The Library tle_YYYYMMDD processes TLE files and converts the information
from them to state vectors, [X, XDOT] at a given epoch. Most of the
routines for the ingestion are taken directly from Vallado. Each such
routine credits the author, and explicitly states any changes made from
their original text. The ingestion of the files and conversion is based
on two articles:
     1.  Hoots, F. R. and Roehrich, R. L. (1980), "Models for Propagation 
         of NORAD Elements", Spacetrack Report No. 3.
     2.  Hoots, F. R., Schumacher Jr, P. W., and Glover, R. A., (2004).
         "History of Analytical Orbit Modeling in the U.S. Space 
         Surveillance System", Journal of Guidance, Control, and Dynamics,
	 Vol. 27, No. 2, p 174-185, doi:10.2514/1.9161

The following source codes are included, with their general functionality
described:

dpper            -- Through this routine, the current values of the orbital
                    elements are passed to the deep-space subroutine which
		    in turn adds the appropriate deep- space lunar and solar
		    periodics to the orbital elements.

dscom            -- Provides the deep space common variables used both by the
                    secular and periodic subroutines

dsinit

dspace           -- provides any third body contributions to deep space objects

getgravconst

gstime

initl

newtonnu  

rv2coe

sgp4

sgp4init

tle_angle   

tle_asinh

tle_cross

tle_days2mdhms   -- Converts tle days to month, day, hours, mins, and secs

tle_dot

tle_driver

tle_invjday

tle_jday

tle_mag

tle_parser

tle_to_crs

tle_to_trs

tledate_to_mjdsec

twoline2rvsgp4

