Mars orbiter faces NASA’s ‘Ghoulish’ past

James Oberg NBC News space analyst

HOUSTON - In the early years of interplanetary exploration, probes to Mars failed often, and sometimes for reasons that weren't clear. To combat disappointment with humor, space engineers developed a fantasy folklore of outer space in the "Here Be Dragons" motif of ocean voyagers from half a millennium earlier. The mythical sea serpent on the route to Mars was called "the Great Galactic Ghoul."

In the late 1960s and early 1970s, space teams strove to build probes that could survive or outwit the Ghoul's malevolent hunger. Of course, engineers knew that the creature was only a comical personification of the hazards Mars had in abundance. The simplest flight paths to the Red Planet required months of travel. Radio communication was weak, with signal gaps that lasted large fractions of an hour.

Such challenges have long since been overcome. But as Earth's latest emissary, the Mars Reconnaissance Orbiter, hurtles toward its arrival in orbit around Mars on Friday, you may hear once again from some quarters that Mars is "hard," and that failures are only to be expected in such difficult endeavors.

Mars Reconnaissance Orbiter stands a good chance of dodging the Ghoul this time around: It will arrive in orbit using a technique that has worked before — starting with a rocket burn to slow down and enter a widely looping orbit, then skimming the atmosphere repeatedly to further lower that orbit. It has a well-honed suite of scientific instruments for a mission agenda that includes the sharpest-ever photo survey of the planet's surface.

Best of all, its designers, builders and operators are armed with the lessons learned from previous Mars missions, both successful and disastrous.

When bad things happen to good orbiters
Two of NASA's biggest debacles involving Mars orbiters occurred in the 1990s, long after the Great Galactic Ghoul was supposed to have been conquered. In 1993, Mars Observer fell silent only days before its scheduled arrival. Six years later, Mars Climate Orbiter passed behind the planet during its slowdown rocket burn, and never came out the other side.

MARS MAPPING MISSION The $720 million Mars Reconnaissance Orbiter mission is designed to gather more data than all past missions to Mars combined. MRO has the largest camera ever sent to another planet, and its detailed mapping survey will be used to select future landing sites. It will also serve as a communications relay for future missions. • Graphic: All about the orbiter • Replay last year's blastoff • NASA learns from 'Ghoulish' past • Probe enters orbit after risky move • Special report: 'Return to the Red Planet' MSNBC

The 1999 failure is the one most deeply wrapped in a new aura of space folklore. That was the space probe that was supposedly lost because workers mixed up metric and English units of measurement. As a result, so the story goes, they inadvertently steered the probe too close to Mars, and it burned up while skimming the planet's thin atmosphere.

Aside from the late-night TV talk show laughs at the expense of the hapless workers, the story had the virtue of being easy to understand, with well-defined fall guys. But the story was also wrong, or at best only partially true.

The people ultimately at fault were too high in NASA to be "outed," it seems. Mistakes were made, and an expensive Mars probe was lost — but the root cause of the failure went largely unpublicized by NASA and remains so to this day. It turns out there had indeed been a mixup over measurement units. But the reason this mistake ultimately doomed the mission wasn't the fault of those directly involved at that level.

Mars Climate Orbiter had been designed with a single solar panel that on the long cruise between worlds inadvertently acted like a small "solar sail." Photon pressure gradually torqued the spacecraft away from its preferred orientation, and from time to time small rocket thrusters had to be turned on briefly to push it back to face the desired direction.

Because of where they were installed on the probe, those thrusters didn't just make the spacecraft spin gently — they also imparted a smaller, but not negligible, push that altered its path through space. It was a data table listing the amount of this disturbing "push' for each thruster, originally calculated in newtons (the metric unit of force) but later interpreted in pounds-force (the English unit equivalent), that began the process that ended in tears.

Problem discovered too late
Because the probe had been a showcase for "faster, better, cheaper" space missions, the revolutionary philosophy espoused at the time by NASA Administrator Dan Goldin and touted by Vice President Al Gore, standard levels of double checking had been eliminated. The space navigators who might have anticipated the problem, or even identified it, were not budgeted to begin participating in the mission soon enough.

NASA Mars Climate Orbiter, shown in this artist's conception, had a single solar panel that inadvertently acted like a small solar sail to push the probe away from its proper orientation.

According to private contacts within NASA's Jet Propulsion Laboratory, the "units" mistake was noticed, since it caused some of the midcourse corrections to be larger than they should have been. The navigators even correctly guessed that the tables were in error by about a factor of four — the actual ratio between the two units of measurement. Unfortunately, they were never given the time or the resources to track down the cause.

The navigators reportedly voiced their uneasiness during the probe's final approach to Mars — only to be told they had to "prove we are off course" before the path could be altered.

The proper approach to space safety is to assume a hazard is present until you can prove it is absent, and only then to proceed. In this case — as in the case of the shuttle Challenger, where the doubting engineers were ordered to prove the seal wouldn't work at record low temperatures — the presence of doubt should have required verification. Instead, the uncertainty was used as an excuse to avoid even trying to get verification.

In the end, cutting corners in space led to cutting the corner at Mars too closely. In the final hours of the approach, as better navigation data poured in, the control team was horrified to see the predicted path swerve deeper into the atmosphere. But nothing could be done except hope for a miracle, and to withhold those anxieties from the public — then and later.

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