SGP4 propagation#

Classes#

`sgp4_propagator_dbl`	SGP4 propagator (double precision).
`sgp4_propagator_flt`	SGP4 propagator (single precision).

`sgp4`([inputs])	Produces the expressions for the SGP4 propagator.
`gpe_is_deep_space`(n0, e0, i0)	Check whether a GPE is deep-space.
`sgp4_propagator`(sat_list[, diff_order])	Construct an SGP4 propagator.