# Optical COmms experiment

From: Richard Bassan (rbassan@cantv.net)
Date: Sat Apr 28 2001 - 19:13:59 PDT

• Next message: Tony Beresford: "Re: Optical COmms experiment"

```I read this mail from AMSAT list and I thought in this list someone could
help.

----- Original Message -----
From: Bob Bruninga <bruninga@usna.edu>
To: <amsat-bb@AMSAT.Org>
Sent: Friday, April 27, 2001 9:01 PM
Subject: [amsat-bb] Optical COmms experiment

> Can someone compute the optical visibility of a 3 Watt lightbulb from 500
> miles up?
>
> We are going to put a 3 Watt radiator (resistor) on our PCsat to see if we
> get about 8 degrees of cooling by radiating away excess solar/electrical
> power.  It could just as easily be a lightbulb on the bottom of the
> satellite.  At night, occassionally, we could blink it just for fun.
>
> Can somone compute the stellar magnitude of this to see if it is worth
> doing with a light bulb?  Assume only .3 Watts is actually in the visual
> wavelengths.
>
> Or if it is mildly possible, then we could go to bright LEDs and improve
> the visual efficiency (WHat is the efficiency of an LED?  I assumed 10%
> for an incandescent bulb? Might be closer to 5?)
>
> Oh yes, assume a 90 degree directivity...(or more) or about say 3 dB of
> transmit "antenna" gain...  And do power LED's generate RF noise?  I
> thought all forward biased diodes generate noise to some degree?)
>
> de WB4APR@amsat.org, Bob
>
> PCsat Design        http://web.usna.navy.mil/~bruninga/pcsat.html
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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