[amsat-bb] Re: Asymetric doppler curves?
domenico.i8cvs at tin.it
Sat Jun 9 19:23:05 PDT 2012
Hi David, G0MRF
If you read the old issues of OSCAR-News from AMSAT-UK you
will realize that a serious traking program like PLAN-10 written
by James Miller G3RUH take into calculation all perturbations due
to inclination and velocity of the satellite due to Earths rotational
speed added / subtracted at either end of the pass and so doppler.
----- Original Message -----
From: <g0mrf at aol.com>
To: <amsat-bb at amsat.org>
Sent: Sunday, June 10, 2012 1:20 AM
Subject: [amsat-bb] Asymetric doppler curves?
> Hi all.
> I'm doing a small demonstration for a physics class using Doppler
> measurements on the HO-68 beacon.
> Hopefully we'll be able to calculate spacecraft velocity and from that
> result, go on to calculate orbit altitude. However, in thinking about
> this I realised that there is a potential source of error. We are not
> stationary !! - OK, it's obvious really, but I've never seen this
> mentioned in topics like Doppler correction programs and I've not seen
> it visually in displayed Doppler curves.
> The issue is that while a spacecraft with zero eccentricity will have a
> constant velocity, the speed relative to an observer on Earth at AOS
> and LOS will be different for each half of the pass depending on the
> observers latitude and the inclination of the satellite.
> The worse case would be something travelling East to West or West to
> East as the velocity of the satellite would have the Earths rotational
> speed added / subtracted at either end of the pass.
> Has anyone seen this effect? Perhaps on the ISS? I think it could be
> as much as 7% which may be measurable. - But not on HO-68 which is
> polar orbiting....
> Just want to make the most of my 45 minutes.
> David G0MRF
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