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RE: Small CUBEsat command decoders



On Tue, 15 Apr 2003, Charles Adams wrote:

> 	Hello, I'm working on the Buzzsat project at Georgia Tech, and
> was very interested in your email (below). Do you have the test plan for
> both the SEU tests and the TID tests that you ran on the PIC and the
> DTMF decoder? I am a coop at JPL, and have worked a lot with space
> qualifying components, and I was extremely surprised that you didn't
> have any problems with the EEPROM. That's great!
> 	Also, how did you determine the length of time in space:

We assumed about 100 Rads per year. so 10,000 Rads would be 100 years, but
since someone told us that Neutrons were only about 1/4th the total dose
equivalence, we divided tht by 4.  But again, its hard to say, becuase
with no errors, the statistics of small numbers are pretty well
meaningless..  We assume there must have been SEU's but the firmware must
have had internal watchdogs or restart-code that somehow just kept on
ticking...

> what
> orbit were you calculating it for?

LEO orbit at about 300 miles up...

Bob
Please answer if you have a chance!
> I'm very interested in these results.
>
> -----Original Message-----
> From: Tim Cailloux [mailto:tim@cailloux.com]
> Sent: Tuesday, April 01, 2003 10:26 PM
> To: Kyle Mark Hershberger; Charles R. Adams
> Subject: FW: [amsat-bb] Small CUBEsat command decoders
>
> This is from the Amsat-BB mailing list.  I thought you might be
> interested...
>
> tim
>
> -----Original Message-----
> From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org] On
> Behalf
> Of Bob Bruninga
> Sent: Tuesday, March 25, 2003 7:40 PM
> To: amsat-bb@AMSAT.Org
> Subject: [amsat-bb] Small CUBEsat command decoders
>
> CUBESAT Builders:
>
> Today we tested an off-the-shelf DTMF decoder in a neutron radiation
> environment and after subjecting it to the equivalent of 26 years in
> space, it was still working flawlessly.  Since it is about the size of a
> large postage stamp, it seems to be a good candidate for the TINY
> cubesat and other simple student satellite designs.
>
> It was a SPEC-COMM 809B DTMF 3 function decoder.  Typically advertised
> in all radio magazines.  It was exposed to 3 rads per second for an hour
> for a total dose of over 10,000 rads.
>
> The professor in the Nuclear lab was amazed at its performance.
> Another very RAD-HARD RAM chip was exposed at the same time and it
> suffered 5 SEU's in the same time.  We powered up the DTMF module
> throughout the test with no power cycles hoping to see if any SEU's
> would lock it up.  None.
>
> So we doubt seriously that the DTMF PIC Processor is a hard device, but
> that it probably has internal watch dog timers and good firmware that
> receovers from any wandering code.  Our main concern was that the EEPROM
> that stores the command sequences would not suffer any corrupted bytes.
> None occured.
>
> Our test consisted of simply sending the six command sequences over and
> over for an hour and observing a proper decode every time.
>
> de WB4APR@amsat.org, Bob
>
> CUBESAT Designs     http://www.ew.usna.edu/~bruninga/cubesat.html
>
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not
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> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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>

de WB4APR@amsat.org, Bob

PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html
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CUBESAT Designs     http://www.ew.usna.edu/~bruninga/cubesat.html
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MIM/Mic-E/Mic-Lite  http://ssdl.stanford.edu/mims/

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