CL_gm_eclipseCheck

Description

• Computes quantities that characterize the eclipse conditions: ratio of solid angle that is eclipsed, or characteristic angles defining umbra or penumbra.

  - Eclipse ratio ("eclrat"):

  It is the hidden solid angle fraction of a body (body1) eclipsed by the second body (body2), as seen from the observer.

  - ratio = 1.0 : 100% of body1 is eclipsed (umbra),

  - ratio = 0.7 : 70% of body1 is eclipsed (penumbra),

  - ratio = 0.0 : 0% of body1 is eclipsed.

  

  - Eclipse angles ("angu","angp","angc"):

  Characteristic angles (positive or negative) that define the type of event:

  - angu: umbra

  - angp: penumbra

  - angc: umbra or penumbra, the eclipse region being defined by a cylinder of radius that of the occulting body (i.e. body2). The radius of body1 is not used in this case.

  All the angles are:

  - continuous quantities (of the input data),

  - positive if the eclipse condition is met and negative otherwise.

• Notes:

  The bodies are assumed spherical. The spheres should have positive radii, and should not intersect.

Parameters

pos_obs:

Position of observer [m] (3xN or 3x1)

pos1:

Position of body1 (= potentially eclipsed body) [m] (3xN or 3x1)

pos2:

(optional) Position of body2 (= occulting body) [m]. Default is [0;0;0] (3xN or 3x1)

sr1:

(optional) Radius of body1 (sphere) [m]. Default is %CL_body.Sun.eqRad (1x1)

sr2:

(optional) Radius of body2 (sphere) [m]. Default is %CL_eqRad (1x1)

res:

(string, optional) Names of computed quantities: "eclrat", "angu", "angp", "angc". Default is "eclrat" (1xP)

val1, val2...:

Computed quantities [rad or -] (1xN)

Authors

• CNES - DCT/SB

See also

• CL_gm_inters3dConesSa

Examples

// Eclipse of the Sun by Earth from an observer in space: theta = linspace(2.88, 3.05, 1000); pos_sat = 42164.e3 * [cos(theta); sin(theta); zeros(theta)]; au = CL_dataGet("au"); pos_sun = au * [1; 0; 0]; // Sun eclrat = CL_gm_eclipseCheck(pos_sat, pos_sun); angp = CL_gm_eclipseCheck(pos_sat, pos_sun, res="angp"); angu = CL_gm_eclipseCheck(pos_sat, pos_sun, res="angu"); // Plot the results scf(); plot(theta*180/%pi, eclrat, "k"); plot(theta*180/%pi, angp, "r"); plot(theta*180/%pi, angu+1, "b"); CL_g_legend(gca(), ["eclrat", "angp", "angu + 1"]);