Contained within a shipping crate, the OSIRIS-REx spacecraft arrived at NASA’s Kennedy Space Center in Florida in late May. A transport crew rolled the white container down the ramp of an Air Force C-17 cargo plane and onto the center’s Shuttle Landing Facility runway.
Two days later, the Origins, Spectral Interpretation, Resource Identification, Security – Regolith Explorer, or OSIRIS-REx, spacecraft began its final pre-launch tests. The first involved a weight and center-of-gravity verification test on a spin table. Engineers also removed the spacecraft’s solar panels and inspected, tested and cleaned all of its solar cells.
Next, engineers from NASA’s Deep Space Network meticulously tested the various communications systems on the OSIRIS-REx spaceraft. These tests simulate the millions of miles that signals from the spacecraft must travel to reach the gigantic antennas of the Deep Space Network in California, Spain and Canberra, Australia.
OSIRIS-REx is the first U.S. mission designed to return a piece of an asteroid to Earth. The spacecraft is scheduled to launch on Sept. 8 at 7:05 p.m. EDT (4:05 p.m. Arizona time) aboard an Atlas V rocket. The University of Arizona-led mission has a 34-day launch window beginning on that date.
In 2018, the spacecraft is set to rendezvous with near-Earth asteroid Bennu. It is scheduled to return a pristine sample of at least 2.1 ounces of surface material to Earth in 2023.
Few outside of Tucson and the planetary science community are aware that the UA has had a hand in nearly every interplanetary spacecraft sent from Earth. From its founding in 1960 by Gerard Kuiper to its growth into a research powerhouse under Michael Drake to the present day, the Lunar and Planetary Laboratory has had a steady stream of successes.
The mission’s principal investigator, UA planetary sciences professor Dante Lauretta, is a Tucson native who was a NASA Space Grant intern during his undergraduate years at the University. He later worked as a young assistant professor under Drake’s tutelage, and he has a keen appreciation of what he has inherited.
“A lot of what we do is in his honor,” Lauretta says of Drake, who died of cancer in 2011. “He was really dedicated to the science and to student involvement and the inspiration of the next generation. This (mission) establishes a range of new capabilities for the University of Arizona. I’m really interested in the role (asteroids) have played or potentially play in the origin of life on Earth and the establishment of the habitability of our planet.
“We’re really going back 4.5 billion years in history,” he says. “We’re getting rocks that record the processes that were taking place right at the dawn of our solar system, when the planets were being born and the materials that would go into those planets were being formed.”
To capture a sample of the regolith, the spacecraft will hover over a carefully chosen area on the asteroid’s surface and then “will be sent down at a very slow and gentle” 10 centimeters per second to make five seconds of contact with the asteroid’s surface to vacuum up the regolith, Lauretta says.
The precise maneuvering of the spaceship around the asteroid — or proximity operations capabilities, as it is known — was one of the greatest challenges involved in developing OSIRIS-REx.
“That’s a real important capability for any mission that’s going to interact with asteroids in the future,” Lauretta says.
Bennu is one of more than 700,000 asteroids in our solar system. It was chosen for many reasons, but chiefly because it’s one of the most accessible carbonaceous asteroids and one of the most well-characterized ones. Scientists have a good read on the radar data and telescopic data that tell about its orbit and composition.
“When you know a lot about an object, it really helps you plan the mission,” Lauretta says.
Data show that Bennu, provisionally known as 1999 RQ36, has a polar diameter of 508 meters and mean diameter of 492 meters. It also has a spinning-top shape; that is, it sports a bulge along its equator, a common feature among near-Earth asteroids.
“What we think this means is that this is a rubble-pile object,” Lauretta says.
That means Bennu is probably made of many boulders tens to hundreds of meters across.
“(The boulders) are loose, and they’re responding to the forces of the asteroid spinning, and material is migrating from the pole of the asteroid and accumulating at the equator and building up a ridge,” Lauretta says. “That’s the theory. The good news is that we’re going to get out there and take a good look at the asteroid, and we’re going to test that theory, and we’re going to try and figure out why so many asteroids have that spinning-top shape.”
No matter the reason, Bennu is in an unstable orbit, which means it probably won’t last more than 10 million years before it collides with Earth or another planet, or falls into the sun, Lauretta says.
Which is of concern to Lauretta and other scientists. In fact, Bennu is considered a potentially hazardous object and has a relatively high probability of impacting the Earth. So scientists are interested in understanding how asteroids’ orbits evolve.
In addition to a touch-and-go sample acquisition mechanism and a sample return capsule, the spacecraft will carry a laser altimeter; a suite of cameras to which the UA contributed; spectrometers; and lidar, which is similar to radar, using light instead of radio waves to measure distance.
“I never dreamed I’d be in charge of a program of this magnitude and this significance and this much fun,” Lauretta says. “I’m anxious to get through the launch phase and into space and change our mode of operation, because we’ve been building this thing and designing it for so long.
“Getting to fly it is going to be a new and exciting challenge.”