JUNO: A Picture's Worth

This color view from NASA's Juno spacecraft is made from some of the first images taken by JunoCam after the spacecraft entered orbit around Jupiter on July 5th (UTC).

Credits: NASA/JPL-Caltech/SwRI/MSSS

The image returned by the Juno Jupiter probe on July 10, 2016, was remarkable. This low-resolution image was prepared after JunoCam was activated 2.7 million miles past the planet, on the outward leg of the long, elliptical orbit it braked into on July 4 by firing its main rocket engine for over a half hour. The spacecraft is currently in a hugely elongated capture orbit that will take almost 54 days to circle the giant planet and will soon return stunning high-resolution images from that part of Juno’s journey.

After another engine firing in October, that orbit will be diminished to a 14-day science orbit, and Juno’s camera will return images for as long as it can. This first image proved that JunoCam survived its long 5-year voyage to Jupiter, and its first entry into the high-radiation, electronics-killing environment of the planet. But it’s a challenge: while NASA’s earlier Galileo Jupiter orbiter approached to within 135,000 miles of the machinery-frying gas giant in the 1990s, Juno will be, at its closest, just a few thousand miles above the cloud tops. That’s a true danger zone, as TV secret agent Sterling Archer might say.

That first image also demonstrated something far more amazing, however: it’s the result of a marvelous piece of technology that did not really need to go along.

“Our questions aren’t necessarily answered best by taking pictures,’ Says Steve Levin, the Juno project scientist. “We want an understanding the interior of the planet, to know how Jupiter formed, because that tells us how other planets in solar system formed. You don't learn this by looking at the cloud tops, you learn about how it formed by understanding the interior, what its core is like and how big it is. You also want to know much water there is, and what the structure of the planet looks like if you probe deep inside. That's a kind of information were not going to get from just taking pictures.”

Some have called Juno “the squiggly line mission,” referring to the readouts generated by the instruments used to get the measurements researchers need to answer these questions. Microwave emissions, spectrometer measurements, magnetometer plots and radio-signal tracking are all critical components. The stunning visuals, not so much.

Pictures of Jupiter look at the tops of the clouds, with the pretty colored bands representing the end result of the many processes that drive the gaseous bands circulating around the planet, as well as convecting from top to bottom. But what Juno seeks to understand is what exists below those convecting, revolving bands, so why include a camera at all?

Levin answers with a smile: “We put JunoCam on board because everybody agreed that it would be crazy to send a space craft all the way to Jupiter without a camera on it. It was not a matter of what science we’re going to with a camera—it doesn’t have any real science requirements. But people will still work with the imagery; we obviously will not throw away data.”

While Juno closes in on its science orbits, which will dip into the most intense parts of Jupiter’s radiation for hours at a time, JunoCam will be sending back increasingly stunning views of the planet because there might be some science to be gleaned from them, because there is solid public relations value to showing people visuals depicting where the mission is operating, and because by seeing pictures from faraway, scary and beautiful places, humanity's natural desire for inclusion in great adventures is generously, sensually fed.

In short, we all get to ride along. And that might be the best reason to include a camera, after all.