Introduction - If you have any usage issues, please Google them yourself
SGP is the first orbital propagator. It was developed by Hilton and kurman in 1966, thanks to a study by Kozai in 1959. It is made for satellites orbiting the earth, including those with an orbital period of less than 225 minutes. The model assumes low eccentricity and constant perigee height.
SDP4, developed by hujsak in 1979, is a SGP4 propagator for deep space objects. This includes satellites with orbital periods greater than 225 minutes. For a time period higher than this value, the orbit of the satellite will be interfered by the moon and the sun, as well as by some resonance effects in the 12 and 24-hour orbital periods.
Sgp8 is also used in near earth satellites, almost similar to SGP4 propagator, but the calculation method is different. However, it follows the same model for atmospheric and gravitational effects.
Sdp8 is a sgp8 propagator for deep space effects. In addition, sgp8 and sdp8 better manage orbital attenuation