How often does the CS update the almanac and ephemerides?

Does anybody know how often the CS updates the almanac parameters for
each satellite? Every day? 6 days? I can't find out the exact update
rate at GPS ICD.

For the ephemerides, I guess it is every 1 or 2 hours. Does anybody have
more detail information?

Thanks.

I don't rememeber the exact numbers... but it's more that 2 hours.
More than one ephemeris is uploaded and the satellites knows when
broadcast the correct one.

claudegps wrote:
Maybe I was wrong about the ephemerides update rates. I once read an
article in GPS World, and I still remembered that they said the update
rates were either 1 or 2 hours. Maybe in the future the ephemerides will
be updated at 1 or 2 hours.

Any idea about the update rate of almanac parameters?

ve

You might try browsing the 2008 SPS Performance Specification,
available here:

http://pnt.gov/public/docs/

The document is this link (1.7 MB):

http://pnt.gov/public/docs/2008/spsps2008.pdf

They refer the reader to the Coast Guard web site:

http://www.navcen.uscg.gov/gps/almanacs.htm

You may notice that the Coast Guard posts a new almanac every day.

A caveat from pg. B-41 of the SPS spec:

"The highest fidelity will generally be achieved with the almanac data
time tagged just prior to the window of interest. Using almanac data
from preceding days or following days not recommended due to the
potential for satellite repositioning events which will invalidate
previous valid almanac data."

ve

Mmmm... Maybe you are (or I'm confusing you request :P ) confusing the
broadcast rate of the ephemeris data (new ephemeris every two hours)
from the satellite to the receiver and the upload of the ephemeris
data _to_ the satellites from ground station.
blocks) maybe every 6/12 hours

You should a new almanac at least every day, but I think that there is
not fixed timing. The upload of almanac data should be flexible and
depending on constellation status.