Ethan Zuckerman’s online home, since 2003

Robert Gaskell models faraway worlds

I’m at the Applied Brilliance conference this morning, a gathering of architects and designers in Bolton Landing, NY, a gorgeous corner of Adirondack State Park. I wasn’t actually scheduled to speak here – my friend Omar Wasow had to pull out of the event so he could be on Oprah’s show today. Since I’m just down the road, I’m pinch hitting. (I guess that the fact that Omar’s known for his work on social networking in the African American community and since I study social networking in Africa, I can talk in his stead…)

Robert Gaskell of the Planetary Science Institute describes himself as a “maverick mapmaker of the solar system.” His specialty is interpreting what spacecraft see and turning it into maps of the solar system. He explains that, like a farmer’s son who learns to drive the tractor by riding alongside his father, he learned his craft by being raised by mathematicians, who started his education with “the topology of folding diapers.”

The math Gaskell is now interested in involves modeling asteroids, planetoids and other space features so we can figure out how to navigate around them… and he explains that his knowledge of the field is like that of the son on the tractor. He’s worked on a wide range of outer space projects and learned in the process about modeling the destinations of spacecraft.

He shows us the launch of the Dawn space craft, which is headed towards the asteroid Vespa. It’s making a two year journey powered by ion propulsion, an engine that spews out electrified xenon gas. Dawn will orbit Vespa and dwarf planet Ceres – to navigate, the engineers need accurate models of the asteroids. It’s possible to detect the position of the spacecraft using a huge radio telescope, tracking the craft’s small signal. And you can track craft speed by examining the doppler shift of the signal. But to navigate, you need to be able to see features on these celestial bodies and manuver in response.

Gaskell’s innovation was to realize that the way we generally build these maps was overly difficult and clumsy. Traditionally, we look for images taken in fly-bys that are from the same position, with the same lighting and at a high level of cleanliness and clarity. But Gaskell remembered making a charcoal sketch of a still-life as an eight grader and realized that the techniques of shading he’d learned those years ago could be applied to modeling other worlds. Specifically, he focused on ways to construct “limbs” – the demarcation between a lit portion of an object and space – and “terminators” – demarcation between a shadowed portion and space – which jointly allowed him to build 3d computer models from hybrid images. The inputs included a wide set of images captured in fly-bys, not just the perfect images.

The technique has been used to model several celestial bodies that NASA and other space agencies have wanted to orbit or land craft on. By creating highly accurate models, the spacecraft can find visible features on the asteroid’s surface and pinpoint their location. Gaskell is now modeling Mercury and a few of the satellites of Saturn, finding locations where probes could safely land.

He ends by showing us a 3D movie of the asteroid Itokawa, the destination of Japanese space probe Hayabusa. The asteroid rotates solemly in virtual space as Gaskell points out the “pencil-shaped boulder” that served as lodestar for navigators guiding the probe. As we don red and blue 3D glasses, the film soundtrack swells. It’s “The Rainbow Connection”, and we sit silently in a hotel ballroom, watching a movie of a place none of us will ever see while a stuffed green frog sings. It’s a special moment.

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