CL_eph_de405

Description

• Computes the position, velocity and acceleration of a body using JPL's DE405 ephemerides.

  The results are given in the ICRS frame.

  Available bodies are: "Mercury", "Venus", "Earth-Moon-bary" (or "EMB"), "Mars", "Jupiter", "Saturn", "Uranus", "Neptune", "Pluto", "Moon", "Sun", "Earth", "solar-sys-bary" (or "SSB")

  The computed data are:

  pos: vector from orig to body

  vel: first time derivative of pos

  acc: second time derivative of pos

  By default, the function looks for the appropriate JPL's DE405 ephemeris files located in CL_home()/data/ephem/de405.

  One can also specify the ephemeris to be used with the optional argument ephem. (See function CL_eph_de405Load)

• Notes:

  - For dates that are not covered by the ephemeris file(s), %nan values are returned.

  - The default value for the origin is the solar system barycenter (even for the Moon!)

  - Theoretically the time scale for DE405 is TDB. In practice, using a TT time scale is acceptable. See Dates and time scales for more details.

  - The results returned for all planets except Earth actually are the position velocity and acceleration of the barycenter of the planet system (i.e barycenter of planet + satellites).

  - Body names are case sensitive.

• See Reference frames for more details on the ICRS frame, and Ephemerides for more details on ephemerides of celestial bodies.

Parameters

body:

(string) Name of the body. (1x1)

cjd:

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

orig:

(optional, string) Name of the origin. Default is "solar-sys-bary" (1x1)

tt_tref:

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

ephem:

(optional) Scilab structure of ephemeris (see function CL_eph_de405Load).

pos:

Position of body, relative to orig, in ICRS frame (3xN)

vel:

Velocity of body, relative to orig, in ICRS frame (3xN)

acc:

Acceleration of body, relative to orig, in ICRS frame (3xN)

Authors

• CNES - DCT/SB

See also

• CL_eph_de405Load

Examples

// Position of Mars in ICRS (Origin = Earth) cjd = 21915:21920; pos = CL_eph_de405("Mars", cjd, "Earth"); // Position, velocity, acceleration of Jupiter in ICRS (Origin = Solar system barycenter) cjd = 21915:21920; [pos, vel, acc] = CL_eph_de405("Jupiter", cjd);