OPTIsat  -  A Visual Communications Satellite!                 WB4APR
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Warren Lee and Tony Beresford have both confirmed the 12th magnitude
visibility for a 3w incandescent bulb at 500 miles.  This now leads me to
a new CUBESAT design idea:  OPTIsat!

OPTIsat would be a 4" cube satellite with 225 bright LEDs on the bottom.
The uplink would be 70 cm CW.  THe downlink would be visual CW.  Peak
LED power would be about 10w (does anyone know the power efficiency of
LED's?)

This would pick up about 4 magnitudes and make it quite visible to
binoculars...  THink of the fun of kids out on campouts looking for
OPTIsat and trying their hand at flashing light CW.  And it would be RED.
Easy to distinguish from stars...

The transmit duty cycle is 50% CW, 10% HAM pouplation areas, 50% eclipse
times (only operates in the dark) and half the time no one will be using
it (50%).  THus the average solar power required to keep it running is
only 10W * .5 * .1 * .5 * .5 * 1.4 (charging efficiency) or about  200
miliwatts.  We can do that with just a 2" square solar panel.   Plenty of
power budget...  

Actually, then , we could totally cover the bottom 4" panel with LEDs for
a rated poewr of 20 W and then overdrive them by 100% for 40W peak power
and gain another magnitude in brightness and still stay within the power
budget.

Of course, the CUBESAT would actually have to be split into two halves,
with a 6 foot piano wire between them to get gravity gradient
stabalization.  Then we would have to put a full set of LEDS on the top
box too, in case it stabalized upside down.  But I would then add a second
receiver so that one channel drives the "top" and the other drives the
bottom.  We would only use the one that we could see...

Wow, sure wish I had $30,000 for a CUBESAT flight...
Kids would love this one...

de WB4APR@amsat.org, Bob

CUBESAT Designs     http://web.usna.navy.mil/~bruninga/cubesat.html
APRS SATELLITES     http://web.usna.navy.mil/~bruninga/astars.html