Approximately 80 million miles from the Earth, a spaceship extends.
The probe slowly extended the 11-foot robotic arm this week, something he did not do before his 2016 release. This movement is a precursor to making history, as the robotic arm test this week is a preamble to the final goal of the mission, when the spacecraft will lower the surface of an asteroid to collect a sample.
In December, this intrepid probe, called OSIRIS-REx (Origins, spectral interpretation, resource identification, security, Regolith Explorer) or O-REx (as engineers call it) will reach Bennu, an asteroid of the size of the Empire State Building. When he does, Bennu will become the smallest celestial body that a spacecraft will orbit.
"You are on the list of projects to claim Guinness Book of World Records, when the time comes," says Sandy Freund, Lockheed Martin's operations manager for O-REx.
A complicated landing
Astronomers discovered the asteroid 101955 Bennu in 1990. It is classified as an asteroid type B, with a diameter of 500 meters and 100 floors in length.
This is quite small by cosmic standards, but dangerously large given the thin possibility that this asteroid could reach Earth one day. Every six years, Bennu swings near the Earth – within 65,000 miles, which is closer to the moon. That fact puts a sense of urgency when knowing the composition of asteroids near the Earth like Bennu.
"The longer it is in contact with the surface of the asteroid, the more its design is subject to the uncertainties of surface properties."
To get O-REx in an asteroid, since obstacles in space require careful aircraft, serious engineering and some conjectures. Bennu is too small to have an atmosphere to diminish the spacecraft and without gravity being useful on the surface.
But scientists actually know very little about what is going on this boat, whether it's an implacable rocky surface or a landing area full of regulations, so that O-REx will only connect to the surface for a few seconds. This tactic and tactics required the creation of a collection header called Touch-and-Go Sample Arm Mechanism (TAGSAM).
"We do not really know the surface properties of an asteroid," says Beau Bierhaus of Lockheed. "The asteroid will be what it is going to be".
A solid and disposable surface would require machines that react against it, similar to a gravel bed, but that same system could sink into the surface of an asteroid covered by a soft bed of regolith. But Bennu is so unknown, the engineers did not know what to expect.
"It is said that a landing system to accommodate this whole range of scenarios is very challenging," says Bierhaus. "One of the key design decisions we converge relatively early is that we want the sampling to be done quickly, because the longer it is in contact with the surface of the asteroid, the more its design is subject to the uncertainties of surface properties."
Rendezvous from a dangerous asteroid
Our image of Bennu is becoming clearer since O-REx approaches its objective.
"We had data taken from the Spitzer Space Telescope and we even have a radar-shaped model, so we already know some volumes or some rough aspects of this asteroid for a while," says Bierhuas. "But we really did not know that it really is. And only a few weeks ago, after 10 years of asking, now we are finally seeing how Bennu really is. So yes, the sense of emotion with the whole world is quite exceptional" .
Sandy Freund joined O-REx in late 2013, first as a TAGSAM engineer, working on integrating the payload for the launch and now as the head of Lockheed's missions operations team. The focus on O-REx is becoming increasingly intense, she says, because the mission "is at the heart of science."
The ship will officially come to Bennu on December 3 and will launch a series of flybys to examine the asteroid in unprecedented details, helping researchers understand how asteroids move around the solar system. One question, which scientists expect to answer, is how sunlight can change the conditions of an asteroid surface that can also influence its trajectory. The trade will also map the chemistry and mineralogy of this carbon-rich asteroid, a point of interest for all those interested in a future career in space mining.
In the coming months, O-REx will begin the first steps of its ambitious return mission. Next year, the ground team will start a preprogrammed automatic sequence that will bring the spacecraft a few meters from the surface.
"We can not be in the cycle just due to [seven-minute] waiting time we have, "says Freund." Then, we will send the ground commands to start essentially TAG and, from that point on, it will be autonomous. "
Asteroid sampling per unit
Following the tests this week, the O-REx robot arm will expand to the necessary position to touch the surface. The circular pickup device is at the tip of the arm, and the round face is the only part of the spacecraft that touches Bennu, resting on the surface. The contact pushes springs that trigger a burst of nitrogen gas that shakes pieces of the regolith. These are collected, and then O-REx moves away from the surface. The entire process will take five seconds, but the engineers have enough fuel to make several attempts.
"We can try many times," says Freund. "The limiting factor is the number of bottles [of nitrogen] that we carry. "And they only have three.
The use of nitrogen speaks the demand of the mission of pristine samples. The mission, among other things, is the hunting of organic matter in asteroids, which includes molecules such as carbon and hydrogen. Nitrogen does not react to anything, so it's great to preserve documents such as the Declaration of Independence and safely defuse fuel from rocket engines.
"We will meet a few hours after the TAG event that the sequence was executing as expected," Freund says. "But really, the measure of success is how we showed and that is a process of several days for us."
This extreme and ambitious mission has many milestones to go through, but even the team of engineers who built it says that science is more convincing than machinery.
"OSIRIS-REx, by virtue of the material returned from Bennu, is receiving the first ingredients that led to the formation of the Earth," says Bierhaus. "We started to solve these really strange engineering challenges, but they're basically going after these really big questions."
April 12, 2019