Name

CL_gm_orbitalNoon — Latitude argument of the orbital noon on the given orbit

Calling Sequence

   [pso_orb_noon] = CL_gm_orbitalNoon(inc,raan,alpha_sun,delta_sun)
   
   

Description

  • The orbital noon is the position of the satellite where the angle between the Earth centre-to-satellite vector and the Earth centre-to-Sun vector is minimal.

    In other words, it is the orbital position where the satellite crosses the direction of the sun projection perpendicularly to the orbital plane.

    This function computes the latitude argument(w+M) (pso_orb_noon) of the orbital noon on the given orbit ((raan and inc), and for the given sun's right ascension (alpha_sun) and declination (delta_sun).

    Orbital midnight on the orbit (where eclipses are located) is at the opposite of the orbital noon on the orbit (pso_orb_midnight = pso_orb_noon+%pi

  • Last update : 04/05/2007

Parameters

inc:

orbit's inclination [rad] (1xN)

raan:

orbit's right ascension of ascending node [rad] (1xN)

alpha_sun:

sun's right ascension [rad] (1xN)

delta_sun:

sun declination [rad] (1xN)

pso_orb_noon:

latitude argument(w+M) of the solar midday on the given orbit [rad] (1xN)

Authors

CNES - DCT/SB

See also

CL_gm_raan2beta, CL_gm_beta2raan, CL_gm_eclipseCir

Examples

cjd=21482;
raan=0;
sma = 1000000+%CL_eqRad;
inc = CL_deg2rad(98);
[r_sun,rs] = CL_mod_moonSunG50(cjd,'s');
sol_sph = CL_co_car2sph(r_sun.*(rs.*.ones(3,1)));
alpha_sun = sol_sph(1,:);
delta_sun = sol_sph(2,:);
pso_orb_noon = CL_gm_orbitalNoon(inc,raan,alpha_sun,delta_sun)

// Comparison with CL_gm_eclipseCir :
[eS,eE,s_orb,deltaT] = CL_gm_eclipseCir(cjd,sma,inc,raan)
pso_midnight = (eS(1) + eE(1) ) / 2 // pso_midnight = pso_orb_noon + %pi
pso_noon = pso_midnight + %pi