ULA Atlas V sends OSIRIS-REx on its way toward asteroid Bennu
CAPE CANAVERAL, Fla. — The team for NASA’s Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) mission cheered as a United Launch Alliance (ULA) Atlas V 411 powered the asteroid explorer spaceward. Liftoff occurred on time at 7:05 p.m. EDT (23:05 GMT) from Cape Canaveral Air Force Station’s Space Launch Complex (SLC) 41 to send OSIRIS-REx into a hyperbolic orbit to catch up with the asteroid 101955 Bennu.
The 45th Weather Squadron had predicted weather to have an 80 percent chance of favorable conditions. However, as the countdown proceeded, that improved to 90 percent (a rare event given how turbulent Florida weather is). Skies were clear and the Atlas V and OSIRIS-REx teams saw no issues during the launch campaign.
“ULA and our heritage vehicles have successfully launched NASA missions to every planet in our solar system,” said Laura Maginnis, ULA’s vice president of Custom Services. “ULA’s commitment to mission launch is unparalleled, and we’re proud of our team for continuing our unprecedented track record of 100 percent mission success.”
The Russian-made RD-180 main engine and single Aerojet Rocketdyne AJ-60A solid rocket booster (SRB) lit up with a roar and a plume of orange and white flame. Its 1.2 million pounds (5.3 million newtons) of thrust lofted the Atlas V past SLC-41’s launch towers and into the evening sky.
The Atlas V got going in a hurry, reaching Mach 1 in less than a minute. As the rocket arced over the Atlantic Ocean, it rolled so the SRB was on top relative to Earth.
The SRB burned out after about 2 minutes, 9 seconds. The booster stage burned through its 626,309 pounds (284,089 kilograms) of kerosene and liquid oxygen in just over 4 minutes. At that time, the first stage separated with the Centaur upper stage as planned.
Ten seconds after separation, the Centaur upper stage ignited its single Aerojet Rocketdyne RL10A-4-2 engine. It consumed liquid hydrogen, liquid oxygen for an eight-minute burn to reach low-Earth orbit (LEO). Eight seconds after Centaur’s ignition, the payload fairing separated, exposing OSIRIS-REx to space.
Once in LEO, the Centaur’s engine cut off as expected for a 22-minute coast phase.
Just under 34 minutes into the flight, the Centaur engine fired for a second time. This time, it burned for nearly eight-and-a-half minutes to send the spacecraft shooting away from Earth. Fifty-five minutes, 38 seconds after liftoff, OSIRIS-REx separated from Centaur, continuing its journey at an escape velocity of over 3.5 miles (5.4 kilometers) per second.
A long journey begins
Like many NASA planetary explorers, the spacecraft will use a gravity-assist maneuver around Earth in September 2017. This will allow the spacecraft to make a plane change to reach Bennu’s inclined orbit. OSIRIS-REx is expected to catch up with the asteroid in August 2018.
Christina Richey, deputy program scientist at NASA Headquarters, explained to SpaceFlight Insider that getting into orbit around the asteroid will be one of the biggest early challenges for the mission.
“Once we catch up with Bennu, we don’t know if the gravity will be strong enough to capture it. We’ll have to rely on our thrusters to get us there,” Richey said.
Another challenge for OSIRIS-REx will be the surface of Bennu itself. Sometime in 2020, OSIRIS-REx will descend to the surface to collect samples. To do this, the spacecraft will use a robotic arm called the Touch and Go Sample Acquisition Mechanism (TAGSAM).
TAGSAM’s collection head will extend to the surface like a palm pressing flat against a wall. The sampler is built assuming the surface has enough loose material to pick up and is smooth enough for the collector head to touch it.
Dante Lauretta, OSIRIS-REx’s principal investigator from the University of Arizona-Tucson, believes Bennu itself will determine the success of TAGSAM.
“I’m looking forward to that first fully resolved image of the asteroid, where we finally know what we’re up against: are we facing rugged terrain or a literal walk on the beach?” Lauretta told SpaceFlight Insider. “We want a walk on the beach so TAGSAM can reach out and get a good sample.”
Once a sample is confirmed inside the collector, it will be placed inside a Sample Return Capsule on the spacecraft. In March 2021, OSIRIS-REx will depart Bennu and return to Earth in 2023.
What makes OSIRIS-REx special?
“We’ll return a pristine sample from Bennu – the first time ever that an asteroid sample of this quality and quantity will be returned to Earth.” said Scott Bellamy, Mission Manager for the New Frontiers Program. “The way we’re collecting and returning the sample protects it from contamination, so that we’ll be able to study what Bennu has preserved for likely millions of years.”
OSIRIS-REx also offers the opportunity for private citizens to get involved in asteroid investigations. Target Asteroids! is a citizen science project run by Dolores Hill, Senior Research Specialist at the University of Arizona. The project engages amateur astronomers in observations of potential asteroid spacecraft targets. The purpose is to collect data (e.g., astrometry and photometry) on asteroid targets to better characterize them. Additionally, the project aims to engage amateurs in the mission and encourage interest in STEM education and careers. OSIRIS-REx team members will work with amateur astronomy groups to provide guidance, monitoring, and collection of data.
Given B612 Foundation‘s interest in planetary defense, their Chief Operating Officer, Danica Remy, was also on hand for the launch.
“B612 hopes that the composition, density, and structure strength are better understood for predicting impact damage and planning mitigation missions,” Remy told SpaceFlight Insider. “The more we learn about *any* asteroid, the better we can understand the kind of operations that will be required to move an asteroid in the future.”
Reveling in the moment, but what’s next?
The OSIRIS-REx team has a seven-year odyssey ahead of them. During that time, NASA’s New Frontiers and Discovery office has other adventures to pursue as well.
“We have a lot coming: Mars Insight, the Europa mission – that will be a big one, it’s a flagship mission – and we’re providing three instruments for the European Jupiter Icy moons Explorer (JUICE),” Bellamy told SpaceFlight Insider. “There’s a lot more to come.”
Video courtesy of NASA
Bart Leahy is a freelance technical writer living in Orlando, Florida. Leahy's diverse career has included work for The Walt Disney Company, NASA, the Department of Defense, Nissan, a number of commercial space companies, small businesses, nonprofits, as well as the Science Cheerleaders.