Mars Climate Orbiter

Mars Climate Orbiter (MCO ) was a NASA probe to Mars as part of the Discovery Program. You fell in 1999 due to a unit error in the navigation system lost.


Mars Climate Orbiter was built along with Mars Global Surveyor for it, but to be able to still get to use the instruments of the lost Mars Observer. While on Mars Global Surveyor Mars Observer flown four experiments, Mars Climate Orbiter was equipped with only one: the PMIRR (Pressure Modulated Infrared Radiometer), which was to investigate the Martian climate by analyzing the reflected radiation from Mars. In addition, a camera, the Mars Color Imager ( MARCI ) has been integrated. In addition to the Environmental Investigation the role of the MCO was to act as a relay for the Mars Polar Lander also failed.


MCO was launched on 11 December 1998 aboard a Delta II 7425 from the Cape Canaveral Spaceport. On 23 September 1999, the probe reached Mars and began her engine to be captured by the Mars gravity. The plan was first an elliptical orbit of 150 km x 21,000 km, through aerobraking MCO should reach the final, near-circular orbit at 421 km altitude within 44 days. But when the probe should be leaked out of the radio shadow of Mars after braking maneuvers, no contact could be established.


The Commission of Inquiry found very quickly the reason for the loss of contact with the probe. From the telemetry data was determined that the martian next point was not at 150 km, but at only 57 km. At this height, however, the Martian atmosphere is already so dense that the probe was destroyed by the friction forces and heat. The cause of this navigational error was also quickly became clear: While the NASA pulse with the unit Newton calculated x seconds in customary international SI system, the navigation software of the MCO by the manufacturer Lockheed Martin for the imperial system with the pulse unit Pound -force was designed x seconds, therefore greater by a factor of 4.45. In order to compensate for the damage caused by the effects of solar pressure on the asymmetrically attached solar panel swirl, be made to course corrections from time had. Due to the differing units of the course was, however, corrected and brought up the probe too close to Mars.

As other causes of loss of lack of experience, overloading and poor cooperation of the ground crews were cited. Coordinated teams have the unit error also can discover during flight, thus preventing the loss.