28.10.2020
SwRI STUDY OFFERS MORE COMPLETE VIEW OF MASSIVE ASTEROID PSYCHE
A new study authored by Southwest Research Institute planetary scientist Dr. Tracy Becker discusses several new views of the asteroid 16 Psyche, including the first ultraviolet observations. The study, which was published today in The Planetary Science Journal and presented at the virtual meeting of the American Astronomical Society’s Division for Planetary Sciences, paints a clearer view of the asteroid than was previously available.
At about 140 miles in diameter, Psyche is one of the most massive objects in the main asteroid belt orbiting between Mars and Jupiter. Previous observations indicate that Psyche is a dense, largely metallic object thought to be the leftover core of a planet that failed in formation.
“We’ve seen meteorites that are mostly metal, but Psyche could be unique in that it might be an asteroid that is totally made of iron and nickel,” Becker said. “Earth has a metal core, a mantle and crust. It’s possible that as a Psyche protoplanet was forming, it was struck by another object in our solar system and lost its mantle and crust.”
Becker observed the asteroid at two specific points in its rotation to view both sides of Psyche completely and delineate as much as possible from observing the surface at ultraviolet (UV) wavelengths.
“We were able to identify for the first time on any asteroid what we think are iron oxide ultraviolet absorption bands,” she said. “This is an indication that oxidation is happening on the asteroid, which could be a result of the solar wind hitting the surface.”
Becker’s study comes as NASA is preparing to launch the spacecraft Psyche, which will travel to the asteroid as part of an effort to understand the origin of planetary cores. The mission is set to launch in 2022. Metal asteroids are relatively rare in the solar system, and scientists believe Psyche could offer a unique opportunity to see inside a planet.
“What makes Psyche and the other asteroids so interesting is that they’re considered to be the building blocks of the solar system,” Becker said. “To understand what really makes up a planet and to potentially see the inside of a planet is fascinating. Once we get to Psyche, we’re really going to understand if that’s the case, even if it doesn’t turn out as we expect. Any time there’s a surprise, it’s always exciting.”
Becker also observed that the asteroid’s surface could be mostly iron, but she noted that the presence of even a small amount of iron could dominate UV observations. However, while observing Psyche, the asteroid appeared increasingly reflective at deeper UV wavelengths.
“This is something that we need to study further,” she said. “This could be indicative of it being exposed in space for so long. This type of UV brightening is often attributed to space weathering.”
Quelle: Southwest Research Institute
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Update: 30.03.2021
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NASA Begins Final Assembly of Spacecraft Destined for Asteroid Psyche
Set to launch next year, the agency’s Psyche spacecraft will explore a metal-rich asteroid in the main asteroid belt between Mars and Jupiter.
A major component of NASA’s Psyche spacecraft has been delivered to the agency’s Jet Propulsion Laboratory in Southern California, where the phase known as assembly, test, and launch operations is now underway. Over the next year, the spacecraft will finish assembly and undergo rigorous checkout and testing before it’s shipped to Cape Canaveral, Florida, for an August 2022 launch to the main asteroid belt.
The Solar Electric Propulsion (SEP) Chassis, crafted by Maxar Technologies’ team in Palo Alto, California, is the size of a van and represents more than 80% (by mass) of the hardware that will ultimately make up the Psyche spacecraft. The large, box-shaped structure made a dramatic entrance as it rolled into the white-walled clean room of JPL’s storied High Bay 1 of the Spacecraft Assembly Facility. Some of the chassis’ most visible features include the 6.5-foot-wide (2-meter-wide) high-gain antenna, the frame that will hold the science instruments, and bright red protective covers to safeguard delicate hardware.
“Seeing this big spacecraft chassis arrive at JPL from Maxar is among the most thrilling of the milestones we’ve experienced on what has already been a 10-year journey,” said Arizona State University’s Lindy Elkins-Tanton, who as principal investigator leads the Psyche mission. “Building this complex, precision piece of engineering during the year of COVID is absolutely a triumph of human determination and excellence.”
Psyche’s target is a metal-rich asteroid of the same name, which orbits the Sun in the main asteroid belt between Mars and Jupiter. Scientists think that Psyche is largely iron and nickel and could be the core of an early planet. Exploring the asteroid Psyche (about 140 miles, or 226 kilometers, wide) could lend valuable insight into how Earth and other planets formed.
Over the next 12 months, the project team will be working against the clock to meet deadlines in the runup to launch.
“It’s exciting watching it all come together, and it’s the part of the project life cycle that I love the most,” said Psyche Project Manager Henry Stone of JPL. “But it’s a really intense phase as well. It’s intricate choreography, and if one activity runs into a problem, it can impact the whole process. Staying on schedule at this phase of the mission is absolutely critical.”
The SEP Chassis comes to JPL with most of the engineering hardware systems already integrated. The Maxar team built the entire structure and integrated the hardware needed for the high-power electrical system, the propulsion systems, the thermal system, and the guidance and navigation system. The Psyche mission will take advantage of Maxar’s superefficient electric propulsion system to push Psyche through deep space. Maxar will also deliver the large, twin five-panel solar arrays that provide the power for the spacecraft systems.
Delivering the SEP Chassis to NASA’s JPL is an incredible accomplishment for us at Maxar,” said Steven Scott, Maxar’s Psyche program manager. “I am so proud of our team. We’ve managed to design and build an SEP spacecraft for a billion-mile journey through a low-power environment, all while prioritizing the health and safety of our team during a global pandemic. The collaboration between Maxar, Arizona State University, and NASA’s JPL is a model for success, and we’re honored to be part of the Psyche Mission.”
Building and Testing
The assembly, test, and launch operations phase kicked off March 16, when engineers gathered in High Bay 1 to begin checking out the JPL-supplied subsystems, the flight computer, the communications system, and the low-power distribution system to be sure they work together. Now that the chassis has arrived, JPL and Maxar engineers will begin installing the remaining hardware, testing as they go.
The mission’s three science instruments will arrive at JPL over the next few months. The magnetometer will investigate the asteroid’s potential magnetic field. The multispectral imager will capture images of its surface. And the spectrometer will analyze the neutrons and gamma rays coming from the surface to determine the elements that make up the asteroid. JPL is also providing a technology demonstration instrument that will test high data-rate laser communications that could be used by future NASA missions.
Once the full spacecraft is assembled, the orbiter will move from the Spacecraft Assembly Facility to JPL’s large thermal vacuum chamber – a massive undertaking in itself – to simulate the harsh environment of deep space. The chamber is where JPL engineers will begin the heavy-duty testing to ensure the entire machine can survive deep space, thrust with the electric propulsion system, take science measurements, and communicate with Earth.
By next spring, the fully assembled Psyche will be shipped to NASA’s Kennedy Space Center in advance of its August 2022 target launch date. The spacecraft will fly by Mars for a gravity assist in May 2023 and in early 2026, will go into orbit around the asteroid, where it will spend 21 months gathering science data.
Quelle: NASA
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Update: 11.06.2021
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Asteroid 16 Psyche Might Not Be What Scientists Expected
The widely studied metallic asteroid known as 16 Psyche was long thought to be the exposed iron core of a small planet that failed to form during the earliest days of the solar system. But new University of Arizona-led research suggests that the asteroid might not be as metallic or dense as once thought, and hints at a much different origin story.
Scientists are interested in 16 Psyche because if its presumed origins are true, it would provide an opportunity to study an exposed planetary core up close. NASA is scheduled to launch its Psyche mission in 2022 and arrive at the asteroid in 2026.
UArizona undergraduate student David Cantillo is lead author of a new paper published in The Planetary Science Journal that proposes 16 Psyche is 82.5% metal, 7% low-iron pyroxene and 10.5% carbonaceous chondrite that was likely delivered by impacts from other asteroids. Cantillo and his collaborators estimate that 16 Psyche's bulk density – also known as porosity, which refers to how much empty space is found within its body – is around 35%.
These estimates differ from past analyses of 16 Psyche's composition that led researchers to estimate it could contain as much as 95% metal and be much denser.
"That drop in metallic content and bulk density is interesting because it shows that 16 Psyche is more modified than previously thought," Cantillo said.
Rather than being an intact exposed core of an early planet, it might actually be closer to a rubble pile, similar to another thoroughly studied asteroid — Bennu. UArizona leads the science mission team for NASA's OSIRIS-REx mission, which retrieved a sample from Bennu's surface that is now making its way back to Earth.
"Psyche as a rubble pile would be very unexpected, but our data continues to show low-density estimates despite its high metallic content," Cantillo said.
Asteroid 16 Psyche is about the size of Massachusetts, and scientists estimate it contains about 1% of all asteroid belt material. First spotted by an Italian astronomer in 1852, it was the 16th asteroid ever discovered.
"Having a lower metallic content than once thought means that the asteroid could have been exposed to collisions with asteroids containing the more common carbonaceous chondrites, which deposited a surface layer that we are observing," Cantillo said. This was also observed on asteroid Vesta by the NASA Dawn spacecraft.
Asteroid 16 Psyche has been estimated to been worth $10,000 quadrillion (that's $10,000 followed by 15 more zeroes), but the new findings could slightly devalue the iron-rich asteroid.
"This is the first paper to set some specific constraints on its surface content. Earlier estimates were a good start, but this refines those numbers a bit more," Cantillo said.
The other well-studied asteroid, Bennu, contains a lot of carbonaceous chondrite material and has porosity of over 50%, which is a classic characteristic of a rubble pile.
Such high porosity is common for relatively small and low-mass objects such as Bennu – which is only as large as the Empire State Building – because a weak gravitational field prevents the object's rocks and boulders from being packed together too tightly. But for an object the size of 16 Psyche to be so porous is unexpected.
"The opportunity to study an exposed core of a planetesimal is extremely rare, which is why they're sending the spacecraft mission there," Cantillo said, "but our work shows that 16 Psyche is a lot more interesting than expected."
Past estimates of 16 Psyche's composition were done by analyzing the sunlight reflected off its surface. The pattern of light matched that of other metallic objects. Cantillo and his collaborators instead recreated 16 Psyche's regolith – or loose rocky surface material – by mixing different materials in a lab and analyzing light patterns until they matched telescope observations of the asteroid. There are only a few labs in the world practicing this technique, including the UArizona Lunar and Planetary Laboratory and the Johns Hopkins Applied Physics Laboratory in Maryland, where Cantillo worked while in high school.
"I've always been interested in space," said Cantillo, who is also president of the UArizona Astronomy Club. "I knew that astronomy studies would be heavy on computers and observation, but I like to do more hands-on kind of work, so I wanted to connect my studies to geology somehow. I'm majoring geology and minoring in planetary science and math."
"David's paper is an example of the cutting-edge research work done by our undergraduate students," said study co-author Vishnu Reddy, an associate professor of planetary sciences who heads up the lab in which Cantillo works. "It is also a fine example of the collaborative effort between undergraduates, graduate students, postdoctoral fellows and staff in my lab."
The researchers also believe the carbonaceous material on 16 Psyche's surface is rich in water, so they will next work to merge data from ground-based telescopes and spacecraft missions to other asteroids to help determine the amount of water present.
Quelle: The University of Arizona
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Update: 25.08.2021
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Astronomers capture most detailed images of large, rare metal asteroid
Astronomers have used the Atacama Large Millimeter/Submillimeter Array (ALMA) to gain a more detailed picture of the composition of the asteroid Psyche. The asteroid, which orbits the Sun at a distance of between 179.5 and 329 million kilometres from Earth, is the target of a NASA mission scheduled to arrive in 2026, and the latest results suggest that its surface is both rocky and highly metallic.
Psyche was discovered in 1852 by the Italian astronomer Annibale de Gasparis. It is classed as an M-type asteroid, meaning that its spectrum resembles that of an iron meteorite, and its diameter of more than 200 km means that it is the largest of its kind ever found.
Asteroid observations
In principle, Psyche’s thermal emissions could offer further clues to its composition. By monitoring the heat radiated from its surface, scientists can infer its thermal inertia, which measures “how much the surface heats during the day and cools at night,” explains Katherine de Kleer, an assistant professor of planetary science and astronomy at the California Institute of Technology and the first author of a paper in The Planetary Science Journal describing the latest measurements. However, Psyche’s small size and relatively large distance from Earth makes it difficult to get in-depth observations of the asteroid’s surface using ground-based infrared detectors. Past efforts have produced only single-pixel images.
To overcome this problem, de Kleer and her colleagues combined data from the 66 radio telescopes that make up the ALMA facility in Chile. By observing all of Psyche’s surface multiple times per day, the team gained more insight into its thermal inertia, producing 50-pixel images.
Metallic composition inferred from thermal emissions
These new images reveal that some regions of the asteroid have surface temperatures different from the average, indicating that Psyche’s composition is not uniform. The researchers also found that Psyche has a relatively high thermal inertia compared to other asteroids, yet it radiates approximately 60% less heat than would be expected for an object with such a high inertia. The researchers hypothesize that this is because the asteroid’s surface is at least 30% metal. However, the light reflecting off Psyche’s surface is unpolarized, which would not be the case for an object with a smooth or solid metallic surface. They therefore hypothesize that metallic grains are spread throughout its surface material, causing the light to scatter.
If Psyche is mostly metal, it could mean that it is a pre-planet that had a core, mantle and crust before it suffered a major collision with another object. Alternatively, the researchers suggest that an abundance of enstatite chondrite on Psyche’s surface could indicate that the asteroid formed in a different area of the solar system, from material being accreted closer to the Sun.
While this study is the first to make highly spatially-resolved thermal observations of an M-type asteroid, and to map its thermal emissions, the nature of millimetre observations of rocky and metallic astronomical objects makes it impossible to measure their composition more than a few millimetres below the surface. NASA’s Psyche mission, which is due to launch in August 2022 with various payloads, will explore the asteroid’s composition further, with the goal of determining whether it is a core fragment or unmelted material. According to de Kleer, “both possibilities remain viable” for now, though she hopes “that future observations, whether from Earth or from the Psyche mission, may be able to differentiate between them”.
Quelle: physicsworld
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Update: 21.09.2021
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Solar Electric Propulsion Makes NASA’s Psyche Spacecraft Go
Futuristic electric thrusters emitting a cool blue glow will guide the Psyche spacecraft through deep space to a metal-rich asteroid.
When it comes time for NASA’s Psyche spacecraft to power itself through deep space, it’ll be more brain than brawn that does the work. Once the stuff of science fiction, the efficient and quiet power of electric propulsion will provide the force that propels the Psyche spacecraft all the way to the main asteroid belt between Mars and Jupiter. The orbiter’s target: a metal-rich asteroid also called Psyche.
The spacecraft will launch in August 2022 and travel about 1.5 billion miles (2.4 billion kilometers) over three and a half years to get to the asteroid, which scientists believe may be part of the core of a planetesimal, the building block of an early rocky planet. Once in orbit, the mission team will use the payload of science instruments to investigate what this unique target can reveal about the formation of rocky planets like Earth.
The spacecraft will rely on the large chemical rocket engines of the Falcon Heavy launch vehicle to blast off the launchpad and to escape Earth’s gravity. But the rest of the journey, once Psyche separates from the launch vehicle, will rely on solar electric propulsion. This form of propulsion starts with large solar arrays that convert sunlight into electricity, providing the power source for the spacecraft’s thrusters. They’re known as Hall thrusters, and the Psyche spacecraft will be the first to use them beyond the orbit of our Moon.
For propellant, Psyche will carry tanks full of xenon, the same neutral gas used in car headlights and plasma TVs. The spacecraft’s four thrusters will use electromagnetic fields to accelerate and expel charged atoms, or ions, of that xenon. As those ions are expelled, they create thrust that gently propels Psyche through space, emitting blue beams of ionized xenon.
In fact, the thrust is so gentle, it exerts about the same amount of pressure you’d feel holding three quarters in your hand. But it’s enough to accelerate Psyche through deep space. With no atmospheric drag to hold it back, the spacecraft eventually will accelerate to speeds of up to 200,000 miles per hour (320,000 kilometers per hour).
Because they’re so efficient, Psyche’s Hall thrusters could operate nearly nonstop for years without running out of fuel. Psyche will carry 2,030 pounds (922 kilograms) of xenon in its tanks; engineers estimate that the mission would burn through about five times that amount of propellant if it had to use traditional chemical thrusters.
“Even in the beginning, when we were first designing the mission in 2012, we were talking about solar electric propulsion as part of the plan. Without it, we wouldn’t have the Psyche mission,” said Arizona State University’s Lindy Elkins-Tanton, who as principal investigator leads the mission. “And it’s become part of the character of the mission. It takes a specialized team to calculate trajectories and orbits using solar electric propulsion.”
Quelle: NASA
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Update: 5.10.2021
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Science of Psyche: Unique Asteroid Holds Clues to Early Solar System
Set to launch next year, NASA’s Psyche mission marks the first time the agency has set out to explore an asteroid richer in metal than rock or ice.
More than 150 years have passed since novelist Jules Verne wrote “Journey to the Center of the Earth,” but reality has yet to catch up with that science fiction adventure. While humans can’t bore a path to our planet’s metallic core, NASA has its sights set on visiting a giant asteroid that may be the frozen remains of the molten core of a bygone world.
Called Psyche, this asteroid orbits the Sun in the main asteroid belt, between Mars and Jupiter. Using data gathered from Earth-based radar and optical telescopes, scientists believe that Psyche is made largely of metal. It could be part or all of the iron-rich interior of an early planetary building block that was stripped of its outer rocky shell as it repeatedly collided with other large bodies during the early formation of the solar system.
The asteroid, which is about 173 miles (280 kilometers) at its widest point, could also be something else. It could be the leftover piece of a completely different kind of iron-rich body that formed from metal-rich material somewhere in the solar system.
NASA’s Psyche mission hopes to find out. Set for an August 2022 launch, the spacecraft will for two years orbit the asteroid it was named after, taking pictures, mapping the surface, and looking for evidence of an ancient magnetic field. Psyche also will study the neutrons and gamma rays coming from the asteroid’s surface to help determine its elemental composition.
“There are a lot of basic questions about Psyche that are unanswered,” said the mission’s principal investigator, Lindy Elkins-Tanton of Arizona State University. “And with every detail that gets added from data we can collect from Earth, it just becomes harder to make a sensible story. We really don’t know what we’re going to see until we visit, and we’re going to be surprised.”
For instance, previous ground-based observations led scientists to believe that the asteroid was as much as 90% metal. Recent research led by Elkins-Tanton used updated density measurements to estimate that the asteroid is more likely between 30% and 60% metal.
And scientists are puzzled why Psyche appears to be low in iron oxides, which are chemical compounds made of iron and oxygen. Mars, Mercury, Venus, and Earth all have them. “So if we’re correct that Psyche is a mixture of metal and rock, and the rock has very little iron oxide, then there’s got to be a strange story about how it was created – because it doesn’t fit the standard stories of planetary creations,” Elkins-Tanton said.
Mystery of Psyche
Scientists also don’t know where Psyche formed. It might have originated inside the main asteroid belt, but it’s also possible that it was born in the same zone as the inner planets like Earth – or in outer solar system, where giant planets like Jupiter now reside. Neither origin story follows a simple path to where Psyche lives now, 280 million miles (450 million kilometers) from the Sun.
Asteroids in general can offer insight into planet formation and how the early solar system worked 4.6 billion years ago. But Psyche is particularly interesting to scientists because of how unusual it is, with its metal content, high density, and low concentration of iron oxides.
“The fact that it’s so unusual is telling us a new story that we haven’t seen before about how asteroids evolved,” said Bill Bottke, Psyche mission scientist of the Southwest Research Institute in Boulder, Colorado. “That’s a piece of the story we don’t have right now. By getting that piece together with all the others we have, we continue to refine our story of how the solar system formed and evolved early on.”
Tools of the Trade
To help figure out the asteroid’s origins, the mission’s science investigation will rely on a magnetometer, a gamma ray and neutron spectrometer, and a multispectral imager. Scientists know that the asteroid doesn’t generate a magnetic field the way Earth does, but if Psyche had a magnetic field in the past, it could still be recorded in the asteroid’s material today. With sensors mounted onto a 6-foot (2-meter) boom, the magnetometer can determine whether Psyche is still magnetized. If so, that would confirm that the asteroid is part of the core of an early planetesimal, the building block of an early planet.
The orbiter’s gamma ray and neutron spectrometer instrument will help scientists determine the asteroid’s chemical elements. As cosmic rays and high-energy particles impact Psyche’s surface, the elements that make up the surface material absorb the energy. The neutrons and gamma rays they emit in response can be detected by the spectrometer, allowing scientists to match their properties to those emitted by known elements to determine what Psyche is made of.
Meanwhile, a pair of color cameras make up the multispectral imager. The imager is sensitive to light just beyond what humans can see, using filters in the ultraviolet and near-infrared wavelengths. The light reflected in these filters could help determine the mineralogy of any rocky material that may exist on Psyche’s surface.
The spacecraft’s telecommunications system will help with the science as well. The X-band radio system is primarily used to send commands to the spacecraft and receive engineering and science data from it. But scientists can also analyze subtle changes in these radio waves to measure the body’s rotation, wobble, mass, and gravity field, providing additional clues about the composition and structure of Psyche’s interior.
Eyes on Psyche
But before any of this science analysis gets underway, there will be pictures. By late 2025, three years after launch, Psyche will be within sight of the asteroid, and the imager team will be on high alert.
“Even before we get into orbit, we’ll start getting much better pictures than we can from telescopes on Earth. We’ll start to resolve features, see big craters, crater basins – maybe mountain ranges. Who knows what we’ll see?” said Jim Bell of Arizona State University, deputy principal investigator of Psyche and imager team lead. “All we know is that the reality of Psyche is going to be even weirder and more beautiful than we can imagine.”
More About the Mission
ASU leads the Psyche mission. NASA’s Jet Propulsion Laboratory in Southern California is responsible for the mission’s overall management, system engineering, integration and test, and mission operations. The mission phase known as assembly, test and launch operations is currently underway at JPL. By next spring, Psyche will be fully assembled and ready to ship to NASA’s Kennedy Space Center.
JPL also is providing a technology demonstration instrument called Deep Space Optical Communications that will also fly on Psyche, which will test high-data-rate laser communications that could be used by future NASA missions.
Quelle: NASA
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Update: 23.12.2021
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How NASA’s Psyche Mission Will Explore an Unexplored World
Launching in August 2022 and arriving at the asteroid belt in 2026, NASA’s Psyche spacecraft will orbit a world we can barely pinpoint from Earth and have never visited.
The target of NASA’s Psyche mission – a metal-rich asteroid, also called Psyche, in the main belt between Mars and Jupiter – is an uncharted world in outer space. From Earth- and space-based telescopes, the asteroid appears as a fuzzy blur. What scientists do know, from radar data, is that it’s shaped somewhat like a potato and that it spins on its side.
By analyzing light reflected off the asteroid, scientists hypothesize that asteroid Psyche is unusually rich in metal. One possible explanation is that it formed early in our solar system, either as a core of a planetesimal – a piece of a planet – or as primordial material that never melted. This mission aims to find out, and in the process of doing so, they expect to help answer fundamental questions about the formation of our solar system.
“If it turns out to be part of a metal core, it would be part of the very first generation of early cores in our solar system,” said Arizona State University’s Lindy Elkins-Tanton, who as principal investigator leads the Psyche mission. “But we don’t really know, and we won’t know anything for sure until we get there. We wanted to ask primary questions about the material that built planets. We’re filled with questions and not a lot of answers. This is real exploration.”
Elkins-Tanton led the group that proposed Psyche as a NASA Discovery-class mission; it was selected in 2017. A huge challenge, she said, was choosing the mission’s science instruments: How do you make sure you’ll get the data you need when you’re not sure of what, specifically, you’ll be measuring?
For example, to determine what exactly the asteroid is made of and whether it’s part of a planetesimal core, scientists needed instruments that could account for a range of possibilities: nickel, iron, different kinds of rock, or rock and metal mixed together.
They selected a payload suite that includes a magnetometer to measure any magnetic field; imagers to photograph and map the surface; and spectrometers to indicate what the surface is made of by measuring the gamma rays and neutrons emitted from it. Scientists continue to hypothesize about what Psyche is made of, but “no one’s been able to come up with a Psyche that we can’t handle with the science instruments we have,” Elkins-Tanton said.
How to Tour an Unknown World
But before scientists can put those instruments to work, they’ll need to reach the asteroid and get into orbit. After launching from NASA’s Kennedy Space Center in August 2022, Psyche will sail past Mars nine months later, using the planet’s gravitational force to slingshot itself toward the asteroid. It’s a total journey of about 1.5 billion miles (2.4 billion kilometers).
The spacecraft will begin its final approach to the asteroid in late 2025. As the spacecraft gets closer to its target, the mission team will turn its cameras on, and the visual of asteroid Psyche will morph from the fuzzy blob we know now into high-definition, revealing surface features of this strange world for the first time. The imagery also will help engineers get their bearings as they prepare to slip into orbit in January 2026. The spacecraft’s initial orbit is designed to be at a high, safe altitude – about 435 miles (700 kilometers) above the asteroid’s surface.
During this first orbit, Psyche’s mission design and navigation team will be laser-focused on measuring the asteroid’s gravity field, the force that will keep the spacecraft in orbit. With an understanding of the gravity field, the team can then safely navigate the spacecraft closer and closer to the surface as the science mission is carried out in just under two years.
Psyche appears to be lumpy, wider across (173 miles, or 280 kilometers, at its widest point) than it is from top to bottom, with an uneven distribution of mass. Some parts may be less dense, like a sponge, and some may be more tightly packed and more massive. The parts of Psyche with more mass will have higher gravity, exerting a stronger pull on the spacecraft.
Scientists don’t yet have images of the asteroid Psyche; this interactive version is based on modeling. To see how it compares to other asteroids, zoom in and give it a spin. View the full interactive experience and fly along with the mission in real time at Eyes on the Solar System. Credit: NASA/JPL-Caltech
To solve the gravity-field mystery, the mission team will use the spacecraft’s telecommunications system. By measuring subtle changes in the X-band radio waves bouncing back and forth between the spacecraft and the large Deep Space Network antennas around Earth, engineers can precisely determine the asteroid’s mass, gravity field, rotation, orientation, and wobble.
The team has been working up scenarios and have devised thousands of “possible Psyches” – simulating variations in the asteroid’s density and mass, and orientation of its spin axis – to lay the groundwork for the orbital plan. They can test their models in computer simulations, but there’s no way to know for sure until the spacecraft actually gets there.
Over the following 20 months, the spacecraft will use its gentle electric propulsion system to dip into lower and lower orbits. Measurements of the gravity field will grow more precise as the spacecraft gets closer, and images of the surface will become higher resolution, allowing the team to improve their understanding of the body. Eventually, the spacecraft will establish a final orbit about 53 miles (85 kilometers) above the surface.
It’s all in an effort to solve the riddles of this unique asteroid: Where did Psyche come from, what is it made of, and what does it tell us about the formation of our solar system?
“Humans have always been explorers,” Elkins-Tanton said. “We’ve always set out from where we are to find out what is over that hill. We always want to go farther; we always want to imagine. It’s inherent in us. We don’t know what we’re going to find, and I’m expecting us to be entirely surprised.”
More About the Mission
ASU leads the Psyche mission. JPL is responsible for the mission’s overall management, system engineering, integration and test, and mission operations. The mission phase – known as assembly, test and launch operations – is currently underway at JPL.
JPL also is providing a technology demonstration instrument called Deep Space Optical Communications that will fly on Psyche in order to test high-data-rate laser communications that could be used by future NASA missions.
Psyche is the 14th mission selected as part of NASA’s Discovery Program.
Quelle: NASA
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Update: 3.01.2022
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This year, NASA will launch a mission to a valuable, unexplored world
Where we're going, we don't need roads."