NASA’s OSIRIS-REx to Attempt a “Grab-and-Snatch” on Asteroid Bennu Today
This mosaic image of asteroid Bennu is composed of 12 PolyCam images collected on Dec. 2, 2018 by the Origins Spectral Interpretation Resource Identification Security - Regolith Explorer (OSIRIS-REx) spacecraft from a range of 15 miles (24 km). The spacecraft has traveled to the near-Earth asteroid Bennu (formerly 1999 RQ36) and bring at least a 2.1-ounce sample back to Earth for study. The mission will help scientists investigate how planets formed and how life began, as well as improve our understanding of asteroids that could impact Earth. (Image Credit: NASA, Goddard Space Flight Center, University of Arizona)
NASA’s OSIRIS-REx to Attempt a “Grab-and-Snatch” on Asteroid Bennu Today
Today, OSIRIS-REx will attempt a historic feat for NASA -- to collect the first samples from an asteroid’s surface.
During the Touch-And-Go (TAG) phase, the spacecraft will maneuver down to the selected Nightingale site on Bennu’s rocky and dusty surface to collect a sample for return to Earth in 2023. OSIRIS-REx launched Sept. 8, 2016, from Cape Canaveral Air Force Station, and many folks at NASA’s Katherine Johnson Independent Verification and Validation (IV&V) Facility, NASA's Goddard Space Flight Center in Greenbelt, Maryland, and across other parts of NASA worked hard to make the project happen.
Roger Harris, who served as Project Manager for OSIRIS-REx work at IV&V, explained exactly what to expect during the TAG. “The OSIRIS-REx spacecraft will make its first TAG attempt at gathering at least 2 ounces regolith from the asteroid Bennu. Since Bennu is so far away, the operators on the ground will issue instructions to the software, and then it will autonomously approach Bennu and extend its robotic arm, called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM),” he said. “The solar panels will pull back safely away so they can’t touch Bennu’s surface, and the Natural Feature Tracking system will enable the spacecraft to pull back before the spacecraft is in danger of colliding with a hazardous area of the “Nightingale” landing site, which while our best option for gather surface material, is surrounded by massive mission-ending boulders.”
“If all goes well, TAGSAM will stow the gathered material and begin the trip home. IV&V performed analysis on the critical software necessary to execute this activity as well as the software that controlled the essential steps leading up to this,” Harris said. “It’s exciting to know that we contributed to this mission and positively affected the development of the spacecraft and instrument software with the results of our hard work!”
NASA’s Origins, Spectral Interpretation, Resource Identification, Security - Regolith Explorer asteroid sample return mission (OSIRIS-REx), is the first U.S. mission to collect a sample of an asteroid and return it to Earth for study. Analyzing the sample will help scientists understand the early solar system, as well as the hazards and resources of near-Earth space.
Asteroids are remnants of the building blocks that formed the planets and enabled life. Those like Bennu contain natural resources such as water, organics and metals. Future space exploration and economic development may rely on asteroids for these materials.
- SCIENCE GOALS AND OBJECTIVES
The OSIRIS-REx name is an acronym of the mission objectives, which are:
- Origins: Return and analyze a pristine carbon rich asteroid sample
- Spectral Interpretation: Provide ground truth or direct observations for telescopic data of the entire asteroid population
- Resource Identification: Map the chemistry and mineralogy of a primitive carbon rich asteroid
- Security: Measure the effect of sunlight on the orbit of a small asteroid, known as the Yarkovsky effect—the slight push created when the asteroid absorbs sunlight and re-emits that energy as heat
- Regolith Explorer: Document the regolith (layer of loose, outer material) at the sampling site at scales down to the sub-centimeter
- MISSION OVERVIEW
OSIRIS-REx launched from Cape Canaveral, Florida, on an Atlas V 411 rocket on Sept. 8, 2016. OSIRIS-REx will orbited the sun for a year, then used Earth’s gravitational field to assist it on its way to Bennu. In August 2018, OSIRIS-REx’s approach to Bennu began. It used an array of small rocket thrusters to match the velocity of Bennu and rendezvous with the asteroid. The spacecraft began a detailed survey of Bennu two months after slowing to encounter Bennu. The process lasted over a year, and as part of it, OSIRIS-REx mapped potential sample sites.
Today, the spacecraft will maneuver down to the selected Nightingale site on Bennu’s rocky and dusty surface to collect a sample for return to Earth. The sampling arm will make contact with the surface of Bennu for about five seconds, during which it will release a burst of nitrogen gas. The procedure will cause rocks and surface soil to be stirred up and captured in the sampler head. The spacecraft has enough nitrogen to allow three sampling attempts, to collect between 60 and 2000 grams 2–70 ounces (60–2000) grams.
In March 2021, the window for departure from the asteroid will open and OSIRIS-REx will begin its return journey to Earth, arriving two and a half years later in September 2023. The sample return capsule will separate from the spacecraft and enter the Earth’s atmosphere. The capsule containing the sample will be collected at the Utah Test and Training Range. For two years after the sample return (from late 2023-2025) the science team will catalog the sample and conduct the analysis needed to meet the mission science goals. NASA will preserve at least 75% of the sample at NASA’s Johnson Space Flight Center in Houston for further research by scientists worldwide, including future generations of scientists.
- SCIENCE PAYLOAD
OSIRIS-REx contains five instruments to explore Bennu, each of which provides important information for the mission. This suite of instruments is used for remote sensing or scanning the surface of the asteroid. They were used to map Bennu and establish the composition of the asteroid, including the distribution of elements, minerals, and organic material.
OSIRIS-REx Camera Suite (OCAMS) – a system consisting of three cameras provided by the University of Arizona in Tucson observed Bennu and provided global image mapping, as well as sample site image mapping. The suite consists of these cameras:
- MapCam – a camera that will map the surface of the asteroid in four colors
- PolyCam – an 8-inch (20 centimeter) telescope that will be the first to image the asteroid from 1.24 million miles (2 million kilometers) away and also provide high-resolution microscope-like images of the surface
- SamCam – a camera that will image (as fast as 1.6 seconds) the sample acquisition event and examine the sample collector to verify successful acquisition
OSIRIS-REx Laser Altimeter (OLA) – a scanning LIDAR (Light Detection and Ranging) contributed by the Canadian Space Agency in Saint-Hubert, QC was used to measure the distance between the spacecraft and Bennu’s surface and map the shape of the asteroid.
OSIRIS-REx Thermal Emission Spectrometer (OTES) – an instrument provided by Arizona State University in Tempe that provides mineral and temperature information by observing the thermal infrared spectrum.
OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) – an instrument provided by NASA’s Goddard Space Flight Center in Greenbelt, Maryland which measures visible and infrared light from Bennu to identify mineral and organic material.
Regolith X-ray Imaging Spectrometer (REXIS) – a student experiment provided by Massachusetts Institute of Technology and Harvard University, both in Cambridge, Massachusetts, that observe the x-ray spectrum to determine what elements are present on Bennu’s surface and how abundant they are.
- SAMPLE COLLECTION AND RETURN
Touch-And-Go Sample Acquisition Mechanism (TAGSAM) – an articulated robotic arm with a sampler head, provided by Lockheed Martin Space Systems Company, to collect a sample of Bennu’s surface.
OSIRIS-REx Sample Return Capsule (SRC) – a capsule with a heat shield and parachutes through which the spacecraft will return the asteroid sample to Earth, provided by Lockheed Martin Space Systems Company.
Lockheed Martin Space Systems Company built the spacecraft at its facility near Denver, CO.
Length: 20.25 feet (6.2 meters) with solar arrays deployed
Width: 8 feet (2.43 meters) x 8 feet (2.43 meters)
Height: 10.33 feet (3.15 meters)
TAGSAM Length: 11 feet (3.35 meters)
Dry Mass (unfueled): 1,940 pounds (880 kilograms)
Wet Mass (fueled): 4,650 pounds (2,110 kilograms)
Power: Two solar panels generate between 1,226 watts and 3,000 watts, depending on the spacecraft’s distance from the sun.
Things to Know About Bennu
NASA’s first mission to return a sample from an ancient asteroid arrived at its target, the asteroid Bennu, on Dec. 3, 2018. This OSIRIS-REx mission is a seven-year long voyage set to conclude upon the delivery to Earth of at least 2.1 ounces (60 grams) and possibly up to almost four and a half pounds (two kilograms) of sample. It promises to be the largest amount of extraterrestrial material brought back from space since the Apollo era. The 20-year anniversary of the asteroid’s discovery was in September 2019 — and scientists have been collecting data ever since. Here’s what we already know (and some of what we hope to find out) about this pristine remnant from the early days of our solar system.
1. IT’S VERY, VERY DARK...
Bennu is classified as a B-type asteroid, which means it contains a lot of carbon in and along with its various minerals. Bennu’s carbon content creates a surface on the asteroid that reflects about four percent of the light that hits it — and that’s not a lot. For contrast, the solar system’s brightest planet, Venus, reflects around 65 percent of incoming sunlight, and Earth reflects about 30 percent. Bennu is a carbonaceous asteroid that hasn’t undergone drastic, composition-altering change, meaning that on and below its deeper-than-pitch-black surface are chemicals and rocks from the birth of the solar system.
2. ...AND VERY, VERY OLD.
Bennu has been (mostly) undisturbed for billions of years. Not only is it conveniently close and carbonaceous, it is also so primitive that scientists calculated it formed in the first 10 million years of our solar system’s history — over 4.5 billion years ago. Thanks to the Yarkovsky effect -- the slight push created when the asteroid absorbs sunlight and re-emits that energy as heat -- and gravitational tugs from other celestial bodies, it has drifted closer and closer to Earth from its likely birthplace: the Main Asteroid Belt between Mars and Jupiter.
3. BENNU IS A “RUBBLE-PILE” ASTEROID
Is Bennu space trash or scientific treasure? While “rubble pile” sounds like an insult, it’s actually a real astronomy classification. Rubble-pile asteroids like Bennu are celestial bodies made from lots of pieces of rocky debris that gravity compressed together. This kind of detritus is produced when an impact shatters a much larger body (for Bennu, it was a parent asteroid around 60 miles [about 100 km] wide). Bennu, for contrast, is about as tall as the Empire State Building. It likely took just a few weeks for these shards of space wreckage to coalesce into the rubble-pile that is Bennu. Bennu is full of holes inside, with 20 to 40 percent of its volume being empty space. The asteroid is actually in danger of flying apart, if it starts to rotate much faster or interacts too closely with a planetary body.
4. ASTEROIDS MAY HARBOR HINTS ABOUT THE ORIGIN OF ALL LIFE ON EARTH...
Bennu is a primordial artifact preserved in the vacuum of space, orbiting among planets and moons and asteroids and comets. Because it is so old, Bennu could be made of material containing molecules that were present when life first formed on Earth. All Earth life forms are based on chains of carbon atoms bonded with oxygen, hydrogen, nitrogen and other elements. However, organic material like the kind scientists hope to find in a sample from Bennu doesn’t necessarily always come from biology. It would, though, further scientists’ search to uncover the role asteroids rich in organics played in catalyzing life on Earth.
5. ...BUT ALSO PLATINUM AND GOLD
Extraterrestrial jewelry sounds great, and Bennu is likely to be rich in platinum and gold compared to the average crust on Earth. Although most aren’t made almost entirely of solid metal (but asteroid 16 Psyche may be), many asteroids do contain elements that could be used industrially in lieu of Earth’s finite resources. Closely studying this asteroid will give answers to questions about whether asteroid mining during deep-space exploration and travel is feasible. Although rare metals attract the most attention, water is likely to be the most important resource in Bennu. Water (two hydrogen atoms bound to an oxygen atom) can be used for drinking or separated into its components to get breathable air and rocket fuel. Given the high cost of transporting material into space, if astronauts can extract water from an asteroid for life support and fuel, the cosmic beyond is closer than ever to being human-accessible.
6. SUNLIGHT CAN CHANGE THE ASTEROID’S ENTIRE TRAJECTORY
Gravity isn’t the only factor involved with Bennu’s destiny. The side of Bennu facing the Sun gets warmed by sunlight, but a day on Bennu lasts just 4 hours and 17.8 minutes, so the part of the surface that faces the Sun shifts constantly. As Bennu continues to rotate, it expels this heat, which gives the asteroid a tiny push towards the Sun by about 0.18 miles (approximately 0.29 kilometers) per year, changing its orbit.
7. THERE IS A SMALL CHANCE THAT BENNU WILL IMPACT EARTH LATE IN THE NEXT CENTURY
The NASA-funded Lincoln Near-Earth Asteroid Research team discovered Bennu in 1999. NASA’s Planetary Defense Coordination Office continues to track near-Earth objects (NEOs), especially those like Bennu that will come within about 4.6 million miles (7.5 million kilometers) of Earth’s orbit and are classified as potentially hazardous objects. Between the years 2175 and 2199, the chance that Bennu will impact Earth is only 1-in-2,700, but scientists still don’t want to turn their backs on the asteroid. Bennu swoops through the solar system on a path that scientists have confidently predicted, but they will refine their predictions with the measurement of the Yarkovsky Effect by OSIRIS-REx and with future observations by astronomers.
8. SAMPLING BENNU WILL BE HARDER THAN WE THOUGHT
Early Earth-based observations of the asteroid suggested it had a smooth surface with a regolith (the top layer of loose, unconsolidated material) composed of particles less than an inch (a couple of centimeters) large — at most. As the OSIRIS-REx spacecraft was able to take pictures with higher resolution, it became evident that sampling Bennu would be far more hazardous than what was previously believed: new imagery of Bennu’s surface show that it’s mostly covered in massive boulders, not small rocks. OSIRIS-REx was designed to be navigated within an area on Bennu of nearly 2,000 square yards (meters), roughly the size of a parking lot with 100 spaces. Now, it must maneuver to a safe spot on Bennu’s rocky surface within a constraint of less than 100 square yards, an area of about five parking spaces.
9. BENNU WAS NAMED AFTER AN ANCIENT EGYPTIAN DEITY
Bennu was named in 2013 by a nine-year-old boy from North Carolina who won the Name that Asteroid! competition, a collaboration between the mission, the Planetary Society, and the LINEAR asteroid survey that discovered Bennu. Michael Puzio won the contest by suggesting that the spacecraft’s Touch-and-Go Sample Mechanism (TAGSAM) arm and solar panels resemble the neck and wings in illustrations of Bennu, whom ancient Egyptians usually depicted as a gray heron. Bennu is the ancient Egyptian deity linked with the Sun, creation and rebirth — Puzio also noted that Bennu is the living symbol of Osiris. The myth of Bennu suits the asteroid itself, given that it is a primitive object that dates back to the creation of the Solar System. Themes of origins and rebirth are part of this asteroid’s story. Birds and bird-like creatures are also symbolic of rebirth, creation and origins in various ancient myths.
10. BENNU IS STILL SURPRISING US
The spacecraft’s navigation camera observed that Bennu was spewing out streams of particles a couple of times each week. Bennu apparently is not only a rare active asteroid (only a handful of them have been as of yet identified), but possibly with Ceres explored by NASA’s Dawn mission, among the first of its kind that humanity has observed from a spacecraft. More recently, the mission team discovered that sunlight can crack rocks on Bennu, and that it has pieces of another asteroid scattered across its surface. More pieces will be added to Bennu’s cosmic puzzle as the mission progresses, and each brings the solar system’s evolutionary history into sharper and sharper focus.
Goddard Spaceflight Center provides overall mission management, systems engineering, and the safety and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator, and the University of Arizona also leads the science team and the mission’s science observation planning and data processing. NASA’s Katherine Johnson Independent Verification and Validation (IV&V) Facility provides software verification. Lockheed Martin Space 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, which is managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington.
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