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Brief (maybe) SEDSAT Update



Hi Everyone,
	Time for a brief SEDSAT report.  We got several reports from around the world
today (New Zealand, Australia, England, Uraguay) of people that did hear telemetry
every minute, with strong signal.  A few had telemetry, but there appears to be a
good amount of bit errors in that, so its not too diagnostic (there's no error
correction on the 1 minute telemetry).  However, most people did have telemetry
which indicated uptimes between 16 hours and 23 hours.  
	UAH has reviewed the orbit 13-16 data from the Tucson ground station and
concluded that the satellite is running approximately 3-5 watts power negative
when it is RX/TX mode, but should be about 5 watts power positive when it power
cycles and comes up in "safe mode".  Over the next 10 hours, when it is neither
transmitting nor receiving, it should store up enough power to operate for
somewhere between 20 and 30 hours.  Given the data that we've seen today (if the
up times are correct), this is a good estimate, as the last data was heard in
England on Orbit 54, but only one packet (I didn't hear any in Tucson before this,
so I question the data).  Just prior to passing over Tucson, the satellite
produced data at regular 1 minute intervals, so it may have gone under before it
got to the states, and England may be a spurious report. Also, we didn't see any
telemetry from anyone before the 16:00 hour uptime -- I don't know if that's due
to no one listening, or no one hearing it -- I've got to compile a good matrix of
all this data soon.
	So, depending on how long it is "under" for we should see it sometime after 14:00
UTC on the 28th. Since it was up for 23 hours after the last cycle, we should have
a good chance of hearing it again in Tucson, where we've been very successful in
decoding previous telemetry.

	So everyone is probably wondering, what can be done to "fix" this?  The UAH
people have been discussing a number of options, but the primary objective is to
establish an uplink to the satellite (this hasn't been achieved yet, for a number
of reasons unrelated to SEDSAT's current problems), and upload the new code
necessary to allow changes in the flight parameters.   This should be possible in
the amount of uptime the satellite is currently experiencing.  Once the new code
is up, we basically will put the satellite into a more aggressive power
conservation mode -- turn off RX and TX for longer periods, possibly transmit
packets at a lower rate than once every minute.  In this mode, many of SEDSAT's
objectives can be achieved (Images, Mode-A, etc...) just not on a 24 hour basis --
something like operate for a day, charge up for two might be a workable scenario.

	For those collecting telemetry:  Please continue mailing it to telemetry@seds.org
(this way it will go to the UAH team as well).  If you just send it to me, I may
not get to it right away while I'm studying for midterms this week! 
	Also, we've had a number of reports of various inconveniences with the software
-- it doesn't automate well with WiSP (won't take a file argument, and won't shut
down), and it won't run on anything under Win 95.  We'll see what we can do about
this.  Some people have been logging the KISS packets, and sending them in.  This
preserves the "uptime" information, which is good, but it is not evident that
there are any other valid packets in there (They begin with an ASCII "5" (Ox35) ).
 For those who can't use the program, or prefer not to, make your best efforts to
log *binary data*.  Logging KISS data to a terminal program, and logging that
doesn't appear to work. Also, if you can indicate orbit number, this help us
easily work out the timezones and such.

	That's all for now.  Hopefully the satellite can continue to work through these
frequent power cycles, and we can effect a workaround.  Thanks to everyone for
their constant help and support.  We appreciate it!

[Well, I guess the report wasn't too brief, but there's a lot of detail that I
skipped -- More later I guess].
-- 
------------------------------------------------------------------------------
Christopher A. Lewicki KC7NYV 520.977.0758 Maintainer of SEDS.LPL.Arizona.EDU
     Project Manager, University of Arizona Student Satellite Project
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