CL_mod_IAUBodyAngles

Description

• This function computes the three rotation angles that define the IAU body-fixed rotating frame.

  The body fixed frame axes are obtained from the ICRS axes by applying 3 successive rotations of respective angles [alpha0+pi/2, pi/2-delta0, W] around the respectives axes [3,1,3], where:

  - alpha0 and delta0: right ascension and declination of the North pole of the body in the ICRS frame,

  - W: angle defining the prime meridian of the body.

  The function also optionally computes the time derivatives of these angles: angles_der = [alpha0dot;delta0dot;Wdot].

  Available bodies are: "Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune", "Sun" and "Moon".

• Notes:

  - The date should be given in TDB time scale. In practice using TT time scale leads to a negligible error (about 2 ms).

  - Body names are case sensitive

  - This implementation of the function is compliant with the 2009 IAU report. (See bibliography)

Parameters

cjd:

Modified (1950.0) julian day (Time scale: TREF) (1xN)

body:

(string) Name of the body. ("Mercury","Venus","Earth","Mars","Jupiter","Saturn","Uranus", "Neptune", "Sun" or "Moon") (1x1)

tt_tref:

(optional) TT-TREF [seconds]. Default is %CL_TT_TREF. (1xN or 1x1)

angles:

Angles [alpha0;delta0;W] defining the orientation of the body [rad]. (1xN)

angles_der:

Time derivatives of Angles = [alpha0dot;delta0dot;Wdot] [rad/s]. (1xN)

Authors

• CNES - DCT/SB

Bibliography

• Report of the IAU/IAG working group on cartographic coordinates and rotational elements: 2009

See also

• CL_fr_bodyConvertMat

• CL_fr_bodyConvert

Examples

cjd = CL_dat_cal2cjd(2010,02,03,05,35,25); // TREF time scale [angles,angles_der] = CL_mod_IAUBodyAngles(cjd, "Mars")