One of the 24-foot solar arrays did not fully open (the other is open and latched). NASA said the partially unfurled solar array is generating "nearly" the expected power compared to if the wing was fully open. It's enough power to keep Lucy healthy and functioning.
The Lucy team is assessing the issue and won't try to fully open the solar array before the end of next week, at the earliest.
This spacecraft is designed to travel farther from the sun than any other solar-powered spacecraft. The Juno spacecraft orbiting Jupiter holds the current record, but Lucy will be farther when it flies through the Trojan asteroids. Other far-flung predecessors have relied on nuclear power.
The spacecraft's two solar arrays were too big to be opened simultaneously on Earth; the testing facility couldn't accommodate the wingspan. So Lucy’s team opened one solar array, closed it, moved the spacecraft and then opened the other solar array.
The spacecraft never attempted to open them at the same time before reaching microgravity.aside">
These solar arrays (if both are fully open) should generate 18,000 watts of power when the spacecraft is near Earth. Katie Oakman, Lucy’s structures and mechanisms lead at Lockheed Martin Space, said that’s enough to power her house and a couple of her neighbors.
Near the Trojan asteroids, Lucy’s two solar arrays would generate just 500 watts of power. This would turn on a few lights in the living room but not power the microwave. Yet it’s sufficient for Lucy’s science instruments that will need 82 watts of power when flying by the asteroids.
Source : https://www.houstonchronicle.com/news/houston-texas/space/article/NASA-s-Lucy-spacecraft-is-struggling-to-unfurl-16549759.php327