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Re: Speed

• Subject: [sarex] Re: Speed
• From: "Murray Peterson" <promise@xxxxxxxxxx>
• Date: Thu, 2 Dec 1999 13:41:26 +1100

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----- Original Message -----
From: James B Sibley <rocketkid14@juno.com>
To: <sarex@AMSAT.Org>
Sent: Thursday, December 02, 1999 9:55 AM
Subject: [sarex] Speed

> Is there a satellite tracking program that also tells you how fast the
> orbiting body is going based in where it is located (gravitational
> constant changes)?

This might not be the exact answer you were looking for but you might find
it interesting.

While most satellite tracking programs don't tell you the velocity of the
sattelite, they do tell you the Doppler Shift for a given frequency. You can
use this to readily calculate the velocity of the sattelite either towards
or away from you. In fact if you measure the Doppler shift frequency of say
a beacon on a satellite, you can calculate the sattelite's velocity!

It is quite a simple calculation. You simply multiply the Doppler shift by
the wavelength of the frequency concerned and divide it by 2. If the
wavelength is in metres and the frequencies are in Hertz then the answer
will be in metres per second. To calculate the velocity in km/h simply
multiply the m/s by 3.6 to get km/h. If you want the velocity in miles per
hour, just divide the velocity in km/h by 1.61 to get the velocity in m.p.h.

For example
for 146000000 Hz  the wavelength is 2.055 m
For a Doppler shift of 3000 Hz the velocity will be 3082.19 m/s or 11095.89
km/h

Regards,

Murray Peterson

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