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Re: [aprssig] PCsat Optical Comms Experiment



PCsat LEDs Experiment:

Since many folks will be looking skyward over the night of 17/18 Nov for
the Leonids Meteor Shower, this is a good time to test the optical
radiator on PCsat. This radiator consists of 80 standard RED LED's and
"might" be visible to someone with binoculars.

We will enable the LEDS at 9:35PM Eastern Standard Time (8:35 CST) on the
night of 17 Nov as PCsat passes over New Orleans and turn them off as
PCsat passes out of view 6 minutes later over Toronto. The pass will go
across Louisiana, Miss, ALa, Tenn, Ky, Ohio, and Ontario.  PCsat will be
in view of everyone in the USA at the time, but those viewers will be
further away and looking through more atmosphere...

Presumably it may be visible with binoculars and only rarely pointed in
"your" direction, but we have not yet completed our "visibility"
analysis...  But if you do see it, it will be "red", like LED's.

de WB4APR, Bob

On Tue, 13 Nov 2001, Bob Bruninga wrote:

> In conjunction with the Leonids meteor show, this may be a good time for
> the first test of the Optical Comms experiment on PCsat.
>
> PCsat has 80 standard red LEDs on the side facing the earth in the
> horthern hemmisphere.  We can turn them on to see if anyone can see them.
> This takes a good 50% of our power budget and so they can only be on for a
> few minutes, so this will only be over the east coast and only one pass
> which appears to be about 930 PM on Saturday night the 17th of Nov.
>
> This is not the optimum time relative to  power budget, but it is an
> opportunity when more people will be watching.  When I get to work
> tomorrow and have a new set of Keps, I will nail down the exact time and
> path over the usa.  So this is only a heads up...
>
> We have not done a detailed analysis, but with 3 watts of DC power going
> into the LEDs, some have estimated a magnitude 5 or 6 straight down
> (barely visible with eyeball) and maybe a mag 8 off to the side
> (binocluars).  ANy other estimates are welcome.  We have no pedigree on
> the LEDS other than "standard red leds"...
>
> PCsat appears to be spinning at about 1/4 RPM (exact attitude unknown)
> so for any given viewer, you will only see the narrow field of view (about
> 30 degrees) occassionally (if at all), but someone somewhere should get a
> straight shot at some time...
>
> We may cycle the LEDS on and off at about a few second rate to save
> power, this is TBD.  Even if this test fails to be seen, we will conduct
> the test again later in the month when the optimum power is available.
> That orbit is one that occurs just after dark, and just after PCsat enters
> eclipse.  At that point the batteries are fully charged and so we get
> maximum power to the LEDS.
>
> The LEDS have a fail-safe turn-on circuit that will only allow them to
> conduct current when the battery voltage is above 1.25 volts per cell
> and this only occurs while the batteries are on charge (in the sun) nd
> just afterwards...  So we must pick an orbit when the satelltie just
> enters eclipse while in view of the command station (on the east coast)...
> 2000 EST on the 24th might be such a date.  More later...
>
> However, Since I will be out in the field camping on the 17th with the
> kids, in a dark area for the Leonids, I figured why not go ahead and see
> what we can see now too...
>
> de WB4APR@amsat.org, Bob
>
> PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html
> ISS-APRS FAQ:       http://www.ew.usna.edu/~bruninga/iss-faq.html
> CUBESAT Designs     http://www.ew.usna.edu/~bruninga/cubesat.html
> APRS LIVE pages     http://www.ew.usna.edu/~bruninga/aprs.html
> APRS SATELLITES     http://www.ew.usna.edu/~bruninga/astars.html
> MIM/Mic-E/Mic-Lite  http://www.toad.net/~wclement/bruninga/mic-lite.html
>
>
>
> ---
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de WB4APR@amsat.org, Bob

PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html
ISS-APRS FAQ:       http://www.ew.usna.edu/~bruninga/iss-faq.html
CUBESAT Designs     http://www.ew.usna.edu/~bruninga/cubesat.html
APRS LIVE pages     http://www.ew.usna.edu/~bruninga/aprs.html
APRS SATELLITES     http://www.ew.usna.edu/~bruninga/astars.html
MIM/Mic-E/Mic-Lite  http://www.toad.net/~wclement/bruninga/mic-lite.html


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