Spirit and Opportunity, the famous rovers that have been making
headlines, are the planetary explorers in the MER (Mars Exploration
Rover) mission; but, in order to do their jobs, they need a little help
from the scientists behind the scenes. To navigate hazardous terrain, to
communicate with the scientists on earth, and to excavate the Martian
surface, these rovers need to "see" the landscape that surrounds them.
So, the MER scientists have given these lucky robots the gift of sight.
This gift is in the form of twenty cameras, nine for each rover, and one
for each of their landers. Prior to, and during the mission, these
cameras get lots of TLC (tender loving care). And, that's just FYI (for
Heather Arneson, our latest Way Cool Scientist, has been intimately
involved with the cameras since before they were airborne. Heather
graduated from Cornell University with a degree in Mechanical
Engineering in 2002. Just after graduation—really, just days
after graduation—she went to JPL (the Jet Propulsion Laboratory)
in Pasadena, California, to get started on the MER mission.
Prior to launch, Heather helped to test the cameras and configure them
to perform specific functions. This process is called "calibration."
Since these cameras were designed to operate on Mars, they had to be
calibrated in Mars-like conditions. The Red Planet is a very cold place;
therefore, they were tested at a range of temperatures between
-110˚ C to 5˚ C. Brr!
Heather was involved in the calibration of all twenty of the MER
cameras, plus several flight spare cameras and engineering model
cameras. She spent about nine months at JPL testing the cameras before
and after they were installed on the rovers. When she returned to
Cornell, Heather began analyzing calibration data, while training for
her new role as PUL (Payload Uplink Lead) for the Pancams.
Each rover has two eyes with 20/20 vision—the Pancams. While these
high-resolution stereo cameras help to determine the rover's exact
position and orientation, navigation is not their primary purpose. The
twin cameras take high-resolution images of the surface and sky through
eight different colored filters. As the rover surveys the landing site,
the Pancams capture images of the surrounding environment, allowing
scientists to tag specific soils and rocks for further analysis. Images
taken at various wavelengths reveal aspects of the mineralogical make-up
of the Martian surface.
The Pancam cameras sit on top of a mast that rotates 360˚,
providing the rovers with a full panoramic view. The bar mounted on the
mast tilts, pointing the cameras up and down. To take quality images,
the cameras must be programmed to focus on a particular target. Heather
utilizes a variety of software tools that assist her in positioning the
Pancams by referencing images from other cameras.
The rovers are designed to make intelligent and safe decisions about
where to drive and how to obtain scientific measurements. About once a
day, each rover is given a series of orders for the next day's
activities. As PUL, Heather writes sequences that tell the cameras what
to do. When she instructs a camera to capture an image, her command
consists of 47 parameters (values which specify exactly how to take an
image). In order to set each parameter accurately, she must understand
both what the scientists want and how each camera behaves. A PUL's
primary job is to turn the science team's requests into commands that
the rovers can carry out.
An average PUL shift takes place at night, and consists of two parts.
Heather usually spends the first five hours determining how the
scientists would like to utilize the Pancams the next "sol" (Martian
Day). After that, she spends about six-and-a-half hours writing
commands for the rovers.
For Heather, this project is the exploration of the unknown. She is
intrigued by all the potential hypotheses that have been made about this
mysterious planet. "It's so exciting to be right out of college and have
the chance to work on such an amazing mission," says Heather. At night,
she peers up at the sky, settling her gaze on a small red sparkle of
light. Heather marvels at the notion that on that sparkle is an
extraordinary piece of hardware, and she's thrilled to have the
opportunity to "tell it what to do!"