Schoolkid blunder brought down Mars probe

日期:2019-03-07 03:06:14 作者:屈突鹪蕨 阅读:

By Jeff Hecht in Boston NASA lost its $125 million Mars Climate Orbiter spacecraft as a result of a mistake that would shame a first-year physics student—failing to convert Imperial units to metric. The problem arose from a culture clash between spacecraft engineers and navigation specialists, says Mary Hardin, a spokeswoman for NASA’s Jet Propulsion Laboratory in Pasadena. “Propulsion people talk in pound-seconds of thrust and navigators talk in newton-seconds,” she says. The spurious data came from the craft’s attitude-control system, a design which had worked fine on the Mars Global Surveyor. But there was one crucial difference in the system on the orbiter. “There was a different propulsion supplier for the Mars Climate Orbiter, and its data package was in English [Imperial] units,” says Noel Hinners, vice president for flight systems at Lockheed Martin Astronautics in Denver, Colorado. No one adapted this data-processing software for the second probe, so JPL’s navigation software thought the numbers it received were newton-seconds rather than pound-seconds. The attitude thrusters only made small corrections, but the error was enough to leave the probe 100 kilometres too close to Mars when it tried to enter orbit. NASA normally monitors spacecraft positions extensively, but observers speculate that stressed controllers missed the error. “Everyone on NASA projects is incredibly overworked, and mistakes are happening not just because we’re faster, but because we’re working nights and weekends,” says Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. Lockheed,