How NASA protected JunoCam from 100 million X-rays worth of radiation

How do you take a close-up shot of Jupiter? With an 8,000 pound spacecraft, a five-year journey, and a small piece of specialty glass.

That’s how the Juno probe, in the early morning hours of August 27, came to fly closer to Jupiter than any other man-made satellite before it. During the flyby, the probe’s full array of scientific instruments were active and ready to learn more about the gas giant.

Onboard was JunoCam, the spacecraft’s camera that delivers two 360-degree panoramic shots per minute. JunoCam has sent back our highest-resolution views of the Jovian atmosphere and the first glimpse of Jupiter’s poles. But it wouldn’t have been possible without a small component that has already journeyed to asteroids, Mars, and the very edge of our solar system.

This is the story of the specialty glass that has made these incredible photos and new discoveries possible as we explore the solar system.

The challenges Jupiter poses

Jupiter is an imposing force in the solar system. It’s twice as massive as all of the other planets combined, and its magnetic field is the strongest of all the planets (and nearly 20,000 times the strength of Earth’s). It’s a stormy place — the Great Red Spot has been brewing for centuries — and winds gust up to 400 miles per hour in Jupiter’s upper atmosphere.

Juno’s mission to gather data on the Jovian atmosphere and the planet’s poles will aid NASA research into Jupiter’s origin, and by extension, the formation and early history of our solar system.

But one big obstacle stood in the way of that research: Jupiter’s strong magnetic field and cosmic radioactivity. At its close proximity to the planet, Juno is being subjected to radiation levels equivalent to 100 million doctor’s office X-rays every day. That would completely disable Juno’s cameras and other equipment, if not for a small piece of glass.

Finding clarity 2,600 miles above a planet

The lens of JunoCam is protected by a SCHOTT optical glass capable of withstanding the incredibly harsh radiation of Jupiter’s atmosphere. This shield not only protected the components over Juno’s five-year journey to the gas giant, but it also allows JunoCam to capture high-resolution photos of Jupiter throughout its 20-month mission; JunoCam has already snapped photos from about 2,600 miles above Jupiter’s north polar region.

The glass is doped with cerium oxide, which makes it highly radiation resistant and prevents damage from Jupiter’s strong magnetic field and cosmic radioactivity.

Electrons from the cerium oxide plug damage caused by radiation and reduce the radiation’s solarization, or darkening effect on the camera’s lenses, which allows greater light transmission into the camera systems. The lens would quickly darken without this specialty glass protection, making photography impossible. The glass effectively extends the lens’s lifespan in this harsh environment, maintaining image quality.

While JunoCam’s small aperture and excellent image quality were key to this mission, so too was its size and weight; large camera systems would be too expensive to put into orbit. As a result, this glass protects cameras in other space missions, including the Curiosity and Opportunity rovers on Mars, Pluto’s New Horizon probe, and the Philae lander on Jupiter-family comet 67P/Churyumov–Gerasimenko. It ensures high-resolution images without adding much weight.

JunoCam’s big canvas

Jupiter still holds many mysteries. Using data collected by Juno, NASA and scientists around the globe hope to better understand Jupiter’s role in the young solar system, as well as explain how Earth and the other planets formed.

But for many of us, we’ll get an unprecedented view of Jupiter thanks to the probe’s on-board camera. Shielded by SCHOTT optical glass against extreme radiation, JunoCam continues to provide NASA scientists and everyday star-gazing astronomers with detailed photos of the giant gas planet.

September 13, 2016


David Schimmel
Advanced Optics
SCHOTT North America, Inc.