NASA’s OSIRIS-REx Spacecraft Heads for Earth with Asteroid Sample


May 10, 2021
RELEASE 21-061

After nearly five years in space, NASA’s Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) spacecraft is on its way back to Earth with an abundance of rocks and dust from the near-Earth asteroid Bennu.

On Monday, May 10, at 4:23 p.m. EDT the spacecraft fired its main engines full throttle for seven minutes – its most significant maneuver since it arrived at Bennu in 2018. This burn thrust the spacecraft away from the asteroid at 600 miles per hour (nearly 1,000 kilometers per hour), setting it on a 2.5-year cruise towards Earth.

After releasing the sample capsule, OSIRIS-REx will have completed its primary mission. It will fire its engines to fly by Earth safely, putting it on a trajectory to circle the sun inside of Venus’ orbit.

After orbiting the Sun twice, the OSIRIS-REx spacecraft is due to reach Earth Sept. 24, 2023. Upon return, the capsule containing pieces of Bennu will separate from the rest of the spacecraft and enter Earth’s atmosphere. The capsule will parachute to the Utah Test and Training Range in Utah’s West Desert, where scientists will be waiting to retrieve it.

“OSIRIS-REx’s many accomplishments demonstrated the daring and innovate way in which exploration unfolds in real time,” said Thomas Zurbuchen, associate administrator for science at NASA Headquarters. “The team rose to the challenge, and now we have a primordial piece of our solar system headed back to Earth where many generations of researchers can unlock its secrets.”

To realize the mission’s multi-year plan, a dozen navigation engineers made calculations and wrote computer code to instruct the spacecraft when and how to push itself away from Bennu. After departing from Bennu, getting the sample to Earth safely is the team’s next critical goal. This includes planning future maneuvers to keep the spacecraft on course throughout its journey.

“Our whole mindset has been, ‘Where are we in space relative to Bennu?’” said Mike Moreau, OSIRIS-REx deputy project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Now our mindset has shifted to ‘Where is the spacecraft in relation to Earth?’”

The navigation cameras that helped orient the spacecraft in relation to Bennu were turned off April 9, after snapping their last images of the asteroid. With Bennu in the rearview mirror, engineers are using NASA’s Deep Space Network of global spacecraft communications facilities to steer the OSIRIS-REx by sending it radio signals. By measuring the frequency of the waves returned from the spacecraft transponder, engineers can tell how fast OSIRIS-REx is moving. Engineers measure how long it takes for radio signals to get from the spacecraft back to Earth in order to determine its location.

Exceeding Mission Expectations

The May 10 departure date was precisely timed based on the alignment of Bennu with Earth. The goal of the return maneuver is to get the spacecraft within about 6,000 miles  (approximately 10,000 kilometers) of Earth in September 2023. Although OSIRIS-REx still has plenty of fuel remaining, the team is trying to preserve as much as possible for a potential extended mission to another asteroid after returning the sample capsule to Earth. The team will investigate the feasibility of such a mission this summer.

The spacecraft’s course will be determined mainly by the Sun’s gravity, but engineers will need to occasionally make small course adjustments via engine burns.

“We need to do regular corrections to bring the trajectory increasingly closer to Earth’s atmosphere for the sample release, and to account for small errors that might have accumulated since the last burn,” said Peter Antreasian, OSIRIS-REx navigation lead at KinetX Aerospace, which is based in Simi Valley, California.

The team will perform course adjustments a few weeks prior to Earth re-entry in order to precisely target the location and angle for the sample capsule’s release into Earth’s atmosphere. Coming in too low could cause the capsule to bounce out of the atmosphere like a pebble skipping off a lake; too high and the capsule could burn up due to friction and heat from the atmosphere. If OSIRIS-REx fails to release the capsule, the team has a backup plan to divert it away from Earth and try again in 2025.

“There’s a lot of emotion within the team about departure,” Moreau said. “I think everyone has a great sense of accomplishment, because we faced all these daunting tasks and were able to accomplish all the objectives thrown at us. But there’s also some nostalgia and disappointment that this part of the mission is coming to an end.”

OSIRIS-REx exceeded many expectations. Most recently, in the midst of a global pandemic, the team flawlessly executed the most mission’s critical operation, collecting more than 2 ounces (60 grams) of soil from Bennu’s surface.

Leading up to sample collection, a number of surprises kept the team on its toes. For example, a week after the spacecraft entered its first orbit around Bennu, on Dec. 31, 2018, the team realized that the asteroid was releasing small pieces of rock into space.

“We had to scramble to verify that the small particles being ejected from the surface did not present a hazard to the spacecraft,” Moreau said.

Upon arrival at the asteroid, team members also were astonished to find that Bennu is littered with boulders.

“We really had this idea that we were arriving on an asteroid with open real estate,” said Heather Enos, OSIRIS-REx deputy principal investigator, based at the University of Arizona, Tucson. “The reality was a big shocker.”

To overcome the extreme and unexpected ruggedness of Bennu’s surface, engineers had to quickly develop a more accurate navigation technique to target smaller-than-expected sites for sample collection.

The OSIRIS-REx mission was instrumental in both confirming and refuting several scientific findings. Among those confirmed was a technique that used observations from Earth to predict that the minerals on the asteroid would be carbon-rich and show signs of ancient water. One finding that proved unsuccessful was that Bennu would have a smooth surface, which scientists predicted by measuring how much heat radiated off its surface.

Scientists will use the information gleaned from Bennu to refine theoretical models and improve future predictions.

“This mission emphasizes why we have to do science and exploration in multiple ways – both from Earth and from up-close in space – because assumptions and models are just that,” Enos said.

Goddard 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. The university leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space in Littleton, Colorado, built the spacecraft and provides 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, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate Washington.

For more information about OSIRIS-REx, visit:


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May 11, 2021 2:56 am

I would assume by landing on it (retro firing) and taking off the asteroid’s orbit was perceptibly altered. Since rocket firing force is known it should be possible to calculate what is required to deflect trajectory of any asteroid that may in the future head our way.

Reply to  Vuk
May 11, 2021 3:42 am

Yes, probably. Of course, one other thing you’d need to know is how the asteroid body is composed. Which was one of the reasons for returning with this sample that I don’t think they repeated in this article.

Mike Jonas(@egrey1)
Reply to  Vuk
May 11, 2021 4:40 am

Bennu’s mass is thought to be about 70 million tons.
OSIRIS-REx is about 1 ton.
OSIRIS-REx’s departure speed from Bennu is about 1,000kph. Some of the thrust would be at some distance from Bennu so Bennu’s trajectory is likely to change by less than in direct proportion, say about 1cm ph or less than 1km per decade.

If I’ve got those calcs right, then I suggest it indicates how hard it will be, if a large asteroid is ever heading for Earth, to change its course.

Joseph Zorzin
Reply to  Mike Jonas
May 11, 2021 5:34 am

“If I’ve got those calcs right, then I suggest it indicates how hard it will be, if a large asteroid is ever heading for Earth, to change its course.” But if a spacecraft just sat there and pointed its rocket thrust straight up- the effect would be much greater.

John Tillman
Reply to  Mike Jonas
May 11, 2021 7:11 am

Which is why Earth crossing asteroids need to be spotted as far away as possible, to allow more time for thrust to work.

Steve Z
Reply to  Mike Jonas
May 11, 2021 8:19 am

Probably the best option to save the Earth from an asteroid collision would be to send a spacecraft equipped with a nuclear bomb which would detonate on contact with the asteroid. It may not change the course of the asteroid much, but it could smash the asteroid into smaller pieces, some of which may burn up in the Earth’s atmosphere, and those that reach the Earth would have a smaller effect than a large asteroid.

Bennu is estimated to have a diameter of about 530 meters, compared to about 50 meters for the meteorite that caused the Meteor Crater in Arizona, so that Bennu would have about 1,000 times its mass.

The problems with trying to “nuke an asteroid” would be:

1) Detecting the asteroid and its path early enough to prepare an intercept
2) Preparing, fueling, and arming the required rocket
3) Moving the rocket to the correct side of the earth for minimum travel time to the asteroid
4) Guiding the rocket to the impact point and ensuring the detonation of the nuclear bomb

There have been several “near misses” over the past few years where asteroids have passed closer to the Earth than the Moon’s orbit, or about 240,000 miles. With the Earth’s diameter of about 8,000 miles, there is about a 1 in 900 chance that an asteroid passing within the Moon’s orbit would actually strike the Earth. Within that chance, there is about a 30% chance that the asteroid would hit land, which would have a more devastating effect (due to dust projected high into the atmosphere, similar to the effect of a gigantic volcanic eruption) than hitting the ocean, which would cause tsunamis affecting the closest coasts, but little effect inland.

Since the WUWT site is mostly about climate change, in the event of a possible asteroid collision with the Earth, the best way of preventing catastrophic climate change (cooling!) may be a nuclear bomb!

Reply to  Steve Z
May 11, 2021 11:11 am

Isn’t it true that asteriods circle the sun, on their own orbits? If so, using a rocket to nudge it away from earth would also change it’s orbit, too. Then, the next time it ‘comes around’ would it be more or less likely to impact the earth? it might cause a whole NEW worry, every time it passes near the earth! We might find ourselves dealing with it every few years (or months) and never really solve the problem. Maybe nuclear IS the way to go?

Tombstone Gabby
Reply to  Steve Z
May 11, 2021 6:27 pm

G’day Steve,

“3) Moving the rocket to the correct side of the earth for minimum travel time to the asteroid.”

What’s wrong with just letting the earth rotate? Probably faster.

Reply to  Vuk
May 11, 2021 5:04 am

If you followed the video of the touchdown, you’d see that contact was more like bumping into a damp sponge. There was a lot of particle movement. The probe went deep into the asteroid, not just surface contact. It’s difficult to conceive that you’d see any effect on the asteroid’s overall path due to that.

Gary Pearse
Reply to  Vuk
May 11, 2021 8:24 am

Good thinking Vuk. Maybe need the nuclear option to push it harder.

May 11, 2021 4:13 am

One thing I do find enjoyable about Nasa missions is the acronyms they come up with!

Reply to  fretslider
May 11, 2021 11:47 am

Fairly sure these are called Backronyms.

May 11, 2021 4:52 am

“[…] NASA’s Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) spacecraft […]”

I’ve always suspected that NASA has an Acronym Department, probably staffed with a few dozen or so English and History majors.

NASA’s missions and equipment acronyms are generally pretty good; memorable and fairly descriptive of what is going on.

The Department probably pays for itself when it comes to begging for more budget. The Directors can point to a bunch of missions that were funded and propose more slick-sounding missions. The politicians say, “Oh, yeah… that stuff. You’re getting good press. Here’s a few $Billion more.”
So this is really something! Send out a highly specialized bit of kit, have it meet up with an asteroid, land, take samples, take off and return to Earth.

It’s not like anyone can run down to the corner drugstore, buy a bit of asteroid, and run it back to the lab for analysis. (Although, did NASA check first on e-Bay before going to all the trouble? 😜)

This is good stuff. I wish NASA would stick to this type of work and get out of the ‘Climate Change’ biz altogether.

Reply to  H.R.
May 11, 2021 5:45 am

If NASA are so clever with their English, why do they say things like “OSIRIS-REx’s many accomplishments demonstrated the daring and innovate (sic!) way in which exploration unfolds in real time”?

John Tillman
Reply to  H.R.
May 11, 2021 7:13 am

Yet Earth is littered with asteroid samples, ie meteorites.

Reply to  John Tillman
May 11, 2021 9:28 am

I asked, did they check e-Bay?

Reply to  H.R.
May 11, 2021 11:13 am

Yep, you can find AND BUY, just about anything on eBay! And at a good price too, usually!

John Tillman
Reply to  H.R.
May 11, 2021 2:52 pm

Iron-nickel meteorite, hence from the cooled core of a differentiated planetesimal:

The price is about $33 USD.

Reply to  John Tillman
May 11, 2021 7:24 pm

LOL! Tillman pulls up… shoots from 3-point range… and scores! Swish… nothing but net.
They didn’t have to go to all the trouble. But it’s still pretty cool in my book.

John Tillman
Reply to  H.R.
May 12, 2021 10:06 am

I’d rather have a carbonaceous chondrite containing amino acids and other organic compounds. A space alien microbe might be too much for which to hope.

Last edited 1 year ago by John Tillman
peter schell
May 11, 2021 4:53 am

It might be fun to figure out just how many movies have been made in the last seventy-five years that feature an opening scenario somewhat like what is happening here. Returning drone carrying rock samples from space.

What could go wrong?

Hope they have very sterile and secure holding facilities prepared. ^_-

Reply to  peter schell
May 11, 2021 6:07 am

But space is a pristine environment

David Attenborough tells us that it is Hom Sap who is the intruder here.

John Tillman
Reply to  peter schell
May 11, 2021 7:15 am

The building blocks of life exist on asteroids, so living things are possible.

oeman 50
Reply to  peter schell
May 11, 2021 7:22 am

Hmm. Do you suppose a piece of The Blob is on the sample? The only thing to eat out in the Utah desert will be the scientists waiting for the capsule.

Steve Z
May 11, 2021 7:32 am

I’m wondering why the controllers of OSIRIS-REx want it to orbit the Sun twice inside the orbit of Venus before coming back to Earth, taking 2.5 years. Depending on the relative positions of Bennu and the Earth, if Bennu is farther from the Sun than Earth, the Earth would pass between OSIRIS-Rex and the Sun sometime within the next year, and the sample capsule could be recovered on Earth much earlier.

The controllers might want to use the Sun’s gravity as a “slingshot” to propel the craft toward another asteroid, but then why orbit the Sun twice inside the orbit of Venus? If it got closer to the Sun than Venus, it would be traveling faster than Venus, and without any firing of its rockets, would pass back outside the Earth’s orbit within less than a year. In order to make two orbits inside of the orbit of Venus, the craft would have to fire its rockets in order to slow down, then refire its rockets to speed up again to escape the Sun’s much stronger gravity at that distance.

Reply to  Steve Z
May 11, 2021 1:10 pm

Remember that Near Earth Asteroids are just orbiting the sun close to the Earth. The most efficient way (remember in deep space fuel is extremely precious)to get to earth is just a small boost that will change the solar orbit a bit, eventually intersecting Earth’s orbit.

I suspect the reason for the 2 solar orbits is just waiting for the new (post boost) orbit to arrive at Earth.

May 11, 2021 7:45 am

Who says mathematics is boring.
Probably the most important task is to redirect an incoming high velocity crater making size rock.

Give the rock a nudge in the right direction so it becomes someone else’s problem in a trillion years or so.

Gary Pearse
May 11, 2021 8:18 am

“This mission emphasizes why we have to do science and exploration in multiple ways – both from Earth and from up-close in space – because assumptions and models are just that,”

A beautiful project unfolding. The engineers should help their climate colleagues down the hall by sending them the above quote, noting that even with careful measurements of real objects in real time, “models and assumptions are just that”.

Climate models are are based on a single huge overarching assumption, the CO2 ‘control knob’. When they discover boulders on their research object, they simply adjust the data to clear them away.

May 11, 2021 9:20 am

the spacecraft fired its main engines full throttle for seven minutes

A throttle is depression device based on the Bernoulli effect. OSIRIS Rex is hydrazine driven. I seriously doubt this space craft has anything resembling a throttle.

Last edited 1 year ago by Greg
Bill Rocks
May 11, 2021 11:58 am

Thanks for this interesting post.

May 11, 2021 4:47 pm

I Am amazed at this engineering feat.

Reply to  Stevek
May 11, 2021 6:58 pm

Yes, it is an amazing feat. But let’s not forget the Japanese did all this back in with Hayabusa 1 launched in 2003 which eventually returned a sample of Asteroid Itokawa back to Earth. They are the real pioneers but full marks to NASA just the same for pulling off a difficult mission too. I wouldn’t like to have to do the maths!

May 11, 2021 7:20 pm

This mission is the first tiny step towards the eventual goal of space mining.

NASA will launch an exploratory spacecraft in 2022 to the Psyche asteroid (arrives at Psyche in 2026) and will orbit it for a number of years to determine its composition and topography.

Psyche is estimated to contain $10,000 quadrillion worth of metals and it’s theoretically possible we’ll have the technology to space mine in about 100 years, which is good timing as US’ national debt may be $10,000 quadrillion in a 100 years…

May 12, 2021 5:38 pm

Hmmm”’….. Doesn’t anyone on this site remember “The Andromeda Strain”? So, what could possibly go wrong, eh?

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