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data-stream clock with just a little doppler shift

Discussion in 'Electronic Design' started by Winfield Hill, Oct 22, 2004.

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  1. John Miles

    John Miles Guest

    Another good article by the same guy:

    "After all, these switches were reportedly developed as a nuclear
    warhead safety device, so one could just assume that they were properly
    wired." Um... did the nuke guys make the same assumption?

    Amazing how it's usually the simple stuff that hoses the mission.
    Someone mounts the G-sensors upside down (Genesis), conflates metric and
    English units (Mars Climate Orbiter), misses a bug in some mundane user-
    interface code (Therac-25), or fails to check the specs of reused
    software components against the requirements of new hardware (Ariane 5,
    and now Huygens).

    How do we treat human error as an input to our otherwise-exhaustive
    engineering models? That question seems to be worth its own
    disciplinary field.

    -- jm
  2. Randomly select a sample of manufactured units and test them.
    Good question. I wonder to what extent each of the aforementioned goofs
    can be traced back to a requirements or design communications error
    between the systems level engineering folks and the component or
    subassembly design/manufacturing groups.

    If you model each component of the design and manufacturing team as a
    node on a graph and the data flow between each as a link, an error rate
    and latency can be assigned to each link depending on such things as its
    length and method (the people in the next cubicle vs. an engineering
    group a few time zones away) and the cost each node must incur to
    correct errors in the communications channel or time wasted working with
    outdated data.
  3. Joerg

    Joerg Guest

    Hi Paul,
    In this case it seems to boil down to a serious lack of communication
    and, consequently, failure to adhere to a proper review process. Quote
    from the article:

    Quote: "JPL's Horttor admitted that NASA probably could have insisted on
    seeing the design if it had agreed to sign standard nondisclosure
    agreements, but NASA didn't consider the effort worthwhile,
    automatically assuming Alenia Spazio would compensate for the changing
    data rate." End of quote.

    We see that a lot these days, unfortunately. Especially in the world of
    software. Either one party assumes the other party did it all just fine,
    or one party decides that a certain information does not need to be

    Regards, Joerg
  4. Rich Grise

    Rich Grise Guest

    Ah, what a fantasy! George the Anointed pushes the button, the missiles
    all take off, fly their majestic ballistic trajectories, and ten
    thousand multiple independently retargetable reentry vehicles go "plop."

    My heart wants to sing just thinking about it!

  5. Right. Now multiply this by the number of inter-organizational
    interfaces that exist within a project. Granted, these interfaces also
    exist between groups within an existing organization. But when the
    decision is made to cross corporate boundaries, what was shared without
    concern for cost or information security must now be covered by
  6. Joerg

    Joerg Guest

    Hi Paul,
    Yes, it has to be covered by contract. But this can be one single
    contract and a good dose of mutual trust. We have had a lot of
    cooperation with outside companies and other organizations in the
    medical field. So far there was never any breach of confidentiality, no
    IP scuffles and we were totally open with each other. In medical you
    just have to open in order to achieve an efficient and most of all safe
    design. Everything needs to come together on the table during a design
    review, no hidden code, no hidden HW architectures.

    Regards, Joerg
  7. dd

    dd Guest

    I believe cellular phone base station receivers have the same
    characteristic introduced deliberately.
    Max velocity for mobile 280km/sec.
    A correspondent in the Science mag New Scientist gave the wrong answer
    recently on their back page questions answered as the RF bw and not the
    modulation rate was employed to calculate doppler tolerance.
    Gave a result orders of magnitude out.
    I emailed to point out their error without any response, and so it

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