NASA’s first mission to touch an asteroid and collect a sample of pristine space dirt is now viewable in high-resolution images sent overnight Tuesday from 200 million miles away.
The OSIRIS-REx mission completed its first and possibly only touchdown on the asteroid Bennu at approximately 4:12 p.m. on Tuesday, as operators and engineers monitored the event from Lockheed Martin Space Systems mission control room in Littleton.
But the science team won’t know if it was mission accomplished until Saturday at the earliest, after they’ve analyzed the photos and data to gauge how much dirt, pebbles and dust from Bennu was collected by Lockheed’s 11-foot robotic arm with a ring-shaped container, called the TAGSAM, short for touch-and-go sample acquisition mechanism.
“A lot of us were up really late last night,” Dante Lauretta, principal investigator of the OSIRIS-REx mission at the University of Arizona, Tucson, said Wednesday during a media call. “We were watching the images come down one by one. By about 2 a.m. here local time in Denver, we got what I call the money shot, where we saw TAGSAM contacting the surface, and then the effect of injecting that high purity gas down into the asteroid regolith (dirt).”
A day earlier in Lockheed Martin’s ground control room, each step of the process was announced over the speaker as the OSIRIS-REx spacecraft made its descent to the asteroid, when the TAGSAM touched the surface and when a canister of compressed nitrogen gas was released to stir up the particles for the TAGSAM to collect anything that flew into its ring-shaped container. The device touched the surface for a mere 6 seconds.
The event was broadcast on NASA TV, as well as YouTube and other video sites. The hour-long build up to the actual “tag,” as the team called the touching of the asteroid’s surface, included commentary from Michelle Thaller, a scientist at NASA’s Goddard Space Flight Center, and various experts. They would pause every now and then as a voice in flight control announced updates on OSIRIS-REx’s progress to the room.
“O-Rex has processed its next image. Position uncertainty is zero-point-nine meters,” it announced.
Lockheed developed many pieces of the mission, including the OSIRIS-REx spacecraft, the TAGSAM and the container the material will be stored in for the long flight home. The University of Arizona developed several high-resolution cameras, including the SamCam that was devoted to documenting the sample capture.
The spacecraft launched into space four years ago, took two years to travel to Bennu and then another two years to orbit the asteroid and study it.
But the mission has long been the same: Get a sample of at least 60 to 2,000 grams of the carbon-rich Bennu to see if it could shed light on how the solar system came together.
“As a result, we have to have a very smart spacecraft,” Lauretta said during the broadcast build up to the tagging event on Tuesday. “It has to make its own guidance calculations and make its own decisions. In fact, instead of getting high data back, we’re only getting a very low data rate, what we call breadcrumbs, just key pieces of information from the spacecraft to tell us when key events have taken place in the TAG sequence.”
Images of the actual touchdown and capture weren’t available live on Tuesday because photos and video are too data heavy. At 200 million miles away, the data takes 18.5 minutes to travel back to Earth. And it’s not like engineers could use a joystick to maneuver the robotic arm or spacecraft.
Only after the material was collected and OSIRIS-REx backed away from the asteroid could it face its high-gain antenna towards Earth and send the data faster.
“I must have watched it 100 times last night before I finally got a little bit of shut eye,” Lauretta said.
But it will take several days to verify how much asteroid material was collected. One way is for the spacecraft to use its cameras to see if the TAGSAM picked up any sandy grains on the contact pads that hit the surface.
The team also developed a way to measure the sample so they know whether they got enough asteroid bits, said Sandra Freund, lead engineer and Lockheed Martin’s OSIRIS-REx Mission Operations Manager
To measure the amount, the spacecraft will stick its arm to the side and spin itself around.
“We’ll extend the arm and spin the spacecraft,” said Freund, noting that they already tested this out to measure the mass of the empty container. “We’ve got a pre-TAG and this will be the post-TAG. That way, we can compare the moment of inertia, which will help us determine how much mass is actually in the sampler head.”
That will happen on Saturday. If the TAGSAM didn’t collect enough material, the OSIRIS-REx will try tagging up to two more times before it’s scheduled to head back to Earth in March.
“I was hopeful that the surface was going to be soft and crushable and that was confirmed by our contact with the TAGSAM analysis of the images,” Lauretta said on Wednesday. “We still have all the confirmation activities (still needed) to verify all that but the trend right now is that we have sample and that we were successful here based on analysis of this image.”
Should the team decide another attempt must be made, it’s already been determined to take place in mid-January at an undisturbed location in a small crater called Osprey.
On Tuesday, the most exciting update for everyone in the control room came just as the spacecraft neared the asteroid.
“O-Rex has descended below the 5-meter mark. Hazard map is go for tag. Tag expected in 15 seconds. Touchdown declared. Sampling is in progress,” announced flight control.”
Blue-shirted Lockheed employees clapped and cheered and raised their arms in victory. About a minute later, the announcer shared the next update: “Sample collection is complete.”
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