Lucy.
the most complicated mission yet to visit asteroids. Asteroids. Plural.
At the completion of its primary mission, Lucy will become the only spacecraft to have
ever visited eight separate deep space objects. It will also be the first spacecraft to ever
investigate the Trojan asteroids -- a group of rocks Jupiter has dutifully collected over the
last 4.6 billion years into “pockets” ahead of and behind the planet in its orbit of the Sun.
Hi guys, this is DK with NASASpaceflight, and in this video, we’re gonna break down Lucy’s mission,
it’s instruments, scientific goals, and what to expect from the spacecraft after the completion
of its 12-year mission through the solar system.
In late-2014, NASA released an Announcement of Opportunity for the selection of the 13th and 14th missions under their Discovery Program.
The Discovery Program is designed to select low-cost, deep space missions with the
primary goal of researching a specific scientific area in the solar system.
Missions such as MESSENGER, Dawn, GRAIL, and InSight were -- and
are -- part of the Discovery Program. Managed by NASA’s Goddard Space Flight
Center in Maryland, Lucy’s mission proposal proposed a spacecraft that would visit not one.
Not just two. Not even just three, but EIGHT separate asteroids during a nearly 12-year mission.
Seven of the asteroids are Trojans collected at Jupiter’s L4 and L5 Lagrange points.
and real quick, remember those pockets we talked about Jupiter having? Their proper term is a Lagrange
point, which is a place where quote -- “the gravitational pull of two large masses precisely
equals the centripetal force required for a small object to move with them.” That’s a fancy way of
saying that objects placed in Lagrange points tend to stay there until a force acts on them.
This is why Jupiter has been able to collect the trojan swarms as it has:
they stay there once captured there.
But, we’re gonna get to more on Trojans and the asteroids Lucy will visit in a bit.
On September 30, 2015, NASA announced Lucy as the 13th mission under the Discovery Program.
Over the next five years, teams finalized the mission design, and in 2019, Lucy was
formally targeting for a launch in October 2021 on a United Launch Alliance Atlas V 401 rocket.
In August 2020, Lucy was given the green light to begin final assembly and testing.
This included integration of Lucy’s four science instruments on its Instrument Pointing
Platform for remote-sensing science. These instruments are the L'Ralph,
L'LORRI, L'TES, and a High Gain Antenna.
L'Ralph will be used as a color visible imager and an infrared imaging spectrometer.
The color visible imager, known as the M-VIC, will take standard color images of the Trojans,
showing each asteroid’s characteristics and activity.
The infrared imaging spectrometer, known as LEISA, will allow Lucy to see absorption lines
on asteroids that show different silicates, ices, and organics that are present on Trojan
asteroids -- all in an attempt to determine their composition and, critically, where in
the solar system they formed before Jupiter grabbed them into one of its Lagrange points.
Additionally, Lucy will use its T2CAM to take wide-field images of the asteroids
to better determine their shapes. Meanwhile, L'LORRI is a high spatial
resolution visible instrument that will take monochromatic images across the 0.35
to 0.85 microns wavelength. Which is to say that L'LORRI will provide scientists
with incredibly detailed images of the surfaces of the Trojans -- which will also reveal their sub-surface characteristics via impact craters.
Complementary to L'LORRI, the L'TES instrument will use an infrared thermal emission spectrometer
covering wavelengths of 6 to 75 microns.
Having an infrared thermal emission spectrometer will allow scientists to learn more about a
Trojan asteroid’s thermal inertia, body heat retainment, and surface material structure.
The High Gain Antenna on Lucy will measure the mass of each asteroid using the Doppler
shift of the radio signal from the antenna. To power these endeavours, Lucy features two
circular solar panels -- which unfold from a thickness of 10 cm to a full size of 7.3
meters in diameter after launch. Solar panels of this size are needed to help
power the spacecraft when at Jupiter’s orbital distance, being so far away from the sun means
we need large solar panels to get enough juice.. Additionally, Lucy carries a plaque -- aptly
named the “Lucy Plaque” -- that features many names, quotes, and images that will
be sent to space in hopes of being seen by our future explorers. Unlike the Voyager and
Pioneer plaques meant for life outside our solar system, the Lucy plaque is meant for
our descendants who may one day re-discover the spacecraft after thousands of years.
Assembly of Lucy was completed in mid-2021, and the spacecraft was shipped to Florida
in July for final testing and integration before launch. Lucy was then moved to a clean room where
it was fueled for launch and encapsulated in the Atlas V’s 4-meter payload fairing.
Lucy was then transported from its cleanroom to ULA’s Space Launch Complex
41 -- usually pronounced “Slick-41” -- at Cape Canaveral Space Force Station and hoisted
into placeplaced atop the Atlas V in ULA’s Vertical Integration Facility.
On launch day, the Atlas V will first carry Lucy into a stable Earth parking
orbit before the Centaur upper stage reignites to place Lucy on its interplanetary trajectory.
Lucy will separate from the Centaur 58 minutes after launch to begin her journey to a place
where no spacecraft has gone before. BUT FIRST… she comes back to visit us twice.
Lucy’s unique mission means she can’t just go straight to Jupiter’s Lagrange points. Her
speed and trajectory must be precisely managed so she doesn’t just fly by one
asteroid and then exit the Lagrange point. To manage this, Lucy will use two gravity
assists with Earth in 2022 and 2024 to alter its trajectory (or orbit of the Sun) to intercept
Jupiter’s L4 Lagrange point first at just the right speed to arc through the point and swing
by the asteroids it needs to visit there. While the trajectory might look weird on a
“space map,” it’s actually a heliocentric orbit around the Sun with an aphelion -- farthest
point from the Sun -- at Jupiter’s orbital distance and a perihelion -- closest point
to the Sun -- at Earth’s orbital distance. On April 20, 2025, Lucy will fly past the
first of the eight asteroids on its checklist. This first object is 52246 DonaldJohanson.
This is not a Trojan asteroid but rather a perfectly aligned main belt asteroid that
Lucy’s trajectory just happens to pass while traveling to Jupiter’s L4 point.
The flyby of Donaldjohanson will serve as a dress rehearsal of Lucy’s seven other flybys -- similar
to how Cassini and New Horizons used their gravity assist flybys of Jupiter to prepare for their main
missions at Saturn and Pluto, respectively.
In 2027, Lucy finally will arrive in Jupiter’s L4 location. Located at the L4 and L5 points are
“swarms,” or collections, of Trojan asteroids trapped by Jupiter’s gravity.
These pockets that we mentioned earlier
These swarms of Trojans are located 60 degrees ahead of and 60 degrees behind Jupiter.
On August 12, 2027, Lucy will fly past 3548 Eurybates -- the first Trojan of its mission.
Eurybates is a prime target because the 64 km wide asteroid has a 1 km wide moonlet named Queta.
Other flybys in the L4 location will occur on September 15, 2027 when Lucy
visits the 21 km wide 15094 Polymele. After this, Lucy will cruise by 11351
Leucus , a 34 km wide asteroid, on April 18, 2028. The craft will close out its L4 journey with the
51 km diameter 219000 Orus on November 11, 2028.
After Orus, the craft’s orbit will bring it back to Earth in 2031 for another gravity assist to
send it onward to Jupiter’s L5 point. There, it will visit one - but really
two - objects: 617 Patroclus. And Patroclus is like no other Trojan Lucy will visit.
It’s a near equal mass binary with Menoetius. Patroclus is 113 km in diameter while Menoetius
is 104 km in diameter. The two orbit each other at a distance of 680 km around a center of mass --
called a Barycenter, or the point around which they both orbit -- that is outside the both of them.
Now... here’s the best part. The Patroclus/Menoetius binary is likely
a primordial survivor of the Cold Classical Kuiper Belt -- a group of objects left
undisturbed from the original accretion of the first stuff of the solar system.
This hypothesis, which Lucy will test, is based on Hubble Space Telescope observations
of Cold Classical Kuiper Belt objects -- more than half of which are known
binaries like Patroclus and Menoetius. As Dr. Hal Levison said to NASASpaceflight,
quote: If that’s true, then Patroclus is one of the remnants of that really early
population that just happens to survive. It’s probably extremely primordial, and that’s why I
think for somebody who’s interested in planet formation, seeing one of these things close
up — it’s going to be cool. End quote.
And that last point is actually the reason for Lucy’s mission. The answer to the question
“What’s Lucy’s mission all about?” is that it’s trying to determine how the solar system formed.
And that might sound weird given Lucy is looking at asteroids captured by Jupiter.
But those asteroids are time capsules. They can tell us -- from their type -- where and how they
formed. And they come from different parts of the solar system... having been jostled and nudged
by gravity before eventually passing close enough to Jupiter to be captured in its Lagrange points.
The types of asteroids in the Trojan swarms are important, too. The grayer
asteroids -- C-type -- formed closer to the Sun while the redder ones -- D-type -- likely formed
beyond 20 Astronomical Units from the Sun, which is to say 20 times the average orbital
distance of Earth from the Sun, where the ices needed to create the red color can survive.
What’s more, the redder Trojans captured by Jupiter are not as red as their Kuiper Belt
extended family members. Why is that? That’s part of what Lucy seeks to answer -- and with that
answer could come invaluable insight into how the solar system formed and came to its present state.
But… what about after Patroclus? Is that really it for Lucy?
I mean, Kind of, but not really. NASA never throws out a still functioning spacecraft if fuel and systems
health will allow for an extended mission. While Patroclus will mark the end of Lucy’s
12-year primary mission, its orbit at this point will be specially designed to
remain stable for the next 700,000 years. While Lucy’s systems certainly won’t last that long,
the craft -- if healthy -- could be used for other observations of main belt asteroids and objects
whose trajectories align with Lucy’s. Lucy could be giving us data for years and years to come.
Don’t forget to subscribe so you don’t miss out on any future videos talking about past
present and future NASA Missions. This video was written by Thomas
Haygen and Chris Gebhardt, and once again I’m DK - thank you so much for watching.