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From: nigel@access1.digex.net (Nigel Tzeng)
Subject: Re: Ariane 5 - not an exception?
Date: 1996/08/05
Message-ID: <4u5nau$77b@access1.digex.net>#1/1
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references: <Dv45EJ.8r@fsa.bris.ac.uk> <4t9vdg$jfb@goanna.cs.rmit.edu.au>
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 <Pine.GSO.3.92.960804145456.23377A-100000@nunic.nu.edu>
organization: Express Access Online Communications, Greenbelt, MD USA
newsgroups: comp.software-eng,comp.lang.ada,comp.lang.pl1
Date: 1996-08-05T00:00:00+00:00
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In article <Pine.GSO.3.92.960804145456.23377A-100000@nunic.nu.edu>,
Richard Riehle  <rriehle@nunic.nu.edu> wrote:
>On 29 Jul 1996, Bill Angel wrote:

[snip]

>  I have been following this thread with interest.  I am no expert on
>  Ariane, but lack of expertise has not an obstacle to others who have
>  posted on this topic.
>
>  1) redundant processors
>
>     The idea of using different processor architectures is a good
>     one and often employed for other systems such as the Boeing 777.
>     However, if I recall correctly, Ariane has a "rad-hard" requirement
>     (right or wrong) and uses Mil-Std 1750A processors to satisfy that
>     requirement. This would not permit using multiple processors of
>     differing architectures.

There are several space qual'd processors, including the 386.  We
flew one on SAMPEX and will also fly them on XTE and TRMM.  I think
the R3000 has also been flight qual'd for space (fairly sure there was
one on Clementine).  IIRC the 68K has been on a getaway special
although when I last looked it had not ever been flight qual'd.

And yeah...I'd say there's good reason to spec out rad tested components
for use on any launch vehicle or spacecraft.

(As an aside, SAMPEX did not use two different CPUs...SAMPEX was a
cheaper, faster, better NASA project that no one ever heard about.  It
was around 40 million as well and unlike Clementine isn't spinning
uselessly about.  I've worked for both NRL and NASA.  NRL Code 5100 is
as competent as NASA Code 700 in producing small inexpensive
satellites but NRL/BMDO's PR dept blows away NASA's PR dept).

[snip]

>  4) Software Reuse
>
>     If one intends to "reuse" software, such as Ariane 4xx software in
>     Ariane 5xxx, in a significantly different architecture, there is some
>     virtue in extensive testing.

Understatement.  Goddard regression tests the flight software between
releases much less between missions (ie TRMM and XTE are based on the
SAMPEX flt hw/sw) using their simulator to feed sensor data to the
actual flight s/w running on the engineering test unit boards and
later on the actual flight h/w itself during I&T.

Screw ups still happen. :)

>   Richard Riehle

Nigel