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Re: RX only satellite?



bruninga@usna.edu wrote:
> There may be a Satellite opportunity for a ham radio RX only
> payload. No TX allowed.
> Any ideas?  

Hi Bob,
    When you say "No TX allowed" I am assuming you
mean no RF transmissions allowed. What about light?

    Would visible or infrared transmissions be allowed?
Could you include a laser or a couple hundred high
intensity LEDs? If so, these could be pulsed with
a forward error corrected signal (or just plain
old CW) or connected to an analog (or digital
receiver). The LEDs would be more visible when the
satellite is in eclipse. Very slowly pulsed LEDs
might be decoded with a webcam (and maybe a telescope)
to send short bulletins or short QSOs.

    No? Okay, how about a suitcase-sized sphere of
highly reflective multi-faceted mirrors with "something"
over the mirror(s) which you can electronically make
opaque or translucent very quickly. No moving parts --
just reflective or not-reflective. This could then be
turned on-off to send a FEC encoded signal or even CW.
Depending on the orientation of the mirror(s), the sun,
and the groundstation(s), when the orientation is just
right then you could then communicate with an RF
uplink and a reflected sunlight downlink. Just how
fast you could send a signal would depend on how fast
you could switch between opaque and translucent.

    Possibly whoever said "No TX allowed" wouldn't
object to passively reflected (and not-reflected)
sunlight. :-)

    Before you say it won't work, consider the small
size of the mirrors on the Starshine satellite (about
one inch diameter, if I recall) and the "not huge"
size of the highly reflective surface on the iridium
satellites, which is very bright, very predictable
(see www.heavens-above.com to predict iridium flares)
and at times briefly outshines even the ISS.

    I think a two meter uplink with a light downlink
could be very interesting.

Hope this helps,

Douglas KA2UPW/5
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