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Lucy navigates NASA's first mission to the Trojan asteroids



  Lucy finds her place in the solar system

This diagram shows Lucy's orbit. The spacecraft's path (green) is shown in a frame of reference where Jupiter remains stationary, giving the trajectory its pretzel-like shape. After launching in October 2021

, Lucy has two nearby fly-bys before meeting her Trojan targets. In the L4 cloud, Lucy will fly past (3548) Eurybates (white), (15094) Polymele (pink), (11351) Leukus (red) and (21900) Orus (red) from 2027-2028. After another dive on Earth, Lucy will visit the L5 Cloud and in 2033 encounter the (617) Patroclus Menoetius binary color (pink). As a bonus, on her way to the L4 in 2025, Lucy flies past a small asteroid of the main belt (52246) Donaldjohanson (white), named after the discoverer of the Lucy Fossil. After Lucy flew the Patroclus Menoetius binary in 2033, every six years Lucy cycled between the two Trojan clouds. Credits: Southwest Research Institute

In science fiction, researchers can hop in futuristic spaceships and cross half the galaxy in the blink of an eye. However, this requires the navigation acrobatics required to ensure the mission's success.

In 2021, the performance of the navigation that represents the Lucy mission will begin. Driving Lucy to his goals does not mean simply programming a map into a spacecraft and accelerating – in six years' time, it will fly past six asteroid targets that are in different orbits.

Lucy's target includes Jupiter's Trojan asteroids, clusters of rocks almost as old as the Sun itself, and visiting these asteroids can help discover the secrets of the early Solar System. In 2025, Lucy will encounter an asteroid of the main belt, where she will perform a training run with her instruments before encountering the first four Trojan targets from 2027 to 2028. In 2033, Lucy will end her mission with a study on a binary system that circles two Trojans.

Getting the spaceship where it belongs is a daunting task. The solar system is in constant motion and the gravitational forces will affect Lucy at all times, especially from the targets she wants to visit. Past missions have passed multiple targets and even orbited them, but not as many as Lucy.

Scientists and engineers involved in the design of trajectories are tasked with identifying this route under the direction of Flight Dynamics team leader Kevin Berry of NASA's Goddard Space Flight Center in Greenbelt, Maryland. One such engineer is Jacob Englander, the technical manager for the Lucy mission. "There are two ways to navigate on a mission like Lucy," he said. "You can either burn a huge amount of propellant and try to find more targets in zig-zag mode, or you can look for an opportunity where everyone will randomly position themselves." The change of Lucy's high-speed track will be done by gravity assistants with minimal use of powered tweaks.

Although Lucy is programmed to throw herself into a celestial alignment that will not take place for decades, she can not be left to her own resources. As the spacecraft approaches its asteroid targets, optical navigation represents the next step required.

"OpNav," as Coralie Adam, Head of Optical Navigation, points out, is the use of footage from the on-board cameras to determine Lucy Position relative to the goal. This is a useful measurement that the navigation team uses to optimize Lucy's route and ensure that it stays on the nominal flyby path. Adam is working in the Simi Valley, California with KinetX, NASA, which has chosen to implement space navigation from Lucy.

Using the spacecraft communication link to Earth, the Lucy team gets information about the spacecraft's position and direction and speed. The spacecraft captures images and sends them to Earth, where Adam and other optical navigators use software to determine where the image was taken, based on the position of the stars and the target. The orbital investigation team uses this data, along with data from the communication link, to determine where the spacecraft is and where it is likely to be, relative to the Trojans. The team then designs a flight correction maneuver to get Lucy on track. "The first maneuver is tiny," said Dale Stanbridge, who is also responsible for KinetX. "But the second is 898 meters per second. This is a feature of Lucy: very large Delta V maneuvers. "Delta V refers to the speed change during the maneuver.

The communication of all these navigation commands with Lucy is an independent process." Lockheed Martin sends the orders to the spacecraft via the Deep Space Network, "Adam said Lockheed and the Southwest Research Institute where the instruments are sequencing the instruments and determining the spacecraft's orientation to make sure Lucy takes the pictures we want when we want them. "

" The Maneuvers Lucy & # 39 Correcting its trajectory will be very critical as the spacecraft must encounter the Trojan at the intersection of the spacecraft with the Trojan's orbital aircraft, "Stanbridge said." Changing the orbital plane of the spacecraft requires a lot of energy. Therefore, the maneuvers must be performed at the optimum time to get to the next body while minimizing fuel costs. "

While Lucy performs deep space maneuvers to correct her trajectory towards his targets, communication with the spacecraft sometimes occurs "Blackout times can be up to 30 minutes on some of our larger maneuvers," Stanbridge said. "At other times, you might lose communication when, for example, the sun comes between the Earth Tracking Station and the spacecraft where the Contact loss is not catastrophic, but still. "We have high-precision predictions about the trajectory of the spacecraft that are light enough to continue tracking the spacecraft when the event is causing a communication loss caused, is over, "said Sta nbridge.

What route will Lucy take when her mission is nearly completed? In 15 years? "We'll just leave it out," said Englander. "We've done an analysis to see if it's passively passive, and if we look far into the future, that's not the case." The Lucy team has been giving the spaceship a clear path for thousands of years long after Lucy rewrote the textbooks The History of the Solar System.

For more information on NASA's Lucy mission, see: www.nasa.gov/lucy & lucy.swri.edu


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