Sallyportal: Madly Blogging Reed

Reedie Designs Sundial for Mars Rover


On a clear Southern California night, Tyler Nordgren '91 stepped outside to take a last look at Mars through his home telescope before stepping inside to watch the landing of the Curiosity rover on NASA TV.

By this time, Curiosity was already slamming into the Martian atmosphere at more than 13,000 miles per hour. After four minutes of aerobraking, the largest supersonic parachute ever deployed off the planet Earth slowed the rover to 220 miles per hour. Then the lander cut away from the chute, firing retro-rockets and searching for a good landing spot. Twenty-five feet above the Martian surface, the lander lowered the rover to the ground and fired explosives that cut the tethers that held them together.

"It's on Mars," Nordgren noted as the signal journeyed back to Earth. "It's either in one piece or a million pieces."

Fourteen minutes later, Nordgren—along with other Reedies around the world—listened to the live feed at the Jet Propulsion Lab as Curiosity reported its perfect arrival. But unlike other Reedies, he had skin in the game. Something he had helped build was aboard the probe. Within a day, Curiosity's camera boom was aloft, photographing the surface of Mars. In the foreground of these photographs was a small, colorful sundial.

Nordgren helped design sundials for Curiosity and its predecessors to the Red Planet, Spirit and Opportunity. The sundials are not mere hood ornaments for the rovers, but serve as calibration targets for the color cameras, providing them with known, well-defined red, green, blue and yellow color samples. Scientists need reference colors to ensure that the object in the camera is really the color it appears to be because the lighting, sky, soil, and rocks of Mars are not perfectly understood.

Other missions have done this using simple color chips, but NASA's rover teams opted for the sundial because top space experts agreed: sundials are cool.

Nordgren was brought onto the sundial project as a graduate student in astronomy at Cornell because of his artistic talents, well-known to Reedies of the late 1980s by way of his political cartoon, "The Last Liberal," a regular feature in The Quest.

Nordgren contributed to the design, layout, and wording of the sundials. The central post, or gnomon, of the sundial is a short stalk topped with a glare-proof, blackened aluminum sphere that represents the sun. Two engraved rings surround the base, representing the orbits of Earth and Mars, enclosing color-calibrated gray regions, bracketed by reflective patches that help establish the Martian sky's background color and brightness. The base's four quadrants bear Mars's name in 16 different languages.

He says he's most proud of his contribution to the legend that circumscribes the base of the Curiosity's sundial:

For millennia, Mars has stimulated our imaginations. First we saw Mars as a wandering red star, a bringer of war from the abode of the gods.

In recent centuries, the planet's changing appearance in telescopes caused us to think that Mars had a climate like the Earth's.

Our first space age views revealed only a cratered, Moon-like world, but later missions showed that Mars once had abundant liquid water.

Through it all, we have wondered: Has there been life on Mars? To those taking the next steps to find out, we wish a safe journey and the joy of discovery.

"It's sort of that Reedie ethos," he says of the legend. "We're not scientists just for today. We are part of a long tradition of understanding our world."

Tags: art, Curiosity rover, gnomon, Mars, physics, sundial