Re: Hello from the ISS

From: Tony Beresford (
Date: Sat Jun 15 2002 - 02:19:52 EDT

At 13:10 15/06/02, Tom  Wagner wrote:
>Now, I have a Navy signal mirror that a person can accurately aim. You can
>tell where the light is being directed by aiming a fuzzy spot of light that
>is seen in a hole in the center of the mirror. This is probably a rhetorical
>question but, is it conceivable that an astronaut could signal someone on
>the earth below with a 4 x 6 inch mirror held up to a window in the ISS?
>Would be nice huh. Probably never happen though. That would be a great
>school project!
If you calculate it properly, a square inch of a specular reflector
at 1000 miles is magnitude 2.0 . So your 24 sq. inch mirror would give
a maximum brightness at 1000 miles of magnitude -1.5, and at a range
of 500 miles , 4 times brighter at -3.0. allowing for all the projections
involved lets allow a magnitude less , so its -2, just a bit fainter than
jupiter. Unlike its use by the Navy, the system would only work for unassisted
vision under the usual visual satellite observing geometry, unless you made the mirror a bit bigger say 31 by 31 inches to get mag -6 flashes, which could be observed in daylight.
Of course if a school had an lx200 mounted telescope and the satellite tracking software to drive it, daylight working would seem a strong possibility
Tony Beresford

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