A year from launch, the Europa Clipper spacecraft nears finish line

KENNEDY SPACE CENTER, Fla.—The launch window for one of the most expensive robotic space missions in NASA's history opens one year from Tuesday. Coming in at $5 billion, Europa Clipper will try to help scientists answer a bold question commensurate with its eye-popping cost: Are there places below the surface of Jupiter’s icy moon, Europa, that could support life?

Europa is slightly smaller than Earth's Moon, and is significantly more interesting to scientists searching for life. The icy world harbors a vast global ocean of liquid water underneath a frozen crust. Clipper will sail past Europa nearly 50 times, coming as close as 16 miles (25 kilometers) from its icy surface to interrogate the moon with a sophisticated suite of nine instruments.

Jordan Evans, who leads the team developing Europa Clipper at NASA's Jet Propulsion Laboratory in California, told Ars on Tuesday the mission is on track to depart for Jupiter during a 21-day planetary launch window opening on October 10, 2024.

The engineers who map out intricate interplanetary trajectories have even determined exactly when Europa Clipper needs to launch. If it flies on the first day of the launch window, liftoff will occur at 11:51 am EDT, according to Evans. That could be slightly adjusted as navigators refine the mission's trajectory.

"It’s a 6,000-kilogram [13,000-pound] spacecraft with 100-foot [30-meter] wingspan solar arrays, with sensitive radar instruments on them, where all instruments have to operate simultaneously," Evans said. "So it’s a beast."

Evans spoke with Ars on Tuesday at the Kennedy Space Center, Europa Clipper's launch site, almost exactly one year, to the minute, before the mission's targeted liftoff time. Evans is at the site this week, familiarizing himself with SpaceX's operations as the company readies for the launch of a Falcon Heavy with NASA's Psyche asteroid mission.

"Clipper is doing great," Evans said, while acknowledging the mission has gone through its share of struggles.

Managers had to overcome staffing issues at JPL, which developed Europa Clipper in parallel with at least four other major missions. Then, a political battle was waged over which rocket would send Clipper into the Solar System. NASA officials finally ruled out launching Clipper on the Space Launch System after engineers discovered the spacecraft could be damaged by vibrations induced by the rocket's solid-fueled boosters.

In 2021, NASA selected SpaceX's Falcon Heavy for the job. The decision saved an estimated $2 billion, and some novel trajectory design allowed Europa Clipper to take a more direct route toward Jupiter than originally thought possible with a launch on a commercial rocket. That means Clipper will enter orbit around Jupiter in 2030.

The pandemic also threw a wrench into the mission. Delivery dates slipped for some of Clipper's science instruments as they encountered technical snags. But Evans said Tuesday that technicians assembling Clipper at JPL recently installed the final components needed for the spacecraft to start a final round of tests before shipment from the California lab to the launch site in Florida next May.

Those final additions included all but one of the mission's science instruments, a suite of cameras, spectrometers, and magnetometers to image Europa and measure the detailed composition of its icy shell. Clipper's electronics vault, an armored box to shield computers from the damaging radiation at Jupiter, was also recently installed on the main body of the spacecraft, along with a high-gain communications antenna to transmit data back to Earth.

“At launch minus one year, we have taken the flight vehicle through all of its paces," Evans said. "We’ve simulated launch, we’ve simulated trajectory correction maneuvers, Jupiter orbit insertion, and flybys of Europa with all the instruments operating on the flight hardware and software. The system performed great."

Testing on tap

Later this month, Clipper's ground team at JPL will move the spacecraft into a test chamber to blast it with sound, mimicking the acoustic environment it will have to withstand during launch. They will also put Clipper through vibration and shock testing to see how the craft responds to the shaking of a rocket flight.

Then comes an electromagnetic compatibility test, a milestone to ensure all of the electronics aboard Clipper can operate together as designed. Around the end of the year, engineers will transfer the spacecraft into a thermal vacuum chamber to subject it to the extreme hot and cold temperature swings it will see in space.

Some of the tests still to come for Clipper will be simulations to check the spacecraft's response to problems. Can the spacecraft detect, diagnose, and protect itself against the glitches that could crop up during its mission?

“From here on out, it’s all system-level testing to ensure that any flaws that got into that vehicle—because it is the work of human hands—that we can find them and correct them, if necessary, before we get to launch one year from today," Evans said.

After transporting the spacecraft across the country to Florida, Clipper's engineers will install the spacecraft's European-built solar arrays. Antennas for the mission's radar instrument will be mounted on the deployable solar panels. This radar package will measure the thickness of Europa's global ice sheet, and study the internal structure of the icy crust, perhaps finding pockets of liquid water that connect the surface with the ocean below.

The radar is one of the instruments that sets Clipper apart from NASA's Galileo spacecraft, which gathered much of the information we know about Europa during its mission at Jupiter more than 20 years ago. Mission managers decided to install the solar panels and radar antennas at the launch site, rather than at JPL, as a hedge against delays in delivering those elements.

“There are always schedule risks," Evans said. "The team knows we’ve got a lot still ahead of us, but we definitely have ample schedule margin (for launch next October)."

Clipper, then what?

NASA's budget, like that of much of the federal government, is facing headwinds after the Biden administration and lawmakers agreed in June on spending caps on discretionary spending. Draft spending plans for fiscal year 2024 released by House and Senate committees earlier this year suggest Congress will primarily target NASA's science division for funding cuts while preserving money for the Artemis human exploration program to return astronauts to the Moon.

Planetary exploration has the largest budget among the disciplines in NASA's science division, about 50 percent more than Earth science and double the agency's astrophysics budget in fiscal year 2023. And planetary science missions aren't cheap. Even a mission like the Psyche asteroid explorer, which is part of NASA's cost-capped, lower-budget "Discovery" program, costs about $1.2 billion.

NASA's next big flagship-class planetary science priority after Europa Clipper is the Mars Sample Return mission, and it's in trouble, according to the results of an independent review released last month. NASA had been planning to launch the critical elements of its Mars Sample Return mission as soon as 2028, with a total budget for the program of $4.4 billion.

The review panel found that's just not realistic. The very earliest the mission could launch from Earth is 2030, and this opportunity would only be possible with a total budget of $8 billion to $11 billion.

NASA is taking the next few months to digest the review panel's recommendations. Going in, NASA's plan for Mars Sample Return was to retrieve tubes of rock specimens collected by the Perseverance rover, currently on Mars, and then launch them into space with a small rocket. A return spacecraft provided by the European Space Agency would pick up the samples and bring them back to Earth.

"They put some very actionable things in there, and some really great suggestions, looking at maybe other ways to implement the mission, and making sure that architecture is absolutely the right one to do," said Nicky Fox, the associate administrator for NASA's science division. "Are there ways that we can just change the mission design so that the annual cost comes down?

“We're very committed to bringing samples back from Mars," Fox said in an interview. "We're very, very committed to doing it. We're just going to take the next few months to make sure that we really are doing it in the best way."

With billions of dollars of expenditures for Mars Sample Return on the horizon and a tight budget environment across the federal government, NASA is taking a pause on approving new planetary science missions for development.

"It definitely has an impact to us," said Lori Glaze, director of NASA's planetary science division. "One of the few knobs that we have at NASA, that we can turn to adjust to those tightening budgets, is to delay some of those new opportunities. It's unfortunate. It’s not what we want to do. But we also don't want to start up new projects when we can't commit to the full funding that's going to be necessary."

Last month, NASA announced it would delay the next opportunity for a medium-class "New Frontiers" planetary science mission from this year until no earlier than 2026 because of budget issues.

The focus now for NASA's planetary science division is executing on the missions already in the pipeline.

“We have four missions in our portfolio that have already passed what we call their confirmation review, which is the point where NASA makes a commitment to the US government on cost and schedule," Glaze said.

Those four missions are Psyche, set for launch this week; Europa Clipper, launching next year; a lunar rover called VIPER, also set for launch next year, that will search for water near the Moon's south pole; and the Near Earth Object Surveyor, a telescope scheduled to launch no later than 2028 to find asteroids that might threaten Earth.