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GPS satellites orbital planes and RAAN
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clau...@gmail.com
Jul 26, 2012, 12:47:02 PM7/26/12
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Hi all,
I'm looking informations related to the Longitude of the ascending node of the GPS satellites orbital planes.
The RAAN should be equal to Longitude of the ascending node, since the orbit is geocentric. (rigth?)
I found from different sources, different RAAN values for the orbital planes.
For example here: http://www.colorado.edu/geography/gcraft/notes/gps/gif/oplanes.gif
The RAAN of the planes is: 317, 17, 77, 137, 197, 257
Here http://www.gpsworld.com/survey/gps-243-configuration-a-closer-look-9488
The RAAN of the planes is: 272, 332, 32, 92,152, 212
Am I misintepreting something or maybe the RAAN drifts over time?
It's also strange that as indicated in teh above article, alla the satellites of an orbital plane have the excat same RAAN, isn't it? I expect satellites to have slightly different orbits, also related to RAAN parametners.
May a yuma almanac be the source for this information?
Many Thanks
I'm looking informations related to the Longitude of the ascending node of the GPS satellites orbital planes.
The RAAN should be equal to Longitude of the ascending node, since the orbit is geocentric. (rigth?)
I found from different sources, different RAAN values for the orbital planes.
For example here: http://www.colorado.edu/geography/gcraft/notes/gps/gif/oplanes.gif
The RAAN of the planes is: 317, 17, 77, 137, 197, 257
Here http://www.gpsworld.com/survey/gps-243-configuration-a-closer-look-9488
The RAAN of the planes is: 272, 332, 32, 92,152, 212
Am I misintepreting something or maybe the RAAN drifts over time?
It's also strange that as indicated in teh above article, alla the satellites of an orbital plane have the excat same RAAN, isn't it? I expect satellites to have slightly different orbits, also related to RAAN parametners.
May a yuma almanac be the source for this information?
Many Thanks
Alan Browne
Jul 26, 2012, 3:25:35 PM7/26/12
to
On 2012-07-26 12:47 , clau...@gmail.com wrote:
> Hi all,
> I'm looking informations related to the Longitude of the ascending node of the GPS satellites orbital planes.
> The RAAN should be equal to Longitude of the ascending node, since the orbit is geocentric. (rigth?)
GPS is 2 orbits per stellar day (~23h 56m). The RAAN drifts west
> Hi all,
> I'm looking informations related to the Longitude of the ascending node of the GPS satellites orbital planes.
> The RAAN should be equal to Longitude of the ascending node, since the orbit is geocentric. (rigth?)
accordingly (about 4 minutes per solar day).
Check my arithmetic but that's about 1 degree of longitude per day that
the RAAN of each satellite is moving west.
--
"Civilization is the limitless multiplication of unnecessary necessities."
-Samuel Clemens.
clau...@gmail.com
Jul 27, 2012, 6:25:01 AM7/27/12
to
Il giorno giovedì 26 luglio 2012 21:25:35 UTC+2, Alan Browne ha scritto:
> On 2012-07-26 12:47 , claudev8gmail.com wrote:
> > Hi all,
> > I'm looking informations related to the Longitude of the ascending node of the GPS satellites orbital planes.
> > The RAAN should be equal to Longitude of the ascending node, since the orbit is geocentric. (rigth?)
> Check my arithmetic but that's about 1 degree of longitude per day that
I checked how the RAAN at week changes using two GPS almanacs one week apart: the average is 7.18 degrees per week.
Thanks
Claudio
> On 2012-07-26 12:47 , claudev8gmail.com wrote:
> > Hi all,
> > I'm looking informations related to the Longitude of the ascending node of the GPS satellites orbital planes.
> > The RAAN should be equal to Longitude of the ascending node, since the orbit is geocentric. (rigth?)
>
> GPS is 2 orbits per stellar day (~23h 56m). The RAAN drifts west
> accordingly (about 4 minutes per solar day).
Oh yes! Makes sense.
> GPS is 2 orbits per stellar day (~23h 56m). The RAAN drifts west
> accordingly (about 4 minutes per solar day).
> Check my arithmetic but that's about 1 degree of longitude per day that
> the RAAN of each satellite is moving west.
Pretty close to 1 degree.
I checked how the RAAN at week changes using two GPS almanacs one week apart: the average is 7.18 degrees per week.
Thanks
Claudio
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