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Mars Pathfinder Lander Preparations
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Share full text access. Please review our Terms and Conditions of Use and check box below to share full-text version of article. Abstract Mars Pathfinder successfully landed at Ares Vallis on July 4, , deployed and navigated a small rover about m clockwise around the lander, and collected data from three science instruments and ten technology experiments. Citing Literature. References Related Information. Close Figure Viewer. Browse All Figures Return to Figure. Previous Figure Next Figure.
Journal list menu Journal. Log in with your society membership Log in with AGU. The JPL engineers fortuitously decided to launch the spacecraft with this feature still enabled. By coding convention, the initialization parameter for the mutex in question and those for two others which could have caused the same problem were stored in global variables, whose addresses were in symbol tables also included in the launch software, and available to the C interpreter.
No more system resets occurred. First and foremost, diagnosing this problem as a black box would have been impossible. Only detailed traces of actual system behavior enabled the faulty execution sequence to be captured and identified. Secondly, leaving the "debugging" facilities in the system saved the day. Without the ability to modify the system in the field, the problem could not have been corrected. Finally, the engineer's initial analysis that "the data bus task executes very frequently and is time-critical -- we shouldn't spend the extra time in it to perform priority inheritance" was exactly wrong.
Mars Pathfinder - Universe Today
It is precisely in such time critical and important situations where correctness is essential, even at some additional performance cost. David told us that the JPL engineers later confessed that one or two system resets had occurred in their months of pre-flight testing.
They had never been reproducible or explainable, and so the engineers, in a very human-nature response of denial, decided that they probably weren't important, using the rationale "it was probably caused by a hardware glitch". Part of it too was the engineers' focus.
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They were extremely focused on ensuring the quality and flawless operation of the landing software. Should it have failed, the mission would have been lost. It is entirely understandable for the engineers to discount occasional glitches in the less-critical land-mission software, particularly given that a spacecraft reset was a viable recovery strategy at that phase of the mission. The bright mound to the upper right of the Twin Peaks is North Knob, seen in Pathfinder images as peaking over the horizon.
At this scale there is no obvious geologic evidence of an ancient flood. Rather, impact craters dominate the scene, attesting to an old surface. The age is probably on the order of 1. Wind-formed linear ripples and dunes are seen throughout and are concentrated within craters. Sets of polygonal ridges of enigmatic origin are seen east of the Pathfinder lander.
Rocks are visible over the entire image, with heavy concentrations near fresh looking craters. Most of them are probably impact ejecta blocks. Landing Site Region K : This is a close-up of the area in the vicinity of the Pathfinder landing site. Major features are named. The white box outlines the area of the image, discussed next, where hardware is seen.
Zooming in, one can discern the ramps, science deck, and portions of the airbags on the Pathfinder lander see next image, right side for greater detail.