Space environment models. Designed to work with SailDisturbance.
   Planet choices include the major planets and the sun.
   Some models, such as AtmDens2 and AtmJ70, only apply to the Earth.
   This function stores certain planet parameters for efficiency, which are
   reset when it is called with a new planet name.
   Ephemeris of the planet should be computed separately.

   See also: Constant, EarthRad, EarthAlb, Eclipse, Altitude

   Since version 7.
   env = SailEnvironment( planet, p, d )

   planet   (:)     Planet name
   p       (1,1)    Profile data structure
                     .jD        (n)   Julian date(s)
                     .r        (3,n)  Position of spacecraft relative to planet
                     .rPlanetH (3,n)  Heliocentric position of planet (ecliptic)
   d       (1,1)    Function data 
                     .magModel   (BDipole)
                     .atmModel   (AtmDens1, AtmDens2, AtmJ70)
                     .j70, needed for that atmosphere model only

   env     (1,1)   Environment model data
                    .planet         (:)   Planet name
                    .radiation     (1,1)  Black body radiation
                    .albedo        (1,1)  Planet albedo fraction
                    .radius        (1,1)  Planet equatorial radius
                    .mu            (1,1)  Gravitational parameter
                    .uSun          (3,n)  Unit vector to sun, ECI frame
                    .solarFlux     (1,n)  Solar radiation flux (W/m2)
                    .altitude      (1,n)  Altitude above the planet
                    .rho           (1,n)  Atmospheric density*
                    .bField        (3,n)  Magnetic field strength*
                    .radiationFlux (1,n)  Planetary radiation flux (W/m2)*
                    .albedoFlux    (1,n)  Planetary albedo flux (W/m2)*
                                           * don't apply to the sun.



AeroUtils: AtmosphericCalculations/AtmDens1
AeroUtils: AtmosphericCalculations/AtmDens2
AeroUtils: AtmosphericCalculations/AtmJ70
Common: Database/Constant
Common: Graphics/Plot2D
Common: Transform/Altitude
Math: Linear/Mag
Math: Linear/Unit
SC: Environs/EarthAlb
SC: Environs/EarthRad
SC: Environs/SolarFluxPrediction
SC: Ephem/CEcl2Eq
SC: Ephem/Eclipse
SC: Ephem/SunV1