Each GNSS constellation - depends on which system you're talking aboutIn the U.S. they're called a GPS constellation every GPS satellite broadcasts a “navigation message” navigation message -- broadcast by each satellite -- contains the information needed to identify ALL the satellites in the constellation -- contains information needed to compute each satellite's approximate position in orbitnetwork of ground-based observing stations constantly tracks the satellites computes predictive models of each satellite’s orbit. predicted orbital parameters for a given satellite recorded in a docuмent called an “ephemeris” ephemeris ------> plural = “ephemerides”satellite orbits vary over timeeach ephemeris needs to be updated regularly ground-based Master Control Station performs regular updates of satellite orbits updated orbits (ephemerides) are transmitted to the GPS satellite constellationAn ephemeris provides the parameters
used to calculate the position of a satellite
along its orbit at any moment in time
An almanac provides the ephemerides
for an entire constellation of satellites
navigation message is broadcast by each satellite it includes its own ephemeris this ephemeris is called the “broadcast ephemeris” updated at frequent intervals contains the “almanac”almanac is the less-frequently updated collection of the ephemerides for ALL GPS satellites in the constellation almanac is updated at much longer intervalsorbital parameters are less accurate in almanacs than the broadcast ephemeris from each individual satellite.What computes each satellite's orbit information?
What does an almanac provide?
Which is plural, ephemerides or ephemeris?
What do ground-based observing stations do?
What kind of updates does a Master Control Station provide?
Where does a GPS satellite constellation obtain its ephemerides?
Does any particular satellite receive and use all the ephemerides broadcast?
What component sends out a navigation message?
What is used to compose a navigation message?
Why are GPS satellites grouped into constellations?
When a particular satellite leaves Libra and moves into Sagittarius does it change constellations?
What is the almanac a collection of?
Which is updated more often: almanac ephemerides or broadcast ephemerides?
Which is more reliable, almanac ephemerides or satellite signals?
Why bother with a less reliable set of data?
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