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NASA's Europa Clipper is already on its way to Jupiter's icy moon Europa, scheduled to arrive in 2030. While its science instruments aren't operational yet, its star trackers are busy taking images of distant stars to help orient the spacecraft. These images of the star field, which includes the constellation of Vor, are crucial for navigation and ensuring that the spacecraft can properly align its antennas and instruments.
Star trackers: cosmic compass
Three months after launching from the Kennedy Space Center in Florida, the Europa Clipper spacecraft still has 1,6 billion miles (2,6 billion kilometers) to travel before reaching Jupiter's orbit in 2030. Once there, it will use its science cameras to take detailed images of Europa, the planet's icy moon.
But even as it makes its long journey, another set of cameras is already at work. These cameras, known as star trackers, don't take pictures for research—they help the spacecraft navigate. By capturing images of stars and using them as reference points, star trackers determine the spacecraft's precise orientation. This is essential to keeping its antennas aligned with Earth for uninterrupted communications.
First look at space
In early December, star trackers captured and transmitted the first images of Europa Clipper from deep space (see below). The composite image, made up of three images, shows faint specks of light from stars located 150-300 light-years away. Although the image represents only 0,1% of the sky around the spacecraft, this small star field provides the orbiter with enough data to confirm its orientation.
Among the stars in the image are the four brightest stars in the constellation Corvus—Hyena, Algorabus, Crassus, and Alcibus. Corvus, which means "crow" in Latin, is associated with Apollo in Greek mythology.
Hardware Check: Ensuring Smooth Operation
In addition to being interesting for stargazers, the photos demonstrate a successful validation of the star trackers. The validation phase of the spacecraft has been ongoing since the Europa Clipper launched aboard a SpaceX Falcon Heavy rocket on October 14, 2024.
“Star trackers are engineering equipment that always takes images that are processed on board,” said Joanie Noonan of NASA’s Jet Propulsion Laboratory in Southern California, who manages guidance, navigation and control operations. “Normally, we don’t transmit images from trackers, but in this case, we did because it’s a really good way to make sure that the hardware — including the cameras and their lenses — made it through the launch safely.”
Preparing for close-ups of Europe
Correctly pointing a spacecraft is not about navigation, which is a separate operation. But orientation using star trackers is crucial for telecommunications as well as for the mission’s science operations. Engineers need to know where the science instruments are pointing. This includes the sophisticated Europa Imaging System (EIS), which will collect images that will help scientists map and explore the moon’s mysterious faults, ridges, and valleys. The EIS’s protective covers are closed for at least the next three years.
Europa Clipper carries nine scientific instruments, as well as telecommunications equipment that will be used to study gravity. During the mission's 49 flybys of Europa, the spacecraft will collect data that will show scientists whether the icy moon and its internal ocean are habitable.
The spacecraft is already 54 million miles (85 million kilometers) from Earth, hurtling at 17 miles per second (27 kilometers per second) relative to the sun, and will soon fly past Mars. On March 1, engineers will loop the craft around the Red Planet, using its gravity to gain speed.
More about Europa Clipper
Europa Clipper is NASA’s ambitious mission to explore Jupiter’s moon Europa, a world believed to harbor a vast subsurface ocean beneath its icy crust. The spacecraft, scheduled to arrive in Jupiter’s orbit in 2030, will fly by Europa in detail to study its potential to support life. The mission has three primary scientific objectives: determining the thickness of the moon’s icy shell and its interaction with the ocean beneath it, analyzing Europa’s composition, and characterizing its surface geology. By studying these aspects, scientists aim to better understand Europa’s habitability and the broader potential for life beyond Earth.
Europa Clipper is a collaborative effort led by NASA's Jet Propulsion Laboratory (JPL) in partnership with the Johns Hopkins Applied Physics Laboratory (APL) and several NASA centers, including Goddard, Marshall, and Langley. APL designed the spacecraft's hull, and NASA's Kennedy Space Center oversaw the launch. Managed by NASA's Planetary Missions Program, Europa Clipper is a major step forward in the search for extraterrestrial life in our solar system.
