Quote:
Originally Posted by Jerry
NASA did not publish the fact Spirit was within a whisker of failure when it safely landed on Mars. I don't know what the margins were for Opportunity, but I would like to.
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Sorry to steer this away from the subject - but I can not let that comment go unchecked. The 'whisker of failure' is, in my opinion, an exaggeration started mainly by Bruce Moomaw, an occasional space writer who wanted to sex up a story.
The IMU data for both landings has been on the PDS, along with the MPF IMU data, for several years.
There are also many reports regarding MER EDL on the JPL Technical Reports server - just a few extracts from one paper in particular
http://trs-new.jpl.nasa.gov/dspace/handle/2014/37788
Quote:
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"Current numerical models for this canopy type were validated to the variation ranges assumed. The drag coefficient for this type DGB is within the range of 0.38 to 0.52, including all sources. The deployments occurred at dynamic pressures between 730 and 764 Pa at a Mach number from 1.71 to 1.94. However, uncertainty in atmospheric properties suggest that the dynamic pressure could have been as high as 842 Pa or as low as 656 Pa. Peak inflation loads were difficult to assess from returned data and are assumed to be well within the limits suggested by pre-landing analyses (64.5 kN)"
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and the rather interesting results from EDL reconstruction. Spirit First, underlined, Opportunity Second, italics - there are the facts you said you wanted to see - they've been available for more than two years - the raw IMU data for more than 3.
Quote:
..
Time from Entry (s) – Pre-Flight Analysis 3σ Range6
237.3-253.8
234.5-249.7
Time from Entry (s) – Reconstruction
251
250
...
TERMINAL DESCENT
Velocity at RAD Initiation (m/s) – Pre-Flight Analysis 3σ Range6
61.6-84.5
61.4-84.1
Velocity at RAD Initiation (m/s) – Reconstruction
67.4
71.2
Parachute CD at RAD Initiation – Pre-Flight Assumption
0.384-0.488A
Parachute CD at RAD Initiation – Reconstruction
0.52
0.43
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Notice that the often repeated ' the chute opened late, but the mission was saved because the chute overperformed ' story is not born out by facts. The chute was predicted to open 237.3 to 253.8 seconds after entry, and opened 251 seconds after entry. The long end of, but within predictions. Spirits 'chute does appear to have overperformed - but the deployment was not 'late' - indeed, a first order analysis would suggest that Opportunity was the one that was 'late' (by 0.3 seconds outside a 15.2 second predicted window)
I'd also recommend
http://trs-new.jpl.nasa.gov/dspace/handle/2014/38898
This is an example of a rumor, a hint of something, turning into a widely held belief because people can not be bothered to get out and find the FACTS of the situation. A lesson that could well be exercised in the case of the old MOC Cydonia image. The full story of what processing was done, when, and why, is out there. Some people just refuse to read it or refuse to believe it when it deflates their over inflated desire for conspiracy and the need to be, to mal-quote Jim Oberg 'Cultural Vandals'
No shading has been subdued. What you are comparing is an image published to the PDS after careful calibration and processing - to a rapidly processed and stretched, uncalibrated, raw image that MSSS put online as rapidly as possible to appease the conspiracists. No corners were cut - the fact that you have the fully calibrated imagery from which to work proves that.
Doug