The computation of a navigation satellite position and clock is a general task in global positioning system (GPS)
positioning that is necessary to compute a user position. The data needed for this task can be obtained from a
broadcasted navigation message. A satellite orbit can be computed by using satellite orbital elements and
perturbations Users should use a precise ephemeris provided by the International GNSS Service (IGS) or National GeospatialIntelligence Agency (NGA). IGS is a voluntary federation of about 400 stations that provides GPS and GLONASS
precise ephemerides [1]. IGS orbit accuracy is believed to be less than 0.05m. The IGS precise ephemeris is
available in 15 minute intervals.
NGA provides GPS-based precise ephemerides, and its accuracy is also less than 0.05m. As a part of GPS
modernization, 28 Block II/IIA satellites were launched between 1989 and 1997 [2]. They utilize L1 and L2
frequencies, and they were designed to have a 7.5-year lifespan. As 3rd generation satellites, Block IIR satellites were
launched from 1997 to 2004. Block II/IIA and IIR satellites have been included in the GPS satellite constellation
since 2005. Block IIR-M satellites were launched between 2005 and 2009. Block IIF satellites, launched from 2010,
use L5 signals and have a 12-year lifespan