I wonder if the design not being done to spec
/
//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),/
qualifies as a "bug" -- vs. a design mistake?
Phil W7OX
On 1/17/15 12:30 PM, KENT TRIMBLE wrote:
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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