NASA soluciona problemas da espaçonave Lucy ligada a asteróides a milhões de milhas de distância

Anomalia da matriz solar da missão Lucy da NASA

Logo após o lançamento do Lucy, um de seus painéis solares não foi totalmente implantado, colocando a missão em risco. A animação conceitual deste artista retrata a anomalia do painel solar de Lucy. Crédito: Laboratório de imagens conceituais do Goddard Space Flight Center da NASA

Logo após o lançamento bem-sucedido de[{” attribute=””>NASA’s Lucy spacecraft on October 16, 2021, a group of engineers huddled around a long conference table in Titusville, Florida. Lucy was just mere hours into its 12-year journey, but a major unexpected challenge had surfaced for the first-ever Trojan asteroids mission.

Data indicated that one of Lucy’s solar arrays — designed to unfurl like a hand fan — hadn’t fully opened and latched. Since the solar arrays power the spacecraft’s systems, the team had to figure out what to do next.

To troubleshoot the problem, teams from NASA and Lucy mission partners quickly came together. Team members from Lockheed Martin’s Mission Support Area outside of Denver, who were in communication with the spacecraft directly, were on the phone.

Although the conversation was quiet, it was intense. At one end of the room, an engineer sat with furrowed brow, folding and unfolding a paper plate in the same way that Lucy’s enormous circular solar arrays operate.

There were so many unanswered questions. What happened? Was the array open at all? Was there a way to fix it? Without a fully deployed array, would Lucy be able to safely perform the maneuvers needed to accomplish its science mission?

Because Lucy was already speeding on its way through space, the stakes were incredibly high.

A missão Lucy da NASA está indo para o[{” attribute=””>Jupiter Trojans – two swarms of unexplored asteroids trapped in Jupiter’s orbit. Lucy made a picture-perfect launch on October 16, 2021, but when the spacecraft began to unfurl its solar arrays, it encountered an anomaly. One of the arrays failed to fully deploy and latch shut, putting the mission at risk. For months, Lucy’s flight operations team worked meticulously to address the issue and put Lucy back on its solar-powered journey to the Jupiter Trojans.

Within hours, NASA pulled together Lucy’s anomaly response team, which included members from science mission lead Southwest Research Institute (SwRI) in Austin, Texas; mission operations lead NASA’s Goddard Space Flight Center in Greenbelt, Maryland; spacecraft builder Lockheed Martin; and Northrop Grumman in San Diego, solar array system designer and builder.

“This is a talented team, firmly committed to the success of Lucy,” said Donya Douglas-Bradshaw, former Lucy project manager from NASA Goddard. “They have the same grit and dedication that got us to a successful launch during a once-in-a-lifetime pandemic.”

United in their pursuit to ensure Lucy would reach its fullest potential, the team began an exhaustive deep dive to determine the cause of the issue and develop the best path forward.

Given that the spacecraft was otherwise perfectly healthy, the team wasn’t rushing into anything.

“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. “Fortunately, the spacecraft was where it was supposed to be, functioning nominally, and – most importantly – safe. We had time.”

At 24 feet (7.3 meters) across each, Lucy’s two solar panels underwent initial deployment tests in January 2021. In this photo, a technician at Lockheed Martin Space in Denver, Colorado, inspects one of Lucy’s arrays during its first deployment. These massive solar arrays will power the Lucy spacecraft throughout its entire 4-billion-mile, 12-year journey through space as it heads out to explore Jupiter’s elusive Trojan asteroids. Credit: Lockheed Martin

Staying focused during many long days and nights, the team worked through options. To evaluate Lucy’s solar array configuration in real-time, the team fired thrusters on the spacecraft and gathered data on how those forces made the solar array vibrate. Next, they fed the data into a detailed model of the array’s motor assembly to infer how rigid Lucy’s array was – which helped uncover the source of the issue.

At last, they closed in on the root cause: a lanyard designed to pull Lucy’s massive solar array open was likely snarled on its bobbin-like spool.

After months of further brainstorming and testing, Lucy’s team settled on two potential paths forward.

In one, they would pull harder on the lanyard by running the array’s backup deployment motor at the same time as its primary motor. The power from two motors should allow the jammed lanyard to wind in further and engage the array’s latching mechanism. While both motors were never originally intended to operate at the same time, the team used models to ensure the concept would work.

The second option: use the array as it was – nearly fully deployed and generating more than 90% of its expected power.

“Cada caminho carregava algum elemento de risco para atingir os objetivos científicos básicos”, disse Barry Noakes, engenheiro-chefe de exploração do espaço profundo da Lockheed Martin. “Grande parte do nosso esforço foi identificar ações proativas que mitiguem o risco em qualquer cenário.”

A equipe mapeou e testou possíveis resultados para ambas as opções. Eles analisaram horas de filmagem de teste da matriz, construíram uma réplica terrestre do conjunto do motor da matriz e testaram a réplica além de seus limites para entender melhor os riscos de novas tentativas de implantação. Eles também desenvolveram um software especial de alta fidelidade para simular Lucy no espaço e avaliar quaisquer potenciais efeitos cascata que uma tentativa de redistribuição poderia ter na espaçonave.

“A cooperação e o trabalho em equipe com os parceiros da missão foram fenomenais”, disse Frank Bernas, vice-presidente de componentes espaciais e negócios estratégicos da Northrop Grumman.

Após meses de simulações e testes, a NASA decidiu avançar com a primeira opção – uma tentativa de várias etapas para reimplantar totalmente o painel solar. Em sete ocasiões em maio e junho, a equipe comandou a espaçonave para operar simultaneamente os motores de implantação do painel solar primário e de backup. O esforço foi bem-sucedido, puxando o cordão e abrindo e tensionando ainda mais a matriz.

A missão agora estima que a matriz solar de Lucy está entre 353 graus e 357 graus de abertura (de 360 graus totais para uma matriz totalmente implantada). Embora a matriz não esteja totalmente travada, está sob tensão substancialmente maior, tornando-a estável o suficiente para que a espaçonave opere conforme necessário para as operações da missão.

A espaçonave agora está pronta e capaz de completar o próximo grande marco da missão – uma assistência da gravidade da Terra em outubro de 2022. Lucy está programada para chegar ao seu primeiro alvo de asteroide em 2025.