Tag Archives: Bennu

OSIRIS-REx’s first survey of Bennu

The OSIRIS-REx science team has released a short movie of Bennu made up of images taken by the spacecraft’s navigation camera during its preliminary approaches to the asteroid from November 30 to December 31, 2018.

You can watch it here. Because this is the navigation camera, the view is generally from far away. Nonetheless, you can see that during the passes over the north pole, the equator, and the south pole, the asteroid’s entire surface became visible as the asteroid rotated. From this they will be able to use the images taken by the high resolution cameras to create an excellent detailed global.

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OSIRIS-REx moves into close orbit with Bennu

OSIRIS-REx has successfully completed an eight second engine burn to place it into a close orbit with the asteroid Bennu.

Now, the spacecraft will circle Bennu about a mile (1.75 kilometers) from its center, closer than any other spacecraft has come to its celestial object of study. (Previously the closest orbit of a planetary body was in May 2016, when the Rosetta spacecraft orbited about four miles (seven kilometers) from the center of the comet 67P/Churyumov-Gerasimenko.) The comfortable distance is necessary to keep the spacecraft locked to Bennu, which has a gravity force only 5-millionths as strong as Earth’s. The spacecraft is scheduled to orbit Bennu through mid-February at a leisurely 62 hours per orbit.

There is a bit of hype here. Other spacecraft have gotten far closer (NEAR, Hayabusa-1, Hayabusa-2) but then retreated for a variety of reasons. What makes this different is the plan to stay this close while they compile detailed data about Bennu’s surface in preparation for touchdown to grab a sample.

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OSIRIS-REx flies over Bennu’s north pole

Bennu's north pole

Cool movie time! OSIRIS-REx has completed its first planned fly-over of Bennu, this time above its north pole, and the science team has released a short movie showing part of that fly-over. I have embedded the movie below the fold.

This series of MapCam images was taken over the course of about four hours and 19 minutes on Dec. 4, 2018, as OSIRIS-REx made its first pass over Bennu’s north pole. The images were captured as the spacecraft was inbound toward Bennu, shortly before its closest approach of the asteroid’s pole. As the asteroid rotates and grows larger in the field of view, the range to the center of Bennu shrinks from about 7.1 to 5.8 miles (11.4 to 9.3 km).

They have four more fly-overs of the asteroid’s poles and equator as they assemble a detailed map of its surface.
» Read more

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Comparing Ryugu and Bennu

Link here. As much as they are alike, which is not surprising as they both come from the same asteroid family, the article notes the surprising differences.



Both asteroids are also liberally strewn with boulders – a challenge to mission planners on each team, who hope to descend close enough to scoop up samples for return to Earth. “It’s certainly more rugged than we had expected,” Lauretta says. 

But while boulders on Ryugu look to be unpleasantly ubiquitous, Bennu’s terrain is more varied, with more-obvious places where a safe touchdown might be possible. And, Lauretta notes, the OSIRIS-REx spacecraft is only recently arrived.

“We have a long time to explore and make the crucial decisions about where to go,” he says.

The biggest difference has to do with water. Even though scientists believe them to be portions of the same parent body, which broke apart between 800 million and one billion years ago, Bennu appears to be water rich, while Ryugu is less so. Within a week of arrival, infrared spectrometers on OSIRIS-REx were finding evidence of water-bearing minerals, and not just in localised patches. “We saw this in every single one of the spectra we have taken to date,” says Amy Simon, of NASA’s Goddard Space Flight Centre in Greenbelt, Maryland. 

One of the reasons Bennu was chosen as OSIRIS-REx’s target, Lauretta says, was the hope it would be rich in water, and possibly in organic compounds.

The similarities and differences in the samples both spacecraft will bring back will be most revealing.

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OSIRIS-REx finds evidence of water on Bennu

Bennu from 15 miles

One of OSIRIS-REx’s instruments has now found evidence of water on the rubble-pile asteroid Bennu.

Recently analyzed data from NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) mission has revealed water locked inside the clays that make up its scientific target, the asteroid Bennu.

During the mission’s approach phase, between mid-August and early December, the spacecraft traveled 1.4 million miles (2.2 million km) on its journey from Earth to arrive at a location 12 miles (19 km) from Bennu on Dec. 3. During this time, the science team on Earth aimed three of the spacecraft’s instruments towards Bennu and began making the mission’s first scientific observations of the asteroid. OSIRIS-REx is NASA’s first asteroid sample return mission.

Data obtained from the spacecraft’s two spectrometers, the OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) and the OSIRIS-REx Thermal Emission Spectrometer (OTES), reveal the presence of molecules that contain oxygen and hydrogen atoms bonded together, known as “hydroxyls.” The team suspects that these hydroxyl groups exist globally across the asteroid in water-bearing clay minerals, meaning that at some point, Bennu’s rocky material interacted with water. While Bennu itself is too small to have ever hosted liquid water, the finding does indicate that liquid water was present at some time on Bennu’s parent body, a much larger asteroid.

The image on the right, reduced to show here, was created from 12 images taken on December 2, 2018 from about 15 miles. If you click on the image you can see the full resolution photograph, which is quite incredible. While the asteroid’s shape is approximately what was expected from ground-based observations and computer modeling, the giant boulder on the limb on the bottom right is about four times bigger than expected.

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Calculating Bennu’s future

In order to better constrain Bennu’s future fly-bys of the Earth, including the possibility that it could impact the planet, scientists will be using the data sent from OSIRIS-REx to better understand its orbit, its composition, its surface make-up, and its thermal properties, all factors that can influence its future path in space.

This is really important, as Bennu has a good chance of hitting the Earth in the future.

About a third of a mile, or half a kilometer, wide, Bennu is large enough to reach Earth’s surface; many smaller space objects, in contrast, burn up in our atmosphere. If it impacted Earth, Bennu would cause widespread damage. Asteroid experts at the Center for Near-Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory in Pasadena, California, project that Bennu will come close enough to Earth over the next century to pose a 1 in 2,700 chance of impacting it between 2175 and 2196. Put another way, those odds mean there is a 99.963 percent chance the asteroid will miss the Earth. Even so, astronomers want to know exactly where Bennu is located at all times.

The article provides a good overview of the difficulty of properly calculating Bennu’s orbit into the future, and how the data from OSIRIS-REx will help make those calculations more precise.

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OSIRIS-REx at Bennu

OSIRIS-REx has successfully completed its last maneuver engine burn to place it in proximity orbit around the asteroid Bennu.

The link takes you to the live NASA stream, which has been a bit hokey. This event is actually not that visually exciting, a bunch of engineers staring at computer screens awaiting data back from the spacecraft indicating that all has occurred as planned. In fact, some felt a bit staged, though the actual event was really happening.

The OSIRIS-REx team has released relatively little data so far, compared to most NASA missions. There will be a press conference in a week when they say they will release more information. I guess we will have to wait until then.

Update: the live stream has shifted to the docking of the manned Soyuz capsule at ISS, which is in itself a more riveting event than OSIRIS-REx’s last engine burn.

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OSIRIS-REx unfolds its robot arm

In preparation for its December 3 rendezvous with the asteroid Bennu OSIRIS-REx successfully unfolded its robot arm for the first time since launch this week.

The website has a nice short video showing how the arm will grab its samples. Very innovative, and not what you would expect. The technique had to be clever because Bennu is so small and has such a tiny gravity.

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Bennu’s two hemispheres

Bennu's two hemispheres

The image above of the two hemispheres of the asteroid Bennu, cropped and reduced very slightly to post here, was created from several images taken by OSIRIS-REx on two different days last week.

These two super-resolution views of asteroid Bennu were created using eight 2.5-millisecond exposure images captured by OSIRIS-REx on two separate days. The view on the left is composed of eight PolyCam images taken over the span of two minutes on Nov. 1, 2018, when the spacecraft was about 126 miles (203 km) from the asteroid. The one on the right – showing the opposite side of the asteroid – was generated using eight images taken during the same two-minute time slot on Nov. 2, from a distance of about 122 miles (196 km).

The rock on the southern limb is the same in both images, merely seen from opposite sides. Bennu appears very similar to Ryugu, except that there do appear to be dark areas on its surface, possibly crater sites, that might be smooth enough for landing.

The rendezvous at Bennu will occur on December 3.

UPDATE: The OSIRIS-REx science team has now released a short movie showing Bennu’s rotation as imaged during this same time period.

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OSIRIS-REx snaps image of target asteroid Bennu

Bennu

OSIRIS-REx has snapped its sharpest image yet of its target asteroid Bennu, set for a rendezvous on December 3. The image on the right is that image, at full resolution but cropped.

This “super-resolution” view of asteroid Bennu was created using eight images obtained by NASA’s OSIRIS-REx spacecraft on Oct. 29, 2018 from a distance of about 205 miles (330 km). The spacecraft was moving as it captured the images with the PolyCam camera, and Bennu rotated 1.2 degrees during the nearly one minute that elapsed between the first and the last snapshot. The team used a super-resolution algorithm to combine the eight images and produce a higher resolution view of the asteroid. Bennu occupies about 100 pixels and is oriented with its north pole at the top of the image.

It is beginning to appear that the OSIRIS-REx engineering team is going to have the same kind of problems now faced by the Hayabusa-2 engineering team. In this first glance Bennu appears very similar to Ryugu, a rubble pile shaped approximately like a box, rotating on one point. If so, they are also going to find it difficult to locate a smooth landing site.

Bennu by the way is in an orbit that makes a collision with the Earth possible in the late 22nd century. Knowing its composition, density, and solidity is critical for determining what to do, should that collision become likely.

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OSIRIS-REx makes second course correction

OSIRIS-REx, on its way to a December rendezvous with the potentially dangerous asteroid Bennu, successfully made its second course correction last week.

Rendezvous is scheduled for December 3rd. The probed will orbit the asteroid for about six months, then dive in to get a sample in July 2020, returning it to Earth in 2023.

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ULA shuffles Atlas 5 schedule

ULA has rearranged the upcoming launch schedule of its Atlas 5 in the wake of its investigation of the valve issue that causes a premature shutdown of the first stage Russian engine during the Cygnus launch in March.

Originally they had intended to do three launches before the September 8 launch of NASA’s Osiris-REX asteroid mission. Now they will only do two, to give them additional time to test the rocket that will launch Osiris-REX.

August will be spent stacking an Atlas 5 rocket with a single solid booster, the 411 configuration, and rolling the vehicle to the pad for a rare countdown dress rehearsal to ensure systems are operating correctly ahead of the time-sensitive launch of NASA’s OSIRIS-REx probe to asteroid Bennu.

The spacecraft has a launch window that closes October 12.

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OSIRIS-REx to get more fuel for its asteroid mission

In what might be a first for the planetary science/engineering community, an unmanned probe, being built to bring samples back from the asteroid Bennu, is turning out to be lighter than expected, thus allowing engineers to stuff its tanks with extra fuel to extend its mission.

The OSIRIS-REx spacecraft, being built at a Lockheed Martin facility in Denver, is coming in lighter than the lift capability of the Atlas 5 rocket, which will lift off in its “411” configuration with a four-meter payload fairing, a single-engine Centaur upper stage, and one strap-on solid rocket booster.

The proposal — described as a “heavy launch option” — would add an extra 341 pounds of fuel to the spacecraft’s fuel tank.

Planetary probes never end up lighter than planned, at least until now. During construction scientists have always found it impossible to resist adding more instruments or capabilities, and thus engineers always struggle to get the spacecraft built within its weight budget. For OSIRIS-REx to have this wonderful problem is surely astonishing.

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In a NASA contest, a nine-year-old has named asteroid 1999 RQ36 after the Egyptian god Bennu.

A rose by any other name: In a NASA contest, a nine-year-old has named asteroid 1999 RQ36 after the Egyptian god Bennu.

1999 RQ36, or Bennu, is an important asteroid for two reasons. First, NASA is sending an unmanned sample return mission to it in 2016. Second, some calculations suggest the asteroid has a 1 in a 1000 chance of hitting the Earth in 2182.

In other naming news, the private space company Uwingu has launched its “Adopt-a-Planet” campaign.

This open-ended campaign gives anyone in the public—worldwide—the opportunity to adopt exoplanets in astronomical databases via Uwingu’s web site at www.uwingu.com. Proceeds from the naming and voting will continue to help fuel new Uwingu grants to fund space exploration, research, and education.

As noted earlier, they are ignoring the IAU’s stuffy insistence that only the IAU can name things in space.

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