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NASA’s Lucy mission is heading to the Jupiter Trojans
two swarms of primitive asteroids trapped in Jupiter’s
orbit that may hold clues to the formation of the planets.
Lucy launched on October 16, 2021.
After a year in orbit around the Sun,
it is returning home on its launch anniversary
for the first of three Earth gravity assists.
On October 16, 2022, Lucy will fly by the Earth
like a partner in a swing dance, boosting its speed
and elongating its orbit around the Sun.
Two years later, it will return for a second gravitational
tango to lengthen its orbit even further, allowing it to reach
the L4 Trojan asteroids that travel ahead of Jupiter.
After Lucy completes its first tour of the Trojans,
it will make its third pas de deux with Earth
in December 2030.
This final flyby will increase its orbital tilt
and bend its path toward the L5 Trojans
that follow Jupiter.
As Lucy approaches its first gravity assist,
it will use the Earth and the Moon
to calibrate its instruments.
A day before it arrives, NASA will begin scanning
for potential collisions.
Lucy’s path runs through a cloud of over six thousand
Earth-orbiting satellites, and about twenty times as many
bits of inactive debris.
If any potential collisions are detected, the spacecraft will
fire its thrusters to speed up its arrival by a few seconds,
avoiding a catastrophic impact.
Because Lucy will approach from Earth’s dayside,
it will initially be invisible to observers on the ground.
It will take pictures of the Eastern Hemisphere
and attempt to image Ethiopia, home of the famous
hominin fossil for which the mission is named.
Lucy will then pick up speed as it races toward the
evening terminator, or boundary between day and night.
It will emerge from the Sun’s glare as night falls
on Western Australia – with its expansive solar arrays
reflecting the daylight.
An hour after sunset, at 6:55pm, Western Australia time,
stargazers will be treated to a magnificent sight
as Lucy streaks across the sky.
Seven minutes later, Lucy will once again
slip from view as it crosses into the
shadow of the Earth.
At 7:04 pm, Lucy will make its closest approach at just
219 miles above the planet: lower than the
International Space Station.
This exceptionally close shave will increase its velocity
by four-and-a-half miles per second.
Lucy will traverse the night side of Earth,
rapidly gaining in altitude, and emerge from the planet’s shadow
at 4:26 am, Pacific Time.
If skies are clear, early birds in the Western US
will be able to spot the spacecraft through binoculars.
Lucy will appear in the southwestern sky
between Cetus and Pisces, rising eastward until it is
overtaken by the dawn.
As the Sun rises over the Rocky Mountains,
Lucy will speed away from Earth at more than
14,000 miles per hour,
crossing the lunar orbit in less than a day.
Lucy will take a few final images as it
approaches the Moon and bids farewell to home,
preparing for over two years in deep space,
until it returns for its second gravity assist in December 2024.
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