"...analysis has uncovered a potential problem with computer time tagging..." "NASA's Deep Space Comet Hunter Mission Comes to an End" http://www.jpl.nasa.gov/news/news.php?release=2013-287 --ado
Deep Impact's chief mission scientist Mike A'Hearn said, "Basically, it was a Y2K problem, where some software didn't roll over the calendar date correctly." The fault-protection software misread any dates after 2013-08-11, and the misreads triggered an endless series of computer reboots. The failure was in the fault-protection software -- i.e., if they hadn't tried to prevent failure, Deep Impact would still be working. What timescale wraps around on 2013-08-11? Perhaps it was something mission-specific, such as the number of deciseconds since the mission began, or the number of milliseconds since the previous reboot, and this was bowdlerized into "calendar date" for the general public. My source: Vargano D. NASA Declares End to Deep Impact Comet Mission. National Geographic 2013-09-20 http://news.nationalgeographic.com/news/2013/09/130920-deep-impact-ends-come...
Paul Eggert wrote:
The failure was in the fault-protection software -- i.e., if they hadn't tried to prevent failure, Deep Impact would still be working.
I always recall the analysis of one of the radar systems I was involved with as an apprentice. 95% of failures were due to the 'fault-protection system' and the system failed to meet it's design brief. The fix was simply to disable the fault system :) -- Lester Caine - G8HFL ----------------------------- Contact - http://lsces.co.uk/wiki/?page=contact L.S.Caine Electronic Services - http://lsces.co.uk EnquirySolve - http://enquirysolve.com/ Model Engineers Digital Workshop - http://medw.co.uk Rainbow Digital Media - http://rainbowdigitalmedia.co.uk
Reddit[1] making a guess: Put another way, if you represented time as the number of tenths of a second since midnight on January 1, 2000, then you would hit 4294967296 tenths of a second on August 11, 2013[2]. 4294967296 is significant because it's 2^32, which is the smallest number that can't be represented as a 32-bit integer. Generally this will wrap around to 0 (as in calculating 4294967295 + 1 will give you 0). [1] http://www.reddit.com/r/programming/comments/1mtsoy/nasa_officials_declared_... [2] http://www.wolframalpha.com/input/?i=2%5E32+*+0.1+seconds+after+midnight+on+... -----Original Message----- From: tz-bounces@iana.org [mailto:tz-bounces@iana.org] On Behalf Of Paul Eggert Sent: 22 September 2013 23:37 To: Arthur David Olson; tz@iana.org Subject: Re: [tz] Deep Impact: wrong time zone? Deep Impact's chief mission scientist Mike A'Hearn said, "Basically, it was a Y2K problem, where some software didn't roll over the calendar date correctly." The fault-protection software misread any dates after 2013-08-11, and the misreads triggered an endless series of computer reboots. The failure was in the fault-protection software -- i.e., if they hadn't tried to prevent failure, Deep Impact would still be working. What timescale wraps around on 2013-08-11? Perhaps it was something mission-specific, such as the number of deciseconds since the mission began, or the number of milliseconds since the previous reboot, and this was bowdlerized into "calendar date" for the general public. My source: Vargano D. NASA Declares End to Deep Impact Comet Mission. National Geographic 2013-09-20 http://news.nationalgeographic.com/news/2013/09/130920-deep-impact-ends-come... This email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please delete all copies and notify the sender immediately. You may wish to refer to the incorporation details of Standard Chartered PLC, Standard Chartered Bank and their subsidiaries at http://www.standardchartered.com/en/incorporation-details.html.
participants (4)
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Arthur David Olson -
Lester Caine -
Paul Eggert -
Wallace, Malcolm