CL_gm_beta2raan

Description

• Computes the right ascension of the ascending node from the beta angle (beta angle = angle between the satellite's orbit plane and the Sun direction).

  There are 2 solutions (raan1) and (raan2) such that:

  - raan2 = pi - raan1 + 2*alpha_sun

  - raan1 is in the interval [ alpha_sun - pi/2 ; alpha_sun + pi/2] modulo 2*pi

  - raan2 is in the interval [ alpha_sun + pi/2 ; alpha_sun + 3*pi/2] modulo 2*pi

  

• Notes:

  - The beta angle is a signed quantity. If it is positive then the Sun direction is less than 90 degrees from the orbit's angular momentum vector (vector perpendicular to the orbit plane and oriented according to right hand rule).

  - Rhe right ascension can be undefined (%nan) if there are no solutions.

  - Be careful about the order of arguments: beta angle, inclination...

Parameters

betaa :

Beta angle [rad] (1xN)

inc :

Inclination of the orbit [rad] (1xN)

alpha_sun :

Sun right ascension [rad] (1xN)

delta_sun :

Sun declination [rad] (1xN)

raan1 :

Right ascension of the ascending node (solution 1) [rad] (1xN)

raan2 :

Right ascension of the ascending node (solution 2) [rad] (1xN)

See also

• CL_op_locTimeG50

• CL_gm_raan2beta

• CL_mod_moonSunG50

Authors

• CNES - DCT/SB

Examples

// Get alpha_sun and delta_sun cjd = 20050; pos_sun = CL_eph_sun(cjd); pos_sun_sph = CL_co_car2sph(pos_sun); alpha_sun = pos_sun_sph(1); delta_sun = pos_sun_sph(2); betaa = %pi/4; inc = CL_deg2rad(98.7); [raan1,raan2] = CL_gm_beta2raan(betaa,inc,alpha_sun,delta_sun)