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Re: Open-Source Flight Operating Systems

At 04:17 PM 09/14/2002 -0500, Timothy J. Salo wrote:
>What is the status of thinking of open-source operating
>systems for microsat flight computers?
>Has anyone looked at using RTEMS in microsats?  I don't
>believe that an 80186 port exists, but the person who
>seems to be the main RTEMS guy thinks that it
>wouldn't be a difficult port.  Of course, RTEMS undoubtedly
>doesn't contain an AX.25 driver [insert long tirade about
>utility of moving beyond AX.25 for microsat command and
>control here...].  On the other hand, it does support
>a POSIX-like API, which might permit spacecraft software
>to be developed and debugged under UNIX and then ported
>to RTEMS.

RTEMS has been examined by several folks in various programs and looks 
good.  The footprint is larger than SCOS but not terribly so.  One thought 
would be to not use AX.25 at all but use UDP and FTP instead.

>Is anyone looking at open-source RTOSs for the RUDAK and
>SpaceQuest FCV-53 flight computers?

Not RUDAK.  SCOS is working just great there (and in bunches of other 
birds) and there is no point in burning the man hours to change.

>Has anyone looked at RTEMS for microsats?

At the Small Sat conference it was mentioned a couple of times.  Also 
VXWorks was mentioned as having been ported to a couple of university class 
small satellites.  It's always difficult to know just how real some of 
these projects are, but I'm aware of VXWorks in use in a couple of birds 
presently in orbit, so it is doable.

>Would a RTEMS port to the 80186 be of any use?

Possibly but only if a real project came along that used a x86 or clone 
flight computer.  It would have to be ported to the target flight CPU at 
some point but development would need to be done on garden variety PCs for 
it to be a viable alternative.

>Would anyone actually run RTEMS if it were available?

At present both of the AMSAT-NA birds under design and construction have 
software selected and development is under way, so not for them.  It might 
be a candidate for some Amateur university project.  There are bunches in 
the works some of which might actually get build.  The cubesat web page is 
a good place to looks at what's going one.

>Perhaps, on one of the RUDAKs?

No.  There is nothing to be gained from rewriting everything we have on 
RUDAK to run under RTEMS or anything else.  What development and test time 
we have is totally consumed with continuing the efforts that have been 
underway for some time, principally to get the DSPs running some modems so 
we can move toward links usable with reasonable hardware and get one of the 
RUDAKs open for general use.  See the AO-40 Steve Fraser assembled for the 


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