On Saturday, NASA’s Lucy spacecraft will become the first-ever probe launched toward the Trojan asteroids, eons-old rocks trapped in Jupiter’s orbit. These rocks are the fossilized building blocks of our solar system and may hold records of the giant planets’ evolution.
But for Lucy to make history and ultimately unlock secrets of our corner of the universe, this weekend’s liftoff must be flawless. Given the spacecraft’s unique trajectory — billions of miles will be covered over a dozen years by harnessing the power of the sun — there are a few checkpoints poised to keep mission specialists on their toes.
As outsiders, we usually only stare in astonishment as rockets launch, engulfed in flame and smoke. But there’s much more to Lucy’s success than just its fiery departure from Earth. I spoke with one of the spacecraft’s engineers from Lockheed Martin and got the inside scoop on what milestones her team will be watching for during liftoff.
Here’s the launch sequence from the eyes of NASA.
“When the rocket lifts off from the ground, that’s very visual and exciting,” said Emily Gramlich, a system integration and test engineer at Lockheed Martin and a Lucy mission specialist. “As the rocket ascends, we go through the atmosphere.”
During that phase, Lucy will reach its maximum speed and pressure. “Then,” Gramlich continued, “we have separation from the boosters and then the bearing will deploy and open us up to outer space.”
Lucy’s epic launch doesn’t end there. Arguably the most crucial part of the launch pattern will be the unfurling of the spacecraft’s two solar arrays after its 62-mile (100-km) journey up into space.
When fully open, the arrays together reach the height of a five-story building. “They are enormous,” Gramlich said. It will take about 20 minutes to completely extend them from their origami-like folds.
They’re so large because Jupiter’s orbit, where Lucy is headed, is so far from the sun. And Lucy will need all the sun power it can get to travel those 530 million miles (853 million km).
“These 20 minutes will determine if the rest of the 12-year mission will be a success,” NASA planetary scientist and principal investigator of the Lucy mission, Hal Levison, said in a statement.
“Mars landers have their seven minutes of terror, we have this,” he said.
After the solar arrays stretch out in their entirety, Lucy will have another vital task: It must adjust itself so the sun can shine onto all the solar panels that make up the two arrays. Without sun, the solar panels cannot provide power. Without power, the mission is over.
“Once we’ve done that,” Gramlich said, “the spacecraft will then move itself a little bit more so that it can also point its antenna down at the Earth, so we can get our initial acquisition.”
Let me repeat that last bit: “initial acquisition.” That means every step up to that point is pre-programmed. That’s right. No one will be controlling the spacecraft during its most crucial moments. Each precise movement has already been coded into its software.
“Lucy has been encapsulated since last week and so we have not seen it … other than through a small access window,” Gramlich said. “The next time it will be open is out in outer space.”
NASA engineers will just have to sit tight and keep their fingers crossed until Lucy finds its cosmic footing.
You name it, Lucy’s been through it. Several times.
“We do an acoustic test and a vibration test in a large building on the Waterton campus,” said Gramlich referring to Lockheed Martin’s testing grounds in Colorado. “We shake the spacecraft really hard and then we blast it with sound to simulate mostly the launch.”
The most physically intense part of Lucy’s 12-year journey, she said, will be the launch happening this weekend. Once it’s in space, the situation will become much calmer. But space has its own extremes, so the team has tried to ensure that Lucy will be shielded from those, too.
“We take the spacecraft and put it into a giant thermal chamber and run it through all the temperature ranges that it is going to see in space — hot and cold, light and no light,” Gramlich said.
Lucy’s complexities aren’t only in regard to its mechanics. The software piloting the metal space explorer has a sizable number of integral components, like the computer, thermometer, cameras and battery. Each one had to be tested over and over again.
Gramlich explained one important device on Lucy is the star tracker that helps with navigation similar to how the north star aids in deducing what direction we’re facing.
“We have extra ground support equipment to simulate the star that it might be seeing,” she said. “And to rotate those stars and make sure that the star tracker detects that the stars [actually] rotated on its little simulator.”
Once Lucy stabilizes and beyond
“I am beyond excited to see Lucy lift off on Saturday,” Gramlich said. “We have been working towards this launch date for a long time, and there are a lot of long hours in the pandemic, and I have been just extra energetic for the last few weeks.”
If all goes well on NASA’s launch day on Saturday, Lucy will continue on toward the Trojan asteroids at about 39,000 mph (62,764 kph). It will use Earth’s gravitational pull as leverage during the long journey and visit seven of the prized ancient rocks. It’ll also make a pit stop on another world between Mars and Jupiter.
During the expedition, Gramlich said the team will check up on Lucy about once every two weeks to input commands based on newly discovered information, such as photographs and spectroscopic data, about the asteroids that Lucy sends back to Earth. Each command will take about 55 minutes to reach the craft, she said.
And after the mission wraps up next decade, the possibilities are endless.
“Our last flyby is in 2033,” Gramlich said. “We will have done three Earth flybys by then, and have learned a lot about our trajectory and how to make it most efficient to continue exploring other asteroids.”
Calling that an extended mission, Gramlich says Lucy’s solar arrays can continue powering the spacecraft as it traverses through the solar system indefinitely. That means Lucy can theoretically continue sending information back about other forms of cosmic matter.
“The solar arrays that we have for Lucy are incredibly efficient and will allow us to operate the spacecraft for a long time,” she said. “Even out at the distances of Jupiter. And the battery on board is also designed to be used and recharged.”
But first, Lucy must get past its legendary launch.
“I am so honored that I was part of this team to see how much everybody cares and put into it,” Gramlich said.
“We are just ready for a successful science mission to the Trojans.”
Correction, 2:20 p.m. PT: An earlier version of this story misstated where one of the spacecraft’s engineers works. Emily Gramlich works for Lockheed Martin. Also, the deck headline was changed to clarify that the Trojan asteroids share Jupiter’s orbit.