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RE: Small CUBEsat command decoders



	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: what
orbit were you calculating it for? Please answer if you have a chance!
I'm very interested in these results. 

-Charley Adams
http://buzzsat.gatech.edu


-----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

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