The view of Jupiter through a telescope is nothing like images in a book or on a website. A single image makes the giant planet with its Great Red Spot and multi-colored cloud belts look like a jewel suspended in space, unchanging and timeless. But that’s far from true. Jupiter is a dynamic planet: cloud belts grow and shrink; storms erupt and fade away; jet streams push storms across the planet’s face. Even the Great Red Spot - that vast storm larger than entire planets - is smaller than when first seen hundreds of years ago.
Jupiter’s constantly-changing features fascinated Hans-Jörg Mettig, a young East German growing up in the Dresden during the Cold War. He found the Sternwarte Radebeul, a public observatory that encouraged the youth of Dresden to use its 150-millimeter refracting telescope. Mettig sketched his observations of Jupiter through the telescope every chance he got. A technique called central meridian timing let him map the coordinates of the features in his sketches. During the time that passes between observing sessions Jupiter’s jet streams push and pull the planet’s cloud formations, making each session’s sketched observations different. A drift chart maps the coordinates from multiple observing sessions to show how a feature moves. But there was a limit to how many observations Mettig could make on his own. He analyzed other amateur astronomers’ observations to produce annual reports for the local astronomy society .
But even that wasn’t enough. Local libraries and observatory archives held historical astronomical observations hidden away among the stacks. Mettig trawled these sources for any observations of Jupiter, netting his own archive of the planet’s history going back centuries. By the 1980s these historical records, the observations from other amateur astronomers, and his own observations of the giant planet outgrew his paper file system. He needed a computer.
East Germany’s collapsing economy came to the rescue. Mettig worked at an electronics company but had no responsibilities. The company had computers and printers that nobody used. Mettig seized the opportunity to write his own software. But he didn’t just replace his paper filing system. His code converted the positions of cloud features into drift charts. Mettig’s varied collection of observations forced him to write flexible code. Each sketch or photograph of Jupiter was a different size, made by a different person, at different times over the past two centuries. Mettig’s approach mapped the cloud features into a standard format so the software could combine data from any observation.
The end of the Cold War and German reunification marked the next stage in Mettig’s work. A long-standing contributor to the British Astronomical Association’s Jupiter Section despite the geopolitical tensions of the Cold War, Mettig became a full member of one of the longest-lived astronomy societies. At that time digital communications emerged from universities and government research labs and entered the mainstream. Bulletin boards, online communities, and a new thing called the Internet let amateurs around the world share their passion for astronomy. Mettig received even more observations, making it increasingly difficult to manage the Jupiter Positions, or Jupos, project on his own. Mettig fostered a network of Observers who followed a set of procedures to make observations that produced the best position data. At the same time Mettig recruited a small team of Measurers - amateur astronomers from across Europe who analyzed the Observers’ data with his software to produce scientific reports.
Moore’s Law brought even more changes to amateur astronomy - and to the Jupos project - as the century came to a close. Amateur astronomers now had access to technology that had revolutionized professional astronomy a decade earlier. CCD cameras and personal computers brought amateur astronomy into the digital age. Image processing techniques once limited to the high-performance workstations at research universities, combined with inexpensive webcams, now let amateur astronomers produce images of the planets that rival what professionals produced in the 20th Century.
Grischa Hahn, another Dresden amateur astronomer, took responsibility for the Jupos project’s software in 1992, freeing Mettig to focus on the network of amateur astronomers and the scientific work they produced. The software, now called WinJupos, became a powerful tool for observing any planet as well as the Sun. While it has several powerful features for processing images, WinJupos’ core purpose remains the same: mapping the position of atmospheric features and converting that data into drift charts to track the features’ movements over time.
The combination of high-quality amateur observations, WinJupos’ analytical power, and a database of feature positions approaching 1,000,000 entries places the Jupos project in a unique position. It’s an amateur-run project, composed of amateur-generated data, that produces professional-level science. For example the director of the BAA’s Jupiter Section, John Rodgers, used 16 years of Jupos data to track a Little Red Storm’s progress across Jupiter. He published the results in the Journal of the British Astronomical Association (PDF).
Mission planners at the world’s space agencies regularly turn to the Jupos project for help as when Nasa’s New Horizons space probe passed Jupiter in 2007 on its journey to Pluto. The Galileo mission ended four years earlier when the orbiter plunged into Jupiter’s atmosphere. The next mission to Jupiter, Nasa’s Juno orbiter, doesn’t arrive until 2016. New Horizon’s fly-by would be the only chance in a decade to collect data this close to the planet. They had a long list of targets: moons, rings, and different aspects of Jupiter’s surface. As the Jupiter Encounter Science Team lead, Nasa’s Dr. Jeff Moore, said at the time, "From constant changes in Jupiter's magnetosphere and atmosphere, to the evolving surfaces of moons such as Io, you get a new snapshot every time you go there." The mission team had one chance to get the timing right. But how could they know when to turn New Horizon’s instruments towards Jupiter’s surface? Mettig and the Jupos project provided the position data they needed.
Planetary scientists also depend on Jupos in their own research. (See our article on the role of amateurs in planetary science) A Nasa-led team of professional and amateur planetary scientists published a paper in the peer-reviewed journal Icarus that studied the dynamics of Jupiter’s atmosphere. (DOI: 10.1016/j.icarus.2012.01.022) The researchers measured the interactions between jet streams, Rossby waves, and gravity inertia waves and the effects those interactions have on Jupiter’s cloud features. They used images taken by the Voyager and Cassini space probes as they flew by Jupiter in 1979 and 2000, respectively, as well as fresh observations from the Hubble Space Telescope. But they also used the Jupos database’s amateur-generated data. Jet streams and waves in Earth’s own atmosphere produce effects similar to what the researchers saw at Jupiter. "We are just starting to investigate the long-term behavior of this alien atmosphere," Jupos Measurer Gianluigi Adamoli said in Nasa’s press release. "Understanding the emerging analogies between Earth and Jupiter, as well as the obviously profound differences, helps us learn fundamentally what an atmosphere is and how it can behave." 3 of the paper’s 7 co-authors - Adamoli, Rodgers, and Mettig - are Jupos members.
In his acceptance message for the British Astronomical Association’s 2007 Merlin Medal and Prize, Mettig described how Jupos reflects the dramatic changes in amateur astronomy:
I started with a few hundreds of positional records in the 80s. Now we derive tens of thousands of longitudes and latitudes from electronic images every year.
Jupos will only become more valuable in the coming decades. None of the planetary archives at the world’s space agencies can match its historical reach nor do they have the volume of observations that Jupos’ amateur Observers produce. As amateur technology improves and become more accessible to a wider range of amateurs, Jupos will let new generations of amateur astronomers around the world contribute to humanity’s exploration of space.