Editing Mars Climate Orbiter (section)

== Cause of failure ==
{{quote box
|width=30%
|quote=The problem here was not the error; it was the failure of NASA's systems engineering, and the checks and balances in our processes, to detect the error. That's why we lost the spacecraft.
|author=—Edward Weiler, NASA associate administrator for space science{{r|NASA}}}}

On November 10, 1999, the ''Mars Climate Orbiter'' Mishap Investigation Board released a Phase I report, detailing the suspected issues encountered with the loss of the spacecraft.

Previously, on September 8, 1999, Trajectory Correction Maneuver-4 (TCM-4) was computed, and was then executed on September 15, 1999.  It was intended to place the spacecraft at an optimal position for an orbital insertion maneuver that would bring the spacecraft around Mars at an altitude of {{cvt|226|km|mi}} on September 23, 1999.

However, during the week between TCM-4 and the orbital insertion maneuver, the navigation team reported that it appeared the insertion altitude could be much lower than planned, at about {{cvt|150|–|170|km|mi}}.  Twenty-four hours prior to orbital insertion, calculations placed the orbiter at an altitude of {{cvt|110|km|mi}}. {{cvt|80|km|mi}} was the minimum altitude that ''Mars Climate Orbiter'' was thought to be capable of surviving during this maneuver.

During insertion, the orbiter was intended to skim through Mars's upper atmosphere, gradually [[aerobraking]] for weeks, but post-failure calculations showed that the spacecraft's trajectory would have taken it within {{cvt|57|km|mi}} of the surface.  At this altitude, the spacecraft would likely have skipped violently off the denser-than-expected atmosphere,{{citation needed |date=December 2021}} and it was either destroyed in the atmosphere, or re-entered heliocentric space.{{r|MCO_report}}

The primary cause of this discrepancy was that one piece of ground software supplied by [[Lockheed Martin]] produced results in a [[United States customary units|United States customary unit]], contrary to its Software Interface Specification (SIS), while a second system, supplied by NASA, expected those results to be in [[International System of Units|SI units]], in accordance with the SIS. Specifically, software that calculated the total [[impulse (physics)|impulse]] produced by thruster firings produced results in [[Foot–pound–second system|pound-force second]]s. The trajectory calculation software then used these results – expected to be in [[newton-second]]s (incorrect by a factor of 4.45){{r|MCO_report}} – to update the predicted position of the spacecraft.{{r|MCO_report}}

Still, NASA does not place the responsibility on Lockheed for the mission loss; instead, various officials at NASA have stated that NASA itself was at fault for failing to make the appropriate checks and tests that would have caught the discrepancy.{{r|NASA}}

The discrepancy between calculated and measured position, resulting in the discrepancy between desired and actual orbit insertion altitude, had been noticed earlier by at least two navigators, whose concerns were dismissed because they "did not follow the rules about filling out [the] form to document their concerns". A meeting of trajectory software engineers, trajectory software operators (navigators), propulsion engineers, and managers was convened to consider the possibility of executing Trajectory Correction Maneuver-5, which was in the schedule. Attendees of the meeting recall an agreement to conduct TCM-5, but it was ultimately not done.{{r|NASA}}

The loss of the Mars Climate Orbiter took place two and a half months before the loss of the [[Mars Polar Lander]]. Inadequate funding and poor management have been cited as underlying causes of the failures. According to Thomas Young, chairman of the Mars Program Independent Assessment Team, the Mars Surveyor '98 program "was under funded by at least 30%."{{r|PBS-20000414}}

=== Project costs ===
According to NASA, the cost of the mission was $327.6 million (${{Inflation|US-GDP|327.6|1998|r=2}}&nbsp;million in {{Inflation/year|US-GDP}}){{Inflation/fn|US-GDP}} total for the orbiter and lander, comprising $193.1 million (${{Inflation|US-GDP|193.1|1998|r=2}}&nbsp;million in {{Inflation/year|US-GDP}}){{Inflation/fn|US-GDP}} for spacecraft development, $91.7 million (${{Inflation|US-GDP|91.7|1998|r=2}}&nbsp;million in {{Inflation/year|US-GDP}}){{Inflation/fn|US-GDP}} for launching it, and $42.8 million (${{Inflation|US-GDP|42.8|1998|r=2}}&nbsp;million in {{Inflation/year|US-GDP}}){{Inflation/fn|US-GDP}} for mission operations.{{r|mco_cost}}