Flashing the ISS with a mirror

[SonicIce]

I've been wondering, since you can see Iridium satellites flaring in broad daylight, why couldn't astronauts on board the ISS see flashes from a person holding up a mirror? The antennas on Iridium satellites are only about the size of a door. If you had a mirror about that size, and the astronauts were informed of when and where to look, I bet they could see it. That would be something cool to try out if it was possible to inform them...

 

[MeteorWayne]

It wouldn't be as easy as you think Iridium flares are from the sun reflection, against a background of black space.

If you used a mirror to refect the sun from earth, it would be against a background of a daytime illuminated earth.

Have you ever tried to see a daytime Iridium flare? It can be done, but it isn't easy...I've been successful about once out of 25 attempts

 

[adrenalynn]

A large enough parabolic mirror would get it done.

If you want to communicate with the ISS, I suggest doing it the right way - go get your amateur radio license.

 

[CalliArcale]

Yeah, the size of the mirror is the other problem. The Iridum flares are reflections off the antennas, which are about six feet long and a few feet wide. So to get a flare you could see from the ISS, you'd be limited to daytime (so you have sun to bounce off the mirror), and would have to gather enough sunlight with that mirror for it to be visible against the backdrop of a fully illuminated Earth. The parabolic mirror is probably the best way to ensure you get it where you want it, but I wonder if anybody's bored enough to do the math and work out how big it needs to be? :-D

There ARE solar glints that the ISS crew sees. The most common are, of course, sunlight reflecting off of water. But I wonder if some of the solar collection facilities might sometimes be visible to the ISS crews in this way?