The night before Nasa’s Juno spacecraft entered orbit around Jupiter, I stood beneath the Mount Wilson Observatory’s 100” Hooker Telescope. Amateur astronomer Christopher Go had invited me to join him and a group of professional astronomers as they gathered images of Jupiter to support the Juno mission.
The cavernous dome protecting the Hooker Telescope has a surprisingly industrial feel. The roar of giant fans masks nearby conversations. The scent of machine oil wafts from the century-old gears and motors. As dusk fell across the San Gabriel Mountains north of Los Angeles, you can almost feel the history. This was the telescope Edwin Hubble used to measure the Universe's expansion. The first measurements of the size and distance of stars, the identification of "spiral nebulas" as separate galaxies, and more were all made possible thanks to the huge telescope.
The telescope was the largest research telescope in the world for three decades. Even bigger telescopes and Los Angeles’ light pollution eroded its scientific role. Today the observatory is used for public outreach and amateur astronomy. But sometimes that amateur astronomy produces real science. The night of my visit modern technology gave the giant telescope renewed purpose as an astronomical camera fed images of Jupiter to a laptop below.
The astronomers, professional and amateur, gathered around that laptop are part of a global team making Jupiter observations for the Juno mission. Why does Nasa need Earth-based observations when it has a spacecraft orbiting Jupiter?
Juno is either too close or too far from Jupiter through much of its orbit to give scientists the context they need. Juno swings far away from the planet and its intense radiation belt for much of its fourteen-day orbit. That protects the spacecraft and its instruments but it reduces Jupiter to a small dot in its camera. At the other end of its orbit Juno’s instruments will gather unprecedented data about Jupiter’s atmosphere, but it will be so close to the planet - around 4,200 kilometers - that Juno’s camera will only see a narrow swath of Jupiter’s clouds.
Observers here on Earth can see the entire planet. The images they collect will let the Juno team plan each close-approach and set the data Juno collects within the context of Jupiter’s global structure and weather. Professional members of the ground campaign will use the Hooker Telescope’s modern successors in Hawai’i and Chile - as well as orbiting observatories like the Hubble Space Telescope.
But they also will rely on amateur astronomers like Christopher Go. I had a chance to speak with Chris before that night’s observing session got too hectic. He explained why the planetary science community relies on amateur astronomers.
One thing about the professional astronomers - they don’t have a lot of data. They can’t easily use an observatory. In the pecking order of things, planetary is way down below [astrophysics]. With the number of amateurs all over the world you can have 24x7 coverage of any planet that you want.
Whenever there’s a slight change [on Jupiter], for example when there’s an [asteroid] impact or there’s a new outbreak of a new spot, the professionals know immediately and they can call on the big guns like the Hubble Space Telescope for support.
The collaboration between professional and amateurs is very strong. Professional astronomers always credit amateurs with their contributions and they are very grateful for it.
The 1986 apparition of Halley’s Comet introduced Chris to amateur astronomy while he was still a young student. By 2003 a hacked webcam let him collect planetary images through his telescope. He began collaborating with professional astronomers soon after. In 2006 Chris was the first astronomer - amateur or professional - to see that one of Jupiter’s white storms had turned red. His discovery spurred a global team of amateurs and professionals to study Red Spot Junior.
Chris is just one of the amateur astronomers who contribute to planetary science. They have discovered asteroid impacts in Jupiter’s atmosphere and helped study Saturn’s storms. This community of planetary observers held a workshop in France earlier this year to prepare for Juno’s rendezvous with Jupiter.
We already have a network set up. That workshop basically reinforced that network. It’s a good way to meet people to talk to them. It was mostly amateurs teaching others their techniques, making their images better, making a better workflow for what they are doing.
My part of the meeting was to rationalize the images that are submitted by amateurs so when they [submit] the data they’ve placed significant data that can be used by professionals easily. There’s this software called WinJupos that we all use so one nice thing is that everything is standardized.
Back at Mount Wilson, the team was using the giant 100-inch telescope’s light gathering power to collect data in the narrow band of the spectrum where methane in Jupiter’s atmosphere absorbs light. Chris had a much smaller telescope set up to collect images in the visible spectrum. The 14” amateur telescope on loan from Celestron was much more like Chris’ equipment back home in the Philippines. Cebu City hosts the country’s largest port and nearly one million residents. I asked Chris how he can get such amazing images of Jupiter through the humid, light-polluted skies of a modern city.
The climate is actually perfect for planetary imaging. You don’t need the dark sky and you can do it in the middle of the city. The most important thing is the “seeing”, the stability of the atmosphere. The higher the humidity the better the seeing because when you have laminar flow or wind from the ocean, that’s the most stable condition that we can have for planetary imaging. Also one advantage which I have is I’m so close to the equator so planets are very high up in the sky.
Planetary imaging is so accessible that the Juno team created the JunoCam program to let the public produce science at Jupiter. Amateur astronomers around the world upload images of Jupiter to the every day. That lets the public see new and interesting features in Jupiter’s ever-changing weather. A voting system will let the public recommend their favorite targets for each orbit. To make sure JunoCam is not taking pictures of the Great Red Spot over and over again, the JunoCam science team will set the final targets.
What will an aurora look like? Will we see lightning? How will Jupiter’s storms compare to storms on Earth? What unexpected discoveries will we make? Whether you are an advanced amateur astronomer like Christopher Go or a citizen scientist fascinated by Nasa’s latest mission to the outer planets, you can help explore Jupiter.
- Want more detail on JunoCam's science goals? Head to Space Science Reviews.
- To learn more about the state of amateur planetary science, check out the Juno Amateur Workshop presentations.
- The Planetary Society provides some of the best overviews of Juno and JunoCam.
Want more? Check out more articles about amateur space explorers and the pros who support them: