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From: rebelsky@grinnell.edu
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Subject: Simple Mix-Up Caused Mars Accident, NASA Finds
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This story from The Chronicle of Higher Education 
(http://chronicle.com) was forwarded to you from: rebelsky@grinnell.edu



  Simple Mix-Up Caused Mars Accident, NASA Finds

  By VINCENT KIERNAN
  
   
  
  A $125-million space probe was lost last week because of a
  simple error that freshman engineering students are taught to
  avoid: The spacecraft's engineers failed to convert a key set
  of numbers from English measurements to metric before using
  them to program the spacecraft's rockets, the National
  Aeronautics and Space Administration announced Thursday. 
  
  Engineers at Lockheed Martin Astronautics, in Denver, one of
  two teams involved in the Mars Climate Observer project,
  calculated firings of the spacecraft's rockets in pounds, the
  unit used for acceleration in the English system of
  measurement.	However, researchers at the Jet Propulsion
  Laboratory at the California Institute of Technology, in
  Pasadena, Cal., who controlled the spacecraft, did not
  translate those numbers to newtons, the unit used in the
  metric system, before firing the rockets. 
  
  The spacecraft, which was supposed to orbit Mars, instead flew
  too close to the planet's atmosphere on September 23. Its fate
  is uncertain. 
  
  Douglas Isbell, a NASA spokesman, said the error occurred with
  rocket thrusters that were used to slow down internal
  flywheels that stabilized the spacecraft and not with rocket
  firings used to change its trajectory. The discrepancies in
  the Mars Climate Orbiter's course were so small that they were
  not noticed until after the spacecraft had gone missing. 
  
  Mr. Isbell said that engineers at the Jet Propulsion
  Laboratory knew that Lockeed Martin's figures were expressed
  in English units, not metric. But for some still-undetermined
  reason, the figures were not converted to metric, he said.
  NASA and the Jet Propulsion Laboratory both have begun
  investigations into the circumstances of the error. 
  
  A second spacecraft, the Mars Polar Lander, is scheduled to
  arrive at Mars on December 3, and officials of NASA and the
  Jet Propulsion Laboratory will seek to make sure that the
  conversion error does not happen to that spacecraft. "Our
  clear short-term goal is to maximize the likelihood of a
  successful landing of the Mars Polar Lander," Edward Weiler,
  NASA's associate administrator for space science, said in a
  prepared statement. 
  
  The history of the space program is replete with mishaps that
  were caused by seemingly obvious errors. But the latest error
  seems likely to further tarnish NASA's reputation on Capitol
  Hill, where some lawmakers regularly complain about its
  management of the international space station. As one hint of
  what may be in store for NASA, Rep. F. James Sensenbrenner,
  Jr., of Wisconsin, the Republican chairman of the House
  Science Committee, issued a two-word reaction to the space
  agency's disclosure: "I'm speechless." 
  

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Copyright 1999 by The Chronicle of Higher Education