,what kind of battery is install on this kind of satellite? how does it react in the cold space where it is?
We placed the batteries in the middle of the satellite. It is quite immune to the +90C and -100C possible fluctuations on (unattached) solar panels (if they were not attached to the sides of the satellite). Since the solar panels are attached to the aluminum frame and the satellite rotates at about 1 RPM, we don't see any temperature variations even on the panels of more than about 10C (per orbit).
And then these 10C fluctuations on the sides only penetrate to about a +/- 1 degree variation at the batteries per orbit and per day. Though there is a long term variation with the Sun/Orbit beta angle.
The average temperature of PCsat is around 10C, getting as low as 0C during full eclipse seasons (High Beta angles) and as high as 40C for a weak or so when it is in full sun. This cycle moves over a 2 month or so cycle.
Right now, PCsat inside is a nice comfortable 25C.
Our problems with PCSAT (now 12 years old) is our own fatal flaw of designing it with a reboot-after-fault-detection mode of turning on backup transmitters and backup receivers to regain contact with the command station. Now with 20/20 hindsight, that was dumb... especially if the reason it faulted is due to low power!
We can get in and turn off the extra XMTRS and RCVRS any time we want during high beta angles (maximum peak solar power available), but then there is only 15 minutes left before it goes back into eclipse and dies (not enough ttime to charge each orbit).
But then 2 or 3 times a year, it enters full sun periods when, if we can get the command in, then we can send those commands to turn off all the spares and they will hold... BUT this time of full sun, is also the time of the worst sun angle (least average power), and so it is iffy if we can get the command in.
See http://pcsat.aprs.org (raw packets at the bottom) and you will see that today's attempt resulted in achieving 9 minutes of operation before it died. See the telemetery serial numbers starting at 001 each time it resets. That occurred at 2013-02-02-14:29:24z
Hope that helps Bob, Wb4aPR
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Gervais Fillion Sent: Saturday, February 02, 2013 9:53 AM To: [email protected] Subject: RE: [APRS] QRT all PCSAT transmissions!
Hi Bob,what kind of battery is install on this kind of satellite?i wonder how it react in the cold space where it is?Do you have any data that gave the temperature upthere?i am just curious,here in the Eastern part of Quebec we are used to have in the -20 celcius,,,,and battery are built for that,,how it is in space?? 73 Bob Thanks for all the info you are tellng us. Gervaisve2cknLe Bic,Quebec
> Question: PCSAT,does it transmit at 144.390 like other APRS hardware ?
No and yes. It operates up and down on 145.825 like all other APRS
But it also has a backup transmitter on 144.39 which we can use as a
national broadcast downlink.
Problem is, most people cannot hear it due to local QRM on 144.39... but it
If you live in the boonies and there is no other local traffic, sometimes
you can pick it up.
But there is no UPLINK there for obvious reasons.
Even in congested areas, sometimes you can receive it on 144.39 if there is
a moment of silence when it transmits.
In fact, it was that clever idea that kills PCSAT on every orbit. The old
batteries do not have enough power to power both XMTRS at the same time
which is what it is trying to do.
We can send the command to turn off the other XMTR, but then on the next
eclipse, it resets back to BOTH ON. Darn...
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