How engineers fixed Lucy spacecraft’s solar array issue

NASA’s Lucy spacecraft has had a troubled start to its mission, with a deployment issue affecting its solar power system — but fortunately, engineers were able to address the issue. Now, NASA has shared more information on how members of the Lucy team worked to troubleshoot and fix the problem from Earth and the craft raced through space.

Lucy launched in October 2021, with its two circular solar arrays folded up to fit inside the rocket fairing. Once in space shortly after launch, Lucy was to deploy the two arrays to collect the solar energy which would power the craft on its long journey to the Trojan asteroids, located in the orbit of Jupiter. One array deployed as expected, however, the other did not fully deploy. The arrays were supposed to unfurl like the hands of a clock and latch into place, but one deployed only partway and did not latch.

The good news was that the craft was generating enough power to sustain itself even with the array only partly deployed. However, when not latched into place the array was not under tension which made it flimsy, and there were concerns that the forces of future maneuvering could shake or damage the array. The Lucy team, consisting of engineers and scientists from NASA, Lockheed Martian, Northrop Grumman, and the Southwest Research Institute (SwRI), got to work to figure out what they could do.

“We have an incredibly talented team, but it was important to give them time to figure out what happened and how to move forward,” said Hal Levison, Lucy’s principal investigator from SwRI, in a statement. “Fortunately, the spacecraft was where it was supposed to be, functioning nominally, and – most importantly – safe. We had time.”

The team discovered that the problem had been caused by a lanyard, which was tugged by a motor to pull the array into its round shape. Something seemed to have snagged the lanyard and prevented the array from fully opening. They faced a choice: Leave the craft as it was, currently healthy but potentially risking problems in the future, or use extra force from a backup motor to pull more firmly on the lanyard.

“Each path carried some element of risk to achieve the baseline science objectives,” said Barry Noakes, Lockheed Martin’s deep space exploration chief engineer. “A big part of our effort was identifying proactive actions that mitigate risk in either scenario.”

Having modeled out the risks of each option using test footage and a replica of the craft here on Earth, the team decided to attempt to fix the issue. It took several sessions of tweaking and tugging at the lanyard through May and June this year, but eventually, the array was almost completely deployed. It still isn’t latched into place, but it has deployed to between 353 and 357 degrees of 360 degrees, which is stable enough for the craft to perform its mission.

Lucy now continues its long journey, scheduled to arrive at the Trojans in 2027.

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