With the successful launch of OSIRIS-REx on September 8, 2016, NASA is on its way to orbit, survey, and sample a “time capsule” in space: the near-Earth asteroid Bennu.
Bennu is a small, primitive body that was formed around the same time as the solar system. The Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) mission is charged with traveling to the carbon-rich asteroid, investigating it, and bringing back a sample to Earth in hopes of gaining insight into the origins of life on Earth, the potential distribution of life elsewhere, and the development of the solar system.
Speaking at a briefing after the launch, NASA Chief Scientist Ellen Stofan said, “We’re going to be answering some of the most fundamental questions that NASA really focuses on: How does this planet work? How did this planet form? And we’re even going to be looking at questions as basic as Where did life and how did life originate on this planet? This mission has huge contributions to science.”
Answering questions about the formation of Earth and the solar system is only one goal of the complex mission.
“OSIRIS-REx is an awesome acronym that describes the principle science objectives of our program,” said Dante Lauretta, the mission’s principal investigator from the University of Arizona in Tucson. During its seven-year journey to and from Bennu, OSIRIS-REx will deliver on science goals that range from exploring the origins of life on Earth, to proving technologies and operational procedures that may be used in the future for asteroid-mining missions, to learning more about how to protect Earth in the future.
“By virtue of our mission design, we’re going to an asteroid that has a reasonable chance of intersecting the earth at some point,” said Lauretta. Following an orbit between Venus and Mars, Bennu at times crosses paths with Earth. The team will study the asteroid’s behavior to better understand where it will be in the future—and, by extension, to predict where other potentially Earth-threatening asteroids may travel as well.
Of greatest interest to many is the mission’s role as regolith explorer. “Regolith is what we call the loose blanket of gravel and dust on the surface of these airless bodies,” said Lauretta. “We’re going to send a spacecraft down to make contact with that surface to collect our sample, and that’s the prime science objective of the mission. Just the act of doing that is of itself a great science experiment because we’re going to see how the surface of the asteroid responds.”
The mission got off to a strong start on Thursday, September 8, as the spacecraft launched on an Atlas V from Kennedy Space Center (KSC) precisely on time.
“The Atlas V rocket performed impeccably this evening,” said Scott Messer, United Launch Alliance (ULA) project manager for NASA missions. “We hit all of our milestones just right on time and in most cases just a little bit ahead of time.”
Rich Kuhns, OSIRIS-REx project manager from Lockheed Martin, which built the spacecraft, agreed. “We started the journey with a phenomenal launch on the Atlas V. It delivered us right where we needed to be, and we separated on plan, within a minute of when we said we would. Since then, it’s just been knocking milestone after milestone.”
Shortly after launch, the propulsion system was initialized, the solar arrays deployed, and the spacecraft established two-way communications with the ground station in Canberra. In two weeks, the team will turn on the instruments to check their status. The next milestone for the mission will come a year later, in September 2017, when the spacecraft performs an Earth gravity assist to change the inclination of its orbital plane to match that of the target asteroid.
OSIRIS-REx is scheduled to reach Bennu in August 2018. For the next two years, it will orbit and survey the asteroid, seeking the safest and most scientifically interesting site for sample acquisition, which it will attempt in July 2020. Although the spacecraft won’t land on Bennu, it will make contact using the Touch-And-Go Sample Acquisition Mechanism (TAGSAM). Essentially a sampler head with an articulated arm, the TAGSAM will perform what the team calls a “gentle high-five” with the asteroid surface as it obtains material from Bennu. The mission can try up to three times to acquire at least 60 grams of regolith from the surface, and has until the following March to do so.
“[B]ased on the capabilities of the spacecraft propulsion system and the orbital phasing between Bennu and target Earth, we have to wait till our departure window opens up. And so we won’t be able to leave until March of 2021. All return trajectories get us back on September 24, 2023,” said Lauretta.
A key goal of the mission is to return a pristine sample to Earth. “Lockheed Martin really took on the challenge of delivering us a clean sampling mechanism and a clean sample return capsule. But we recognize that there’s always going to be some level of contamination,” said Lauretta. “And so, in addition to flying the sampling mechanism and the return capsule, we’ve got a phenomenal collection of witness plates on the TAGSAM head itself, inside the sample return capsule, and they’re time phased. They’ll open and they’ll close at different stages of the mission to document any contamination that was acquired before the sampling event, during the sampling event, and then during the return cruise phase home. And so we’ll be able to remove that signal from any chemical analysis that we perform.”
The complex mission, with its multiple science objectives and applications to future missions as well as Earth security, is unique to the space community. Nonetheless, OSIRIS-REx fits into a larger international investigation concerning comets and asteroids, which includes the European Space Agency’s (ESA) Rosetta mission and the Japanese Aerospace Exploration Agency’s (JAXA) Hyabusa 2 mission.
“The Rosetta team has been particularly generous in…sharing a lot of their operational lessons learned,” said Lauretta. “In fact, our team has gone out to visit them in their operation center on multiple occasions. And we’ve brought a lot of important lessons back with us about how you orbit around a small body like this, how you operate, how you use your optical navigation systems to determine your spacecraft state, and then how you go through the process of sample site selection.”
He added, “I do want to give a lot of credit to the Japanese space agency. We learned a lot about asteroid proximity operations from the first Hyabusa mission, and we have a nice strong collaboration that the agency has established with JAXA for working with the Hyabusa 2 team.”
Jim Green, director of NASA’s Planetary Science Division, concurred: “JAXA’s going, with Hyabusa 2, to another asteroid much like Bennu.” The goal is for NASA and JAXA to exchange samples so each can learn more about asteroids in a broader sense than their individual missions permit. In addition, scientists around the world who conduct sample analyses are working with the agencies involved to deepen understanding of these primitive bodies.
“I think over time, as we see each of these international groups improve their ability to do sample analysis, we’ll be able to share a lot more of the science with them as we all work together internationally,” said Green. “It’s really an international effort. Planetary science is all about our solar system—it’s humanity’s solar system.” With OSIRIS-REx, NASA will expand humanity’s understanding of our past while looking to better protect our planet’s future as well.