Beyond a Shadow of a Doubt
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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, 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.
"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.
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
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.