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VK3ABK > SAT 22.02.03 15:24l 42 Lines 1377 Bytes #999 (0) @ WW
BID : 55859_VK3VSW
Read: DB0FHN GUEST
Subj: Satellite Visibility
Path: DB0FHN<DB0RGB<OK0PPL<RZ6HXA<SP7MGD<VK3VSW
Sent: 030222/1005Z @:VK3VSW.#WEV.VIC.AUS.OC #:55859 [Geelong] $:55859_VK3VSW
From: VK3ABK@VK3VSW.#WEV.VIC.AUS.OC
To : SAT@WW
I have just come across a bulletin request from Johan, ZR4LP who asks about
the visibility of a satellite and the Sunset.
Johan, you asked about the effective reflectivity of a satellite at a
particular time about sunset (or sunrise). You may like to experiment with a
basic relationship between height and distance to the horizon, which can then
be used with a time lapse (Earth rotation) to estimate the visibility of
a satellite at known or predicted location.
The equation for distance d to the horizon, where r is the Earth radius
and h the height above Earth surface, is.........
/--------------
d = / 2
\/ 2rh + h
Given that the radius of Earth is about 6378km, and say, 300km is a satellite
orbit height, then the distance to the horizon (Sun cut off point) would be
/--------------------
/ 2
d = \/ 2 X 6378 X 300 + 300 = 1979km
This distance would be about 2 time zones from your location, so you could
add 2 hours to the satellite visibility. This is about your estimate for the
Sunset and would be an approximation for satellite visibility.
A good piece of deduction, Johan, and good thinking.
73. Dick. VK3ABK.
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