Courtesy NASA.
Detail from an artist's rendition of the Mars Climate Orbiter
Courtesy NASA.
An artist's view of the Mars Polar Lander.
Polar slander
Incidentally, the data came from Mars Global Surveyor, which is orbiting Mars. Surveyor was pressed into service to listen for signals from Polar Lander. As you read this, Surveyor may be playing interplanetary undertaker, photographing the South Pole for wreckage or other signs of its sister craft, Polar Lander.
Since Lander's disappearance, NASA followed an elaborate plan to reestablish contact, with nil results.
At present, there's little evidence of what went wrong, says Sanjay Limaye, a scientist at the Space Science and Engineering Center at the University of Wisconsin-Madison. The last communication was sent 11 minutes before Lander was due to enter the atmosphere, he says. One minute later, a pair of small instrument packages were due to be released.
These packages were designed to survive a crash-landing on Mars and send signals to a satellite orbiting the planet. Since they have not done so, Limaye speculates that some kind of general failure doomed Lander. "I don't think they landed successfully on the surface," he says. It's possible -- but "pure speculation" that the packages did not separate from the lander.
Overall, the lesson being learned is simple, Limaye says. Interplanetary travel is complex and dangerous. "People forget that going to Mars is not the same as going into Earth orbit." Even though systems are tested on Earth, during eight or 10 months in space, alternating extremes of heat and cold can damage rocket motors needed for safe landing or entry into Mars orbit.
One of Polar Lander's jobs was to determine how much water is present on Mars -- a key to the hunt for ancient life. That search becomes all the more intriguing with the recent announcement of evidence for a giant, ancient ocean on Mars.
Metric mess
If the loss of Polar Lander is still mysterious, the Sept. 23 destruction of Mars Climate Orbiter is now understood. An internal NASA investigation, published Nov. 10, blamed the loss on these factors:
Inadequate computer models of the rockets.
Poor team communication.
Navigation failures (the team did not know the spacecraft's position and orientation!).
Inadequate checking of mission components.
Overwork of the two-member navigation team.
Confusion over metric and English units.
It's that last problem that really pinches. In a world dominated by the metric system, the United States stands out for its reliance on the English system, which rests on such constants of nature as the length of a king's thumb.
Instead of using the simple metric system, where about all you need to know is how to move a decimal point, American children, especially those contemplating scientific careers, must learn English, metric, and the mystifying math for converting them.
The English system is so awkward that even the English have dumped it.
Deadly confusion
According to the Los Angeles Times, a Lockheed official admitted that the company had been required to send data in metric units: "To be very blunt, it was overlooked" (see "String of Missteps... " in the bibliography). A planned, last-minute course correction was not done because controllers were unprepared (see "A System Fails..." in the bibliography).
A gram of prevention -- worth a kilo of cure?
But enough carping. What exactly happened with Climate Explorer? From the best we can make out, when the spacecraft was slowing to enter Mars orbit Sept. 23, the rockets were fired using data from Lockheed Martin, the prime contractor. Sadly, Lockheed had been talking in pounds, while the contract specified newtons (both units measure rocket thrust, incidentally).
