[X] My Assistant

[Phil Stooke]

Starting a new topic here - hopefully that's OK! Clearly there will be a lot of action around this in the next weeks and months with descent images and HiRISE views of the hardware.

I thought I had posted this map earlier but apparently not. This shows the various landing ellipses in this area. The original plan was for an ellipse oriented NW-SE, but it changed with the different launch date and is now nearly E-W. Note that the ellipse shown in the recent ESA release is the envelope of all ellipses over a given launch period, but the actual landing ellipse for the given launch date is smaller. Opportunity's final landing ellipse is shown for comparison.

http://exploration.esa.int/mars/57445-exom...6-landing-site/

http://exploration.esa.int/mars/57446-exom...6-landing-site/

Phil

[tolis]

Reported in Anatoly Zak's website:

"By October 24, engineers narrowed down a possible culprit to an error in the software of the Schiaparelli's Doppler radar altimeter, which misled the main computer into thinking that the spacecraft had already reached the landing altitude."

That sounds like something you should catch during testing on the ground (Earth ground, that is)

[nogal]

That sounds like something you should catch during testing

I've been writing code since 1970 (when the world was "young and uncomplicated" ), but I never dealt with real-time, or near-real-time handling code which, I suspect, Schiparelli must use, and imposes a lot of constraints on code, including path-length (the time available for a given algorithm to execute).

I red somewhere that it has been mathematically proved that, except for simple cases, it cannot be demonstrated that a program is 100% correct. So, given one has to live with errors, what can be done to minimize them? Software building, coding methodologies can be used. "Proven" code can be reused - as long as the context of the proof remains valid for the case at hand and people are aware of it. And, of course, testing. A lot of testing. Automated testing can catch some errors, and test cases are specifically created. Can one foresee everything? Every possible combination of inputs? Some errors are caught by sheer luck, others may remain hidden for a long time, until a rare set of conditions manifests itself. Every time an error is caught its correction is included in the next release of the software. It works for the relatively forgiving environments of every day life. Space is much, much more harsh.

I'm just offering my own experience, not excusing anyone or anything. Sometimes, getting the kinks out of a program, feels harder than landing on Mars [pun intended].
Fernando