$LastChangedDate: 27-Juil-2011 $

# CL_gm_orbitalNoon

Argument of latitude at the position of orbital noon

## Calling Sequence

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

## Description

- Orbital noon refers to the position in the orbit where the angle between the satellite radius vector and the Sun direction is minimal.

  In other words, it is the orbital position where the satellite radius vector crosses the projection of the Sun onto the orbit plane.

  This function computes the argument of latitude at the position of orbital noon (pso_orb_noon) as a function of the orbit's right ascension of ascending node (raan) and inclination (inc), and the Sun's right ascension (alpha_sun) and declination (delta_sun).

## Parameters

inc:

  Orbit inclination [rad] (1xN)

raan:

  Orbit right ascension of ascending node [rad] (1xN)

alpha_sun:

  Sun right ascension [rad] (1xN)

delta_sun:

  Sun declination [rad] (1xN)

pso_orb_noon:

  Argument of latitude(w+M) at the position of orbital noon [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 :
    [result] = CL_gm_eclipseCir(sma,inc,raan,alpha_sun,delta_sun)
    pso_midnight = (result.start.pso + result.end.pso ) / 2
    pso_noon = pso_midnight + %pi