Upcoming Gravity Assist

On December 12, 2023, at 11:15 p.m. EST, NASA's Lucy spacecraft is set to make a remarkable maneuver: a second gravity assist from Earth. Flying a mere 220 miles (360 kilometers) above our planet's surface, this close approach will not only alter Lucy's trajectory but also propel it deeper into our solar system, advancing its mission to explore the enigmatic Jupiter Trojan asteroids.

Mission Timeline

Having embarked on its mission in October 2021, Lucy is currently in a two-year orbit around the sun. The upcoming gravity assist marks a pivotal moment three years into its ambitious twelve-year journey. The first gravity assist, executed just a year after its launch on October 16, 2022, provided the necessary boost to reach a crucial two-year orbit, allowing it to encounter its first asteroid, Dinkinesh, and its moon, Selam.

Journey Through the Asteroid Belt

The December flyby will transition Lucy into a six-year orbit, enabling it to journey through the main asteroid belt. During this phase, it will pass by the asteroid Donaldjohanson before venturing into the region of the Trojan asteroids, which are located at a similar distance from the sun as Jupiter. This historic approach will culminate in Lucy's first encounter with a Trojan asteroid in 2027, paving the way for significant scientific discoveries.

Safety Measures

As Lucy heads towards Earth, it will stealthily approach from the sun's direction, making it nearly invisible from our vantage point due to overwhelming solar glare. Even as it skims the atmosphere below the altitude of the International Space Station, NASA has implemented rigorous safety measures to navigate this densely populated orbital region. Should there be any risk of collision with Earth-orbiting satellites or space debris, Lucy can execute a minor trajectory adjustment 12 hours prior to its closest approach, shifting its path by a couple of seconds—a small but potentially vital maneuver.

Visibility for Skywatchers

Skywatchers in the Hawaiian Islands will have a fleeting opportunity to spot Lucy shortly after sunset as it approaches Earth, disappearing into the planet's shadow at 6:14 p.m. HST. The spacecraft will then race across the continental U.S. in the dark, reaching speeds exceeding 33,000 miles per hour (14.8 kilometers per second). After emerging from Earth’s shadow, it will reappear around 11:34 p.m. EST, becoming visible again to fortunate observers in western Africa and eastern South America, as sunlight reflects off its solar panels.

Significance of the Gravity Assist

This gravity assist is more than a simple flyby; it will boost Lucy’s solar system speed by over 16,000 miles per hour (7.31 kilometers per second), setting the stage for a series of groundbreaking encounters with objects from our solar system's early history. Lucy's innovative journey not only holds the promise of unveiling the mysteries of the past but also emphasizes the importance of human ingenuity in expanding our understanding of the cosmos.

Conclusion

Stay tuned for updates on Lucy's thrilling mission—who knows what astonishing discoveries await just beyond the horizon!