Name

CL_op_searchRepeatOrbits — Search for repeat orbits

Calling Sequence

   [params]=CL_op_searchRepeatOrbits(smaMin,smaMax,QMin,QMax,ecc,sso,incInput,[er,[mu,[j2,[om_earth,[om_sun]]]]])
   
   

Description

  • This function computes all repeat (or phased) orbits for a given range of semi major axes and number of earth revolutions per cycle.

    An orbit is considered phased if after an given number of planet revolutions (with respect to the orbit's node), the satellite has done a whole number of orbits and is back on the same ground track.

    Each solution is defined by 3 integers (N,P,Q) such that:

    N+P/Q is the (fractionary) number of orbits per orbital day, where an orbital day is defined as the time between 2 consecutive crossings of the ascending node by a same meridian. Q is the number of orbital days per cycle. N*Q+P is the number of orbit periods per cycle.

    For a sun synchronous orbit, an orbital day is the same as a usual day (86400 s).

    If sso = 1 then the computed orbits are sun-synchronous orbits (inclination is defined implicitly).

    If sso = 0 then the computed orbits have the inclination as given.

  • params is a Mx11 matrix (M number of solutions).

    --> params(:,1): semi major axis [m]

    --> params(:,2): eccentricity

    --> params(:,3): inclination [rad]

    --> params(:,4:6): N, P, Q

    --> params(:,7): number of nodal periods per phasing cycle (=N*Q+P)

    --> params(:,8): nodal period [s]

    --> params(:,9): cycle duration in days [days]

    --> params(:,10): longitude gap between 2 closest ascending nodes [rad] = 2*%pi/(N*Q+P)

    --> params(:,11): longitude gap after one cycle modulo 2*pi [rad] (for checking)

Parameters

smaMin:

Minimum semi major axis (m) (1 x 1)

smaMax:

Maximum semi major axis (m) (1 x 1)

QMin:

Minimum number of orbital days per repeat cycle (integer) (1 x 1)

QMax:

Maximum number of orbital days per repeat cycle (integer) (1 x 1)

ecc :

eccentricity (1 x 1)

sso:

1 = search for sun-synchronous orbits, 0 = search for orbits with imposed inclination (1 x 1)

incInput :

(optionnal; mandatory if sso=0) inclination (rad) (1 x 1)

er:

(optional) equatorial radius [m] (default is %CL_eqRad)

mu:

(optional) gravitational constant [m^3/s^2] (default value is %CL_mu)

j2:

(optional) zonal coefficient (second zonal harmonic) (default is %CL_j2)

om_earth :

(optional) angular rotation rate of the Earth (default is %CL_om_earth) (1 x 1)

om_sun :

(optional) mean apparent revolution speed of the Sun around the Earth (default is %CL_omSun) (1 x 1)

params :

results (See description) (Mx11) with M : number of solutions

Authors

CNES - DCT/SB

See also

CL_op_repeatGroundTracks, CL_op_repeat2smaInc, CL_op_ssoJ2

Examples

smaMin = 7000.0 * 1000;
smaMax = 7050.0 * 1000;
QMin = 2;
QMax = 6;
ecc = 0.0001;
sso = 1;
[params]=CL_op_searchRepeatOrbits(smaMin,smaMax,QMin,QMax,ecc,sso)

sso = 0;
incInput = CL_deg2rad(98.5);
[params]=CL_op_searchRepeatOrbits(smaMin,smaMax,QMin,QMax,ecc,sso,incInput)