Re: Mariner 1 / FORTRAN bug

[Keith Thompson <kst-u@mib.org>]

robin.vowels@gmail.com writes:
> On Saturday, December 5, 1992 at 7:18:16 AM UTC+11, srhe...@happy.colorado.edu wrote:
>
>> I heard a rumer about a multi-million (or multi-billion) dollar satellite going
>> astray because some one left a comma out of a FORTRAN DO loop and it was still
>> syntactically legal.  Can anybody give me a reference on this?  
>
> A google search produced this first try:
>
>
> This has come up in a couple of threads in the last month or two, so I
> finally got around to looking it up. The famous FORTRAN punctuation
> error occured on Mariner 1 in 1962. Here is a description of the
> error:
>
> "There is a useful lesson to be learned from the failure of one of the
>earliest planetary probes launched by NASA. The cause of the failure
>was eventually traced to a statement in its control software similar to
>this:
>
> DO 15 I = 1.100
>
> when what should have been written was:
>
> DO 15 I = 1,100
>
> but somehow a dot had replaced the comma. Because Fortran ignores
> spaces, this was seen by the compiler as:
>
> DO15I = 1.100
> which is a perfectly valid assignment to a variable called DO15I and
> not at all what was intended."
>
> Information found here:
>
> http://www.star.le.ac.uk/~cgp/prof77.html#tth_sEc1.3

According to https://en.wikipedia.org/wiki/Mariner_1 :

    In other accounts, the bug consisted of:

    * a period typed in place of a comma, causing a FORTRAN DO loop
      statement to be misinterpreted (although there is no evidence that
      FORTRAN was used in the mission), of the form "DO 5  K=1. 3"
      interpreted as assignment "DO5K = 1.3" There are anecdotal
      reports that there was in fact such a bug in a NASA orbit
      computation program at about this time, but it was a program for
      Project Mercury, not Mariner, and the claim was that the bug was
      noticed and fixed before any serious consequences resulted.

Also discussed on RISKS Digest, including an account from someone who
worked at NASA in 1963.  The error caused a DO loop to execute just once
rather than iterating to a more precise solution.  The resulting
calculation was good enough for the Mercury suborbital flights, but not
for the later orbital flights.

http://catless.ncl.ac.uk/Risks/9.54.html#subj1.1

And see here:
http://catless.ncl.ac.uk/Risks/8/75#subj1
for a description of a missing "bar" in a hand-written calculation that
apparently caused the loss of the Mariner 1 Venus probe in 1962.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Will write code for food.
void Void(void) { Void(); } /* The recursive call of the void */