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How Do We Beam Pictures Back From Jupiter? It Takes A Village

Before Juno, the uncrewed spacecraft that NASA successfully inserted into orbit around Jupiter on July 4, there was Cassini, a similar multimillion-dollar amalgam of scaffolding and scientific instruments that entered orbit around Saturn in 2004. Cassini’s success helped pave the way for Juno, but in 1992, a congressional budget cut nearly grounded that earlier mission before it even reached the launchpad. Tasked with the suddenly urgent job of making Cassini cheaper to build, engineers at the Jet Propulsion Laboratory took an ax to the bits that made the engineers nervous — the moving parts.

That included the spacecraft’s scan platforms. The periscopes to Cassini’s submarine, these rotating arms would have allowed NASA to point the 12 scientific instruments in different directions without tilting and turning the spacecraft itself. Without them, you could rotate Cassini and point, say, the camera, at Saturn, or turn it a different way and point the radar at Saturn — but not both. Instead of each planetary flyby offering data-collecting opportunities to many teams of scientists at once, now only one or two teams could operate simultaneously. The mission leaders were left in the awkward position of deciding whose research would meet the executioner’s sword. “People saw all of their plans being really decimated,” said Candice Hansen, senior scientist at the Planetary Science Institute.

In the midst of this upheaval, Hansen — along with Scott Bolton, now an associate vice president of the space science and engineering division at the Southwest Research Institute — became a sort of combination traffic cop/psychotherapist, gently guiding research teams through anger, bargaining and depression and on to acceptance. Eventually, the two were able to craft a new science plan where nobody got what they wanted, everybody gave up something, and all parties were at peace. Their job was a stark reminder that although a spacecraft can exist in a vacuum, data does not. Collecting detailed information about our solar system is as much about people as it is about technology. In fact, the two are almost always inextricably intertwined — lessons that have played a big role in shaping the Juno mission to Jupiter.

Today, Bolton is the primary investigator on Juno, and Hansen, besides running the spacecraft’s public outreach camera JunoCam, is back in the intersection/on the couch, helping scientific teams negotiate the use of Juno’s most limited resource — on-board data storage capacity — as co-chair of the mission’s Science Planning Working Group.

And it is a very limited resource. Consider this: I am writing this article from a laptop that has 8 gigabytes of RAM. Juno has half that.

William Kurth is a research scientist at the University of Iowa and one of the people in charge of two of Juno’s nine instruments. His tools collect data about radio and plasma waves in space. One looks like a 9-foot-long version of those old-fashioned bunny ear antennas that sat on top of TVs in the days before cable and digital broadcast took over. The other is a 6-inch-long bar with 10,000 turns of copper wire wrapped around it. Together, they have been allocated just 2 gigabits of storage. “Not bytes,” he said. “That would be a luxury if we had 2 gigabytes. That’s eight times more.”

Juno doesn’t have to store that data forever. Beginning on Aug. 27, the next time the craft gets a Jovian close-up, Juno’s scientific instruments will start going through cycles of bingeing and purging, gobbling up information as the spacecraft swings through the part of its orbit closest to Jupiter and then sending what they’ve collected back to Earth via the Deep Space Network during the rest of the orbit. But this communications system, too, is limited. Its maximum data capacity is 25 kilobytes per second. In comparison, a USB 3.0 connector can transfer data at a rate of more than 600,000 kilobytes per second. For a tool that collects data, Juno has a lot of limitations on its data collecting. “Somewhere in there is going to be where the shoe pinches,” Hansen told me.

All spacecraft missions have this problem with storage limitations, according to Hansen and other planetary scientists I spoke with. Time and power are the other two resources that researchers are likely to compete for. And almost all spacecraft missions have something like Juno’s Science Planning Working Group — a team that helps build consensus so hard decisions about resource allocations can be made with limited strife.

But what makes Juno unusual, Bolton said, is that the mission has been designed from the start to account for the complicated context that surrounds data collection. He told me that he took what he learned mediating interpersonal conflicts on Cassini and set out to plan a mission that avoided those conflicts to begin with. That meant bringing together the scientists in charge of the data-gathering instruments, the scientists in charge of designing the spacecraft’s orbit and trajectory, and the engineers designing the spacecraft — getting them “all in one room, right from the beginning, to design something synergistic with all of them,” he said.

It’s more common for these different plans that make up a spacecraft mission to be drawn up in series, rather than in parallel. When everyone works together from the start, Hansen said, it’s easier to see potential problems and fix them before they become an issue. For instance, thanks to Bolton’s unconventional managerial system, Juno has more downlink capacity to transfer data than it otherwise would have.

Moving into an apartment with no kitchen is less of a liability if you live above a deli. Same thing here. Having more download capacity makes Juno’s limited storage less of a problem. Hansen realized this during those early meetings that brought together all the people working on Juno. She was able to increase the capacity by talking NASA into letting the mission send its data to larger terrestrial satellite dishes — 70-meter dishes, instead of the 34-meter ones used by most spacecraft.

It’s a big win. Juno’s maximum capacity of 25 kilobytes per second is based on the 70-meter dishes. In contrast, Kurth told me, the 34-meter dishes have a capacity closer to 3.75 kilobytes per second.

Because Hansen increased its data capacity early on, the Juno team has less to disagree about now. In fact, the Juno team has had a science plan in place for every single orbit since long before the spacecraft reached Jupiter. There will likely be adjustments made to those plans after each orbit, Kurth said. But it’s less stressful knowing that there is a plan in place already, rather than starting from scratch.

Unfortunately, not all spacecraft missions can follow this model. Trina Ray, who now has Bolton and Hansen’s old job as co-chair of Cassini’s Titan team, said that mission — which is ongoing — operates at a much larger scale than Juno. Not only are there more scientific instruments, there are more targets to study — Saturn (a planet only a little smaller than Jupiter), its moon Titan, its rings and more — along with more people involved. Cassini could never have gotten all those people in a room at the beginning and had them plan everything in parallel. Likewise, Cassini is too big an investment — in money, in time, in people, in resources — for NASA to put it under the control of a single primary investigator, the way Bolton is in charge of Juno.

But that’s not to say there aren’t lessons a big mission can learn. For instance, Ray uses a system she said she learned from Hansen and Bolton, where each science team has to pitch the others on the merits of its research and why it deserves, say, a certain amount of storage or downlink time. Then the teams make the allocations together, as a transparent consensus process. To her, it’s so obvious that managing people is part and parcel with managing whiz-bang technology that she told me she wouldn’t even have thought to explicitly state that fact.

Kurth agreed. “There’s a lot more to a mission than, ‘This is my instrument, I provided it, and all I’m going to do is write papers,’” he said. “There’s a lot of activities that go on that can’t be done in a vacuum like that. You have to work with your other investigators.”

CORRECTION (July 18, 12:58 p.m.): An earlier version of this article misstated the part of the author’s laptop that has 8 gigabytes of capacity. It is her RAM, not her hard drive.

CORRECTION (July 21, 4:05 p.m.): An earlier version of this article incorrectly described NASA’s Cassini spacecraft. It did not have solar panels.

Maggie Koerth-Baker is a senior science writer for FiveThirtyEight.

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