Hi Sil,
On http://www.amsat.org.ar/pehuene.html# you can read:
Messages Telemetry will be broadcasted in two languages, one of them Spanish. The messages will be recorded on Earth in order to maximize memory. The messages will be, satellite identification, natural numbers, sign, decimal point and the name of the measured variable.
AX25: Telemeter AX25 on the same microcontroller (HC11 family) controlling the ISD to allow telemetry in packet with Ham radio protocol (1200 Bauds). A typical message will require 35 seconds. The information broadcasted will be: i) Announcement (ID) and basic telemetry in two languages (English, Spanish).
So, Pehuensat is sending 1k2 AFSK, not 9k6.
73, Mike DK3WN
----- original Nachricht --------
Betreff: [amsat-bb] PEHEUNSAT-1 heard on 2 metres. Gesendet: Di, 16. Jan 2007 Von: Sil - ZL2CIA[email protected]
Hi,
This may be old news, but PEHEUNSAT-1 seems to be transmitting.I believe that I heard PEHEUNSAT-1 this evening.
Pass ended at 1000 UT (2300 local). Signals seemed to consist of a voice broadcast in Spanish followed by a short burst of carrier. I could not hear any modulation of this carrier and did not decode anything.
I have since googled and see that the downlink in the 2 metre band is at 9k6 b/s. I was still setup for NO-44 at 1200 b/s and of course 9k6 sounds much like noise to the human ear. The satellite may well have been transmitting data.
On hearing the signal, I retuned the rig and tracked the frequency by watching the discriminator output meter. The frequency decreased in a way consistent with Doppler shift.
I caught the last few minutes of the pass by chance, and only because the radio was still tuned to 145.8235 MHz (FM) after an earlier pass of NO-44.
I have another pass at 1129 UT (0029 local time) and I will try to be ready for that one.
Sil - ZL2CIA
Antenna: 6 ele hori - homebuilt. Rig: FT736R Parallel decoding of AX.25 using home built interface and AGWPE/UISS, and Heath Packkit 232 _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
--- original Nachricht Ende ----
This spacecraft will necessarily be out of service for long periods of time and it is to be hoped that during these times the batteries do not freeze solid. The spacecraft mechanical design and thermal design contain a few flaws.
The solar panels are on what I will call the +Z side of the spacecraft in all the pictures we see, especially those at the AATE site where we see launcher close out pictures. I believe that (SHUDDER) there are solar cells only on one face of the spacecraft. The thing is a flat box with horrible asymmetry in the battery placement and a honking antenna coming out the side. But I still believe its principle spin axis is perpendicular to this solar array side with the center of mass nowhere near the center of the +Z face. So it will spin like a pancake on a pencil but the pencil is nowhere near the center of the pancake. There is a large antenna poking out the side and it has unknown mass but this will make the spin geometry quite difficult to guess perfectly, but nevertheless there will still be long periods during which the principle spin axis will be nearly PERPENDICULAR to the satellite-sun vector. This means that the panels will receive almost no illumination and one can expect the small ampere hour batteries to be discharged quickly and also for the VERY large radiating surface (the +Z and -Z) to very quickly cool down the inside of the spacecraft to extremely frigid temperatures.
The following link is to a wma file which contains a recording of PEHEUNSAT
http://www.human.space.edu/pehuensat.wma
and the following is a link to a FLASH video of the launch:
http://www.ibnlive.com/videos/30805/pslvc7-sucessfully-lifts-off.html
Congratulations to AMSAT-LU and AATE and ISRO for their spacecraft and the successful launch.
Enjoy this while it lasts! 73's Bob N4HY
This spacecraft will necessarily be out of service for long periods of time... The spacecraft mechanical design and thermal design contain a few flaws.
It might be more fair to call them design "limitations", since they must have had constraints to what they could design and still get the ride on the side of the conical adapter shown in the photo.
... So it will spin like a pancake...[with] ... long periods [with] the spin axis ... nearly PERPENDICULAR to the sun
vector.
This means that the panels will receive almost no illumination
[most of the time] and the... VERY large radiating surface [will] cool down the inside of the spacecraft to extremely
frigid
temperatures.
Agree completely with your assessment. Lets hope it has practically no spin (that would make it spin in pancake mode) and so maybe it will achieve a gravity gradient posture and may have a better probability of seeing the sun sometimes?
However, the way the long antenna seems to have its own support structure on the side of the colical adapter, then it either had a complicated two-catch release system, or the initial separation was somehow expected to detach the antenna as well. In either case, I see lots of potential for uneven forces and therefore a good liklyhood of a high spin rate...?
Bob, WB4APR
participants (3)
-
Bob McGwier -
Mike Rupprecht -
Robert Bruninga