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