CL_ev_eclipse

Description

• Computes eclipse entry and exit times.

  The type of event is defined by typ:

  - umb: umbra,

  - pen: penumbra,

  - umbc: umbra, whereby the shadowed region is a cyclinder with radius equal to that of the occulting body.

  The positions are interpolated using order 8 Lagrange interpolation (using t and pos).

  The results are computed in the simulation time intervals defined by tperiods.

  Other options can be defined in opts, which is a structure (optionally) containing the following fields:

  - prec: Accuracy on the characteristic angle. Default value is 1.e-3 deg.

  - dmin: Minimum length of eclipse intervals. Default value is 60 s.

  - ninterp: Number of points for interpolating the positions. Default value is 8.

  - impr: True (%t) to activate the improved detection mechanism. Default value is %t.

  The intervals returned in interv define the eclipse entry and exit times.

• Notes:

  - Eclipse intervals with length less than dmin are discarded.

  - The times t should be well chosen so that interpolation errors are small enough.

Parameters

t:

Time at which the observer positions are defined. (1xN)

pos:

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)

typ:

(string, optional) Type of event: "umb", "pen", "umbc". Default is "umbc". (1x1)

tperiods:

(optional) Simulation periods (time intervals). Default is [-%inf; %inf] (2xQ)

opts:

(structure, optional) Additional options (see above). Default value = empty structure.

interv:

Eclipse entry and exit times: [t_start; t_end]. (2xN)

Authors

• CNES - DCT/SB

See also

• CL_gm_eclipseCheck

• CL_detectSign

Examples

// Start/end of eclipse periods (umbra) for an observer in space: t = 0 : 5/1440 : 3; pos_sat = 42164.e3 * [cos(2*%pi*t); sin(2*%pi*t); zeros(t)]; au = CL_dataGet("au"); pos_sun = au * [1; 0; 0]; // Sun CL_ev_eclipse(t, pos_sat, pos_sun, typ="umb")