[amsat-bb] Re: Asymetric doppler curves?
dave at g4dpz.me.uk
Sun Jun 10 05:08:26 PDT 2012
As do 'Predict' and it's derivatives.
My Java open source implementation does u/l and d/l and is used in GENSO
for realtime tracking, amongst others.
On 10/06/12 03:23, i8cvs wrote:
> 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.
> 73" de
> i8CVS Domenico
> ----- 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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