Mission to Bennu

The UA Lunar and Planetary Lab gets ready to head out into space again

The UA Lunar and Planetary Lab team behind OSIRIS-REx, a mission to send a robotic spacecraft to study the asteroid Bennu, recently passed a major milestone when it competed NASA's Mission Critical Design Review. Construction of OSIRIS-REx is now underway. Principal Investigator Dante Lauretta recently sat down to talk about the $800 million mission, which launches in September 2016. For more info, visit asteroidmission.org.

Tell me about the journey that the OSIRIS-REx mission is going on.

OSIRIS-REx is a NASA mission. We are leading the charge to send a robotic spacecraft to a near-Earth asteroid named Bennu. We'll spend about a year surveying that asteroid and trying to understand its geography and its composition and will ultimately select the spot about 30 centimeters in diameter and we're going to fly that spacecraft right into the surface of that asteroid, make contact, grab some sample off the surface, take it away and bring it back to the surface of the Earth for analysis in our laboratories.

Part of this craft is being built right here in Tucson.

The UA is on it is the leader of the program. I'm the principal investigator on that project, so I have the ultimate responsibility for mission success to NASA. The University of Arizona is building the camera system. We have a long legacy—over 50 years—of building scientific instruments to fly on NASA programs. Our key partner is the Lockheed Martin Corporation. We are using a facility in Littletown, Colo. They are actually building the satellite and we will mount our science instruments onto that.

What are you hoping to learn by encountering an asteroid in space rather than here on Earth?

We have several key objectives. The prime motivation for sample return is that we're going to an asteroid we believe is very rich in carbon and may contain organic molecules. It's also a very ancient contract that formed 4 ½ billion years ago from the very start of our solar system. And what we hope to understand by studying this organic material is the role these kinds of objects play in bringing the seeds of life to the Earth. And we think that the precursors to our

DNA and our proteins came from these asteroids. We want to answer those questions by bringing this sample back.

How long does it take to get to Bennu?

It's a two-year journey. What we'll do is loop back and come back to the Earth one year later and we'll use the Earth's gravity to do what we call a gravity-assist maneuver—just take some energy from the earth and speed up the spacecraft and that's what sends it on the rendezvous trajectory with the asteroid. And then about one year later, we get to the vicinity of Bennu. We have over two-and-a-half years to stay at the asteroid but the hope is, for the first year, we have enough time to characterize the asteroid and grab that sample. The rest of that time is what we call "operational margin." We know the asteroid is probably going to surprise us. The spacecraft is going to take some time to learn how to fly it properly, so we want to have that extra time to deal with all the surprises of operating a vehicle 150 million miles away from the earth.

How do you do that? I imagine that the math involved in pretty tricky.

As you can imagine, a project like this takes an enormous team effort. I'm very honored to lead a team of over 400 people all around the world that are working very diligently to make this program a success. The key is to really think through the details—lots of planning, lots of testing and lots of training, so the team really understands the system and how it operates and what its capabilities are when we get to the asteroid.

What's onboard the spacecraft?

We have a series of scientific instruments. We have the three cameras that are being provided by the University of Arizona. Our colleagues up the highway at Arizona State University are building what we call a thermal emission spectrometer, which measures the heat coming off the asteroid, which is related to another one of our other scientific investigations, but it also tells us about the minerals that are on the surface. The NASA Goddard Spaceflight Center, which is our other key partner that does the project management for me, is also providing a chemistry instrument called the visible and infrared spectrometer. And then finally the Canadian Space Agency is providing a laser altimeter. This is a device that literally shoots a laser beam at the asteroid and we measure how long it takes to bounce back to the spacecraft and that tells us how far away we are and we can use that to build up three-dimensional topographic maps.

There's concern that an asteroid could collide with Earth and cause untold amounts of damage. You hope to learn something on this mission about how to change the course of an asteroid.

That's right. One of our other investigations is related to the fact that Bennu is also potentially hazardous, which means it has a reasonable high probability of impacting the Earth. The good news is, that will occur about 150 years from now so we don't have to panic at the moment. But we're going out there to understand this object—its composition, its density, its distribution of material. We also want to understand the details of its orbit and it turns out, in addition to gravity (which dominates its orbital path), there's a phenomenon called the Yarkovsky Effect, which is associated with how it receives sunlight and radiates that energy back out into space as heat. And that heat acts as a thruster and actually changes the course of the asteroid. So this is a process that's occurring naturally. We want to understand that in detail and then if we could control that and direct how that heat is transmitted back out into space, with a 100- or 150-year timeline, we could maybe alter the course of the asteroid if we needed to.

That makes more sense than trying to blow it up with a missile.

Blowing up something the size of a mountain is not an easy task and the real analogy is: Would you rather be hit by a cannonball or a shotgun blast? Blowing it up doesn't change the mass or the orbit, really, it just changes the nature of the particles that are coming at you.

This Q&A is condensed from an interview on Zona Politics with Jim Nintzel. Watch the whole interview and more at the Weekly's daily dispatch, The Range.

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