Satellite Discovered by NASA’s Lucy Mission Gets Name

The satellite discovered during the first asteroid encounter of NASA’s Lucy mission has an official name. On Nov. 27, 2023, the International Astronomical Union approved the name “Selam” or ሰላም, which means “peace” in the Ethiopian language Amharic, for Dinkinesh’s moon.

A small brownish asteroid on the left and a larger brownish asteroid on the right
A false-color image of the asteroid Dinkinesh and its satellite, Selam, created using data collected by the NASA Lucy spacecraft’s color imager, the Multi-spectral Visible Imaging Camera, MVIC, on the L’Ralph instrument. This MVIC image was obtained about 100 seconds before closest approach on Nov. 1, 2023. The orange, green and violet MVIC filters were mapped to the red, green, and blue channels to create this image. Image Credit: NASA/Goddard/SwRI

Dinkinesh is the Ethiopian name for the fossil nicknamed ‘Lucy,’”, says Raphael Marshall of the Observatoire de la Côte d’Azur in Nice, France, who originally identified Dinkinesh as a potential target of the Lucy mission. “It seemed appropriate to name its satellite in honor of another fossil that is sometimes called Lucy’s baby.” The fossil Selam, discovered by Zeresenay Alemseged in 2000 in Dikika, Ethiopia, belonged to a 3-year-old girl of the same species as Lucy; though the “baby” actually lived more than 100,000 years before Lucy.

The Lucy spacecraft flew by Dinkinesh and Selam on Nov 1, 2023. While observations leading up to the encounter had hinted that there was something interesting going on in this system, the team was surprised to discover that not only did Dinkinesh have a satellite, but that the satellite was a contact-binary, the first contact-binary satellite ever observed.

The team has completed downlinking encounter data from Lucy’s first asteroid encounter and is continuing to process it. The Dinkinesh encounter was added in January of this year as an in-flight test of the spacecraft’s systems and instruments, and all systems performed well. The tools and techniques refined with data from this encounter will help the team prepare for the mission’s main targets, the never-before-explored Jupiter Trojan asteroids. In addition to the images taken by Lucy’s high-resolution L’LORRI camera and its Terminal Tracking Cameras (T2Cam), Lucy’s other science instruments also collected data that will help scientists understand these puzzling asteroids.

The two components of the Goddard supplied L’Ralph instrument, the Multi-spectral Visible Imaging Camera (MVIC) and Linear Etalon Imaging Spectral Array (LEISA), both successfully observed the two asteroids from a variety of vantage points around closest approach. During the encounter, the two components scanned across the asteroids’ surfaces, enabling the team to assemble color images and spatially-resolved spectra of the objects.

“To assemble the final images, we must carefully account for the motion of the spacecraft, but Lucy’s accurate pointing information makes this possible,” said Amy Simon of NASA’s Goddard Space Flight Center, Greenbelt, Maryland. “These images will help scientists understand the composition of the asteroids, allowing the team to compare the makeup of the Dinkinesh and Selam and to understand how these bodies may be compositionally linked to other asteroids.”

The Arizona State University-supplied Lucy Thermal Emissions Spectrometer (L’TES) also detected the asteroids, even though, unlike the future Trojan asteroid targets, they filled only a small fraction of the instrument’s wide field of view. Scientists expect that the data will mostly provide insight into the surface properties of the larger asteroid, Dinkinesh.

“L’TES was able to detect and measure the temperature of the system for about nine minutes as the spacecraft flew by at its closest approach,” said Phil Christensen of Arizona State University, Tempe. “Different sized particles, such as sand, pebbles, and boulders, heat up differently as the asteroid rotates. The L’TES temperature measurements will allow us to study the size and physical properties of the materials on the asteroid’s surface.”

A stereo pair of a small gray asteroid on the lower left and a larger gray asteroid in the center of the image
A pair of stereoscopic images of the asteroid Dinkinesh and its satellite, Selam, created using data collected by the L’LORRI camera on the NASA Lucy spacecraft in the minutes around closest approach on Nov. 1, 2023. To use this image pair to get a better sense of the 3D structure of the asteroids, either relax the axes of your eyes, as if staring through the screen to infinity (so that you are looking at the left image with your left eye and the right image with your right eye), or use a stereoscope. These images have been processed to enhance contrast, and the apparent distance between Selam and Dinkinesh has been artificially reduced to facilitate simultaneous stereo view of the two objects. Credit: NASA/Goddard/SwRI/Johns Hopkins APL/NOIRLab for the original images/Brian May/Claudia Manzoni for stereo processing of the images.

Lucy is expected to visit 9 more asteroids over the next decade in 6 separate encounters. After an Earth gravity assist in Dec. 2024, the spacecraft will return to the main asteroid belt where it will encounter asteroid Donaldjohanson in April 2025. Lucy will pass through the main belt and reach the mission’s primary targets, the Jupiter Trojan asteroids, in 2027.

By Katherine Kretke, Southwest Research Institute

NASA’s Lucy Spacecraft Hours Away from 1st Asteroid Encounter

We are only a few hours away from the NASA Lucy spacecraft’s first close up look at the small inner-main belt asteroid, Dinkinesh. Dinkinesh is 10 to 100 times smaller than the Jupiter Trojan asteroids that are the mission’s main targets. The Dinkinesh encounter serves as a first in-flight test of the spacecraft’s terminal tracking system.

Lucy’s closest approach will occur at 12:54 p.m. EDT (16:54 UTC) at a distance within 270 miles (430 km) of Dinkinesh. However, there won’t be much time to observe the asteroid at this distance as Lucy speeds past at 10,000 mph (4.5 km/s).

A graphic illustrating the expected motion of the NASA Lucy spacecraft and its instrument pointing platform (IPP) during the encounter with asteroid Dinkinesh. The spacecraft’s terminal tracking system is designed to actively monitor the location of Dinkinesh, enabling the spacecraft and IPP to move autonomously in order to observe the asteroid throughout the encounter. The yellow, blue, and grey arrows indicate the directions of the Sun, Earth, and Dinkinesh, respectively. The red arrow indicates motion of the spacecraft. An animation is available here. Credit: NASA/Goddard/SwRI

Two hours before closest approach, the spacecraft and the rotational platform that holds Lucy’s science instruments (the instrument pointing platform) will be commanded to move into encounter configuration. After this point, the spacecraft’s high-gain antenna will point away from the Earth and the spacecraft will not be able to return data for the remainder of the encounter.

Shortly thereafter, the high-resolution grayscale camera on Lucy, L’LORRI, will begin taking a series of images every 15 minutes. (L’LORRI, short for Lucy’s Long Range Reconnaissance Imager, is supplied by the Johns Hopkins Applied Physics Laboratory.) Dinkinesh has been visible to L’LORRI as a single point of light since early September when the team began using the instrument to assist with spacecraft navigation. The team estimates that at a distance of just under 20,000 miles (30,000 km), Dinkinesh may appear to be a few pixels in size, just barely resolved by the camera.

Additionally, Lucy’s thermal infrared instrument, L’TES, will begin collecting data. L’TES (formally the Lucy Thermal Emission Spectrometer, provided by Arizona State University) is not designed to observe an asteroid as small as Dinkinesh, so the team is interested to see if L’TES is able to detect the asteroid and measure its temperature during the encounter.

An hour before the closest approach, the spacecraft will begin actively tracking Dinkinesh using the onboard terminal tracking system. The spacecraft will use T2Cam (the Terminal Tracking Cameras, provided by Malin Space Science Systems), to repeatedly image the asteroid. In the minutes around closest approach, this system is designed to autonomously reorient the spacecraft and its instrument pointing platform as needed to keep the asteroid centered in the cameras’ field of view. Testing this system is the primary goal of this encounter.

Ten minutes before closest approach, the spacecraft is instructed to begin “closest approach imaging” with the L’LORRI instrument. In these images, taken every 15 seconds at three different exposure times, the asteroid will be several hundred pixels across, allowing the team an unprecedented view of this small main belt asteroid, which is estimated to be less than half a mile (1 km) in diameter.

Lucy will wait until about six minutes before closest approach to begin taking data with its color imager (the Multi-spectral Visible Imaging Camera, MVIC) and infrared spectrometer (Linear Etalon Imaging Spectral Array, LEISA), which together comprise the L’Ralph instrument (provided by NASA’s Goddard Space Flight Center in Greenbelt, Maryland).

About six minutes after the closest approach, L’Ralph will stop taking data, and Lucy will conclude the closest approach observations. By this time, the spacecraft will already be almost 1,700 miles (2,700 km) past the asteroid. Lucy will begin a maneuver referred to as a “pitchback” in which it reorients its solar arrays toward the Sun while the instrument pointing platform continues to autonomously track the asteroid as the spacecraft departs. This maneuver is designed to be carried out slowly to minimize spacecraft vibrations as the spacecraft moves its large solar arrays. L’LORRI will image Dinkinesh throughout this process to monitor spacecraft stability.

Once the spacecraft is over 8,000 miles (13,000 km) from the asteroid, Lucy will stop actively tracking the position of Dinkinesh. From that point on, the team expects the asteroid to remain visible to the spacecraft’s cameras without the need to reposition the spacecraft or instruments.

Two hours after closest approach, the L’TES instrument will be instructed to stop taking data. L’LORRI will continue periodically observing the asteroid for another four days to monitor the light curve of the asteroid.

Once Lucy turns its high-gain antenna back toward Earth, it will be able to resume communications, with an approximately 30-minute light-travel-time delay in each direction. The team expects to receive the first signal from the spacecraft within two hours of closest approach. After assessing the health and safety of the spacecraft, the team will command the spacecraft to begin downlinking the data taken during the encounter. It will take up to a week for all data to be returned to Earth via NASA’s Deep Space Network.

NASA’s Lucy Spacecraft Ready for 1st Asteroid Encounter

NASA’s Lucy spacecraft is on track for its first asteroid encounter on Nov. 1. Lucy’s optical navigation team has confirmed that the latest trajectory correction maneuver on Sept 29 accurately set the spacecraft on course for its flyby of the small main belt asteroid Dinkinesh. The spacecraft is anticipated to pass approximately 265 miles (425 km) from the asteroid at 12:54 p.m. EDT.

On Oct. 28, the team sent the spacecraft what is known as the final knowledge update, a package of data with the most up to date information about the relative positions of the spacecraft and asteroid. This dataset is precise enough to guide the spacecraft for nearly all the half a million miles (800,000 km) that currently separate Lucy and Dinkinesh.

About an hour before the spacecraft’s closest approach, when it’s approximately 10,000 miles (16,000 km) from the asteroid, Lucy will begin actively monitoring the position of Dinkinesh with its terminal tracking system, although due to Dinkinesh’s small size, the system is not expected to “lock-on” to the asteroid until just a few minutes before closest approach. This system will autonomously reorient the spacecraft to keep the small asteroid within the field of view of the science instruments as the spacecraft zooms by at around 10,000 mph (4.5 m/s). This will be the first use of this terminal tracking system, and this flyby was designed to test the system in real spaceflight conditions.

As Lucy approaches Dinkinesh on the morning of Nov. 1, the spacecraft will rotate into a position that enables it to continually track the asteroid. This will move the high-gain antenna away from Earth, and the spacecraft will not be able to communicate again until it has completed the encounter sequence and reoriented itself so that the high-gain antenna is pointing back toward Earth. Imagery and other science and engineering data from the flyby will then be downlinked over the next weeks.

NASA’s Lucy Spacecraft Adjusts Course for Asteroid Flyby in November

On May 9, NASA’s Lucy spacecraft carried out a trajectory correction maneuver to set the spacecraft on course for its close encounter with the small main belt asteroid Dinkinesh. The maneuver changed the velocity of the spacecraft by only about 7.7 mph (3.4 m/s).

Even though the spacecraft is currently travelling at approximately 43,000 mph (19.4 km/s), this small nudge is enough to move the spacecraft nearly 40,000 miles (65,000 km) closer to the asteroid during the planned encounter on Nov. 1, 2023. The spacecraft will fly a mere 265 miles (425 km) from the small, half-mile- (sub-km)-sized asteroid, while travelling at a relative speed of 10,000 mph (4.5 km/s).

The Lucy team will continue to monitor the spacecraft’s trajectory and will have further opportunities to fine tune the flight path if needed.

The Lucy team is also continuing to analyze the data collected from its spring instrument calibration campaign and make other preparations for the mission’s first asteroid encounter. This encounter will provide a valuable test of the spacecraft’s systems and procedures to make sure that everything operates as expected during the mission’s high-speed asteroid encounters.

NASA’s Lucy Mission Suspending Further Solar Array Deployment Activities

NASA’s Lucy mission team has decided to suspend further solar array deployment activities. The team determined that operating the mission with the solar array in the current unlatched state carries an acceptable level of risk and further deployment activities are unlikely to be beneficial at this time. The spacecraft continues to make progress along its planned trajectory.

Shortly after the spacecraft’s Oct. 2021 launch, the mission team realized that one of Lucy’s two solar arrays had not properly unfurled and latched. A series of activities in 2022 succeeded in further deploying the array, placing it into a tensioned, but unlatched, state. Using engineering models calibrated by spacecraft data, the team estimates that the solar array is over 98% deployed, and it is strong enough to withstand the stresses of Lucy’s 12-year mission. The team’s confidence in the stability of the solar array was affirmed by its behavior during the close flyby of the Earth on Oct. 16, 2022, when the spacecraft flew within 243 miles (392 km) of the Earth, through the Earth’s upper atmosphere. The solar array is producing the expected level of power at the present solar range and is expected to have enough capability to perform the baseline mission with margin.

The team elected to suspend deployment attempts after the attempt on Dec. 13, 2022, produced only small movement in the solar array. Ground-based testing indicated that the deployment attempts were most productive while the spacecraft was warmer, closer to the Sun. As the spacecraft is currently 123 million miles (197 million km) from the Sun (1.3 times farther from the Sun than the Earth) and moving away at 20,000 mph (35,000 km/hr), the team does not expect further deployment attempts to be beneficial under present conditions.

Due to the energy boost that the spacecraft received during last October’s Earth gravity assist, the spacecraft is now on an orbit which will take it over 315 million miles (500 million km) from the Sun before returning to Earth for a second Earth gravity assist on Dec. 12, 2024. Over the next year and a half, the team will continue to collect data on how the solar array behaves during flight. Most significantly, the team will observe how the array behaves during a maneuver in Feb. 2024, when the spacecraft operates its main engine for the first time. As the spacecraft warms up during its approach to Earth in the fall of 2024, the team will re-evaluate if additional steps to reduce risk will be needed.