December 22, 2018 – In science fiction, explorers can hop in futuristic spaceships and traverse half the galaxy within the blink of a plot gap. Nonetheless, this sidelines the navigational acrobatics required with the intention to assure real-life mission success.
In 2021, the feat of navigation that’s the Lucy mission will launch. To steer Lucy in direction of its targets doesn’t merely contain programming a map right into a spacecraft and giving it gasoline cash – it would fly by six asteroid targets, every in several orbits, over the course of 12 years.
Lucy’s vacation spot is amongst Jupiter’s Trojan asteroids, clusters of rocky our bodies virtually as outdated because the Solar itself, and visiting these asteroids might assist unlock the secrets and techniques of the early photo voltaic system. Lucy will encounter a Major Belt asteroid in 2025, the place it would conduct a observe run of its devices earlier than encountering the primary 4 Trojan targets from 2027-2028. In 2033, Lucy will finish its mission with a examine of a binary system of two Trojans orbiting one another.
Getting the spacecraft the place it must go is a large problem. The photo voltaic system is in fixed movement, and gravitational forces will pull on Lucy always, particularly from the targets it goals to go to. Earlier missions have flown by and even orbited a number of targets, however none so many as will Lucy.
Scientists and engineers concerned with trajectory design have the duty of determining that route, underneath Flight Dynamics Workforce Chief Kevin Berry of NASA’s Goddard House Flight Middle in Greenbelt, Maryland. One such engineer is Jacob Englander, the optimization technical lead for the Lucy mission. “There are two methods to navigate a mission like Lucy,” he mentioned. “You’ll be able to both burn an infinite quantity of propellant and zig-zag your means round looking for extra targets, or you possibly can search for a chance the place they only all occur to line up completely.” To go to these aligned targets, the vast majority of Lucy’s high-speed lane modifications will come from gravity assists, with minimal use of fueled tweaks.
Although Lucy is programmed to throw itself out right into a celestial alignment that won’t happen for many years, it can’t be left to its personal units. As soon as the spacecraft begins to strategy its asteroid targets, optical navigation is the following required step.
“OpNav,” as optical navigation technical lead Coralie Adam refers to it, is the utilization of images from the on-board cameras to find out Lucy’s place relative to the goal. This can be a helpful measurement utilized by the navigation crew to tweak Lucy’s route and guarantee it stays on the nominal flyby path. Adam works in Simi Valley, California, with KinetX, the corporate NASA chosen to conduct Lucy’s deep area navigation.
By utilizing the communications hyperlink from the spacecraft to Earth, Adam mentioned, the Lucy crew will get details about the spacecraft’s location, route and velocity. The spacecraft takes photos and sends them all the way down to Earth, the place Adam and different optical navigators use software program to find out the place the image was taken primarily based on the placement of stars and the goal. The orbit willpower crew makes use of this information together with information from the communications hyperlink to resolve for the place the spacecraft is and the place it’s anticipated to be, relative to the Trojans. The crew then designs a trajectory correction maneuver to get Lucy on monitor. “The primary maneuver is tiny,” mentioned navigation technical lead Dale Stanbridge, who can be of KinetX. “However the second is at 898 meters per second. That’s a attribute of Lucy: very giant delta V maneuvers.” Delta V refers back to the change in velocity through the maneuver.
Speaking all of those navigation instructions with Lucy is a course of all by itself. “Lockheed Martin sends the instructions to the spacecraft by way of the Deep House Community,” Adam mentioned. “What we do is we work with Lockheed and the Southwest Analysis Institute, the place groups are sequencing the devices and designing how the spacecraft is pointed, to ensure Lucy takes the images we would like after we need them.”
“The maneuvers to right Lucy’s trajectory are all going to be actually vital as a result of the spacecraft should encounter the Trojan on the intersection of the spacecraft and Trojan orbital planes,” Stanbridge mentioned. “Altering the spacecraft orbital airplane requires plenty of power, so the maneuvers must be executed on the optimum time to achieve to subsequent physique whereas minimizing the gas price.”
Whereas Lucy is conducting deep area maneuvers to right its trajectory towards its targets, communications with the spacecraft are typically misplaced for temporary intervals. “Blackout intervals may be as much as 30 minutes for a few of our greater maneuvers,” Stanbridge mentioned. “Different instances you might lose communications could be when, for instance, the Solar, comes between the Earth monitoring station and the spacecraft, the place the sign could be degraded by passing by means of the photo voltaic plasma.”
Dropping contact isn’t disastrous, although. “We have now high-fidelity predictions of the spacecraft trajectory that are simply ok to renew monitoring the spacecraft when the occasion inflicting a communication loss is over,” Stanbridge mentioned.
What route will Lucy take as soon as its mission is full, practically 15 years from now? “We’re simply going to go away it on the market,” Englander mentioned. “We did an evaluation to see if it passively hits something, and looking out far into the longer term, it doesn’t.” The Lucy crew has given the spacecraft a transparent path for 1000’s of years, lengthy after Lucy has rewritten the textbooks on our photo voltaic system’s historical past.
The Lucy mission is led by Principal Investigator Dr. Hal Levison from Southwest Analysis Institute in Boulder, Colorado. NASA Goddard in Greenbelt, Maryland, manages the mission. Lockheed Martin House in Denver will construct the spacecraft and conduct mission operations.