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The Europa Clipper spacecraft passed a major milestone Monday and is set to launch next month to explore one of Jupiter's moons and search for signs of habitability, NASA said. The launch window for the trip opens on Oct. 10.
The mission passed Key Decision Point E, a critical planning phase that cleared the mission to proceed with launch. The approval was a relief for the Europa Clipper team after the discovery in May of a potential problem with transistors on the spacecraft.
Transistors help regulate the vehicle's electricity flow, and engineers were concerned about the survival of these components in Jupiter's harsh radiation environment.
The transistors were extensively tested for four months at NASA's Jet Propulsion Laboratory in Pasadena, California; the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland; and NASA's Goddard Space Flight Center in Greenbelt, Maryland.
The team was able to complete the necessary tests in time, avoiding a 13-month delay in the launch to explore Europa, an ice-covered world that could potentially support life in its salty subsurface ocean. Europa Clipper carries 10 scientific instruments that could determine whether life is possible elsewhere in our solar system than Earth.
The launch of the Europa Clipper has now been approved, with no changes made to the mission plan, objectives or route.
"It's the last big review before we really get into launch fever, and we're very pleased to say that they've passed that review unequivocally today," Nicola Fox, deputy director of NASA's Science Mission Directorate, said during a press briefing on Monday.
Solving the radiation problem
In May, the manufacturer of the transistors warned the mission team that the components might not be as radiation-resistant as previously thought. The transistors are spread throughout the spacecraft.
Jupiter dwarfs other worlds as the largest planet in our solar system, and has a magnetic field 20,000 times stronger than Earth's. That magnetic field captures charged particles and accelerates them to high speeds. The fast-moving particles release energy in the form of intense radiation that bombards Europa and Jupiter's other nearby moons.
Any spacecraft going to Jupiter will need radiation-hardened electronics.
"Jupiter is surrounded by more radiation than any other planet in our solar system, which is one of the reasons why exploring the Jupiter system is such a challenge," said Jordan Evans, Europa Clipper project manager at JPL.
"Europa is on the outer edge of the worst part of that radiation belt," he added. "Flying near Europa exposes us to this high flux of harmful particles, and so the mission engineers and Europa Clipper have to be sure that the spacecraft components can survive that radiation environment for the duration of our four-year mission."
According to Evans, data from previous NASA missions to Jupiter, including the Juno probe currently studying the planet and some of its moons, were used to validate the transistor testing process.
The tests, which have been running around the clock since May, simulated the conditions of a spaceflight to see how the spacecraft and its components would behave as the craft flew past Europa 49 times over a four-year period, ultimately orbiting Jupiter 80 times.
The team found that the transistors can repair themselves between flybys.
"After all of these tests, we concluded that while Europa Clipper does enter the radiation environment during our orbits around Jupiter, it lasts long enough for the transistors to recover and partially repair themselves between flybys," Evans said.
A radiation monitor on the spacecraft allows the team to check how the transistors are doing.
"I am personally confident that we can complete the original mission to explore Europa as planned," Evans said.
Exploring an ocean world
When Curt Niebur, Europa Clipper program scientist, joined NASA in 2003, he was faced with the task of advancing a Europa mission. With each passing year, the effort to design and build Europa Clipper seemed harder, he said.
"There was no year more difficult than this past year and this past summer in particular," Niebur said. "But through it all, there was one thing we never doubted: This would be worth it. It's a chance for us to explore, not a world that was habitable billions of years ago, but a world that could be habitable today - a chance to do the first exploration of this new kind of world that we've discovered very recently, called an ocean world, which is just completely submerged and covered in a liquid ocean, completely unlike anything we've ever seen before. That's what's in store for us on Europa."
Europa Clipper is not a mission to search for life, Niebur added.
The mission's primary goals are to determine whether the right ingredients to support life as we know it - including water, energy and chemistry - are present on Europa. And without any scientific instrument that can directly determine the existence of life, Clipper can't find definitive evidence of it, he said.
"You can bet your bottom dollar that if the Europa Clipper tells us the ingredients are there, we will knock on the door and fight for a second mission to look for life," Niebur said.
According to JPL director Laurie Leshin, Europa Clipper will play an important role in determining where NASA should send follow-up missions, such as to parts of the icy crust that may be thin and where water from the subsurface ocean could flow.
"If we get there and do this research, and the good news is that it has all the ingredients and is habitable, that means there are two places in one solar system that have all the ingredients for life and are habitable right now," Niebur said.
"Think about what that means if you extrapolate that result to the billions and billions of other solar systems in this galaxy," he added. "Putting aside the question of 'Is there life on Europa?' the question of habitability alone opens up a huge new paradigm for the search for life in the galaxy."
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