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Beyond a Shadow of a Doubt


View a larger image "a)" (70 kB) or larger image "b)" (100 kB) or learn about other sol 14 images.

Scientists use their knowledge of shadows to prevent any doubt about their data. Through visualization technology, mission planners can predict when and where shadows will hit the rover and surrounding land surfaces. This information allows the team to organize the daily activities of the rover so they can tell it when and where to capture good images and other science data.

Wendy Calvin

Wendy Calvin, a geophysicist from the University of Nevada in Reno, explains, "Anyone who has tried to take a good picture of his or her friends while facing the camera into the sun knows that the photograph often gets washed out because the sun's rays shine directly into the camera. It's the same for FIDO cameras as well."

These two images of the FIDO field site demonstrate the strong effect that the position of the sun can have on how well the observations from a remote rover come out. The first image (Image A) was taken just after lunch in the rover's time zone, while the other (Image B) shows pronounced sun rays from the late afternoon position of the sun. The angle between the geology target, the rover "eyes," and the sun can have a profound effect on the quality of both the image and spectral data that the rover acquires.

Larry Edwards

"However, it's not just the relative position of the sun that matters," says Wendy. "The presence of shadows across a layered target can reduce the value of a science observation. The problem of shadows across a rugged cliff face plagued us and we weren't getting good data. We planned a similar observation at a different time of day and voila! All of a sudden, we found a rock type we've been diligently searching for." This desired rock type is a carbonate, which suggests an ancient sea environment. A simple problem like the direction of the sun made all the difference in finding the weak signal of an important, but scarce, mineral signature.

Visualization software predicts shadows on Mars.

Solving this shadow problem is easy with the use of an innovative visualization software technology. "The 'Viz' (visualization) technology uses a clock and a calendar with knowledge of the position of the planets and the sun to predict the shadows," says computer scientist, Larry Edwards from NASA Ames. "This field test is the first time we've provided a visual display of the shadows to scientists. It's the 'hot new feature' of our system during this test, so it's been really popular."

The visualization software does more than just predict shadows. For example, Viz takes the images from the rover and pours virtual water into depressions, helping scientists to formulate hypotheses about past conditions, such as ancient water flow. Viz essentially provides something called situational awareness, which helps the scientists feel like they are right there with the rover.

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Last Updated: 17 August 2002

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