[Elecraft] Buggy software OT

[KENT TRIMBLE]

Facts can also be factual.

Kent  K9ZTV


/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 was computed and 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 226 kilometers on September 23, 
1999. However, during the week between TCM-4 and the orbital insertion 
maneuver, the navigation team indicated the altitude may be much lower 
than intended at 150 to 170 kilometers. Twenty-four hours prior to 
orbital insertion, calculations placed the orbiter at an altitude of 110 
kilometers; 80 kilometers is the minimum altitude that Mars Climate 
Orbiter was thought to be capable of surviving during this maneuver. 
Post-failure calculations showed that the spacecraft was on a trajectory 
that would have taken the orbiter within 57 kilometers of the surface, 
where the spacecraft likely disintegrated because of atmospheric 
stresses. /

/_The primary cause of this discrepancy was that one piece of ground 
software supplied by _Lockheed Martin 
<http://en.wikipedia.org/wiki/Lockheed_Martin>_produced results in a 
_United States customary unit 
<http://en.wikipedia.org/wiki/United_States_customary_units>_("American"), 
contrary to its Software Interface Specification (SIS), while a second 
system, supplied by _NASA <http://en.wikipedia.org/wiki/NASA>_, that 
used those results expected them to be in metric units, in accord with 
the SIS. _Software that calculated the total impulse produced by 
thruster firings calculated results in pound-seconds. The trajectory 
calculation used these results to correct the predicted position of the 
spacecraft for the effects of thruster firings. This software expected 
its inputs to be in newton-seconds.^[16] 
<http://en.wikipedia.org/wiki/Mars_Climate_Orbiter#cite_note-Mishap-17> /

//

/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. 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./



On 1/17/2015 1:41 PM, Lynn W. Taylor, WB6UUT wrote:
> Good quip, but it doesn't agree with the findings of the Mars Climate 
> Orbiter Mishap Investigation Board.
>
> Facts can be so inconvenient.
>
> On 1/17/2015 11:15 AM, KENT TRIMBLE wrote:
>> Good quips always sail over at least one person's head.
>>
>> K9ZTV 
>
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