Next Launch:

Europa Clipper Inches Forward, Shackled to the Earth

David W. Brown
David Kramer
October 6, 202010:00 AM UTC (UTC +0)

“Before you go in, you’ll need this and these and this and this and these,” says the engineer, shoving an armful of protective garments at me, and I’m stripped of my watch and phone and ornamented in a hairnet, latex gloves, white coveralls made of some indeterminate, synthetic material, a fresh face mask, and disposable shoe coverings (sort of like shower caps, but for Chuck Taylors), and moments later I’m on the other side of the glass in a cleanroom at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, face-to-face with the central nervous system of a spaceship that could help us solve the ultimate question: are we alone in the universe?  

What I am looking at is the vast network of wiring to be installed in Europa Clipper, an orbiter that will launch to Jupiter no earlier than 2024. The spacecraft is NASA’s outer planets flagship mission — the agency’s Starship Enterprise — and it will study the habitability of Europa, an ice-covered ocean moon. If the clouds of cruel Venus have the potential for life, the saltwater seas of Europa promise to be a veritable aquatic Eden. To determine whether creatures can exist there, Europa Clipper will orbit Jupiter multiple times, scanning Europa in slices at each encounter, building over time a global map of the frozen moon. This mission is decades in the making, and here, in this room, some small part of it is real. A Europa expedition is no longer “if” or “how,” but “how soon?” And what it promises, to quote Philip K. Dick, is not “what if,” but “my God, what if?

Up close in the cleanroom, the wires are zip-tied in bundles, long and winding plexes every color of the rainbow. The tendrils are attached to a horizontal silver cylinder about the size of a telephone booth. The way they are wrapped, they look like a subway map. Brackets and arms and bolts and ribbing jut from the cylinder — a “harness model,” it is called — and the whole thing is mounted on a rack system that allows the unit to be angled and rotated for engineers to install wires wherever necessary. The wires — called collectively the “wiring harness” — will one day connect all of Europa Clipper’s computers and scientific instrumentation and various spacecraft subsystems, e pluribus unum

The wiring is going to space, but the harness model is only a placeholder. Next year, these wires will be removed from the cylinder and installed on the actual spacecraft being built across the country, at Caltech’s Jet Propulsion Laboratory in Pasadena, California. In ten years, electrons will surge through them as Europa Clipper circles Jupiter, enduring all the while the merciless radiation of the Jovian system. The spacecraft’s instruments will reveal beneath Europa’s ice shell a liquid ocean with three times the amount of saltwater found here on Earth.

If there is complex life anywhere else in the solar system, it is there, in that water. Which means JPL, APL, and a handful of NASA centers across the country are building a spacecraft that will address questions that directly affect philosophy, religion, and humankind’s place in the universe. What NASA finds at Europa might literally change everything, and Europa Clipper is central to this effort. 

But Europa is not easily explored. It is a pitiless Thunderdome setting humanity’s best engineers against the solar system’s most vexing planetary system. And where the science and engineering challenges have been steep, the political difficulties of the mission have at times been maddening, byzantine, preposterous, Kafkaesque. The Jupiter system and its radiation, at least, are constrained by the laws of physics. Washington D.C., on the other hand, is driven by ego and ignorance, neither of which know any limitation. That these wires are real is a triumph of scientific steadfastness against all odds. And it will take more tenacity yet to finish the job; every spacecraft needs a rocket, but the one assigned to Europa Clipper has become an anchor tethering it to the Earth.


Flying a spacecraft a billion miles is easy. It’s the first inch off the launch pad that’s hard. Europa Clipper is not the planetary science community’s first stab at a dedicated mission to the Jovian moon. Since the late 1990s, NASA headquarters has funded study after study after study, with Jet Propulsion Laboratory designing six major mission concepts, and a dozen smaller, internal lab efforts. Before finding success with a “multiple flyby mission,” they tried simple Europa orbiters; fission-powered Battlestars; joint Jovian system missions with the Europeans; behemoth, radiation-hardened orbiters; and a tag-team “split-mission” concept of two spacecraft or more. 

Every step of the way, NASA’s science mission directorate came back with new instructions: make it bigger. Make it smaller. Make it land. Chop a billion from the price tag. Add a billion. OK, not that much. You know what? Let’s just go to Mars instead.

The problem is Europa. Space is hard, but the exploration of Europa is something else entirely. The Jovian radiation belt, where the ocean world resides, is perhaps the least hospitable region in the solar system. Its conditions are similar to those found in the immediate aftermath of a detonated thermonuclear bomb. Spacecraft can survive there temporarily if they carry heavy shielding, but even that is no panacea: in the end, Jupiter’s radiation will have its way, and the robotic spacecraft brains will see zeroes flipped to ones, and it’s goodnight, Gracie. 

A 90-day rover can land on Mars and roll around for fifteen years. A 90-day orbiter at Europa does its best science in the first 30 because after that, who knows? By the time a Europa orbiter’s prime mission is completed, the NASA logo painted on its hull would be crazed and blackened from radiation, and any onboard glasses and lenses discolored and fogged. Scorch marks from electrostatic discharges would scar surfaces on its metallic bus, and the interior systems of the poor, radiation poisoned spacecraft would be bruised and moribund.

Which is why Europa Clipper does not orbit Europa. By orbiting Jupiter instead, it can dip into the radiation and speed to Europa, swinging by only long enough to collect a raft of data and then zipping away before the radiation can do much lasting damage. That doesn’t make the mission easy; it just makes it less impossible. Perhaps no orbiter ever built by NASA has needed the resilience of Europa Clipper. The spacecraft’s computers still must be able to endure regular, severe salvos of charged particles. To understand Europa’s ocean and interior lakes, its delicate instruments must be able to see into a granite-hard ice shell that is miles thick. Moreover, its parts must operate in extreme thermal environments: When the spacecraft is in sunlight, it is relatively warm. When it circles to the other side of Jupiter, it plunges to cryogenic temperatures, the enormous planet blocking the rays of the Sun. And the whole thing is powered by solar panels whose wingspan is that of a basketball court. That’s a lot of imperiled surface area.

There’s a reason why Jet Propulsion Laboratory — the NASA center leading the Europa effort — has as its motto “Dare Mighty Things.” Only the smartest scientists and engineers in the world could build a spacecraft that could enter the Jovian badlands, take an Ivan-Drago-like beating, and emerge intact with the answers to Europa’s myriad, vexing questions. There might be an Ocean of Eden down there. There might be complex life.

In the Europa mission sequence — a multiple flyby mission, and a one day lander — the stakes are too high for ambiguity.


“It's becoming real,” says Cynthia Phillips, a Jet Propulsion Laboratory-based project staff scientist on Europa Clipper. “Right now, seeing the engineering models of these instruments get built, and then starting to see actual flight hardware get built? Oh my god — I mean, this is everything that I've been holding my breath for — for 20 years now!” 

Phillips has been in the trenches since the days of the Galileo spacecraft, which flew from 1989 to 1995. “It still surprises me how emotional the experience is,” she says, “for me to see a picture of, you know, this is a piece of this instrument that's going to actually be on the spacecraft and go to Jupiter and take pictures of Europa, or take observations of Europa. It's phenomenal, right?”

The Europa Clipper project is in what NASA calls development phase C, during which time its designs are tightened until the screws won’t budge. During this phase, components begin fabrication and things start getting built. The wiring harness at the Applied Physics Laboratory is among those critical spacecraft subsystems that once existed only as dreams, and then as bits, and now are atoms. In December, a successful “project critical design review” will unleash engineers in force to spark blowtorches and start building themselves a spaceship.

That doesn’t mean the challenges of spacecraft design and development are over. To study Europa, the spacecraft will carry nine scientific instruments devised to do everything from determining surface composition to map the ice shell in three dimensions. Each instrument is its own multi-million-dollar project being developed by various institutions in government, academia, and the private sector. Each is led by a principal investigator, has its own goals, its own culture, and its own obligations to the wider project through interdisciplinary working groups. 

The mission has of late been going through a “continuation review risk assessment,” part of a cost trigger process imposed by NASA headquarters. Each instrument has been under unprecedented scrutiny to stay on time and on budget. Start bleeding dollars, and you need to come up with a plan, stat, to get your house in order. The message to instrument teams has been unambiguous: stay on target or risk removal from the project.

“That’s really been the sword that’s been hanging over the heads of so many of the teams for the last year,” says Philips. “A couple of the instruments were always right around the danger zone and it was really stressful. I’ve been really impressed by how the principal investigators have dealt with this constant pressure.”

The simple reason for all this is that flagship missions — and Mars missions in particular — have historically experienced uncontrolled cost growth during development, with missions blowing their budgets and then going to headquarters, hat in hand, asking for more and more money. If a two-billion-dollar mission needs an extra $500 million, that essentially eats a small, Discovery-class mission to some other world — something akin to the MESSENGER mission to Mercury, or the Dawn mission to Vesta and Ceres. Instruments on flagship missions have historically been an area with unexpected design challenges that cost big dollars to correct.

Last month, NASA headquarters and Europa Clipper project leadership announced that two instruments are in danger. The Mass Spectrometer for Planetary Exploration experiment, or MASPEX, will, among other things measure organic compounds in Europa’s plumes — the columns of water vapor being blasted from the ice shell’s interior to perhaps hundreds of miles in space. The ratios of organics allow scientists to infer the ocean’s habitability. Meanwhile, the wide-angle camera of the Europa Imaging System (EIS) will capture those big, beautiful images of Europa that will one-day grace textbooks —  images that will both engage the public, and for researchers, provide greater context for the findings of the rest of the science payload. 

Both instruments have experienced untenable cost growth and were given orders to modify their designs to stop the bleeding. For MASPEX, NASA increased the level of risk it was willing to take in its development, and reduced the overall mission’s reliance on the data it would collect, looking to other instruments to pick up the slack should things go south. The principal investigator of the MASPEX instrument was also replaced. For EIS, the team was told to focus on the narrow-angle camera, and just do what it can with the wide-angle one.

NASA and Europa Clipper leadership are confident that both instruments are on firmer footing now in their development processes, and will fly with the spacecraft as intended. But NASA headquarters stated unambiguously that it is willing to launch the spacecraft without one or both of them.

“MASPEX is the one that everyone is the most worried about,” says Phillips. “The fact that it had a PI change—that’s a big deal. We had that happen once with ICEMAG,” says Phillips. “That was the first round of payload trauma that we went through.”

Last year, ICEMAG—the Interior Characterization of Europa Using Magnetometry—magnetometer instrument breached its cost box during development and was summarily cut from the instrument payload. Europa’s subsurface ocean was discovered in 2000 by the Galileo magnetometer team, led by Margaret Kivelson, a space physicist at UCLA. ICEMAG, led by Carol Raymond of Jet Propulsion Laboratory, was to have constrained the ocean’s characteristics, including its depth, salinity, and thickness. No longer part of the formal instrument payload, it has since been replaced with a “facility instrument.” The new magnetometer is considered a flight system now, wrenched from the hands of scientists, and placed squarely under the aegis of engineers. It has been “descoped”—simplified, in other words, and less powerful—and without a principal investigator to oversee the give-and-take scientific desires and engineering restraint. The project asked Kivelson, the grande dame of space physics, to take lead over the science team.

“A descope is not a minor decision,” says Xianzhe Jia of the University of Michigan, who is the deputy lead on the magnetometer team. “As a facility instrument, there's no role for a PI to manage the entire thing. We have a science team led by Margaret Kivelson, but the project is managing the hardware team.” He says that the two teams have worked well together so far, discussing measurement requirements, design changes, and what kind of impact any design change would have on the science.

“We're being given the opportunity to continue this experiment, and every one of us wants to make the magnetometry experiment a success in the end. Since the descope, we've overcome many obstacles, including the collaboration between two teams, and it's not a trivial task. You not only have to work within our own team, you have to also coordinate with the project and the other instruments.”

Diana Blaney, a planetary scientist and the principal investigator of the Mapping Image Spectrometer for Europa (MISE), explains that the challenges that instruments are encountering relate directly to the challenges of the environment in which they will be operating. 

“We've had technical challenges,” she says of MISE, which will study the surface composition of Europa. “I feel very fortunate that we have managed to resolve all of them, but that doesn't mean that we're not going to have problems. These are all first-time instruments. No one ever has built anything like this before.” Europa's radiation environment, she says, is a hard environment to build for. “We're a cryogenic instrument on a solar-powered spacecraft! The amount of sunlight at Europa is twenty-five times less than Earth, and we're moving over the surface at four kilometers per second, trying to get enough light to take eight to one hundred meters per pixel on the surface. So you know, we have to really push our optical performance, push the radiation shielding, and keep radiation noise low. It's a real challenge to do the science we're trying to do.”

With all those challenges and all those changes — to ICEMAG, to MASPEX, to the wide-angle camera — I asked Robert Pappalardo, the project scientist of Europa Clipper — its Jean-Luc Picard — whether NASA is sacrificing the instrument fidelity of a mission that scientists and engineers have spent decades trying to launch. Compared to what the Europa team wanted all those years ago, how good is the revised and pared-back suite of instruments? Pappalardo doesn’t hesitate in his answer: “Better than ever anticipated or dreamed up,” he says. “That's the honest truth.” 

For example, in the case of the magnetometer, the sensors that were de-scoped were never even envisioned by the “science definition team” that conceived the Europa mission. “The science being done is at least as good as that group had envisioned. The mass spectrometer is still more capable than wished for even if it can't deliver on everything its proposal said it would do. It’s still better than we had hoped.” He says the camera, when conceptualized, did not have a gimbal system where it could point independently and get the unprecedented spatial coverage that it will now be able to achieve. And though there were discussions all those years ago, the team didn’t expect to fly a dust detector or an ultraviolet spectrometer. 

“This is a fantastic payload,” he says, “and despite a couple of hiccups along the way, we are beyond the wildest expectations when this mission was being conceived.”


But for any of this to matter, Europa Clipper has to get to Europa. Which means we have to talk about the rocket.

Outer planets flagship missions have a tortured relationship with NASA’s pet launch vehicle of the moment. The Jovian system seems especially cursed in that regard. The spacecraft Galileo was tied to the space shuttle, which needed big, important missions to justify its existence in the years preceding the construction of the space station. When the shuttle fleet was grounded in the aftermath of the Challenger tragedy, Galileo — which could have launched on any big rocket — moldered for years in a warehouse, where, unknowingly, the lubricant dried on its umbrella-like high gain antenna. When at last the spacecraft launched and the high-gain antenna was ordered to unfurl, it would not open. This was an existential-level crisis for the mission. The high-gain antenna had a sixteen-foot diameter and would have blasted data back to Earth like the Death Star cannon.

Engineers had to find a way to make the low gain antenna somehow work despite it being about the size of a coffee can, with one-ten-thousandth of the high gain’s data capability. Through clever compression algorithms, the inventive use of a vestigial reel-to-reel recorder on the spacecraft, and by cranking up the sensitivity of the Deep Space Network, which communicated with Galileo far from Earth, they managed to improve things by two orders of magnitude. That Galileo achieved anything at all is one of the great stories of space exploration — Apollo 13, with robots — but the mission could have achieved so much more. Though it is an imperfect comparison, the Cassini mission at Saturn was able to return more images every orbit than Galileo managed to return in its entire lifetime.

Thirty-one years after Galileo launched and lessons were supposedly learned, Europa Clipper is wedded to NASA’s Space Launch System (SLS) rocket. In the beginning, the two projects were the perfect pairing. SLS was sold publicly as NASA’s “Mars rocket,” a heavy-lift launch vehicle that would put astronauts at last on the Red Planet. Aerospace lobbyists and eager members of the U.S. Senate willed the rocket into existence and using the power of the purse, coerced NASA to get on board. The problem for a Mars rocket was that NASA needed (indeed, still needs) another twenty years to build a crewed Mars program, and as such, the rocket had nowhere to go, no urgency, no missions of consequence to justify its existence.

Meanwhile, Europa Clipper, bound for the outer solar system, would, on a conventional rocket, take seven years or longer to get to its target. That meant something like $50 million per year would be spent on the cruise phase of the mission alone, to say nothing of the decade-plus that scientists had already spent waiting. The SLS rocket, though? Rather than have Europa Clipper rely on gravity assists from planets along the way, SLS could blast the spacecraft like a cannon, sending it on a straight shot to Jupiter. It could get Europa Clipper there in two-and-a-half years. It was the best deal space science had ever seen. Then the fingers on the monkey’s paw curled up.

On the ninth floor of NASA headquarters, SLS helped seal the deal for a Europa mission, saving money and time, and giving the human spaceflight side of the house a vested interest in a Europa expedition’s success. (SLS would become the first rocket whose design was directly influenced by a robotic mission.) To win support for Europa Clipper in the Senate, House appropriators even inserted language into the appropriations bill mandating the launch of Europa Clipper on the SLS rocket. It was a good decision and kept Europa Clipper safe even after its chief advocate in Congress, Rep. John Culberson of Texas, lost reelection in 2018. 

But while Europa Clipper has maintained a rigid development cadence and painful adherence to cost, SLS… has not. It is at least 33% over budget. Its first launch was supposed to happen three years ago for $10 billion in total development costs; the current best-case scenario for its maiden voyage is now November, though a recent inspector general report states that the launch will likely be pushed to Spring 2021, bringing its already ballooned price to $18.3 billion. Europa Clipper will be ready for the launch pad at the end of 2024. Barring a miracle, an SLS rocket will not be there waiting for it. The gargantuan rocket is not reusable like the Falcon Heavy. Each will launch and then plunge into the ocean, and schools of startled fish will never know that the engines on that rocket came from the space shuttle. They will never know that NASA—under orders from Congress—took reusable rocket engines and forced them onto an expendable rocket.

Each SLS rocket will have to be built from scratch. If NASA actually builds a second or even third SLS, the rocket program will be co-opted by the Artemis moon program (Alas, hashtag #journeytomars). In other words, those rockets are now spoken for. Europa Clipper, which must by law launch on SLS, is not even on the SLS launch manifest. For about a year, in fact, the SLS program essentially stopped taking the Europa Clipper team’s calls, setting back spacecraft development.

The math doesn’t add up. If SLS still exists as a program in 2024—something even Charlie Bolden, former administrator of NASA and an ardent SLS proponent, now concedes is unlikely—it is nearly inconceivable that there will be a rocket ready to launch a Europa mission. NASA is, and has always been, a human spaceflight organization; if the Artemis program needs a rocket, history suggests that the Jupiter system will just have to get in line. This would not be a problem under most circumstances: NASA could simply use a Falcon Heavy rocket to loft Europa Clipper, and leave SLS to the Artemis program. But the agency’s hands are tied. Despite years of surreptitious efforts by NASA’s emissaries, the Senate seems unwilling to let go of the pairing.

The very rocket that elevated Europa Clipper to full mission status within the agency is now tethering it to the Earth. What no one on the Europa Clipper team is willing to say is that Congress has passed an impossibility into law, and may as well mandate that the spacecraft launch on a flying saucer or a space elevator. (The response from headquarters whenever asked about Europa Clipper’s launch vehicle is always the same: “NASA will follow the law regarding launch of the Europa Clipper mission,” as NASA Administrator Jim Bridenstine said last year.) 

Does everyone want SLS to be a success, and for a rocket to materialize with plenty of time to launch Europa Clipper? Yep! Does anyone — anyone — think that will happen? Nope! As I type this, engineers at Jet Propulsion Laboratory are forced to do everything twice: making plans for Europa Clipper to launch on a Falcon Heavy and a completely different set of plans for SLS. 

“We are working parallel paths of SLS and a commercial launch vehicle, and it's starting to strain the system,” admits Pappalardo. 

When the project critical design review was pushed to December, it wasn’t because the Europa Clipper team had fallen behind. Rather, it was to accommodate the SLS dilemma. What once was an annoyance is now a serious problem for the mission. Until a rocket is chosen — and since SLS will not actually be the one — it is metaphysically impossible to refine the spacecraft design at the fidelity necessary to start building the thing. Engineers strive to account for every atom, gram, and molecule of their spacecraft and optimize it for every newton of force anticipated by the launch vehicle. 

This level of design is painstaking and expensive, and they’re having to do it twice: once for the rocket that will fly, and once for SLS. The SLS project is only now doing “coupled loads analysis” for Europa Clipper. That’s where the launch is simulated every which way, and engineers find out if the ensuing forces break the spacecraft. While nothing official has been announced, Lori Glaze, the director of NASA’s Planetary Science Division, revealed recently that “compatibility” issues between SLS and Europa Clipper have been uncovered.

Illuminating the insanity is that the Falcon Heavy rocket, having three launches under its belt, has proven more powerful than originally anticipated. Previously, it was thought that launching Europa Clipper on a Falcon Heavy would require a “kick” stage — essentially a small booster attached to the top of the rocket. The Falcon Heavy’s impressive performance has made that unnecessary. Moreover, mission designers at Jet Propulsion Laboratory have found a path to Jupiter called a MEGA trajectory: after launch on a Falcon Heavy, Europa Clipper would fly to Mars for a gravity assist, and then return to Earth for another, and then on to the Jovian system. (The mission previously believed that the rocket would necessitate a Venus gravity assist, which would require special thermal protection for the spacecraft.) 

The window for a MEGA launch opens in 2024 and would take only three years longer than an SLS flight. A Falcon Heavy expendable launch is about $150 million. A single SLS launch is now estimated to cost $2 billion. Even accounting for the cost during the three extra years of cruise to Jupiter, the money saved could pay for a trio of Discovery-class missions, or make a nice down payment on a future Europa Lander or Venus flagship.

One by one, the obstacles to a Falcon Heavy launch have fallen away. Only the Senate — rocket scientists, none of them — stand in the way.


Those are details to be worked out by others. For Pappalardo, who has been at the forefront of Europa scholarship since such a thing existed, and who has spent his entire career trying to get a Europa mission going, the challenge now is keeping the mission team integrated and motivated over the long journey to Jupiter. “I mean,” he says, “it’s going to be another decade or so before we get there.”

And even so, from his office, time seems ever in short supply. Things that were once notions are now being built, and reveries of a young post-doctoral researcher are now sitting in cleanrooms across the country.

“I recently gave a talk,” he says, “and I emailed the instrument PIs and asked them to send me cool hardware pictures because I wanted to be able to show them, and they did. And I was just—I was just welling up seeing some of this hardware getting built. It was like, Oh my God, that's the mirror that’s going to be in the MISE instrument. That's the detector for the dust analyzer instrument. It's really fantastic to see how it's progressing and how many people are spending their hard days and nights working on this mission to fulfill the dream that many of us had years ago.”

For myself, in that cleanroom, feeling the wires through my latex glove, I was moved deeply, connected somehow to this thing that’s real, this thing that will one day travel so far and do so much for humankind. I spent almost seven years writing a book about the hard road to Europa and the setbacks along the way. As an author, I’ve had to envision Europa Clipper over the years the way Herman Melville imagined the Pequod, or Douglas Adams saw the Heart of Gold. It was real on the page, real in my mind, but never real in the physical. But in the cleanroom, there it is: something made of atoms and a strident sort of braininess.

Europa is hard, but the ramifications of this expedition make the challenge somehow necessary. It must be earned. Europa is an Everest of the human intellect, and what we see from the summit will be far, far beyond any horizon humankind has yet beheld. 

David W. Brown is the author of THE MISSION, or: How a Disciple of Carl Sagan, an Ex-Motocross Racer, a Texas Tea Party Congressman, the World's Worst Typewriter Saleswoman, California Mountain People, and an Anonymous NASA Functionary Went to War with Mars, Survived an Insurgency at Saturn, Traded Blows with Washington, and Stole a Ride on an Alabama Moon Rocket to Send a Space Robot to Jupiter in Search of the Second Garden of Eden at the Bottom of an Alien Ocean Inside of an Ice World Called Europa (A True Story). It will be released in January and is now available for pre-order. He lives in New Orleans.

David W. Brown
David Kramer
October 6, 202010:00 AM UTC (UTC +0)