A Canadian instrument made NASA’s asteroid retrieval possible – and its job is still not over
By Alexandra Mae Jones/CTVNews.ca writer
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Toronto, Ontario (CTV Network) — In a little over a week, samples from the asteroid Bennu will streak down to Earth, a landmark achievement which couldn’t have been achieved without Canadian help.
On Wednesday, scientists with the Canadian Space Agency (CSA) dove into how a specialized instrument provided by Canadian experts allowed the OSIRIS-REx spacecraft to gather the highly-anticipated samples, and how Canada is going to continue to play a role in the analysis of those samples, as well as the spacecraft’s continuing mission.
After seven years in space, the OSIRIS-REx spacecraft will cruise by Earth on Sept. 24 and drop its sample capsule, which will land safe and sound in the Utah desert, if all goes according to plan. The capsule is believed to carry around 250 grams of samples taken from the asteroid Bennu, but the exact amount won’t be known until it’s cracked open.
The OSISIS-REx Laser Altimeter (OLA), which was supplied for the mission by CSA, allowed the spacecraft to create an exquisitely detailed 3D map of the asteroid.
“OLA played a really key role,” John Moores, science advisor to the president of the CSA, said in the digital news conference Wednesday. “It helped the mission team select the best location from which to gather that sample of the asteroid, the one that will be coming back to Earth shortly, and in exchange for this contribution, Canadian scientists have been on the OSIRIS-REx science team from the very beginning.”
Canada will become the fifth country in the world to receive a sample collected in space, Moores noted. It will receive four per cent of the total sample for analysis, and is working on building a facility to house it. Prior to this, scientists at NASA will provide a preliminary report on the contents of the sample capsule in early October.
The samples could shed light on how our solar system came to be and even potentially answer bigger questions about the origins of the Earth.
“It’s been an incredibly exciting mission, and it’s unbelievable really, to think that we’re less than two weeks away from the sample coming back to Earth,” Timothy Haltigin, planetary senior mission scientist with CSA, said. “I love a lot of things about the mission, but I think what I love the most is that it gives us the ability to not only go out and explore the solar system as it is today, but rather this is a mission that allows us to go back in time and explore the very formation of the solar system.”
RENDERING THE CLEAREST PICTURE OF AN ASTEROID YET In 2020, OSIRIS-REx successfully obtained samples from the asteroid Bennu after circling it for 18 months, taking careful measurements.
The most important measurements for sample retrieval were those taken by a box just under the size of a microwave oven. OLA is a lidar machine; while radar uses radio frequency waves, lidar uses light pulses.
“How this works is we send out a little pulse of laser light, it scatters off an object, such as Bennu, and then that light comes back towards our instrument and then we detect it,” Cameron Dickinson explained. Dickinson is a staff engineer at MDA Ltd., a Canadian space technology company that works with CSA.
“By carefully measuring the time that it takes the pulse to go out and to come back, and because we know the speed of light so precisely, we can very, very accurately determine distance for each laser pulse.”
With the aid of a specialized mirror that directs the beam of light across a surface, scientists were able to use this method to scan a broader area and create detailed maps.
When OSIRIS-REx first approached the asteroid, OLA took its measurements from around seven to eight kilometres away from Bennu’s surface. One of the asteroid’s first surprises for them was that there were chunks of rock orbiting the asteroid, pieces of it that had broken off or never fully adhered. The surface was also much rockier than scientists had expected, underlining the importance of OLA’s map to help them find the safest place to touch down on the asteroid.
“Over the course of this mission, Bennu has thrown a lot of curveballs our way,” Dickinson said.
At one stage in building the map of Bennu, the spacecraft sat just 700 metres above the surface of the asteroid as it rotated beneath it. Images of OLA’s scans show highly detailed terrain, with finely rendered textures and individual rocks.
“In total, we laid down more than three billion range measurements on the surface of Bennu,” Dickinson said.
“Bennu is now the most precisely surveyed body in our solar system, which is really exciting that Canada was able to not only participate in this, but provide the instrument that provides such a detailed look at one of these bodies in our solar system.”
Once scientists had selected the sampling site based on OLA’s map of the surface, the spacecraft moved in for the kill. But the asteroid still had one more surprise for the team.
“Bennu didn’t really put up much of a fight for the sampling device,” Mike Daly, OLA lead instrument scientist and a professor at York University’s Lassonde School of Engineering, said in the press conference.
He explained that the sampling head, about 30 cm in diameter on the end of a three-and-a-half-metre robotic arm, was designed to suck rocks and dust into it by blasting nitrogen into the surface of Bennu after making physical contact.
“Like a vacuum, but we had to bring our own air,” he said. “So it’s like a reverse vacuum cleaner.”
But the surface was far less solid than they’d anticipated.
“(The) spacecraft was still moving into Bennu six seconds after its first touch, and it went half a metre below the surface of Bennu. This was a big surprise, how weak the surface was,” Daly said.
“Our best estimates are that we’ve got 250 grams of sample, plus or minus 100 grams or so. This is much greater than the mission requirement of 60 grams and we’re going to be able to do a lot with it.”
BUILDING A DEDICATED FACILITY IN CANADA Although Canada won’t receive its portion of the asteroid sample right away, scientists are making plans for how to best house it already.
“We’re not on the same timeline as NASA to receive the sample, it’s been understood since the beginning, the sample will reside at NASA for a time before it’s transferred to Canada,” Caroline-Emmanuelle Morisset, Program Scientist in Space Exploration Development at CSA, said in the press conference. “We should get between six and 14 grams.”
With even a few milligrams of asteroid sample, they “can do a lot of science,” she said, pointing out that Japan Aerospace Exploration Agency’s Hayabusa 2 mission brought back only five grams of asteroid samples in 2020, and those samples are still being analyzed.
Canadian scientists say they will have the opportunity to study samples before Canada receives its four per cent, but in order to accept our official portion of the sample, they will need a place to host the samples.
“We’re working on developing the facility for receiving the sample at CSA, and there was an RFP (request for proposals) that was out in the spring for the construction of the room. That’s where we’re at now,” Emmanuelle-Morisset said.
The facility would be equipped with what is called a “clean room,” to ensure that the samples are not contaminated by particles from the air on Earth, containing glove boxes that would allow scientists to manipulate the samples without actually touching them or removing them from a sealed environment.
The exact timeline for receiving the samples at a facility in Canada is not yet known.
OLA CONTINUING ON TO ASTEROID NUMBER TWO Although the OSIRIS-REx spacecraft will be dropping off the sample capsule this month, its journey is far from over. The spacecraft is going to continue travelling through space towards a new target: the asteroid Apophis, which is named after the Greek term for an Egyptian god of chaos.
When it was first detected, Apophis loomed as a potentially imminent threat to the Earth, but a distant flyby in 2021 let astronomers update their measurements to reflect that the asteroid won’t come near to colliding with Earth within the next century. However, it will draw relatively near in 2029, and this is when the OSIRIS-REx spacecraft will have a chance to rendezvous with it.
That’s the plan, at least. In the spring of 2024, the OSIRIS-REx spacecraft will have to fly closer to the sun than it was originally designed to in order to put it on the path towards Apophis.
“At that point, the entire team, including Canada, will evaluate the health of the spacecraft and the health of all the instruments to proceed past that,” Haltigin said.
If all is well, OLA will get to scan another asteroid. But it won’t be like the scans it took of Bennu for a couple of reasons, according to Daly, who will still be continuing to work with the OSIRIS-REx project as it transforms into its new mission.
The first reason is that Bennu was “pretty well-behaved,” and had a predictable rotation, while Apophis does not. The spacecraft won’t be able to get as close to take its measurements.
The second reason is that OLA gave its all to scan Bennu, and some of its lasers are simply used up.
“I think the very first estimates I put together for the Orbital B phase suggested we would do two to three hundred million measurements of Bennu. We did 2.7 billion measurements of Bennu,” Daly said. “So it was a great success, however we used up that laser. So we’re going to be measuring Apophis probably from a little further distance out, which forces us into our 100 measurements-a-second laser, and we no longer have the 10,000 measurements-per-second laser in any case.”
The scientists will still get very detailed images of Apophis, he added, just not as incredibly detailed as the ones taken of Bennu.
“We’re really proud of what Canada accomplished here,” he said of OLA’s success with Bennu.
The arrival of the Bennu samples later this month is just the beginning, Haltigin said. Asteroids like Bennu are pieces left over from the process that created our planets billions of years ago, he explained, and “sort of preserve the conditions and the materials from the very beginning of the solar system.”
Studying planets by looking at their composition as it appears today is like looking at a finished chocolate chip, he said. All the ingredients have been mixed together and transformed in the process.
“Getting a sample from an asteroid is sort of like going back into a cosmic mixing bowl and pulling out individual grains of sugar and a bit of flour and maybe a chocolate chip,” he said.
“As a planetary scientist, one of the most fundamental questions we ask is, ‘How do planets form and how do they evolve?'”
Bennu, scientists believe, may hold some of those answers. And in two weeks, we’ll begin to find out.
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