NASA's asteroid mission partly made possible by Canadian technology
TORONTO -- Today, a NASA spacecraft is hoping to fulfil its four-year mission by maneuvering in close to a near-Earth asteroid called Bennu and collecting a sample of asteroid material -- a dramatic event made possible through a special, Canadian-made, piece of tech onboard the spacecraft.
The OSIRIS-REx first launched in September of 2016, and has spent the last two years orbiting Bennu, 320 million kilometres away from Earth, taking pictures and making plans in preparation of today’s sample-gathering.
That planning process relied heavily on the OSIRIS-REx Laser Altimeter (OLA), made by the Canadian Space Agency (CSA).
Using OLA, scientists were able to map out the entire surface of the asteroid in precise 3D, so that an optimal sample site could be selected.
Shortly after 6 p.m. (EST) on Tuesday, NASA confirmed on their Twitter account that the spacecraft had successfully made contact with the asteroid at the sample site and then safely backed off. Whether it was able to collect as much material as scientists were hoping for in those scant few seconds will not be known until later this evening, after more data can be beamed back to NASA.
According to the CSA, this mission marks the first time Canada has participated in a mission to collect samples from an asteroid. If a sample is successfully gathered and transported back to Earth, it is expected to shed light on not only the composition of asteroids, but also help us better understand the formation of planets.
MAPPING AN ASTEROID WITH LIGHT
OLA works by scanning the surface of the asteroid with two lasers and measuring how long it takes the light to bounce back to the spacecraft in order to pinpoint where rocks and grooves in the asteroid are, thus creating a picture of the topography.
To map the asteroid, first OLA used its high-energy laser transmitter (HELT) to create a basic map, firing more than 11 million laser pulses at Bennu at 100 pulses per second.
The final, high-resolution 3D map of the surface was achieved by the more precise measurements of the second laser, the low-energy laser transmitter (LELT), which fired 10,000 light pulses per second at Bennu from less than one kilometre away from the asteroid’s surface.
A study on OLA’s map published this month revealed that the data was actually the most detailed 3D measurements taken of any asteroid or other celestial body yet.
One OLA scan that took just five minutes contained more than 3.3 million measurements. In total, the entire map of the asteroid contains almost three billion individual measurements, according to CSA’s website, each data point spaced less than five centimetres apart on average.
Tim Haltigin, the Canadian Mission Manager on the OSIRIS-REx mission, said in a video on CSA’s website that mapping the surface of the asteroid in perfect detail was extremely important to plan the sampling.
Both the spacecraft and the asteroid are hurtling through space, so it takes exact calculations to match them up without a collision.
“When we’re going in to take a sample, it’s a very, very fine measurement,” Haltigin said in the video. “And so if you’re coming in, you’ve got the sampling head at the end of this arm that has to come in perfectly square to the surface. If you don’t understand shape at sort of a 30-centimetre scale, you’re not going to be able to collect a sample.”
When looking for a good sample site, scientists were scrutinizing OLA’s map to see how accessible and safe a region was, whether it had landmarks that the spacecraft could use to navigate towards it, and whether it contained the fine-grained material that the spacecraft’s arm could fit when collecting a sample.
Eventually, out of four potential sample sites, a site called “Nightingale” was chosen in December of 2019.
This site -- only as wide as a few parking spaces and ringed by massive boulders the size of buildings -- is the one OSIRIS-REx successfully rendezvoused with today. In the process, its arm extended and made contact with the asteroid briefly before the spacecraft backed away. In those few seconds, if all went to plan, the spacecraft should have collected a sample between two ounces and two kilograms. Because of communication delays, and the fact that the spacecraft needs some time to cool off following its daring manoeuvre, NASA scientists on the ground won’t receive the photos and data taken by the spacecraft during the process until later this evening, which should let them know how much sample was obtained.
Although the spacecraft successfully touched down on Bennu today, it hasn’t been a completely even road for the mission. After OLA created its map of the surface, scientists realized that the asteroid was much more rugged than they had anticipated, making it harder to find a sample site.
OLA also went through struggles in early 2020, when it was discovered during a flyover of one of the backup sample sites that one of the laser subsystems on the OLA, the LELT, was not operating properly. Luckily, this was after the high-definition map of the asteroid’s surface had been put together.
If OSIRIS-REx doesn’t collect enough asteroid material today, but is still in working order, it will go in for another try later this year.
Because of Canada’s contribution to the historical mission with the OLA, a portion of the asteroid sample will come here when the spacecraft makes its way home in 2023.
A previous version of the story incorrectly stated Bennu was 320 kilometres away from Earth.