Screenshot from ULA Webcast of the Lucy launch - It's way too early to get up. 30 more minutes
Mission Rundown: ULA - Atlas V 401 - Lucy
Written: November 25, 2022
Let’s go look at some rocks
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.
Atlas V will stand 194 feet tall (59.1 meters) and weigh 749,479 pounds (339,958 kg) at liftoff. Atlas V is ULA’s workhorse rocket, with a total of 88 launches prior to Lucy. The variant in use for this mission, the Atlas V 401, was previously launched 39 times.
Using a three-digit configuration number, the first digit denotes the diameter of the payload fairing, the second indicates the number of solid rocket motors (SRMs), and the third represents the number of RL-10 engines on the Centaur upper stage.
Atlas used the longest-available 4.2-meter fairing known as the Extra Extended Payload Fairing (XEPF), and a single RL-10 engine on the Centaur upper stage.
The LUCY Payload
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.
Lucy will be visiting seven Trojan Asteroids after a flyby of the Donald Johanson asteroid. NASA
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.
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 — 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).
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 four main instruments Lucy is carrying are:
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.
L’LORRI, is a high spatial resolution visible instrument that will take monochromatic images across the 0.35 to 0.85 micron 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.
L-TES is an instrument that 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 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.
On top of the Payload Adapter Fitting is the satellite release mechanism needed to deploy Lucy in its correctly planned heliocentric orbit. The PAF also carries the fairings until their release points 4 minutes into the flight of Atlas V 401 with Lucy.
Lucy will coast through near Earth 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 yet 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 in 2027 and will kick off its Trojan flybys on August 12, 2027, when Lucy flies past 3548 Eurybates and its satellite, Queta.
September 15, 2027, Lucy will fly by 15094 Polymele, the second of the seven Trojans the spacecraft will encounter. 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 do a flyby on November 11, 2028, and will exit the L4 swarm in the weeks following the flyby. It is now time to transmit all the collected data back to Earth.
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 two flyby’s of the primary mission on March 3, 2033, when it flies past Patroclus and Menoetius — two, equal mass binary Trojans. Astronomers are probably planning changes to the flight plan if JWST finds an asteroid on its path back out to L5 Trojan swarm.
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 reserves systems allow.
Lagrange Points L1 - L5
Lagrange Points are positions in space where the gravitational forces of a two body system like the Sun and in this case Jupiter produce enhanced regions of attraction and repulsion. These can be used by spacecraft to reduce fuel consumption needed to remain in their position. Lagrange points are named in honor of Italian-French mathematician Josephy-Louis Lagrange.
There are five special points where a small mass can orbit in a constant pattern with two larger masses. The Lagrange Points are positions where the gravitational pull of two large masses precisely equals the centripetal force required for a small object to move with them. Of the five Lagrange points, three are unstable Lagrange points - labeled L1, L2 and L3 - all lying along the direct line of sight connecting the two large masses.
L1 is behind Jupiter in a balance point where the drift out into outer space is canceled by the common attraction of Jupiter and the Sun. Spacecraft can orbit L1 with relative ease where it comes to propellant consumption. The James Webb Space Telescope - JWST is doing that in Earth's L1 point right now.
L2 is in the balance point between Jupiter and the Sun where a spacecraft can do exactly the same as at L1. Spacecraft can orbit L2 with relative ease where it comes to propellant consumption as well. A number of Earth satellites have done or are doing that.
L3 is behind the Sun and is used extensively by Science Fiction writers as homes for hostile aliens. If a planet Two of equal size there would be an L6 and L 7 that was capable of capturing asteroids and holding satellites in a gravitational flux of balance.
The stable Lagrange points - labeled L4 and L5 - form the apex of two equilateral triangles that have the large masses at their vertices. L4 leads the orbit of Jupiter and L5 follows.
The L4 and L5 points are home to stable orbits so long as the mass ratio between the two large masses exceeds 24.96. Objects found orbiting at the L4 and L5 points are often called the Trojans and the Greeks after the three large asteroids Agamemnon, Achilles and Hector that orbit in the L4 and L5 points of the Jupiter-Sun system.
According to Homer, Hector was the Trojan champion slain by Achilles during King Agamemnon's siege of Troy. There are hundreds of Trojan Asteroids in the solar system. Most orbit with Jupiter, but others orbit with Mars. In addition, several of Saturn's moons have captured their own Trojan companions.
The Atlas V 401 launch
The launch countdown began with the loading of liquid oxygen onboard Atlas V. The rocket was already fueled with RP-1 kerosene two days before during the completed WDR.
Throughout the last four minutes of the countdown, ULA launch teams monitored the health of the rocket and spacecraft.
At T – 2 seconds, the RD-180 engine ignited, and the rocket lifted off at T-0.
At T+1:27, 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.
Lucy has a double figure eight orbit between Earth and Jupiter's Larange points 4 and 5. The first deep space encounter with an asteroid is a training run. The rest is for real. Source
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 at T+4:27 just eight seconds after MES-1. MECO-2 happened at T+13:09.
Centaur shut down after 361 seconds for the final time at T+46:40 seconds and entered a 12-minute coast phase in preparation for spacecraft separation.
Lucy deployed 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 began 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.
The Atlas V 401 rocket
The Atlas V core in use for this mission is AV-096. It was originally delivered to Cape Canaveral to boost the Boeing Starliner on a trip to the ISS. Technical difficulties delayed that launch and AV-096 was reassigned to Lucy.
On June 28 it underwent preparations to go vertical at Mobile Service Tower (MST).
The next day, the Atlas V interstage was installed on top of the first stage followed by the Centaur upper stage installation on July 15. The lower portion of the payload fairing, the boattail, was then installed on top of the 3 meter wide Centaur, completing the majority of the Atlas rocket assembly.
On October 1, Atlas V underwent a Wet Dress Rehearsal (WDR). A WDR is one of the final major tests of all the systems on the Atlas V, which includes fueling the rocket as if it is about to launch. 25000 gallons of RP-1 kerosene was loaded and left there to lift off.
United Launch Alliance (ULA) has completed encapsulation of the payload fairing around NASA’s Lucy spacecraft inside the Astrotech Space Operations Facility in Titusville, Florida. The payload fairing secures and protects the spacecraft during launch and ascent.
The fairing halves that encapsulate the satellite went vertical for encapsulation in the Vehicle Integration Facility at the Cape Canaveral Space Force Station on October 7 where it will be “mated” with the boattail of United Launch Alliance Atlas V 401 rocket. Lucy was approved by NASA to proceed with its October 16 launch.
After receiving this approval, the satellite was stacked on top of the EFS and safely encapsulated in its 4.2-meter payload fairing. On September 15, the encapsulated payload was transported from the Integrated Processing Facility (IPF) to SLC-41 and was later integrated with the Atlas V.
The VIF is a 30-story building where the rocket stages and payload were put together for this mission aboard the Mobile Launch Platform.
The MLP will travel 400 meters to the pad with the help of undercarriage railcars and trackmobile machines that push the entire 1.4-million-pound platform and Atlas V 401 rocket along tracks up the hill to the launch pad.
The Atlas V will lift off from Space Launch Complex 41.The rocket will carry Lucy outside Earth’s atmosphere to begin the long journey to the Trojan asteroids.
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