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Robots at Work
|The leader of the team that created the revolutionary
Mars Sojourner robotic rover chronicles her trailblazing career in space
exploration and tells the fascinating, behind-the-scenes story of the
celebrated Mars Pathfinder mission.
Shirley's 35-year career as an aerospace engineer reached a jubilant
pinnacle in July 1997 when Sojourner -- the solar-powered, self-guided,
microwave-oven-sized rover -- was seen exploring the Martian landscape
in Pathfinder's spectacular images from the surface of the red planet.
The event marked a milestone in space exploration -- no
vehicle had ever before roamed the surface of another planet. But for
Donna Shirley, the manager of the Jet Propulsion Laboratory's Mars
Exploration Program who headed the mostly male team that designed and
built Sojourner, it marked a triumph of another kind. Since her
childhood in Oklahoma, Shirley had dreamed of traveling to Mars, and,
through Pathfinder, she did just that.
Prologue: Six Wheels on Soil
Before dawn on July 4, 1997, I woke with my mind over a hundred million
miles away. My waking thoughts were all of Pathfinder, the United States' first attempt to
land on Mars in twenty years, as it hurtled through the silence of space just hours away
from its encounter with the red planet. The 100-foot-high Delta 2 rocket that had boosted
the spacecraft from Cape Canaveral, Florida, seven months earlier was finally about to
deliver something very precious to me, and I can't say I wasn't anxious.
Cabled down firmly inside this streaking bullet was Sojourner Truth, the world's first
robotic planetary rover. I headed the team that had designed and built this revolutionary
six-wheeled scientific laboratory, a 25-pound robot about the size of a microwave oven
that could do what humans could only dream of: explore the surface of Mars. I'd spent
nearly ten years of my life preparing the two of us for this moment.
I could picture her cradled in the heart of the lander like the tiniest Russian nesting
doll. She crouched with her belly to the floor inside a lander that was packed in a
cushion of deflated airbags. Once off the lander, she would motor over the surface of Mars
taking pictures and poking at the rocks like a tourist. She was a sturdy little gal. We'd
whirled her in a centrifuge at a force 66 times that of gravity, twice as much pressure as
we expected her to endure in flight, and she'd come out perfectly. If Pathfinder landed
the way it was supposed to, I was sure she'd be fine.
I knew the Pathfinder's innovative landing mechanism almost as intimately as I knew the
rover. Retro-rockets would slow the craft to a stop just before it smacked into the
Martian surface. Moments before it hit the ground, huge airbags would pop. If everything
worked--if all the radios communicated, the signals and sequences were sent and received,
every one of the explosive bolts fired promptly and the airbags popped firm exactly on
cue--it would plump up and bounce across the ground like a giant superball until it came
to a rest. It was an inspired and thoroughly tested design, but one that had never before
been used to land on a planet.
Surely this scheme had a better chance of keeping the Sojourner intact than anything
previously devised. The teams that designed the lander and the rover had spent hours
concocting every imaginable disaster scenario and building in ways to overcome those. We
were combating long odds, if history was to be believed. Throughout thirty-seven years of
exploration, Earthlings hadn't been terribly successful landing on Mars.
Two Russian Phobos spacecraft were lost on their way to Mars in 1988. While the United
States' two Viking missions landed safely in 1976, our Mars Observer failed to reach orbit
in 1993. The Russians' Mars 6 and 7 got to Mars in 1971, but couldn't deliver their
landing craft. Mars 6 crashed into the surface and Mars 7 missed the planet completely. As
recently as November 1996, the Russian Mars 96 mission plunged ignominiously into the
Pacific, never getting anywhere near its target. What if something like that happened to
my rover? The data assured me that Pathfinder was approaching Mars just fine, but almost
anything could happen during the punishing six-minute descent to the surface. Crash and
burn was a definite possibility, I knew. Crash and burn.
Of course she wasn't really my rover. I had headed the team of thirty talented engineers
and technicians that had spent four years designing and building the rover. A separate
300-member team, led by project manager Tony Spear, had spent the same amount of time
building the Pathfinder lander. All of us could rightfully think of this mission as our
own. No matter what any of us were doing at that moment on Earth, we could picture
Pathfinder and Sojourner about to begin their descent and we knew our hopes could be
dashed against the forbidding landscape.
I hadn't slept at all well that night. I've always been a fitful sleeper anyway, tossing
and turning in the wee hours anticipating the day to come as my mind races with ideas and
plans. In the early morning hours before Pathfinder entered the Martian atmosphere, dreams
yanked me just to the edge of consciousness time and again. These weren't the idyllic
dreams of me flying solo over the surface of Mars, such as I'd had since I was a small
child in Oklahoma. The dream that eventually convinced me I might as well get out of bed
was more of a farce.
In this dream, I saw the Pathfinder team standing around a field when suddenly our
spacecraft fell from the sky before us. It had landed on Earth! We watched it bound to a
stop but the airbags didn't deflate. My teammates seemed merely befuddled by this
disaster. I hopped around eagerly, wondering how they could be so detached. I wanted to
open it up, see how Sojourner had survived the descent. Everyone else said we had to let
the lander open by itself. I guess I should see this dream as an encouraging omen, I
decided as I got out of bed. If Sojourner could endure the descent through the Earth's
dense atmosphere--even in my dreams--then the wispy carbon dioxide atmosphere of Mars
would feel as gentle as a tropical breeze.
I found no comfort in my morning ritual, no solace from my habitual cup of tea. I barely
tasted my orange as I methodically swallowed it. Sitting at home was just making me
restless. I felt like a child the night before Christmas anticipating a
desperately-wished-for present. I put on my favorite suit--Mars red--and decided it was
best not to wake my daughter, Laura, who was home from college for the summer. She planned
to catch up with me around 10 a.m.,the moment the Pathfinder was scheduled to enter the
Martian atmosphere. She could use the sleep for the eventful day ahead, I thought. I drove
the six miles from my house in La Canada to the Jet Propulsion Laboratory (JPL), in
California, arriving at 6:30 a.m., an hour before I was supposed to report for work.
Though I'd driven the two blocks of Oak Grove Drive nearly every day for the thirty years
I'd worked at JPL, I'd never seen it as packed with journalists as it was that day. Local,
national, and international television trucks lined the street. Von Karman Auditorium,
near the entrance to the JPL campus, bustled with print and radio reporters already hard
at work on this story. Photographers snapped pictures of the full-scale models of the
Pathfinder we'd displayed on the JPL mall and in the auditorium. Video crews jockeyed for
position around the models and on the risers at the back of the auditorium. Competition
for a good spot was so heated that JPL had taped off separate areas for each crew to
prevent squabbles. I knew the Fourth of July was a slow news day, but I'd never expected
the interest to be as high as this. Something about Pathfinder and Sojourner had really
captured the public's imagination.
The generation that had grown up watching Star Trek and Star Wars really hadn't seen a
planetary landing in its lifetime. For this generation, the Pathfinder mission was akin to
Neil Armstrong's moon landing on July 20, 1969. We knew we already had a built-in
international audience of the millions of people who had tracked the mission's progress on
the Internet Web site we'd constructed for Pathfinder before it took off on December 4,
1996. Popular culture fostered an interest in space, but the real world rarely delivered
the goods. Today--on Independence Day no less--the real world was delivering.