Lucy’s massive solar arrays completed their first set of deployment tests in January 2021 in a thermal vacuum chamber at Lockheed Martin Space. Credit: Lockheed Martin Space
Following the successful launch of NASA’s Lucy spacecraft on October 16, 2021, a group of engineers huddled around a long conference table in Titusville, Florida. Lucy was only hours into its 12-year flight, but an unexpected challenge arose for the first-ever Trojan asteroid mission.
The data showed that one of Lucy’s solar arrays powering the spacecraft’s systems — designed to deploy like a hand 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 quickly came together to fix the problem. On the phone were team members at Lockheed Martin’s Mission Support Area outside of Denver, who were in direct contact with the spacecraft.
The conversation was quiet but intense. At one end of the room sat a frowning engineer, 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 array even open? Was there a way to fix it? Would Lucy be able to safely perform the maneuvers necessary to complete her science mission without the grid fully deployed?
With Lucy already speeding her way through space, the stakes were high.
Within hours, NASA assembled the Lucy Anomaly Response Team, including members from the science mission lead Southwest Research Institute (SwRI) in Austin, Texas; mission operations lead at NASA’s Goddard Space Flight Center in Greenbelt, Maryland; spacecraft designer Lockheed Martin; and Northrop Grumman in San Diego, a designer and builder of solar systems.
“This is a talented team firmly committed to the success of Lucy,” said Donya Douglas-Bradshaw, former Lucy project manager at NASA Goddard. “They have the same courage 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 began an exhaustive deep dive to determine the cause of the problem and develop the best way forward.
Given that the spacecraft was otherwise perfectly sound, 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 at SwRI. “Fortunately, the spacecraft was where it was supposed to be, operating nominally and most importantly, safe. We had time.’
Staying focused through many long days and nights, the team worked on options. To assess the configuration of Lucy’s solar array in real time, the team fired the spacecraft’s engines 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 engine module to infer how stiff Lucy’s array was—which helped reveal the source of the problem.
They finally got to the root cause: a strap meant to pull Lucy’s massive solar array had probably snarled on the bobbin-like pulley.
After months of further consideration and testing, Lucy’s team settled on two potential paths forward.
In one, they would pull harder on the belt by firing the backup engine to deploy the array at the same time as the main engine. Power from two motors should allow the jammed belt to wind further and engage the array locking mechanism. While both bikes were never originally intended to run at the same time, the team used models to ensure the concept would work.
The second option: Use the array as it was – almost fully deployed and generating more than 90% of the expected power.
“Each path carried some element of risk to achieve the underlying science goals,” said Barry Noakes, Lockheed Martin’s chief engineer for deep space exploration. “A big part of our effort was identifying proactive actions that reduce risk in both scenarios.”
The team mapped and tested possible outcomes for both options. They analyzed hours of test footage of the array, constructed a ground-based replica of the array’s motor assembly, and tested the replica beyond its limits to better understand the risks of further deployment attempts. They also developed special high-fidelity software to simulate Lucy in space and assess any potential ripple effects the re-deployment attempt might have on the spacecraft.
“The collaboration and teamwork with the mission partners has been phenomenal,” said Frank Bernas, vice president, space components and strategic business at Northrop Grumman.
After months of simulations and tests, NASA decided to move forward with the first option, a multi-stage attempt to completely redistribute the solar array. On seven occasions in May and June, the team directed the spacecraft to simultaneously fire the primary and backup thrusters to deploy the solar array. The effort was successful, pulling on the strap and further opening and tensioning the array.
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). Although the array is not fully locked, it is under significantly greater stress, making it stable enough for the spacecraft to operate as required for mission operations.
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 arrive at its first asteroid target in 2025.
NASA’s Lucy mission is an attempt to deploy solar arrays Courtesy of NASA’s Goddard Space Flight Center
Citation: Team troubleshoots asteroid spacecraft Lucy million miles away (2022, August 3) Retrieved August 3, 2022, from
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