Spacecraft

A compelling and challenging target of study like Europa requires a special spacecraft. Equipped with expansive solar arrays, a suite of sophisticated science instruments, two dozen engines, and a radiation-hardened electronics vault, Europa Clipper is, when its solar arrays and antennas are fully deployed, the largest spacecraft NASA has ever built for a planetary mission.

When stowed for launch, the spacecraft is about 15.5 feet (4.7 meters) tall, 10 feet (3 meters) wide, and 13 feet (4 meters) deep. With solar arrays fully deployed, Europa Clipper stretches over 100 feet (30.5 meters) wide, while the body and its radar antennas measure about 58 feet (17.6 meters) deep.

The heavy radiation environment at Jupiter is tough on spacecraft, so Europa Clipper has a metal vault with thickened walls to protect its sensitive electronics. The vault features a unique plate engraved with messages in the form of artwork and poetry, along with a microchip stenciled with more than 2.6 million names submitted by the public.

Combining elements from multiple NASA centers and partners, the spacecraft was assembled principally at NASA’s Jet Propulsion Laboratory in Southern California. The propulsion module — the structure of the main spacecraft body — was designed and built at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, in collaboration with NASA’s Goddard Spaceflight Center in Greenbelt, Maryland. Engineers at JPL then outfitted the module with key components, including nine science instruments, the electronics vault, and a high-gain antenna measuring 10 feet (3 meters) wide. Europa Clipper’s large solar arrays were added during final prelaunch preparations at NASA’s Kennedy Space Center in Florida.

At launch, the fully fueled Europa Clipper is expected to weigh approximately 12,800 pounds (about 5,800 kilograms). Over 6,060 pounds (about 2,750 kilograms) will be propellant.

Europa Clipper features nine science instruments, plus a gravity and radio science investigation that uses the spacecraft’s communications system. The instruments are located in several places on the spacecraft, with most concentrated on two sides: one set facing Europa’s surface during flybys and one pair facing in the spacecraft’s direction of travel. A 28-foot (8.5-meter) boom extending from the spacecraft bus holds Europa Clipper’s magnetometer sensors, while radar antennas extend in either direction from the spacecraft’s two solar arrays.

Europa Clipper’s appearance is dominated by its two large solar arrays, which span more than 100 feet (30.5 meters) from tip to tip. Each array is composed of five panels, and measures approximately 46.5 feet (14.2 meters) wide and about 13.5 feet (4.1 meters) tall. Together the arrays provide about 1,100 square feet (102 square meters) of surface area for generating power.

Jupiter’s distance from the Sun — over five times that of Earth’s distance — makes such large solar arrays a necessity. The planet’s radiation environment will also slowly degrade the arrays’ performance over time, so the system accounts for that. It is designed to provide at least 700 watts throughout Europa Clipper’s prime mission. When initially deployed shortly after launch, while the spacecraft is closer to the Sun, the solar arrays are expected to generate around 23,000 watts.

Europa Clipper’s propulsion module — the structure of the main spacecraft body — is an aluminum cylinder about 10 feet (3 meters) tall and 5 feet (1.5 meters) wide. Its tanks can hold over 6,060 pounds (2,750 kilograms) of propellant. The system’s 24 engines, each capable of generating 27.5 newtons of thrust, are used up to eight at a time for a maximum thrust of 220 newtons.

Europa Clipper must maintain a delicate thermal balance throughout its mission. While cruising through the inner solar system, the spacecraft endures considerable heating from the Sun, with some components able to reach temperatures above 212 degrees Fahrenheit (100 degrees Celsius). In such an environment, Europa Clipper must actively cool itself. But when operating farther out at Jupiter, the spacecraft must carefully manage its own heat so that it does not freeze during worst-case cold conditions, which could plunge some parts of the spacecraft to minus 382 F (minus 230 C).

Similarly, during flybys of Europa, when all its systems and instruments are turned on to collect and store science data, the spacecraft needs to recirculate the electronics’ heat to prevent overheating. And to optimize the collection of science data, Europa Clipper must cool some detectors on its instruments below minus 310 F (minus 190 C).

To manage these fluctuating extremes, pumps on Europa Clipper circulate fluids through pipes to the spacecraft’s sensitive electronics, carrying heat from hot spots to cold spots. Europa Clipper also has a radiator (which can be opened to shed heat), temperature sensors, heaters, and custom-sewn thermal blankets to help regulate the spacecraft’s temperature.

Europa Clipper is equipped with a 10-foot-diameter (3-meter) dish-shaped high-gain antenna to communicate with Earth. The spacecraft also carries seven smaller antennas that provide redundancy and will be used for gravity and radio science investigations. Mounted in various locations and orientations around the spacecraft, they will allow Europa Clipper to maintain communication even when operations require it to point its high-gain antenna away from Earth. For example, during its cruise through the inner solar system, Europa Clipper will orient itself such that it can use its high-gain antenna as a sun shield. When the spacecraft is flying by Europa, the high-gain antenna will point upward and away from the moon, and not toward Earth.

Like all NASA interplanetary missions, Europa Clipper will send data and receive commands via the agency’s Deep Space Network, which has three ground stations equidistant around Earth to communicate with and track spacecraft at or beyond the Moon. The Deep Space Network then routes the data back to Europa Clipper mission controllers through a ground data system at JPL.

Orbiting close to Jupiter, Europa is subject to intense radiation around the giant planet. To explore this hostile environment, Europa Clipper must orbit Jupiter at a distance, dipping in for a series of targeted flybys of Europa rather than orbiting the icy moon directly. However, even that will not be enough to fully avoid damage to the spacecraft’s sophisticated electronics. To further protect the mission, Europa Clipper is outfitted with a special vault to shield these critical components.

Made from sheets of aluminum-zinc alloy up to 0.36 inches (9.2 millimeters) thick, the vault is bolted to Europa Clipper’s propulsion module, the structure of the main spacecraft body. Inside sit radiation-sensitive electronics that control key systems, such as the science instruments, guidance and control systems, and thermal pumps.

Europa Clipper’s mission team will closely track the spacecraft’s radiation exposure and performance throughout the mission. One of the tools the spacecraft carries is a radiation monitor, which uses a network of sensors to keep tabs on its instruments and engineering subsystems. Primarily used as an engineering tool, the radiation monitor will also allow scientists to gauge how much their data collection is affected by radiation.

In keeping with a long tradition of NASA missions carrying inspirational messages from Earth, Europa Clipper’s design incorporates a unique metal plate engraved with poetry, artwork, and other messages that pay tribute to the connection between Europa’s ocean world and our own. Made of the metal tantalum, the triangular plate is about 7 by 11 inches (18 by 28 centimeters) and seals one of the openings on the electronics vault.

The outward-facing side of the vault plate features a design called “Water Words” — a visual representation of recordings of the words for water in over 100 languages from around the world. Water connects all life as we know it, as well as all human cultures.

Water also connects Earth and Europa, the two ocean worlds that the Europa Clipper spacecraft travels between on its journey. NASA’s “Message in a Bottle” campaign invited people around the world to “sign” their names to a poem written by the U.S. Poet Laureate Ada Limón. The poem, titled “In Praise of Mystery: A Poem for Europa,” is engraved in Limón’s own handwriting on the inward-facing side of the vault plate.

Above the poem is a drawing that represents the Jovian system and the orbits of its four largest moons, including Europa. An illustrated bottle shown at the center contains a dime-size microchip featuring 2.6 million names submitted by the public. The names were stenciled on the chip with an electron beam, which wrote each line of text at less than one-one-thousandth the width of a human hair (75 nanometers).

Also on the inward-facing side of the vault plate are three additional visual elements of particular meaning to the mission team:

• The Drake Equation: a mathematical formula, developed in 1961 by Astronomer Frank Drake (1930-2022), that estimates the possibility of finding advanced civilizations beyond Earth and has inspired related research ever since.
• Radio Emission Lines: an illustrative reference to radio frequencies considered plausible for interstellar communication, symbolizing how humanity uses the language of science and mathematics to follow its curiosity about life in the cosmos.
• A Tribute to Planetary Scientist Ron Greeley: a portrait of one of the pioneers of planetary science, Ron Greeley (1939-2011), whose early efforts to develop a Europa mission two decades ago laid the foundation for Europa Clipper.

For more on the unique design of Europa Clipper’s vault plate, visit go.nasa.gov/makewaves.