Following the successful launch of NASA’s Lucy spacecraft on October 16, 2021, a group of engineers gathered around a long conference table in Titusville, Florida. Lucy was only a few hours into her 12-year flight, but an unexpected challenge had presented itself to the first Trojan asteroid mission.
The data showed that one of Lucy’s solar arrays that power the spacecraft’s systems — designed to unfold like a fan — hadn’t fully opened and locked, and the team was figuring out what to do next.
Teams from NASA and the Lucy mission partners were quickly assembled to address the problems. On the phone were team members at Lockheed Martin’s mission support area outside Denver, who were in direct contact with the spacecraft.
The conversation was quiet, but intense. At one end of the room, an engineer sat with furrowed brows, folding and unfolding a paper plate in the same way that Lucy’s huge circular solar arrays work.
Credit: NASA Goddard Space Flight Center
There were so many questions. What happened? Was the battery open at all? Was there a way to fix this? Could Lucy safely perform the maneuvers required to complete her science mission without a fully deployed array?
With Lucy already speeding through space, the stakes were high.
Within hours, NASA assembled Lucy’s anomaly response team, made up of members from the Southwest Research Institute (SwRI) science mission lead in Austin, Texas. mission operations lead NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Spacecraft manufacturer Lockheed Martin. and Northrop Grumman in San Diego, a designer and manufacturer of solar array systems.
“This is a talented team, steadfastly committed to the success of Lucy,” said Donya Douglas-Bradshaw, former director of the Lucy program at NASA Goddard. “They have the same grit and dedication that led us to a successful launch during a once-in-a-lifetime pandemic.”
United in their quest to ensure Lucy reaches her full potential, the team embarked on an exhaustive deep dive to determine the cause of the problem and develop the best way forward.
Since the spacecraft was otherwise perfectly healthy, the team was in no rush.
“We have an incredibly talented team, but it was important to give them time to understand what happened and how to move forward,” said Hal Levison, Lucy’s principal investigator from SwRI. “Fortunately, the spacecraft was where it was supposed to be, operating nominally and – most importantly – safe. We had time.”
Staying focused for many long days and nights, the team worked through options. To assess the configuration of Lucy’s solar array in real time, the team fired thrusters on the spacecraft and collected data on how those forces caused the solar array to vibrate. They then fed the data into a detailed model of the array’s motor assembly to infer how stiff Lucy’s array was – which helped reveal the source of the problem.
Finally, they’ve nailed down the root cause: A cord designed to open Lucy’s massive solar array was likely snarling on its bobbin-like spool.
After months of further brainstorming and testing, Lucy’s team settled on two possible paths forward.
In one, they would pull the string harder by running the array’s backup deployment engine at the same time as its main engine. Power from two motors should allow the jammed cord to wind further and engage the array’s locking mechanism. While both engines were never meant to work at the same time, the team used models to ensure the concept would work.
The second option: Use the battery as it was—almost fully developed and producing more than 90% of its expected power.
“Each route involved some element of risk in achieving the basic science objectives,” said Barry Noakes, Lockheed Martin’s chief space exploration engineer. “A big part of our effort has been identifying preventative actions that mitigate the risk in both scenarios.”
The team mapped and tested possible outcomes for both options. They analyzed hours of the array’s test video, built a ground-based replica of the array’s motor assembly, and tested the replica beyond its limits to better understand the risks of further development efforts. They also developed special high-fidelity software to simulate Lucy in space and measure any potential ripples that a realignment attempt might have on the spacecraft.
“The collaboration and teamwork with our mission partners has been phenomenal,” said Frank Bernas, vice president, space components and strategic operations, Northrop Grumman.
After months of simulations and testing, NASA decided to go with the first option – a multi-step effort to completely rearrange the solar array. On seven occasions in May and June, the team instructed the spacecraft to simultaneously operate the primary and backup solar array deployment engines. The attempt succeeded, pulling the cord and opening and stretching the array further.
The mission now estimates that Lucy’s solar array is between 353 degrees and 357 degrees open (out of a total of 360 degrees for a fully deployed array). While the array is not fully latched, it is under significantly higher voltage, making it stable enough for the spacecraft to function as needed for missions.
The spacecraft is now ready and able to complete the mission’s next major milestone — an Earth gravity assist in October 2022. Lucy is scheduled to reach its first asteroid target in 2025.
NASA’s Lucy mission is a solar array development effort Provided by NASA’s Goddard Space Flight Center
Reference: Team Troubles Lucy Spacecraft with Asteroids Millions of Miles Away (2022 August 3) Retrieved August 3, 2022 by
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