NASA, ULA launch historic Lucy mission

by Haygen Warren

NASA and ULA (United Launch Alliance) launched NASA’s next asteroid exploration mission — Lucy — from Florida early Saturday morning, kickstarting the spacecraft’s 12-year journey through the solar system. Liftoff of Atlas V and Lucy occurred at 5:34 AM EDT (09:34 UTC) on Saturday, October 16, from SLC-41 (Space Launch Complex 41) at Cape Canaveral Space Force Station in Florida.

Lucy and its mission

Lucy, led by NASA’s Goddard Space Flight Center in Maryland, represents the thirteenth mission under NASA’s Discovery Program. The Discovery Program is a NASA solar system exploration program designed to select low-cost, deep space missions with the primary goal of researching a specific scientific area in the solar system.

During its 12-year primary mission, Lucy will visit a total of eight asteroids. Seven of these asteroids are Trojan asteroids — unique asteroids located at Jupiter’s L4 and L5 Lagrange points, 60 degrees ahead of and 60 degrees behind Jupiter, respectively.

Lucy’s goal is to thoroughly investigate these Trojan asteroids, which, until Lucy, have never been visited by another spacecraft. These asteroids could be remnants of the very first collisions in our solar system, so investigating them with a mission like Lucy will provide incredible data on our solar system’s formation and past environment.

The eight asteroids Lucy will visit during its mission. (Credit: NASA)

What’s more, the mission, upon its completion, will become the first spacecraft to ever visit eight separate planetary bodies in a single mission.

However, for a mission as complex as Lucy, the spacecraft itself has to feature many unique instruments and systems to help it survive the harsh environment of space for twelve years — while simultaneously collecting some of the most valuable information on planetary formation to date.

When fully deployed in space, Lucy will span a massive 15.8 meters in width,  7.2 meters in height, and 2.78 meters in depth — mostly due to the spacecraft’s giant circular solar arrays.

Lucy’s solar arrays, once deployed, will be an impressive 7.3 meters in diameter, and will produce 504 watts of power at Lucy’s furthest distance from the Sun. Additionally, these solar arrays will make Lucy the farthest spacecraft to travel from the Sun that solely relies on solar power (all other spacecraft have used nuclear power sources).

“This particular design (of the circular solar arrays) enables us to stow up closely and tightly next to the spacecraft for launch,” said Katie Oakman, Lucy structures and mechanisms lead, of Lockheed Martin Space. “Having any particular shape other than this really unique design wouldn’t enable us to get to that 51 square meters of active cell area, and still fit within a launch vehicle fairing.”

Lucy’s dry mass, or the mass of the spacecraft when unfueled, is 821 kg. Lucy’s wet mass, or the fuelled mass of the spacecraft, is 1550 kg.

Lucy will carry four primary instruments with it to the Trojan asteroids onboard an Instrument Pointing Platform (IPP). The instruments Lucy is carrying are:

  • L’Ralph
  • L’LORRI
  • L’TES
  • High Gain Antenna

L’Ralph will be used as a color visible imager and an infrared imaging spectrometer. MVIC, the color visible imager, will take standard color images of the Trojans, showing each asteroid’s unique activity and surface characteristics. 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 to determine their composition and, critically, where in the solar system they formed before they were trapped in Jupiter’s Lagrange points.

Next is L’LORRI, a high spatial resolution visible instrument that will take monochromatic images across the 0.35 to 0.85 microns wavelength. L’LORRI will provide scientists with incredibly detailed images of the surface of the Trojans — also revealing their sub-surface characteristics via impact craters.

Lucy in the cleanroom prior to payload encapsulation (Credit: Thomas Burghardt for NSF)

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.

Lastly, Lucy will use its high gain antenna to measure the mass of each asteroid it passes using the Doppler shift of the radio signal from the antenna.

Lucy arrived in Cape Canaveral in late July and was sent to a cleanroom soon after its arrival. In the cleanroom, final tests on the spacecraft were performed, and Lucy was fueled for the final time before being stacked atop its Atlas V rocket.

Lucy was encapsulated in an Atlas V 4-meter payload fairing on September 29, and was transported to SLC-41 in the following days.

As Lucy was undergoing final integration, testing, and preparations for launch, ULA was also preparing the Atlas V rocket at SLC-41.

The Atlas V first stage supporting the launch of Lucy was previously assigned to the now-delayed Boeing OFT-2 (Orbital Flight Test 2) mission of Starliner in July. Following the extended delay of that mission, its Atlas V first stage became available for use.

The Centaur upper stage, featuring one RL-10 engine, was stacked atop the Atlas first stage on September 16, marking the completion of the Atlas V rocket. No solid rocket motors were used for this launch, meaning Atlas is launching in its 401 configuration (4-meter payload fairing, 0 solid rocket motors, 1 RL-10 engine on the upper stage).

Lucy was stacked atop its Atlas V rocket on October 7, and Atlas V and Lucy rolled out to SLC-41 on October 14 for launch.

Launch 

In the hours leading up to launch, Atlas V was filled with RP-1 Kerosene, Liquid Hydrogen, and Liquid Oxygen propellants for use during launch. Meanwhile, the ULA launch teams monitored the rocket’s systems and Lucy’s condition.

At T-4 minutes, ULA launch teams held the count to undergo a final go/no-go poll for launch. This hold lasted 10 minutes and, once Atlas V and Lucy are given the go for launch, the count resumed four minutes prior to liftoff.

Throughout the last four minutes of the countdown, ULA launch teams monitored the health of the rocket and spacecraft. Finally, at T-2 seconds, the first stage’s Russian RD-180 engine ignited, and Atlas V lifted off from SLC-41.

At T+1:30, Atlas V experienced Max-Q, short for maximum aerodynamic pressure. Max-Q occurs when the aerodynamic loads on the vehicle are at their highest during ascent.

Following Max-Q, propellant levels in the first stage depleted, and the RD-180 engine was commanded to shut off in an event called booster engine cutoff (BECO). Spacecraft separation followed six seconds later, at T+4:09.

Over the next 42 minutes, the Centaur upper stage ignited its RL-10 engine twice, starting with main engine start 1 (MES-1) at T+4:19. Payload fairing jettison occurred eight seconds after MES-1.

ULA infographic showing the planned trajectory of Atlas V during launch. (Credit: ULA)

Centaur shut down for the final time at T+46:40 seconds and entered a 12-minute coast phase in preparation for spacecraft separation. Lucy separated from the Centaur upper stage at T+58:00, kicking off its 12-year mission through the solar system.

In the minutes following separation from Centaur, Lucy unfolded its massive circular solar arrays and begin generating power to run its instruments and internal systems. Lucy will be on a trajectory that will take it out of Earth’s sphere of influence in the days following launch.

Lucy will coast through space for a year before it performs the first flyby of its mission — a flyby of Earth in October 2022. The spacecraft will use Earth’s gravity to adjust its orbit, in a maneuver called a gravity assist. Lucy will perform another Earth gravity assist in December 2024 before making the trek to the L4 Trojan asteroids.

However, before performing its L4 asteroid flybys, Lucy will first flyby asteroid 52246 Donaldjohanson on April 20, 2025. The flyby will largely serve as a dress rehearsal for Lucy’s Trojan flybys — just as New Horizons used Jupiter as a practice target ahead of its eventual encounter with Pluto — with the spacecraft using its IPP instruments and internal systems as it would with a Trojan flyby.

Lucy will arrive at the L4 Trojan swarm (collections of Trojans) in 2027 and will kick off its Trojan flybys on August 12, 2027, when Lucy flies past 3548 Eurybates and its satellite, Queta.

One month later, on September 15, 2027, Lucy will fly by 15094 Polymele, the second of the seven Trojans the spacecraft will encounter. Next, Lucy will fly past 11351 Leucus on April 18, 2028.

The last Trojan Lucy will encounter in the L4 swarm is 21900 Orus. Lucy will fly by the Trojan on November 11, 2028, and will exit the L4 swarm in the weeks following the flyby.

Lucy will then coast back to Earth for another gravity assist on December 25, 2030, slingshotting the spacecraft toward the L5 Trojan swarm.

Lucy will arrive at the L5 swarm in 2033 and will perform the final flyby of the primary mission on March 3, 2033, when it flies past Patroclus and Menoetius — two, equal mass binary Trojans.

NASASpaceflight sat down with Lucy’s Principal Investigator, Dr. Hal Levison, to discuss the spacecraft’s daunting trajectory in the weeks leading up to launch. 

Lucy’s primary mission will conclude with the flyby of Patroclus and Menoetius, but future mission extensions could see Lucy flyby other L4 and L5 Trojans if spacecraft power and fuel systems allow.

(Lead image: Atlas V at SLC-41 with Lucy — via Stephen Marr for NSF)

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