On March 1, NASA’s Europa Clipper will streak just 550 miles (884 kilometers) above the surface of Mars for what’s known as a gravity assist — a maneuver to bend the spacecraft’s trajectory and position it for a critical leg of its long voyage to the Jupiter system. The close flyby offers a bonus opportunity for mission scientists, who will test their radar instrument and thermal imager.
Europa Clipper will be closest to the Red Planet at 12:57 p.m. EST, approaching it at about 15.2 miles per second (24.5 kilometers per second) relative to the Sun. For about 12 hours prior and 12 hours after that time, the spacecraft will use the gravitational pull of Mars to pump the brakes and reshape its orbit around the Sun. As the orbiter leaves Mars behind, it will be traveling at a speed of about 14 miles per second (22.5 kilometers per second).
The flyby sets up Europa Clipper for its second gravity assist — a close encounter with Earth in December 2026 that will act as a slingshot and give the spacecraft a velocity boost. After that, it’s a straightforward trek to the outer solar system; the probe is set to arrive at Jupiter’s orbit in April 2030.
This animation depicts NASA’s Europa Clipper as it flies by the Red Planet. The spacecraft will use the planet’s gravity to bend its path slightly, setting up the next leg of its long journey to investigate Jupiter’s icy moon Europa.
“We come in very fast, and the gravity from Mars acts on the spacecraft to bend its path,” said Brett Smith, a mission systems engineer at NASA’s Jet Propulsion Laboratory in Southern California. “Meanwhile, we’re exchanging a small amount of energy with the planet, so we leave on a path that will bring us back past Earth.”
Harnessing Gravity
Europa Clipper launched from Kennedy Space Center in Florida on Oct. 14, 2024, via a SpaceX Falcon Heavy, embarking on a 1.8-billion-mile (2.9-billion-kilometer) trip to Jupiter, which is five times farther from the Sun than Earth is. Without the assists from Mars in 2025 and from Earth in 2026, the 12,750-pound (6,000-kilogram) spacecraft would require additional propellant, which adds weight and cost, or it would take much longer to get to Jupiter.
Gravity assists are baked into NASA’s mission planning, as engineers figure out early on how to make the most of the momentum in our solar system. Famously, the Voyager 1 and Voyager 2 spacecraft, which launched in 1977, took advantage of a once-in-a-lifetime planetary lineup to fly by the gas giants, harnessing their gravity and capturing data about them.
About 4½ months after its launch, NASA’s Europa Clipper is set to perform a gravity assist maneuver as it flies by Mars on March 1. Next year the spacecraft will swing back by Earth for a final gravity assist before heading to Jupiter’s orbit.
While navigators at JPL, which manages Europa Clipper and Voyager, have been designing flight paths and using gravity assists for decades, the process of calculating a spacecraft’s trajectory in relation to planets that are constantly on the move is never simple.
“It’s like a game of billiards around the solar system, flying by a couple of planets at just the right angle and timing to build up the energy we need to get to Jupiter and Europa,” said JPL’s Ben Bradley, Europa Clipper mission planner. “Everything has to line up — the geometry of the solar system has to be just right to pull it off.”
Refining the Path
Navigators sent the spacecraft on an initial trajectory that left some buffer around Mars so that if anything were to go wrong in the weeks after launch, Europa Clipper wouldn’t risk impacting the planet. Then the team used the spacecraft’s engines to veer closer to Mars’ orbit in what are called trajectory correction maneuvers, or TCMs.
Never Miss a Discovery
Mission controllers have performed three TCMs to set the stage for the Mars gravity assist — in early November, late January, and on Feb. 14. They will conduct another TCM about 15 days after the Mars flyby to ensure the spacecraft is on track and are likely to conduct additional ones — upwards of 200 — throughout the mission, which is set to last until 2034.
Opportunity for Science
While navigators are relying on the gravity assist for fuel efficiency and to keep the spacecraft on their planned path, scientists are looking forward to the event to take advantage of the close proximity to the Red Planet and test two of the mission’s science instruments.
About a day prior to the closest approach, the mission will calibrate the thermal imager, resulting in a multicolored image of Mars in the months following as the data is returned and scientists process the data. And near closest approach, they’ll have the radar instrument perform a test of its operations — the first time all its components will be tested together. The radar antennas are so massive, and the wavelengths they produce so long that it wasn’t possible for engineers to test them on Earth before launch.
More About Europa Clipper
Europa Clipper’s three main science objectives are to determine the thickness of the moon’s icy shell and its interactions with the ocean below, to investigate its composition, and to characterize its geology. The mission’s detailed exploration of Europa will help scientists better understand the astrobiological potential for habitable worlds beyond our planet.
Managed by Caltech in Pasadena, California, JPL leads the development of the Europa Clipper mission in partnership with the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, for NASA’s Science Mission Directorate in Washington. APL designed the main spacecraft body in collaboration with JPL and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, NASA’s Marshall Space Flight Center in Huntsville, Alabama, and Langley Research Center in Hampton, Virginia. The Planetary Missions Program Office at Marshall executes program management of the Europa Clipper mission. NASA’s Launch Services Program, based at Kennedy, managed the launch service for the Europa Clipper spacecraft.
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