NASA asteroid explorer leaves planet Earth on Atlas 5 rocket

Bound for a pristine population of ancient asteroids, a NASA science probe named Lucy took off from Cape Canaveral before dawn Saturday and rocketed into space on top of an Atlas 5 launcher to begin a 12-year, $981 million mission seeking out clues about the early solar system.

The mission takes advantage of a unique alignment between Earth and the Trojan asteroids, groups of objects leading and trailing Jupiter in its orbit around the sun. The trajectory will take the Lucy spacecraft near eight asteroids from 2025 until 2033, more than any other mission.

The probe will be the first to visit the Trojan asteroids, which were trapped in two swarms as Jupiter settled into its current orbit around the sun. Scientists believe the Trojan asteroids are primordial leftovers from the early solar system. Similar objects collided or clumped together to form the giant planets of the outer solar system.

“The way we think of them are as fossils, which is why we named the Lucy spacecraft after the human ancestor fossil known as Lucy,” said Hal Levison, principal investigator for the Lucy mission at Southwest Research Institute in Boulder, Colorado. “This is going to tell us how the giant planets formed and how they moved around.”

Lucy will target asteroids in the Trojan swarms that range in size from less than a mile to more than 60 miles. The spacecraft will also fly by asteroids that appear to have color differences in ground-based observations, a sign that they might have different compositions.

After a problem-free overnight countdown, the robot explorer blasted off from pad 41 at Cape Canaveral Space Force Station on top of a United Launch Alliance Atlas 5 rocket at 5:34 a.m. EDT (0934 GMT) Saturday.

Lucy took off at the opening second of a 23-day planetary launch period, hitting a schedule set nearly a half-decade in advance.

Riding a Russian RD-180 engine, the 188-foot-tall (57-meter) launcher arced downrange east from Cape Canaveral over the Atlantic Ocean. The Atlas 5 flew Saturday in the rocket’s basic configuration, without any strap-on solid rocket boosters.

The rocket’s kerosene-fueled first stage shut down and jettisoned to fall into the Atlantic around four minutes into the mission, leaving a Centaur upper stage to complete a pair of burns using its U.S.-made RL10 engine supplied by Aerojet Rocketdyne.

The first RL10 firing placed the Lucy spacecraft into a parking orbit around Earth. About 40 minutes into the mission, the engine reignited for a six-minute burn to accelerate the probe to the require velocity to escape Earth’s gravitational grasp.

The Atlas 5’s flight sequence appeared to go off without a hitch, and the rocket released the Lucy spacecraft about 58 minutes after liftoff. About a half-hour later, ground teams announced the probe completed deployment of its twin fan-shaped solar arrays, each with a diameter of about 24 feet (7.3 meters).

NASA’s Deep Space Network station in Australia acquired the first signals from the Lucy spacecraft about the same time, confirming the probe was functional after riding to space on the Atlas 5 rocket.

Saturday’s launch marked the 89th flight of an Atlas 5 rocket, and the third Atlas 5 flight of this year.

“Right now, the spacecraft is looking good,” Levison told Spaceflight Now after the launch Saturday. “The solar arrays, that was our big concern. They’re producing the power they should be producing. So that seems healthy. It’s on its way.”

Fully unfurled, the solar arrays cover an area of about 548 square feet, or 51 square meters, making Lucy’s solar wings the largest ever sent to deep space. The structures give the Lucy spacecraft a wingspan of more than 52 feet, or 16 meters.

The launch Saturday was a turning point for the Lucy mission after seven years of design, development, construction, and testing. But scientists still have to wait 12 years for Lucy to visit all of its target asteroids.

“I looked, not too long ago, for the first instance of the word Lucy in a subject of an email, and it was March of 2014,” Levison said.

Engineers and scientists finished development of the Lucy mission under threat from the coronavirus pandemic. Despite challenges, they maintained the mission’s schedule and budget

“The analogy I’ve been using is it’s sort of like raising a kid,” Levison said. “And this has been a difficult pregnancy. Now she’s born, and now she’ll grow.”

Built by Lockheed Martin in Colorado, the 3,300-pound (1,500-kilogram) Lucy spacecraft is loaded full of hydrazine and nitrogen tetroxide to perform a series of deep space maneuvers to help guide itself toward its asteroid flyby targets.

Half of the probe’s mass is propellant, giving Lucy the ability to dramatically reshape its orbit around the sun throughout its mission.

But most of the mission’s one-of-a-kind trajectory will be driven by natural forces, when Lucy returns for three close encounters with Earth to gain speed and accelerate farther from the sun, eventually reaching the distance of Jupiter in 2027. Then the mission will fly by five asteroids in 15 months before taking another lap around the sun, setting up for a final flyby of an intriguing binary pair of asteroids in 2033.

Scientists named the Lucy mission after the fossilized remains of a human ancestor, called Lucy by the scientists who discovered her in Ethiopia in 1974.

The diamond-shaped patch for the Lucy mission. Credit: NASA/SWRI
Scientists believe the Trojan asteroids represent a diverse sample of the types of small planetary building blocks left behind after the solar system formed 4.5 billion years ago.

“These objects are interesting because they are the remnants from solar system formation,” said Cathy Olkin, deputy principal investigator for the Lucy mission at SWRI. “We’ve designed our mission to investigate the diversity of these objects in this population. We are going to be visiting the most asteroids ever with one mission. We’re going to be flying past seven Trojan asteroids in this epic journey of nearly 4 billion miles. We’re going to study the geology, surface composition … and we’re going to search for satellites around these objects.”

Like the fossil discovery that informed scientists about human evolution, the Trojan asteroids could provide clues about the solar system’s ancient history. After Jupiter formed and settled into its current orbit, the asteroids became trapped in swarms, each centered on a gravitationally-stable libration point ahead of and behind the solar system’s biggest planet.

“That fossil transformed our understanding of hominid evolution, just like we hope that the Lucy spacecraft will transform our understanding of solar system,” Olkin said.

NASA selected the Lucy mission, along with another asteroid explore named Psyche, for development in 2017. Psyche is scheduled to launch next year to orbit a metal-rich asteroid.

Lucy and Psyche, sometimes called sister missions, will visit different types of objects. But both could tell scientists much about the evolution of the solar system.

The two deep space probes join NASA’s line of cost-capped Discovery missions, a program that has included the Mars Pathfinder rover, the Messenger mission to orbit Mercury, and the Dawn spacecraft that orbited the giant asteroid Vesta and the dwarf planet Ceres.

Picked from a slate of 28 proposals submitted to NASA in 2015, Lucy and Psyche will visit worlds never before seen close-up as scientists seek to sort out the violent early history of the solar system, when proto-planets coalesced from mergers and collisions between rocks and boulders in a disk around the sun.,50467215.html

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