|
The initial findings of a NASA review board appointed to look into
the Climate Orbiter failure were released Nov. 10 at a news briefing
in Washington. The report also was distributed via NASA's Web site.
"The 'main cause' of the loss of the spacecraft was the failed translation
of English measurements into metric measurements in a segment of ground-based,
navigation-related mission software, as NASA has previously announced,"
Arthur Stephenson, the board's chairman, said in a written statement.
"The failure review board has identified other significant factors that
allowed this error to be born, and then let it linger and propagate
to the point where it resulted in a major error in our understanding
of the spacecraft's path as it approached Mars." Many of the shortcomings
had to do with a lack of communication, an incomplete understanding
of Climate Orbiter's systems or a neglect of standing rules for reviewing
spacecraft operations, Stephenson said. "We have a situation where we're
not communicating," he told reporters. "We're not understanding different
sides of the situation." Reduced staffing and inexperience a potential
side effect of NASA's drive toward "faster, cheaper, better" space exploration
also may have played a major role in the failure, the board said.
|
|
Investigators said Lockheed Martin Astronautics in Colorado submitted
acceleration data in English units of pounds of force instead of the
metric unit called newtons. At NASA's Jet Propulsion Laboratory in California,
the measurements were entered into a computer that assumed they were
metric measurements. "To be very blunt about it, it was overlooked.
The specification was there and it was our responsibility to check that
and to assure that the right units were made. It was overlooked by the
engineers coding that software," said Noel Hinners, vice president of
flight systems for Lockheed Martin Astronautics. The error threw off
the program that calculates how slight changes in the spacecraft's angular
momentum affects its path towards Mars. Month by month, the slight discrepancies
built up in NASA's projection of the Climate Orbiter's course. Stephenson
said some members of NASA's navigation team had noted discrepancies
but didn't fully understand the extent of the problem. "They never thought
that the spacecraft was in jeopardy of being lost as it was. They were
more worried about realigning the orbit than they were about a catastrophic
loss," he said. Some officials suggested making an extra course correction,
but Stephenson said, "This was a case of not knowing where the spacecraft
was in time to do this contingency maneuver. When they realized that
they needed it, it was past the point of no return to perform this maneuver."
As it turned out, the orbiter came in far too low once it arrived at
Mars on Sept. 23 1999: Instead of flying about 90 miles (140 kilometers)
above the surface, as planned, it came within 35 miles (57 kilometers).
At that altitude, the spacecraft more than likely broke up in Mars'
thin, dusty atmosphere, mission managers said. Stephenson said, "There
are many things in place that should have caught this error." And NASA
officials agreed. "Our checks and balances process that should have
caught this failed this time," said Ed Weiler, associate administrator
for space science. Mars Climate Orbiter was on a mission to study the
Red Planet's weather and look for signs of water, information key to
understanding whether life ever existed or can exist there. It carried
cameras along with equipment for measuring temperature, dust, water
vapor and clouds.
|
