[amsat-bb] Re: AO-07 Healthy CW]
n4hy at idaccr.org
Wed Nov 29 08:08:38 PST 2006
Tom Clark, K3IO wrote:
> W9GB noted
>> I can identify the lab equipment on the bench (looks like my high
>> school & college labs - 1970s) with the NiCad battery pak, EXCEPT for
>> the rectangular box with metal handles to the right of the NiCads.
>> NiCad battery charger? Homwbrew power supply?
> Greg -- the high-priced hardware (HP+Tek) show NASA Goddard property
> labels. The cheaper power supplies in the back are Heathkits with AMSAT
> The box you are asking about has a yellow Goddard tag. I'm trying to
> recognize it, and to the best of my recollection it is a Coulomb-meter
> that measured (on the mechanical counter you see on its panel) the
> integrated charge/discharge current. Also my fuzzy memory tells me that
> the heatsink device on clip leads was a prototype BCR.
There is nothing wrong with your memory! Notice that it is in series
with the batteries, it has a large transistor being heat sunk and I
can make out two high wattage resistors and an electrolytic
capacitor. I think you are right.
> Sil asked:
>> I guess there's a special "satellite design" reason that double wires
>> are used (instead of one thicker one) for the current carrying battery
> The twin wires go to a pair of pins on the DA-9 connector, with two pins
> providing greater current handling ability and redundancy. It also
> appears that the V/2 telemetry tap has a pair of whit wires even though
> it provided zero current. BTW -- the V/2 telemetry would be on 3B.
>> Leaving aside Geoff's (vk2tfg) point that the telemetry may be
>> irrelevant because of the doggy value in channel 6D, it would seem that
>> the five top cells (between half volt point and +12V - numbers 2,3,4,5,6
>> counting clockwise) are being charged with a current of 80mA and have
>> reached a terminal voltage of 6.4 volts (8.8 - 2.4). This represents a
>> voltage of 1.28 per cell (6.4/5) and is thoroughly reasonable. This idea
>> is supported by the temperature of cell number 5 at 60.28 C.
> The top 5 cells are fed by the black wire and are the LOW voltage side.
> The 5 "high side" batteries terminate in the orange wire on the bottom,
> The thermistor on cell #5 is on the low voltage side.
> The thermal design of the s/c ended up with internal temps ~20°-30°C
> range (i.e. TLM values in the 40-50 range). I find it hard to believe
> that a valid interior temperature would ever be in the 60°C range.
> Regarding all the telemetry speculation -- AFAIK, there is no indication
> that the A/D converter is showing ANY valid data at all -- see also
> Jan's comments at http://www.amsat.org/amsat/sats/n7hpr/ao7_tlm.html.
> FYI -- the TLM and its associate Morse encoder system was built with
> discrete CMOS logic by John Goode, W5CAY in Texas. Memory fails me, but
> I believe that the TLM/Morse board is on the "back wall" in the
> photograph at http://www.amsat.org/amsat/sats/ao7/slideset/slide09.html
> even thought the photo only identifies the module as the command
> encoder. All the white IC's a early RCA ceramic 4000-series parts.
> AFAIK, Oscar-6 & -7 were the first CMOS users in space. AO-7, with much
> of this logic still functioning after 32 years and 2 weeks, certainly
> holds the longevity record!
Jan told me that no reasonable data was found during the times Mike
Seguin and I were attempting to command the spacecraft on the two
possible command channels. That was the last time I really looked at
this data in detail. I wrote a python program to decode it all and it
was all crap.
> [In case you forgot, Nov.15th was AO=7's 32nd birthday -- my favorite
> picture of the launch is the "7-UP" contrail left by the Delta booster
> 73, Tom
Nice job on the memory for an OF like you! (what are friends for after
Robert W. McGwier, Ph.D.
Center for Communications Research
805 Bunn Drive
Princeton, NJ 08540
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