{"id":1138627,"date":"2021-10-16T11:49:25","date_gmt":"2021-10-16T15:49:25","guid":{"rendered":"https:\/\/spaceflightnow.com\/?p=53867"},"modified":"2021-10-16T11:49:25","modified_gmt":"2021-10-16T15:49:25","slug":"nasa-asteroid-explorer-leaves-planet-earth-on-atlas-5-rocket","status":"publish","type":"station","link":"https:\/\/platodata.io\/plato-data\/nasa-asteroid-explorer-leaves-planet-earth-on-atlas-5-rocket\/","title":{"rendered":"NASA asteroid explorer leaves planet Earth on Atlas 5 rocket"},"content":{"rendered":"\n
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A United Launch Alliance Atlas 5 rocket provided the ride to space for NASA\u2019s Lucy asteroid probe. Credit: United Launch Alliance<\/figcaption><\/figure>\n

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.<\/p>\n

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.<\/p>\n

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.<\/p>\n

\u201cThe way we think of them are as fossils, which is why we named the Lucy spacecraft after the human ancestor fossil known as Lucy,\u201d said Hal Levison, principal investigator for the Lucy mission at Southwest Research Institute in Boulder, Colorado. \u201cThis is going to tell us how the giant planets formed and how they moved around.\u201d<\/p>\n

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.<\/p>\n

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.<\/p>\n

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

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Liftoff of NASA\u2019s Lucy asteroid mission on an Atlas 5 rocket, beginning a 12-year journey to explore a population of ancient asteroids. https:\/\/t.co\/tVHTSswphM<\/a> pic.twitter.com\/tN4ZSlUAHQ<\/a><\/p>\n

\u2014 Spaceflight Now (@SpaceflightNow) October 16, 2021<\/a><\/p>\n<\/blockquote>\n

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\u2019s basic configuration, without any strap-on solid rocket boosters.<\/p>\n

The rocket\u2019s 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.<\/p>\n

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\u2019s gravitational grasp.<\/p>\n

The Atlas 5\u2019s 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).<\/p>\n

NASA\u2019s 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.<\/p>\n

Saturday\u2019s launch marked the 89th flight of an Atlas 5 rocket, and the third Atlas 5 flight of this year.<\/p>\n

\u201cRight now, the spacecraft is looking good,\u201d Levison told Spaceflight Now after the launch Saturday. \u201cThe solar arrays, that was our big concern. They\u2019re producing the power they should be producing. So that seems healthy. It\u2019s on its way.\u201d<\/p>\n

Fully unfurled, the solar arrays cover an area of about 548 square feet, or 51 square meters, making Lucy\u2019s 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.<\/p>\n

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NASA confirms the Lucy spacecraft\u2019s circular solar arrays have unfurled after this morning\u2019s launch.<\/p>\n

This will allow the spacecraft to charge its batteries to begin the trek to the Trojan asteroids.https:\/\/t.co\/tVHTSswphM<\/a> pic.twitter.com\/sBnd5OzvIY<\/a><\/p>\n

\u2014 Spaceflight Now (@SpaceflightNow) October 16, 2021<\/a><\/p>\n<\/blockquote>\n

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.<\/p>\n

\u201cI 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,\u201d Levison said.<\/p>\n

Engineers and scientists finished development of the Lucy mission under threat from the coronavirus pandemic. Despite challenges, they maintained the mission\u2019s schedule and budget<\/p>\n

\u201cThe analogy I\u2019ve been using is it\u2019s sort of like raising a kid,\u201d Levison said. \u201cAnd this has been a difficult pregnancy. Now she\u2019s born, and now she\u2019ll grow.\u201d<\/p>\n

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.<\/p>\n

Half of the probe\u2019s mass is propellant, giving Lucy the ability to dramatically reshape its orbit around the sun throughout its mission.<\/p>\n

But most of the mission\u2019s 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.<\/p>\n

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.<\/p>\n

The diamond-shaped patch for the Lucy mission. Credit: NASA\/SWRI<\/figcaption><\/figure>\n

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.<\/p>\n

\u201cThese objects are interesting because they are the remnants from solar system formation,\u201d said Cathy Olkin, deputy principal investigator for the Lucy mission at SWRI. \u201cWe\u2019ve 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\u2019re going to be flying past seven Trojan asteroids in this epic journey of nearly 4 billion miles. We\u2019re going to study the geology, surface composition \u2026 and we\u2019re going to search for satellites around these objects.\u201d<\/p>\n

Like the fossil discovery that informed scientists about human evolution, the Trojan asteroids could provide clues about the solar system\u2019s 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\u2019s biggest planet.<\/p>\n

\u201cThat fossil transformed our understanding of hominid evolution, just like we hope that the Lucy spacecraft will transform our understanding of solar system,\u201d Olkin said.<\/p>\n

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.<\/p>\n

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.<\/p>\n

The two deep space probes join NASA\u2019s 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.<\/p>\n

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.<\/p>\n

This illustration, shown to scale, includes artist\u2019s concepts of the Lucy mission\u2019s asteroid targets. Credit: NASA<\/figcaption><\/figure>\n

The Trojan asteroids, including Lucy\u2019s flyby targets, may still look the same as they did more than 4 billion years ago, before scientists believe the immense pull of Jupiter\u2019s gravity trapped them in their current locations as the outer planets shifted positions. The Trojans are relics of the types of objects that came together to create the giant planets: Jupiter, Saturn, Uranus, and Neptune.<\/p>\n

\u201cIf all this story is true \u2026 these objects really do represent objects that formed throughout the outer solar system, and are now in the Trojan swarms, where a mission like Lucy can go and study them,\u201d Levison said.<\/p>\n

Scientists know little about the Trojan asteroids. Because of their distance from Earth, fragments from the Jupiter Trojans have never fallen to the ground as meteorites, robbing scientists of any insight into their history and make-up.<\/p>\n

Astronomers have found more than 7,000 objects in the Trojan swarms. There may be thousands more awaiting discovery using large telescopes.<\/p>\n

But even the Hubble Space Telescope can\u2019t resolve details about the composition and appearance of the Trojan asteroids. Scientists have a rough approximation of the size of each object to be visited by Lucy, and know a bit about their colors. Some are gray, and some are more reddish in appearance.<\/p>\n

\u201cThis is a mission of exploration,\u201d Olkin said. \u201cWe haven\u2019t seen the Trojan asteroids before. One thing we\u2019re looking at is the composition. So a lot of things are clues, but we don\u2019t have a specific hypothesis that we\u2019re testing that I can tell you, yes or no, because we\u2019ve never been to these objects before. There are lots of questions we have, and we need to continue learning to be able to ask the next deeper level of questions.<\/p>\n

\u201cWe\u2019re sampling different sizes of objects, different spectral types, two different swarms, so we\u2019re looking at diversity across every different axis that we can think of,\u201d Olkin said. \u201cSo we can take this mission, visit the most asteroids ever, and be able to really compare these objects.\u201d<\/p>\n

The largest of Lucy\u2019s asteroid targets, named Patroclus and Menoetius, will be the last worlds visited during the mission. Ground-based observations indicate those asteroids are roughly spherical in shape.<\/p>\n

Artist\u2019s concept of the Lucy spacecraft flying past a Trojan asteroid. Credit: Southwest Research Institute<\/figcaption><\/figure>\n

At the same time teams are readying the Lucy spacecraft for launch, astronomers are trying to learn more about the shapes of the mission\u2019s other targets. Scientists use stellar occupations, when something passes directly between Earth and a distant star, to approximate the size and shape of a distant object.<\/p>\n

By measuring the pattern in which the asteroid blots out the light of the star, astronomers can estimate the object\u2019s shape. Just this month, scientists planned two stellar occultation campaigns to learn more about the shape of two of Lucy\u2019s targets: Polymele and Eurybates.<\/p>\n

After Saturday\u2019s launch, the Lucy spacecraft will spend a year in an orbit around the sun similar to Earth\u2019s, before returning to its home planet next October for a gravity assist slingshot maneuver to begin heading out into the solar system.<\/p>\n

\u201cFinding a trajectory that actually will allow us to visit all these types of objects has been a real chore for Lucy,\u201d Levison said. \u201cWe rattle around the inner solar system using Earth gravity assists to slowly pump up the orbit of the spacecraft so it eventually intersects the orbit of Jupiter.\u201d<\/p>\n

Without the Earth gravity assists, Lucy would have to carry five times more fuel, enough to make the mission unfeasible, according to Coralie Adam, deputy chief of the navigation team at KinetX Aerospace.<\/p>\n

Between now and the first asteroid encounter, scientists will calibrate Lucys instruments. The flybys with Earth will help with instrument checkouts.<\/p>\n

\u201cWe actually have a very active ground-based observing campaign to get the shapes (of the asteroid targets), so that we can actually use those shapes in our simulations of the encounters to make sure they\u2019re going to produce the science that we want them to get,\u201d Levison said.<\/p>\n

\u201cSo there\u2019s a lot to do.\u201d<\/p>\n

This illustration shows the Lucy spacecraft\u2019s unique trajectory through the solar system, taking the probe to both swarms of Trojan asteroids. Credit: NASA\/SWRI<\/figcaption><\/figure>\n

A second flyby of Earth in December 2024 will send Lucy toward its first asteroid encounter. The spacecraft will speed past asteroid Donaldjohanson, named for the scientist who discovered the Lucy fossil, in April 2025.<\/p>\n

Then Lucy will fly into the first Trojan swarm, visiting five asteroids \u2014 including a tiny moon of one of the objects \u2014 in just 15 months between August 2027 and November 2028. Those five asteroids are in the so-called L4, or Greek, swarm.<\/p>\n

At its most distant arc, Lucy will be more than 500 million miles (800 million kilometers) from the sun. The spacecraft will be the farthest spacecraft from the sun to ever rely on solar power.<\/p>\n

A final swing by Earth in 2030 will set up Lucy for the last encounter of the 12-year mission, a flyby of a binary pair of asteroids named Patroclus and Menoetius on March 3, 2033, in the L5, or Trojan, swarm. Each of the two objects are about the same size, with diameters of more than 60 miles (100 kilometers), making them the largest targets of Lucy\u2019s solar system sojourn.<\/p>\n

At each asteroid, Lucy will have just hours to take the best pictures and gather the most useful data. The probe will zip by the asteroids at a relative velocity of several miles per second, using a swiveling platform to point its camera and science instruments.<\/p>\n

\u201cLucy is a flyby mission, so after spending years traveling more than a billion miles to get to our targets, we aim almost directly at them, flying within 600 miles (1,000 kilometers) of their surfaces,\u201d said Keith Noll, NASA\u2019s project scientist for the Lucy mission. \u201cAnd Lucy doesn\u2019t slow down for these flybys.\u201d<\/p>\n

The spacecraft will zip past each of its asteroid targets at relative speeds ranging from 13,000 mph (21,000 kilometers per hour) to 20,000 mph (32,000 kilometers per hour).<\/p>\n

\u201cWhen you look at these cartoon maps, it looks like those dots that represent the Trojans are pretty close to one another,\u201d Noll said. \u201cBut, in fact, the closest pair that we (will visit) is more than 10 million miles apart, and the others are much further than that.\u201d<\/p>\n

During the course of its mission, Lucy will fly by six Jupiter Trojans. This time-lapsed animation shows the movements of the inner planets (Mercury, brown; Venus, white; Earth, blue; Mars, red), Jupiter (orange), and the two Trojan swarms (green) during the course of the Lucy mission. Credit: Astronomical Institute of CAS\/Petr Scheirich<\/figcaption><\/figure>\n

Lucy\u2019s three science instruments are each upgraded versions of payloads flown on previous NASA missions.<\/p>\n

One of the instruments, the Lucy Long Range Reconnaissance Imager, is a black-and-white imaging telescope based on a similar instrument on NASA\u2019s New Horizons spacecraft, which captured the first close-up views of Pluto in 2015.<\/p>\n

The L\u2019LORRI instrument, provided by the Johns Hopkins University Applied Physics Laboratory, will produce the most detailed images of the Trojan asteroids, mapping their surfaces, surveying craters, and searching for small companion asteroids and dust clouds.<\/p>\n

Another payload on the spacecraft comes from NASA\u2019s Goddard Space Flight Center. It\u2019s named L\u2019Ralph, and is two instruments in one.<\/p>\n

One element of the instrument is essentially a color camera, producing images with similar appearance to what the human eye would see. An infrared imaging spectrometer will help scientists identify ices, minerals, and organic molecules on each asteroid.<\/p>\n

Lucy\u2019s Thermal Emission Spectrometer, or L\u2019TES, instrument will measure the temperature of each asteroid\u2019s surface.<\/p>\n

\u201cThe temperature tells us a tremendous amount about the physical properties of the surface,\u201d said Phil Christensen, principal investigator for the L\u2019TES instrument from Arizona State University. \u201cBy comparing day and night measurements, we can determine is the surface made of dense bouldering material, or fine grain dust and sand.\u201d<\/p>\n

Other scientific investigation that is part of Lucy\u2019s mission, but not considered a payload, will help researchers determine the mass of each asteroid, which can yield estimates of the object\u2019s density.<\/p>\n

\u201cAs we fly past the Trojan asteroids, the acceleration of the gravitational pull of the Trojan asteroids will change the velocity of the spacecraft just a little bit,\u201d Olkin said. \u201cWe\u2019re flying by at nearly 15,000 mph past our objects, and the gravitational pull from the Trojan asteroids will change that velocity by about a hundredth of a mile per hour, but we\u2019ll be able to detect that with our telecommunications subsystem and the change in the Doppler frequency as we fly by.\u201d<\/p>\n

That velocity change will tell scientists how much mass each asteroid contains.<\/p>\n

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