OSIRIS-REx Captures First Glimpse of Asteroid Bennu
By Daniel Stolte
By Daniel Stolte, University Communications, and Erin Morton, OSIRIS-REx - August 24, 2018
After an almost two-year journey through space, NASA's asteroid sampling spacecraft, OSIRIS-REx, caught its first glimpse of asteroid Bennu last week and began the final approach toward its target. On Aug. 17, the spacecraft's PolyCam camera obtained the image from a distance of 1.4 million miles.
Led by the University of Arizona's Lunar and Planetary Laboratory, OSIRIS-REx is NASA's first mission to visit a near-Earth asteroid, survey the surface, collect a sample and deliver it safely back to Earth. The spacecraft has traveled approximately 1.1 billion miles since its Sept. 8, 2016 launch, and is scheduled to arrive at Bennu on Dec. 3.
"Now that OSIRIS-REx is close enough to observe Bennu, the mission team will spend the next few months learning as much as possible about Bennu's size, shape, surface features and surroundings before the spacecraft arrives at the asteroid," said Dante Lauretta, OSIRIS-REx principal investigator and professor of planetary science at the UA. "After spending so long planning for this moment, I can't wait to see what Bennu reveals to us."
To boost itself onto Bennu's orbital plane, OSIRIS-REx performed a slingshot maneuver, or gravity assist, around Earth 11 months ago. The craft is now zipping along at almost 32,000 mph relative to Earth, while catching up with Bennu at a little over 1,200 mph relative to the asteroid. The image was acquired using PolyCam, one of three cameras, all developed at the UA, that together comprise the OSIRIS-REx Camera Suite, OCAMS for short.
Polycam, so named because it is poly-functional, has two jobs: one as a long-range acquisition camera, and the second as a reconnaissance camera once the spacecraft gets close to Bennu. Obtaining the first visual of its target asteroid has been meticulously planned since the early development of the mission. According to OCAMS instrument scientist Bashar Rizk, who has been with the OSIRIS-REx team nearly from the beginning in 2006, almost every action that the spacecraft executes is preceded by a nine-week planning process that consists of program development and multiple tests and reviews, before the code is uploaded to the spacecraft via the Deep Space Antenna network.
Once the spacecraft has begun executing a command, there is very little, if any, ground communication involved, Rizk explained, and taking the first image of Bennu was no exception. When OSIRIS-REx reached the pre-determined position on its trajectory and turned on the camera for a series of 30 total exposures, the asteroid was exactly where mission planners predicted it would be weeks earlier.
"It's like a date," Rizk said. "You don't want to be late, and you don't want to be early."
"Right now, Bennu just looks like a star, a point source," said Carl Hergenrother, LPL staff scientist and OSIRIS-REx astronomy working group lead who proposed Bennu as the mission target during the early planning phase when the asteroid was simply known as 1999 RQ36. "That will change in November, when we will begin detailed observations and we'll start seeing craters and boulders. You could say that's when our asteroid will transition from being an astronomical object to an actual geological object."
As OSIRIS-REx approaches the asteroid, the spacecraft will use its science instruments to gather information about Bennu and prepare for arrival. In addition to the OCAMS camera suite, the spacecraft's science payload includes the OTES thermal spectrometer, the OVIRS visible and infrared spectrometer, the OLA laser altimeter and the REXIS X-ray spectrometer.
During the mission's approach phase, OSIRIS-REx will:
- Regularly observe the area around the asteroid to search for dust plumes and natural satellites, and study Bennu's light and spectral properties
- Execute a series of four asteroid approach maneuvers, beginning on Oct. 1, slowing the spacecraft to match Bennu's speed and trajectory
- Jettison the protective cover of the spacecraft's sampling arm in mid-October and subsequently extend and image the arm for the first time in flight
- Use OCAMS to reveal the asteroid's overall shape in late October and begin detecting Bennu's surface features in mid-November.
After arrival at Bennu, the spacecraft will spend the first month performing flybys of Bennu's north pole, equator and south pole, at distances ranging between 11.8 and 4.4 miles from the asteroid. These maneuvers will allow for the first direct measurement of Bennu's mass, as well as close-up observations of the surface. These trajectories will also provide the mission's navigation team with experience navigating near the asteroid.
"Bennu's low gravity provides a unique challenge for the mission," said Rich Burns, OSIRIS-REx project manager at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "At roughly 0.3 miles in diameter, Bennu will be the smallest object that any spacecraft has ever orbited."
The spacecraft will extensively survey the asteroid before the mission team identifies two possible sample sites. Sample collection is scheduled for early July 2020, and the spacecraft will head back toward Earth before ejecting the Sample Return Capsule for landing in the Utah desert in September 2023.
"The story of this asteroid is the story of the solar system," Rizk said. "When we understand Bennu, we will understand something fundamental about our solar system."
NASA's Goddard Space Flight Center provides overall mission management, systems engineering and the safety and mission assurance for OSIRIS-REx. Lauretta is the principal investigator, and the UA also leads the science team and the mission's science observation planning and data processing. Lockheed Martin Space Systems in Denver built the spacecraft and is providing flight operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA's New Frontiers Program. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the agency's New Frontiers Program for its Science Mission Directorate in Washington.
LPL Scientists Gear Up to 'Touch the Sun'
By Daniel Stolte
By Daniel Stolte, University Communications - August 8, 2018
Look at any image of the Earth taken from space and chances are you'll find yourself marveling at what looks like the very essence of tranquility.
But the serenity of our blue-swirled marble floating peacefully in the black void is deceiving. The reality is more like that of soccer ball kicked around in a hail storm. The gentle sunshine warming our cheek on a late autumn afternoon is actually a violent affair that, if it wasn't for our planet's protective layers, would instantly kill us.
Earth, and all the other objects in the solar system, plow through what is known as the solar wind – a constant stream of high-energy particles, mostly protons and electrons, hurled into space by the thermonuclear furnace that is our sun.
"If you take all the energy consumed in the U.S. in one year and multiply that by a million, you get the output of the sun in one second. All forms of energy, except for atomic energy, ultimately come from the sun," says Joe Giacalone, a UA professor and astrophysicist who is excited about the upcoming launch of the first-ever mission to "touch the sun."
NASA's Parker Solar Probe, encapsulated in the nose cone of a Delta IV Heavy rocket, is awaiting countdown to liftoff, which is currently scheduled for Aug. 11 at 3:33 a.m. from Kennedy Space Center in Florida. The mission was named after Eugene Parker, the solar astrophysicist who discovered the solar wind, and has been in the works for more than half a century. It was conceived before a space program, or even NASA, existed.
"I was working at the Jet Propulsion Laboratory at the time – in 1956, pre-space age – to work on rockets and things like that," says Marcia Neugebauer, a professor emerita of the UA's Lunar and Planetary Lab. "Sputnik had just happened, and, shortly after, the Explorer program sent the first U.S. satellite into space, so we thought about how to design something to find out if Parker was right or not."
Parker's theory on solar wind was highly debated at the time because no measurements of the actual phenomenon existed. Neugebauer was part of a team who designed a plasma analyzer that flew to Venus on NASA's Mariner-2 spacecraft.
"Our instrument was pointed at the sun, and whenever a positively charged ion entered, we deflected it and counted it," Neugebauer says. "This was before there were particle counters, so we had to measure the change in an extremely weak current, 10 to the minus 12 amperes. It was high-tech at the time."
Parker's prediction proved correct. Now, 60 years later, a spacecraft is bring sent to "directly sample solar particles and magnetic fields in an attempt to resolve some of the most important questions facing the field of solar science today," according to NASA.
The nearest previous observations came from the Helios spacecraft, says Kristopher Klein, who joined the UA's Lunar and Planetary Lab as an assistant professor last year and, like Giacalone, is a co-investigator on the Parker mission. The pair of probes launched in the 1970s have come as close as the orbit of Mercury, the solar system's innermost planet.
"But that doesn't get you into the regions where the acceleration happens," Klein says. "We have seen what is almost the fossilized remains of any activity happening there and had to piece it together by guess. Now, for the first time, we won't have to rely on simulations and something that’s been traveling and processed for two to three days, as is the case for the particles that I mostly study."
Not unlike the more familiar wind in the Earth's atmosphere, the solar wind can be anything from a gentle particle breeze lighting up the Arctic night sky with green-glowing curtains of the Aurora borealis to violent gusts capable of causing global devastation. The last time a solar superstorm blasted our planet was in 1859.
"If that were to happen today, it could cause up to $1 trillion of damage through power grid failures, lost satellites, communication blackouts," Giacalone says. "The sun constantly changes, but we still do not fully understand how these changes impact Earth."
The Parker Solar Probe is the first attempt to get close to the sun and study the solar wind at its source, rather than in Earth's orbit. Scientists are hoping to find answers to questions that seem fundamental in nature, yet have eluded them for decades.
One of the most vexing problems the probe is sent to investigate is the dramatic jump in temperature the solar wind undergoes as it leaves the sun's surface and enters its atmosphere, or corona. Across the mere relative thickness of an onion's skin, some unknown mechanism heats the particles, also known as plasma, from about 9,000 degrees Fahrenheit at the surface to two million degrees or more in the corona.
Giacalone hopes for answers to other questions, too.
"Where does the solar wind come from? What causes flares and coronal mass ejections? We still don't understand these processes," he says.
The Parker Solar Probe will make "humanity's first visit to a star" as NASA puts it. During seven fly-bys, the spacecraft will approach the sun to within 10 solar radii, far enough to not burn up and close enough to dive into the corona.
"We'll get close enough to where most of the mechanisms that are pushing the particles out are still actively doing that pushing," says Klein, and the results are expected to shed light on many fundamental physical processes.
"It will provide us with a better understanding of the environment the Earth is in," he says. "Our ability to forecast space weather is about as good as our weather forecasts were in the 1970s. If you have a better understanding of the behavior of these solar energetic particles, then you can make better predictions about when to send astronauts to Mars or protect a satellite before it gets ripped apart by a radiation burst."
Paying a close visit to the sun also provides an opportunity to learn about phenomena such as other stars, plasma accretion disks around black holes and the interstellar medium, a very low-density plasma that fills the galaxy.
Sending the Parker Solar Probe to the sun might even help with developing plasma here on Earth – for example, developing fusion reactors that could someday provide sustainable energy.
"The plasma inside these magnetic bottles behaves a lot like the solar wind," Klein says, "Learning how we can control it in confinement is crucial."
Planet-Forming Disks May Resemble Solar System 5 Billion Years Ago
By Emily Litvack, UA
By Emily Litvack, UA Research, Discovery and Innovation - June 14, 2018
To make a planet, you need stuff.
Protoplanetary disks — cosmic frisbees of gas and dust orbiting young stars across the galaxy — spin out new planets. But the size of those planets depends on just how much material these disks have to give.
A team of scientists led by the University of Arizona has imaged a cluster of protoplanetary disks in the Orion Nebula and discovered that they are smaller than those previously studied in closer, less-dense regions. The smallness of these newly imaged disks suggests that making giant planets such as Jupiter (which is 2.5 times more massive than all the other planets in our solar system combined) could be especially difficult.
What's more, the Orion Nebula looks a lot like other planet-forming regions in the Milky Way, meaning our own solar system likely formed in an Orion-like environment. The team's findings have been published in the Astrophysical Journal.
The scientists used the largest telescope in the world, an interferometric array of radio telescopes in Chile called ALMA, to observe about 110 protoplanetary disks in the Orion Nebula in the deepest survey of the region yet.
"The general motivation for the whole field is that we want to understand more about how planets are formed," says Josh Eisner, a UA professor of astronomy who led the study.
In their pursuit of that understanding, scientists have spent decades looking to star-forming regions such as Taurus, a mere 500 light-years away (as compared to Orion's 1,344). While its nearby location makes a slice of the universe such as Taurus easier to observe with less-powerful telescopes, it's not what one might call a "typical" planet-forming region.
Orion, on the other hand, with its many stars (and orbiting disks) clustered together in relatively small area, is typical. It requires a more powerful telescope to take sharp observations, but in terms of regions where planets — or entire solar systems — form, it's a better model.
"Orion is not at all an oddball region. The disks there look a lot like what we think our solar system looked like when it was a protoplanetary disk," Eisner says. "And now with the advent of ALMA, we can study regions like Orion well."
Based on the images, the team — which also included astronomy and astrophysics graduate student Ryan Boyden, Steward Observatory postdoctoral researchers Nicholas Ballering and Min Fang, Steward Observatory associate astronomer Jinyoung Kim, and Lunar and Planetary Laboratory associate professor Ilaria Pascucci — was able to calculate the mass of protoplanetary disks in the Orion Nebula.
"Disk mass tells you how much stuff there is in the disk and that gives you a budget for what you can build out of it," Eisner says. "And what we found was, in this region, mass is actually quite constraining."
Unlike those studied in nearby regions such as Taurus, planet-forming disks in the Orion Nebula don't have enough stuff to build large planets such as Jupiter, for which you would need tens of Earth masses. According to Eisner, this may mean that much of the stuff already has been used to make young planets. Disks in Orion also appear smaller in size than those in Taurus-like regions.
"It's pretty tantalizing that Orion looks so different from all these lower-density, closer regions but it's just one. We want to fill in the data with more of these high-density regions to see if they all look like Orion," says Eisner, who is already seeking grant funding and telescope observing time to do so.
The discovery also will be tantalizing for those interested in what our solar system looked like as it was cooking some 5 billion years ago.
"The initial conditions for planet formation can tell us a lot about the constraints and how the process really unfolds," Eisner says.
One theory about our solar system's formation, called the Nice Model, argues that, early on, the configuration of the planets within a disk was small and compact until resonance finally flung Neptune and Uranus onto longer orbits.
The fact that the small, compact systems Eisner's team observed in the Orion's disks match up so nicely with the initial planetary configuration in the Nice Model, Eisner says, is a compelling hint at the origins of our solar system.
"The solar system probably formed in an Orion-like environment," he says. "Now we've actually got an idea of what systems there look like."
UA Encourages Visually Impaired Teens in STEM
By Alexis Blue
By Alexis Blue, University Communications - June 13, 2018
Maggie Lindsay's long, white cane swishes back and forth through the leaves, as she makes her way up the mountain slope with her fellow students. Tiny twigs snap beneath her sneakers. Trees rustle in a light breeze. Summer sunlight filters through the branches, warming her skin, as the sweet scents of soil and pine mix in the mountain air.
There's a lot for Lindsay's senses to take in on this warm June day — even though she can't see her surroundings.
Seated at a concrete picnic table amid a group of teenagers, 16-year-old Lindsay is handed a living butterfly. She gingerly touches its wings as the insect tiptoes across her knuckles.
"It's definitely still alive — it's crawling on my fingers," she says.
Next come beetles, spiders, dragonflies, ladybugs, wasps, bees — a mix of real insects and plastic models — passed from one student to the next so they can feel them with their hands.
Some, like Lindsay, can't see the insects at all, while others can make them out to some degree.
All of the students have gathered on Mount Lemmon to experience science through the University of Arizona's Project POEM, a National Science Foundation-funded project designed to introduce visually impaired middle and high school students to career possibilities in science, technology, engineering and math.
Project POEM Goes to SkySchool
Lindsay, who will be a junior at Veritas Preparatory Academy in Phoenix in the fall, is one of 10 visually impaired students, from across Arizona, taking part in the program, which kicked off this month with a weeklong stay at the UA's Mount Lemmon SkyCenter, north of Tucson.
There, the students participated in an adapted version of Sky School, a K-12 science education program based at the center.
They spent their first full day on the mountain handling insects, analyzing soil and testing water quality, under the guidance of UA student instructors. They also met with visually impaired working scientists.
The Sky School experience was the first phase of the 14-month Project POEM, which stands for Project-Based Learning Opportunities and Exploration of Mentorship for Students with Visual Impairments in STEM. The project is funded by an NSF grant of more than $1 million.
Lindsay — who is interested physics, biology, chemistry, and science and learning in general — was referred to the program by two of her teachers who work with students with visual impairments in Phoenix. The ever-inquisitive teen had plenty of compelling questions for her Sky School instructors, as she set out to soak up as much information as she could.
"I like learning things about the way the world works," Lindsay said. "And seeing how each little piece is connected to every other little piece to create this beautiful planet that we live on."
Lindsay wants to have a career in science one day. It's the goal of Project POEM principal investigator Sunggye Hong that she, and other young people with visual impairments, feel empowered to pursue that dream.
Underrepresentation in STEM
People with visual impairments often lack encouragement in STEM and remain highly underrepresented in STEM careers, said Hong, an associate professor in the Department of Disability and Psychoeducational Studies in the UA College of Education.
As a child growing up with visual impairment, Hong once thought of becoming a scientist himself, but wasn't encouraged to pursue it.
Now he wants to show students interested in STEM that visual impairment shouldn't be considered a barrier.
"The goal of this project was to break that ice and possibly come up with ways to motivate our own students — have them be equipped with the knowledge and ability and power to seek opportunities or become a scientist with visual impairment," Hong said.
In some cases, vision limitations might even give students a unique advantage in STEM, Hong said.
For example, Lindsay recalls learning about chemical reactions in a high school chemistry class. Since she couldn't see changes in color in lab experiments, she noticed things such as temperature and smell, which her sighted classmates did not.
"I think because the world we live in is so visual, sighted people tend to overlook those things, not on purpose, just because they use their eyes so much," she said. "Since I can't use my eyes, I had to find all the other ways I could do it, and I ended up learning, in some ways, more."
Playing to the UA's Strengths
Project POEM covers a variety of sciences, but it especially leverages two strengths of the UA: astronomy, which is typically thought of as a highly visual field, and the College of Education's training program for teachers of visually impaired students, which Hong oversees.
"We thought the synergistic power of combining these two areas of study would be great," Hong said.
Students were introduced to astronomy at the Sky Center, through telescope viewings augmented with sounds that fluctuate with light intensity.
They will continue learning about astronomy and planetary science in the next phase of the program, as they engage, throughout the coming school year, in a unique STEM curriculum developed by the Project POEM team. As part of the curriculum, students will receive 3-D models of real spacecraft and documented craters discovered in Arizona and on the surface of the moon and Mars.
Many of the models, which are designed to let students experience craters through touch, are based on data and images collected by the UA's Mars HiRISE camera. They're being cast in the lab of Project POEM co-principal investigator Steve Kortenkamp, an associate professor of practice in the UA's Department of Planetary Sciences and the Lunar and Planetary Laboratory.
The Project POEM students each will be paired with two mentors, with whom they will interact virtually — a UA student in a STEM major and a visually impaired professional who currently works in STEM. The industry mentors are located throughout the country and work in a range of disciplines, including oceanography, math, software engineering, biomedical engineering and organic chemistry.
The Project POEM team members hope their curriculum may eventually be adopted on a national scale.
Meanwhile, for students such as Lindsay, the project is helping to realize a dream for the future.
"I know that it's possible to do science being blind, because I know people who do that, but I don't really know how I would do that, so I want to learn," Lindsay said. "I also think that I, hopefully, will learn how to think about the world in a scientific way — as in, see problems and then think of ways to fix them. Or just be extra curious."
What it Takes to Discover Small Rocks in Space
By Daniel Stolte
By Daniel Stolte, University Communications - June 6, 2018
Once every month, on average, somewhere on Earth a fireball appears out of nowhere and for mere seconds, casts a blinding flash across the sky before it blows up in a thunderous explosion. It happened last Saturday over southern Africa, where a small space rock disintegrated in the night sky and – possibly – scattered debris on the ground, awaiting discovery by meteorite hunters.
Despite their relative frequency, of all the small space rocks that have impacted Earth, only three have been spotted by telescopes during the final hours of their collision course with our planet. All of them happened to be discovered by the Catalina Sky Survey, or CSS, and coincidentally by the same man: Richard Kowalski. Kowalski is one of the CSS's senior research specialists and a 13-year veteran of the University of Arizona's Lunar and Planetary Laboratory.
The CSS is the only asteroid search program capable of detecting imminent small impactors, says director Eric Christensen. On June 2, 2018 LA registered as a pixelated smudge on the camera sensor of the UA's 60-inch survey telescope on Mt. Lemmon when it was roughly the same distance from Earth as the Moon. Less than nine hours later, the 6-foot bolide exploded in a ball of fire in the night sky over southern Africa.
"A key part of this sensitivity is processing the data immediately as it’s acquired, and having skilled observers like Richard review the data, and report and follow up anything new and potentially interesting," Christensen says. "Though our primary directive from NASA is to detect and track larger near-Earth objects, our survey is sensitive to smaller but closer asteroids as well."
Over the last 20 years, the CSS has discovered about 8,500 near-Earth objects, or nearly half the known NEO population, plus more than 100,000 non-hazardous Main Belt asteroids and hundreds of comets.
Why does the vast majority of small asteroids like 2018 LA go undetected?
Kowalski: The sky and the solar system are very large, and the field of view with our telescopes is small in comparison. That's why it takes about a whole month to scan the entire visible sky. Other limiting factors are the fact that Earth itself gets in the way, so you can only see certain parts of the sky depending on where you are. Also, daylight prevents us from detecting anything for half the time. The smallest asteroid we detected was about a meter across. But for such small bodies, the conditions have to be just right. You know how you sometimes spot a plane in the sky that's very far away, but because the sun hits it just right, you can see it glinting? Spotting small asteroids is very similar. The telescope has to be looking at the right point in the sky where the object happens to be just as it becomes bright enough to see it. Just due to their small size, many rocks slip through.
Can you walk us through the process that the Catalina Sky Survey uses to find near-Earth asteroids?
Kowalski: We work in a systematic manner; we try to cover the entire visible sky at least once a month with our 60-inch survey telescope on Mt. Lemmon, and at least four times a month with our 30-inch Schmidt Telescope on Mt. Bigelow, which has a wider field of view. Most of the system is automated. Each evening, we program the telescopes to follow a certain pattern. We take a 30-second exposure image of one part of the sky, then the telescope moves to an adjacent part, makes another exposure, and so on. After imaging 12 patches of sky in this manner, it goes back to the first field, and it goes through this sequence four times, spread out 40 minutes apart.
A specialized software gets rid of the stars in the image, looks for things that could be moving and presents those to the human observer sitting in the control room. The human eye-brain combination is better at pattern recognition, and that is why we have humans look at every image. Many of the objects flagged by the software are real asteroids, but some are artifacts caused by cosmic rays, very faint stars, satellites or electronic noise in the system. We look for all those things that don't look right and check them for consistent movement.
Before we start working every night, we download the database of all known asteroids. Once we find a signal that is a real object, we create a digest, which calculates the direction and the apparent motion in our image, and how much it deviates from the predicted movement of main belt asteroids between Mars and Jupiter. If we have a new discovery that shows it is not a known object, we send an email to the Minor Planet Center in Cambridge, Massachusetts, where colleagues will also do a number of checks. Once their computers go through those checks, the objects gets listed on the near-Earth object confirmation page, NEOCP, which anyone can access: it will tell them where to point their telescopes. The entire process, from the time something shows up on my screen to being published, only takes about 10 minutes.
How many new asteroids are discovered this way?
Kowalski: Our current rate of discovery can vary from one object per night to up to 20. Our record for a single night is somewhere around 30. My personal record is 21 in one night. That was just a few weeks ago. With our new cameras, we cover so much of the sky and we are so efficient at the process that we typically average anywhere between eight to 10 per night, which range in size from 1-2 meters up to as much as a kilometer in diameter. But the larger ones are quite rare. Most average from 10 to 50 meters, and nearly all of those are harmless — they won't hit the Earth at any time soon.
Speaking of risk, how dangerous are small asteroids like 2018 LA?
Kowalski: In the case of a small body like 2018 LA, we know that if it drops meteorites, they're going to be small pieces, fist-sized down to pebbles, and the rest turns into dust and vapor. In the grand scheme of things, asteroids in that category put on a light show, but they're not dangerous in any way. As the object slams into the atmosphere, the rock is slowing down so rapidly that the back is traveling faster than the front and the pressures get too high for the material to remain intact. That's why they explode as fire balls. There is a lot of energy output because of their speed and the resulting friction.
What determines whether an asteroid will burn up in the atmosphere or fall to the ground?
Kowalski: In short: direction, velocity and what it's made of. Also, the object's trajectory: If it hits Earth head-on, it is likely to be moving very fast, tens of kilometers per second. Those objects are much less likely to survive the entry unless they are very large. On the other hand, if an asteroid is catching up to the Earth from behind, it could come in very slowly, and therefore could be smaller and still reach the surface. Some meteorites are very brittle, and those tend to go up in vapor and dust very easily, while others literally are cores of iron from another asteroid. Those have much better chance of reaching the ground.
How much do you know about an asteroid once you have discovered it?
Kowalski: We don't do any physical properties assessment. When we discover near-Earth objects, we only point them out so other groups and amateurs can make follow-up observations to find out, for example, how fast they're rotating, what they are made of and things like that. Every once in a while, you'll hear conspiracy theorists say we would deliberately not tell the public if we discovered a large and potentially hazardous impactor on a collision course with Earth. The truth is, every object looks essentially the same, it's just a grey dot on the screen to me. I'm not in any way knowledgeable if it's going to hit, or what it's made of, etc. The very process of discovering these objects and the short time ensure that the information gets out immediately. We want the public involved, and we want to reach as many people with telescopes as possible, because the more follow-up observations we can spread out over the time, the more accurately we can predict where those things may come down.
How did you find out that with 2018 LA, you had discovered another asteroid that ended up impacting Earth?
Kowalski: I typically work until dawn, and I don't sleep very well on the mountain, so I commute home every morning. I didn't know it would impact until I woke up the next morning. Quite often I'm the last to know. Our team of observers is doing the same job — looking for these impacting asteroids — so discovering them is not a big surprise. What was a big surprise was the fact that I happened to be the one who discovered all three observed impactors. My wife suggested I treat myself to a large T-bone steak that day to celebrate, and that's what I did.
Optical Sciences Student Off to Japan for Space Mission
By Amee Hennig, UA
By Amee Hennig, UA College of Optical Sciences - May 31, 2018
Adriana Mitchell, an undergraduate in the University of Arizona's College of Optical Sciences and Honors College who has been working with assistant professor Vishnu Reddy at the Lunar and Planetary Laboratory, is this year's sole UA recipient of the Barry M. Goldwater Scholarship and Excellence in Education. And soon she will be on her way to Japan for a unique opportunity.
The Goldwater Scholarship Program, one of the oldest and most prestigious national scholarships in the natural sciences, engineering and mathematics, seeks to identify and support college sophomores and juniors who show exceptional promise in the aforementioned fields. The scholarship provides a maximum of $7,500 per year to the student for educational expenses.
Mitchell has big plans for her future, and the Goldwater Scholarship could help those dreams come true.
"My professional aspiration is to manage NASA research missions to worlds with astrobiological implications," she says. "To reach my goal, I must first obtain a Ph.D. and learn the inner workings of interplanetary spacecraft missions."
This summer, Mitchell will travel to Japan to work with the Japan Aerospace Exploration Agency, or JAXA, on the Hayabusa2 project, a sample return mission to asteroid Ryugu. Hayabusa2 is the sister project to the UA-led OSIRIS-REx mission by NASA.
Mitchell will be at JAXA headquarters during the approach and arrival phases of the mission, assisting with the creation of digital terrain models, which she says is "a direct application of my current research on asteroids at the University of Arizona." Lucille Le Corre, a NASA-funded co-investigator on the Hayabusa2 mission, will mentor Mitchell.
The opportunity was supported and encouraged by Reddy, who is Mitchell's mentor at the UA.
"She had been working with me for a year as a NASA Space Grant intern and she wanted to do something different for her study abroad, working on a real spacecraft mission," says Reddy, who worked to organize the collaboration with Le Corre. "I'm very proud of her, and she's always been a go-getter. It is a privilege to work with talented undergraduate students like Adriana."
Mitchell, who will leave for Japan on June 27, says, "This would not be possible without the Goldwater Foundation's support and opportunities provided by my mentors here."
Mitchell previously worked with Matt Penn at the National Solar Observatory on a research project, "Polar Plume Dynamics of the Indonesian 2016 Total Solar Eclipse," to determine the true speed of solar winds. The project was presented by Mitchell at two conferences, including the 2017 Graduate and Professional Student Council Student Showcase and the 229th meeting of the American Astronomical Society.
She also has published in journals and presented at other conferences in her growing research career. She has presented research at the Crossroads Eclipse 2017 Research Workshop, the 2017 Eclipse Science Showcase and the 12th American Physical Society Conference for Undergraduate Women in Physics.
Air Force Research Lab, Others Tap UA Space Expertise
By Emily Litvack, UA
By Emily Litvack, UA Research, Discovery and Innovation - May 8, 2018
If we spent 60 years leaving every car that runs out of gas on the side of the highway to rust and crumble, as defunct machinery is wont to do, then our highways would look something like outer space does. Since the Soviet Union flung Sputnik I into low-Earth orbit in 1957, dozens of other countries have sent Earth-orbiting satellites into space with no way to retrieve them when they eventually, inevitably break down.
And, of course, there are no police in space.
Consequently, space is more congested, contested and, in some ways, more dangerous than ever. With a total of $6.65 million in new funding, University of Arizona researchers are working to make space a safer place for our nation's satellites.
As part of the University of Arizona's Cluster Hiring Initiative jointly administered by the provost and the Office of Research, Discovery and Innovation, the UA hired five new faculty members in 2016-2017 with expertise in space situational awareness, or SSA — an emerging research area focused on identifying, characterizing and understanding the behavior of objects in space.
The initiative was dubbed SSA-Arizona, and the idea behind it was to reinforce the UA's existing strength in space science — strength such as managing more than 20 telescopes across the world, contributing to nearly every NASA space exploration mission, discovering more than half of all near-Earth objects and running Steward Observatory, which now uses both optical and radio instruments to characterize objects in space.
The new awards — a $3.3 million cooperative agreement with the Air Force Research Laboratory, a $350,000 award from DARPA, and a $3 million sub-award from Lockheed Martin — collectively represent the first major return on the UA's investment in SSA.
Building a Collaborative Infrastructure
The first of the three awards, from the Air Force Research Laboratory, or AFRL, is designed make it easier for the "Five Eyes" — an international alliance among Australia, Canada, New Zealand, the United Kingdom and the U.S. — to share data and surveil satellites. The project is led by the director of SSA-Arizona, Roberto Furfaro.
With help from Furfaro and a team of UA researchers, AFRL will have a new cyberinfrastructure for collaboration with its Five Eyes allies.
"One part of space situational awareness is trying to find out where things are in space, what their intent is and who are the operators executing that intent," says Vishnu Reddy, an assistant professor of planetary sciences hired in the group of five. "Another issue is managing traffic in space so that things don't hit each other."
The U.S. and its allies are interested in both the national security and environmental aspects of SSA. By leveraging CyVerse, the UA's existing, NSF-funded computational infrastructure to handle huge datasets and complex analyses, they will have what Reddy calls "a digital playground" for collaboration on this front.
"We're going to be able to offer (AFRL) the best possible cyberinfrastructure," Furfaro says. "I think it'll set a new standard for this kind of work. It'll be a collaborative environment where they can seamlessly drop data, make discoveries and acquire knowledge in SSA."
The multimillion-dollar cooperative agreement initially will last for three years, with the potential for further funding thereafter.
Getting Dying Satellites to the Graveyard
The next of the new grants comes from the Department of Defense's Defense Advanced Research Projects Agency, or DARPA. The $350,000, one-year project is led by UA optical scientist Michael Hart.
"Space has become more useful to us as space-based technology develops, and, as a result, it's become rapidly more crowded," Hart says. "Space has become rather full of junk over the last 60 years and it's continuing to get worse, so there's a pressing need to change the way we behave."
One of our most harmful behaviors takes place in the geostationary orbit, or GEO, a little slice of space above the Earth's equator rotating in the same direction as Earth. From Earth, satellites in GEO appear to stand still. Commercial satellites, for uses such as television and GPS, have to be in GEO, so that they have a clear and constant line of sight to your home or car.
For both commercial and government interests, "slots in geostationary orbit are limited, and highly coveted," Hart says.
But satellites go defunct after about 15 years; they can't withstand the toxic solar radiation they encounter for much longer. When they're dead, we have no way of controlling them, so they accumulate as clutter in GEO — literally, wasted space.
The DARPA-funded project is aimed at creating ways to detect a satellite on its way out before it has actually died, so that those who own the satellite have time to direct it to what's called a graveyard orbit — one that is away from common operational orbits such as GEO — before it's too late.
The technology involves measuring vibrations of a satellite that are imprinted on the reflected sunlight that lets us see them.
"In the same way wine glasses 'clink' in different ways, satellites all have different solar panels and antennae that vibrate in different ways," Hart says.
But because that unique vibration remains constant — there's no sense of speed or wind in space to change it — a technology that carefully monitors even the most minute changes in vibration will help operators recognize when not all is right with their satellite, and send it to a designated graveyard before it is defunct and unresponsive.
Taking Clear Pictures of Far-Away Technology
The third and final award — a three-year, $3 million contract with Lockheed Martin — is aimed at taking high-resolution photos of satellites in GEO.
"This project is focused on the same kind of problem as the DARPA-funded project," Hart says. "It's about understanding the health, status and behavior of satellites in the geostationary regime."
While measuring changes in vibration "promises to give us very useful information, in some sense, there's nothing better than an honest-to-goodness picture," he says.
But because these satellites are so far away from Earth, taking photos of them is no walk in the park.
"You'd need an awfully powerful telescope to take a high-resolution picture," Hart says.
The research team led by Hart will develop a small-scale prototype for combining light from several telescopes spread apart from one another and using them to piece together high-resolution images.
Leading the Way in SSA
While there is little precedent for any one of the new projects in the emerging science of SSA, the researchers believe the UA is best suited for the challenge.
"The University should be really proud of the investment it's made in SSA," Reddy says. "This is a really tough nut to crack. It's a huge risk to push for this cluster hire, and this is the first time we're demonstrating major success and that we can do this work collaboratively."
"In this case, the word 'unique' really applies," Hart says. "There's no other university in the world that can match the assemblage of infrastructure and human talent in all things space. We know what it means to operate in space, and it's a very natural arena for the UA to be engaged in."
New Estimates of Mercury's Thin, Dense Crust
By Emily Walla, UA
By Emily Walla, UA/NASA Space Grant Intern, University Communications - April 24, 2018
Mercury is small, fast and close to the sun, making the rocky world challenging to visit. Only one probe has ever orbited the planet and collected enough data to tell scientists about the chemistry and landscape of Mercury's surface. Learning about what is beneath the surface, however, requires careful estimation.
After the probe's mission ended in 2015, planetary scientists estimated Mercury's crust was roughly 22 miles thick. One University of Arizona scientist disagrees.
Using the most recent mathematical formulas, Lunar and Planetary Laboratory associate staff scientist Michael Sori estimates that the Mercurial crust is just 16 miles thick and is denser than aluminum. His study, "A Thin, Dense Crust for Mercury," will be published May 1 in Earth and Planetary Science Letters and is currently available online.
Sori determined the density of Mercury’s crust using data collected by the Mercury Surface, Space Environment and Geochemistry Ranging (MESSENGER) spacecraft. He created his estimate using a formula developed by Isamu Matsuyama, a professor in the Lunar and Planetary Laboratory, and University of California Berkeley scientist Douglas Hemingway.
Sori's estimate supports the theory that Mercury's crust formed largely through volcanic activity. Understanding how the crust was formed may allow scientists to understand the formation of the entire oddly structured planet.
“Of the terrestrial planets, Mercury has the biggest core relative to its size,” Sori said.
Mercury's core is believed to occupy 60 percent of the planet’s entire volume. For comparison, Earth’s core takes up roughly 15 percent of its volume. Why is Mercury’s core so large?
“Maybe it formed closer to a normal planet and maybe a lot of the crust and mantle got stripped away by giant impacts,” Sori said. “Another idea is that maybe, when you're forming so close to the sun, the solar winds blow away a lot of the rock and you get a large core size very early on. There’s not an answer that everyone agrees to yet.”
Sori’s work may help point scientists in the right direction. Already, it has solved a problem regarding the rocks in Mercury's crust.
Mercury's Mysterious Rocks
When the planets and Earth's moon formed, their crusts were born from their mantles, the layer between a planet's core and crust that oozes and flows over the course of millions of years. The volume of a planet's crust represents the percentage of mantle that was turned into rocks.
Before Sori's study, estimates of the thickness of Mercury's crust led scientists to believe 11 percent of the planet's original mantle had been turned into rocks in the crust. For the Earth's moon – the celestial body closest in size to Mercury – the number is lower, near 7 percent.
"The two bodies formed their crusts in very different ways, so it wasn't necessarily alarming that they didn't have the exact same percentage of rocks in their crust," Sori said.
The moon's crust formed when less dense minerals floated to the surface of an ocean of liquid rock that became the body's mantle. At the top of the magma ocean, the moon's buoyant minerals cooled and hardened into a "flotation crust." Eons of volcanic eruptions coated Mercury's surface and created its "magmatic crust."
Explaining why Mercury created more rocks than the moon did was a scientific mystery no one had solved. Now, the case can be closed, as Sori's study places the percentage of rocks in Mercury's crust at 7 percent. Mercury is no better than the moon at making rocks.
Sori solved the mystery by estimating the crust's depth and density, which meant he had to find out what kind of isostasy supported Mercury's crust.
Determining Density and Depth
The most natural shape for a planetary body to take is a smooth sphere, where all points on the surface are an equal distance from the planet's core. Isostasy describes how mountains, valleys and hills are supported and kept from flattening into smooth plains.
There are two main types isostasy: Pratt and Airy. Both focus on balancing the masses of equally sized slices of the planet. If the mass in one slice is much greater than the mass in a slice next to it, the planet’s mantle will ooze, shifting the crust on top of it until the masses of every slice are equal.
Pratt isostasy states that a planet’s crust varies in density. A slice of the planet that contains a mountain has the same mass as a slice that contains flat land, because the crust that makes the mountain is less dense than the crust that makes flat land. In all points of the planet, the bottom of the crust floats evenly on the mantle.
Until Sori completed his study, no scientist had explained why Pratt isostasy would or wouldn't support Mercury's landscape. To test it, Sori needed to relate the planet’s density to its topography. Scientists had already constructed a topographic map of Mercury using data from MESSENGER, but a map of density didn't exist. So Sori made his own using MESSENGER's data about the elements found on Mercury's surface.
“We know what minerals usually form rocks, and we know what elements each of these minerals contain. We can intelligently divide all the chemical abundances into a list of minerals," Sori said of the process he used to determine the location and abundance of minerals on the surface. "We know the densities of each of these minerals. We add them all up, and we get a map of density.”
Sori then compared his density map with the topographic map. If Pratt isostasy could explain Mercury’s landscape, Sori expected to find high-density minerals in craters and low-density minerals in mountains; however, he found no such relationship. On Mercury, minerals of high and low density are found in mountains and craters alike.
With Pratt isostasy disproven, Sori considered Airy isostasy, which has been used to make estimates of Mercury's crustal thickness. Airy isostasy states that the depth of a planet's crust varies depending on the topography.
"If you see a mountain on the surface, it can be supported by a root beneath it," Sori said, likening it to an iceberg floating on water.
The tip of an iceberg is supported by a mass of ice that protrudes deep underwater. The iceberg contains the same mass as the water it displaces. Similarly, a mountain and its root will contain the same mass as the mantle material being displaced. In craters, the crust is thin, and the mantle is closer to the surface. A wedge of the planet containing a mountain would have the same mass as a wedge containing a crater.
“These arguments work in two dimensions, but when you account for spherical geometry, the formula doesn’t exactly work out,” Sori said.
The formula recently developed by Matsuyama and Hemingway, though, does work for spherical bodies like planets. Instead of balancing the masses of the crust and mantle, the formula balances the pressure the crust exerts on the mantle, providing a more accurate estimate of crustal thickness.
Sori used his estimates of the crust's density and Hemingway and Matsuyama's formula to find the crust's thickness. Sori is confident his estimate of Mercury's crustal thickness in its northern hemisphere will not be disproven, even if new data about Mercury is collected. He does not share this confidence about Mercury's crustal density.
MESSENGER collected much more data on the northern hemisphere than the southern, and Sori predicts the average density of the planet's surface will change when density data is collected over the entire planet. He already sees the need for a follow-up study in the future.
The next mission to Mercury will arrive at the planet in 2025. In the meantime, scientists will continue to use MESSENGER data and mathematical formulas to learn everything they can about the first rock from the sun.
UA Researchers Track Chinese Space Station as it Falls to Earth
By Emily Litvack -
By Emily Litvack - March 22, 2018
A defunct Chinese space station, Tiangong-1, is expected to fall to Earth any day now – on March 31, give or take a few days. When it does, it'll be the largest manmade object to re-enter Earth's atmosphere in a decade.
As the day draws near, Vishnu Reddy, University of Arizona assistant professor of planetary sciences, and Tanner Campbell, an aerospace and mechanical engineering graduate student, are tracking its reentry using a $1,500 optical sensor they built in four months.
Tiangong-1 Zooms through Low Earth Orbit
Launched in 2011, Tiangong-1 served as a laboratory for three manned missions and was initially intended to deorbit in 2013. Now as it tumbles, seemingly uncontrollably, through space, researchers across the globe are scrambling to predict when and where it’ll come back down.
Tiangong-1 occupies low Earth orbit, or LEO. LEO is relatively close to Earth's surface compared to other orbits, such as medium Earth orbit and geostationary orbit, a faraway space here communication satellites reside.
For many reasons, it's harder to track and predict the path of objects in LEO than their more distant counterparts, because "objects are moving really fast," Reddy says. At 17,400 mph, Tiangong-1 orbits the Earth every 90 minutes.
On top of that, objects in LEO are up against something called "drag" when they get closer to the Earth – the faster an object travels, the harder it is for it to move through air. In the same way a hand held outside the window of a car going 70 mph is harder to control than one outside of a car going 20 mph, the same goes for Tiangong-1 as it re-enters Earth's atmosphere. Drag makes prediction harder.
Because of the harshness of LEO's environment, no spacecraft stays there forever; Tiangong-1's seven-year flight isn't unusually short.
Tracking Objects in LEO
As of now, researchers primarily track and predict paths of objects in LEO using ground-based radar systems that detect and catalog objects.
It's an extremely expensive operation available only to a select handful of countries whose militaries can afford it. The United States Air Force is one of them, with its highly sophisticated Space Fence.
"Tracking objects with radar is a very expensive exercise," Reddy says.
When the news of Tiangong-1's re-entry to Earth hit the stands, Reddy saw an opportunity to try tracking it with something less sophisticated, and less expensive. He wondered, "From the UA, can we do something meaningful to contribute to our national security interests?"
He and Campbell spent four months designing and building the $1,500 hardware and software optical sensor system to test that very question. They've been collecting data on Tiangong-1's whereabouts for several weeks.
"Over the past few weeks, it's been losing altitude rapidly," Campbell says. As of March 21, it's at an altitude of roughly 136 miles.
As Reddy and Campbell have collected and studied their data, they've been comparing it to orbit data that the Air Force has been publishing daily, gathered using radar.
"Obviously we're not going to be able to get as accurate and precise data as they can get, but we are trying to see what we can get and how closely our derived products match," Campbell says. "A system like ours is a lot more accessible to academia who can also contribute."
"It's giving an opportunity for our students to play a role in space situational awareness," says Reddy.
Taking the Results to the Real World
Reddy and Campbell explain that, for now, they're simply putting their optical sensor system to the test and seeing what it's capable of – a test for which Tiangong-1 is the perfect subject.
"Radar has advantages and disadvantages, as does optical," Reddy says. "If we've come up with something that's even half as good as radar but can be done at a tenth of the cost, there might be some problems we can solve this way."
Reddy uses the example of placing one of these systems at every fire station in the United States. Whereas radar must be manned and operated, the optical sensors can run autonomously and can effectively crowdsource similar data.
"Exactly," Campbell says. "We're not trying to replace radar, but it’s a complement."
Reddy and Campbell are now placing an array of these sensors on a single mount to be installed at Biosphere 2 – all for the purpose of tracking objects in LEO.
"Basically, we're trying to develop methods that are cost-effective for the taxpayer, train the next generation of scientists and engineers like Tanner, and show the world that we can be better stewards of our precious orbital space," says Reddy.
Campbell plans to present the results of their work tracking Tiangong-1 at the Advanced Maui Optical and Space Surveillance Technologies Conference this fall.
LPL Astronomers Track Tesla Roadster in Space
By Emily Walla, UA
By Emily Walla, UA/NASA Space Grant Communications Intern - February 20, 2018
Earlier this month, the Falcon Heavy rocket successfully launched a Tesla Roadster into orbit around the sun. In the days following the launch, University of Arizona astronomers pointed their telescopes toward the car as it sped through space.
Telescopes operated by UA's Catalina Sky Survey, or CSS, were among the first to spot the Roadster, which was given the official designation of 2018-017A. Their observations immediately were submitted to the Minor Planet Center, an organization that determines the orbits of small astronomical objects such as asteroids, comets ... and the Roadster. Once the orbit of the Roadster is known, the CSS researchers can determine where it will be at any given time.
"It's the natural asteroids we are seeking to discover, not artificial satellites, but we still must know where the artificial objects are," said CSS senior research specialist Greg Leonard. The Roadster will be added to CSS' list of man-made objects so that in the future, astronomers will not mistake the car for a never-before-documented asteroid.
CSS' mission is to discover and catalog near-Earth objects. An important aspect of the mission is to identify objects that pose potential impact threats to Earth. Because the Roadster was launched from Earth, its orbit intersects Earth's. The car might come crashing back to Earth one day, or it might be nudged into an orbit that keeps it far away from Earth.
"One of the challenges of predicting the impact is that we don't know the orbit really well right now," said Eric Christensen, lead investigator for CSS. "We've only been able to observe it for a week or so."
What astronomers do know is what the Roadster will not do.
"It's not going to behave like an asteroid," Christensen said.
Astronomers have well-developed models that can be used to determine the paths of near-Earth asteroids or man-made spacecrafts, but the Roadster is an object that had not traveled through space before. No astronomer has ever had to predict how a car orbits the sun.
"Did they deflate the tires? Is air going to leak out and cause some strange thrusts? We don't know," Christensen said.
The sun also might move the Roadster onto a different course. The car is not heavy when compared to large asteroids, so radiation from the sun can push it around. Objects absorb light from the sun and re-emit this light as heat, which provides a small boost to the object. For lightweight objects, such as small asteroids, spacecrafts and space-faring cars, this small boost is sometimes enough to move the object into a different orbit.
The Roadster's current trajectory will take it in an orbit that crosses Mars' path. At its greatest distance from Earth, the car will be 250 million miles away. Even for the most powerful telescopes, detecting something so tiny at such a great distance is impossible. In a matter of weeks, the Roadster will be too far away to detect.
The observations taken while the car is still visible may be the only ones astronomers will be able to get for a long time. It takes 18 months for the Roadster to cruise around the sun, so at this time next year the car will still be millions of miles away from Earth. It may be centuries before the car and Earth meet again.
As well as being scientifically valuable, the nights spent tracking the Roadster were special occasions.
"These observations were fun," Christensen said.
"It's not every day when we attempt to acquire an image of a cherry-red Tesla Roadster hurtling into outer space," Leonard said.
The Roadster is only 13 feet long — minuscule for an astronomical object — and at a distance of more than more than 2 million miles, telescopes cannot discern the details of the car.
"Although the recovery images show only a sequence of bright blips of light moving against a starry background, knowing what the object is was really quite thrilling, as this special launch and mission marks a milestone in human capability for space exploration," Leonard said.
The Falcon Heavy rocket is the first private craft capable of carrying heavy payloads to space — and the first rocket that can send passengers to the moon since NASA retired its Saturn V rocket more than 40 years ago. And the Falcon Heavy is relatively cheap: While the Saturn V's launches each cost more than $180 million in 1969 dollars (more than $1 billion today), launching the Falcon Heavy rocket costs only $90 million.
"It's more than a gimmick," Christensen said. "It's a very significant cost-saving method."
The Catalina Sky Survey is funded by NASA and based at the UA's Lunar and Planetary Laboratory. The survey has discovered more than 8,000 near-Earth asteroids since 1998.