny dots moving across the field of stars, the science team for the asteroid probe Lucy have used the probe to take its first pictures of four of the eight Trojan asteroids it will visit during its travels through the solar system, as shown on the map to the right. The dots along its path show where Lucy will fly past asteroids, some of which are binaries.

The image at the top is a screen capture from a very short movie created from all of the images Lucy took of each asteroid. If you click on the picture you will see that movie. As I say, at this distance, more than 330 million miles away, the asteroids are nothing more than dots. The short films of each were obtained by pictures taken over periods from two to 10 hours long, depending on the asteroid.

These asteriods are all in the L4 Trojans, the first that Lucy will visit from ’27 to ’28.

Lucy science team ends attempt to deploy solar array

Lucy's planned journey
Lucy’s planned mission, the yellow dot indicating approximately
its present position. Click for full image.

The Lucy science team has decided to end further attempts to fully deploy one of the spacecraft’s two solar arrays, leaving it just short of fully deployed.

On seven occasions in May and June, the team commanded the spacecraft to simultaneously run the primary and backup solar array deployment motors. The effort succeeded, pulling in the lanyard, and further opening and tensioning the array.

The mission now estimates that Lucy’s solar array is between 353 degrees and 357 degrees open (out of 360 total degrees for a fully deployed array). While the array is not fully latched, it is under substantially more tension, making it stable enough for the spacecraft to operate as needed for mission operations.

The press release announcing this decision is horribly written. First, it buries this decision to the release’s last three paragraphs so that it can rave about the brilliance of Lucy’s engineers and scientists in solving the overall problem. Second, it never actually states that this is the decision that has been made. It implies it.

Regardless, it appears the engineers are satisfied that the almost fully deployed array will hold its position for the rest of the mission. They have decided that the risk of trying to fully deploy it is greater than the risk of having it slightly open.

Lucy solar panel almost completely open

Engineers have now been able to get the one solar panel that did not deploy completely after launch on the Lucy asteroid probe almost completely open.

From May 6 to June 16, NASA’s Lucy mission team carried out a multi-stage effort intended to further deploy the spacecraft’s unlatched solar array. The team commanded the spacecraft to operate the array’s deployment motor for limited periods of time, allowing them to closely monitor the response of the spacecraft. As a result of this effort, the mission succeeded in further deploying the array and now estimates that the solar array is between 353 degrees and 357 degrees open (out of 360 total degrees for a fully deployed array). Additionally, the array is under substantially more tension, giving it significantly more stabilization. The mission team is increasingly confident the solar array will successfully meet the mission’s needs in its current tensioned and stabilized state.

The spacecraft’s orbit is now moving into a position where communications will be limited until October, so further attempts to completely open the array will have to wait until then.

Astronomers confirm asteroid discovered in 2020 is an Earth Trojan

Astronomers have now confirmed that an asteroid discovered in 2020, dubbed 2020 XL5, is an orbit that makes it the second Earth Trojan asteroid discovered, orbiting the Sun in the same orbit as the Earth but 60 degrees ahead of us.

In December 2020, 2020 XL5 was spotted by astronomers with the Pan-STARRS 1 survey telescope in Hawaii and added to the International Astronomical Union’s Minor Planet Center database. Amateur astronomer Tony Dunn went on to calculate the object’s trajectory using NASA’s publicly-available JPL-Horizon’s software and found that it orbits L4, the fourth Earth-sun Lagrange point, a gravitationally balanced region around our planet and star. 2010 TK7, the first-confirmed Earth Trojan asteroid, is also at L4.

The confirmation that it is definitely a Trojan was then made using both new observations as well as a review of archival images, allowing the astronomers to not only refine the asteroid’s orbit, but determine that it is a C-type asteroid, dark with lots of carbon. The data also suggests that in about 4,000 years, 2020 XL5 will drift from its Trojan point.

There are certainly more such asteroids, but detecting them is difficult from Earth because they can only be seen in twilight.

Lucy update: Engineers testing solar panel fix on ground

Engineers for the asteroid probe Lucy have begun doing ground tests on a duplicate solar array motor on Earth to see if their plan will work to get the partly deployed solar panel in space opened and latched.

If all goes right, they are aiming for an April attempt at deploying the panel.

In the meantime, the spacecraft continues its coast outwards, presently being about 30 million miles from Earth. Even though one solar array is not fully open, it appears the spacecraft is getting “ample power” for its present operations. It is unclear if this power — with one solar panel not fully opened — will be sufficient once the spacecraft reaches the region of Jupiter’s Trojan asteroids, much farther from Earth.

Probe to visit 8 asteroids, not 7

Scientists developing the Lucy mission to visit seven Trojan asteroids that share an orbit with Jupiter have found an eighth satellite they will also be able to visit.

This first-ever mission to the Trojans was already going to break records by visiting seven asteroids during a single mission. Now, using data from the Hubble Space Telescope (HST), the Lucy team discovered that the first Trojan target, Eurybates, has a satellite. This discovery provides an additional object for Lucy to study.

“If I had to bet that one of our destinations had a satellite, it would have been this one,” said SwRI’s Hal Levison, principal investigator of the mission. “Eurybates is considered the largest remnant of a giant collision that occurred billions of years ago. Simulations show that asteroid collisions like the one that made Eurybates and its family often produce small satellites.”

The mission is targeting a 2021 launch date.