Hi,

Firstly, thanks to Mineo Wakita (JE9PEL), Gary Halstead (K8KFJ) and Martin Gillen (VA3SIE) for the reception, copying, and decoding the data from AO-07.

I remember some of the discussion posted here, when AO-07 started working again. The consensus seemed to be that the satellite had failed 25 years previously because too many of the NiCd cells in the battery had become short circuited (as NiCd do with time). This had caused the battery voltage to fall to a level too low to operate the transponder. Time,(and perhaps corrosion caused by the battery chemicals) had eventually created an open circuit and the satellite was now operating directly from the solar panels. Certainly, it goes very dead once it is in darkness which rather supports this idea.

However, channel 2D of the telemetry shows a Battery Charge/Discharge current of 80 ma. Since this is positive, I assume that it represents a "charge" current. I see too that the "half battery voltage" is 2.4 volts, while the full battery voltage is 8.8 volts. So the dead battery is behaving like a 110 ohm resistive load and consuming 0.704 watts.

This doubtless explains why the battery is at a toasty 60 C and most of the rest of the satellite is at -46 C.

Also freezing is the 10m PA (channel 4B). This is not surprising since it was "off" when JE9PEL recorded the CW. Yet this PA is drawing almost 0.8 amps of emitter current and producing nearly 6 watts of RF. It's consumming 7 watts (8.8V * 0.8A)making the PA about 86% efficient). Does this mean that the telementry is unreliable (fair enough, it a very old satellite)?

The 2m PA (channel 5A) is a whole bunch warmer at -5 C. This makes sense since the 2m transmitter was the one sending the data (or perhaps it's installed next to the battery!) I presume that the 2m beacon signal is simply injected into the 2m PA. Is this correct?

The battery voltages (and half battery voltages) give some indication of where the remaining short circuit cells might be (in case anybody wants to go up and fix them - actually, I will do that if someone can give me a lift). I wondered about this in a sort of hypothetical way. I'm curious for its own sake (and clearly have too much time on my hands).

I tried to find some details of the satellites design via google, but didn't (I'm sure others will succeed in this).

I also looked in my own humble Ham library for details of the design, but didn't find any.

I guess that the satellite battery consisted of cells in series and batteries in parallel, or perhaps of cells in parallel then in series to make a battery. Does anybody know exactly? Can anybody point me in the right direction?

Sil - ZL2CIA

----- Original Message ----- From: "Sil - ZL2CIA" [email protected] To: [email protected] Sent: Wednesday, November 15, 2006 9:01 AM Subject: [amsat-bb] Re: AO-07 healthy CW

Hi,

I guess that the satellite battery consisted of cells in series and batteries in parallel, or perhaps of cells in parallel then in series to make a battery. Does anybody know exactly? Can anybody point me in the right direction?

Sil - ZL2CIA

Hi Sil, ZL2CIA

Unfortunately Larry Kayser VA2LK the expert of the OSCAR-7 batteries passed away 5 october 2004

I believe that actually the right people to supply you with the informations about the batteries and BCR are Jan King W3GEY and Dick Daniels W4PUJ

However you can get many useful informations about the batteries of OSCAR-7 reading a lot of letters from Larry Kayser wich are available in the Amsat-BB Archives from june 2001

Best 73" de

i8CVS Domenico

Hi Sil,

"Crushing note?" Perhaps.

On the other hand, I think it would be very instructive for the readers of this BB to use this data as a partly hypothetical exercise in telemetry analysis. If this had been an actual satellite's telemetry (er, you know what I mean), what would it tell us? How can we determine what information is "dodgy", and what may be real. If we were to take it at face value, what would it tell us about the various systems in the bird? AO-07 is simple enough internally that, as a training exercise, we might actually be able to understand what is going on inside.

When it comes time to handle a real satellite emergency, or even just watching one of our operational birds gracefully age, I think having gone through an exercise such as this would be very valuable. It will teach the "armchair control operator" in each of us what is involved, giving us a bit more patience and understanding as the real work goes on. And perhaps, we just might grow the level of interest in one or more members or potential members to become more involved in the design, launch, or operation of a future satellite.

So, good work, Sil! What about another person's view of what the telemetry tells us? Does anyone have a link back to the design documents (such as they might be) where, for example, we could look at the battery charge circuit and try to deduce which cells had gone bad? I for one would enjoy the coaching and mentorship of someone experienced in this art.

Greg KO6TH

----Original Message Follows---- From: Sil - ZL2CIA [email protected] Reply-To: [email protected] To: Geoff [email protected] CC: Martin Gillen [email protected], AMSAT-BB [email protected] Subject: [amsat-bb] Re: AO-07 healthy CW Date: Wed, 15 Nov 2006 21:06:16 +1300

Geoff wrote:

Check channel 6D, anything other than about 0.5 means that the others are likely to be dodgy (invalid).

73 de Geoff vk2tfg.

Martin Gillen wrote:

The moment that I went online and sent my message about the AO-07 telemetry was also the moment that I downloaded Geoff's crushing note.

Sil - ZL2CIA _______________________________________________ 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

_________________________________________________________________ Get the latest Windows Live Messenger 8.1 Beta version. Join now. http://ideas.live.com

Thanks Bob,

I will take a look. I haven't yet been able to learn very much, but I will keep going.

Sil

Robert McGwier wrote:

There was one series string of Nicads as can easily be discerned from this photograph:

http://n4hy.smugmug.com/gallery/2053069/1/105529609

You can notice the series string starts at the upper left and works its way right and then down to the lower string and back to the left.

Bob N4HY