conics_c

Index Page conics_c
A B C D E F G H I J K L M N O P Q R S T U V W X
Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries
#### Procedure
       void conics_c ( ConstSpiceDouble  elts[8],
                       SpiceDouble       et,
                       SpiceDouble       state[6] )
#### Abstract
       Determine the state (position, velocity) of an orbiting body
       from a set of elliptic, hyperbolic, or parabolic orbital
       elements.
#### Required_Reading
       None.
#### Keywords
       CONIC
       EPHEMERIS
#### Brief_I/O
       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       elts       I   Conic elements.
       et         I   Input time.
       state      O   State of orbiting body at et.
#### Detailed_Input
       elts       are conic osculating elements describing the orbit of a
                  body around a primary. The elements are, in order:

                     RP      Perifocal distance.
                     ECC     Eccentricity.
                     INC     Inclination.
                     LNODE   Longitude of the ascending node.
                     ARGP    Argument of periapse.
                     M0      Mean anomaly at epoch.
                     T0      Epoch.
                     MU      Gravitational parameter.

                  Units are km, rad, rad/sec, km**3/sec**2.

                  The epoch T0 is given in ephemeris seconds past J2000.
                  T0 is the instant at which the state of the body is
                  specified by the elements.

                  The same elements are used to describe all three types
                  (elliptic, hyperbolic, and parabolic) of conic orbit.

       et         is the time at which the state of the orbiting body
                  is to be determined, in ephemeris seconds J2000.
#### Detailed_Output
       state      is the state (position and velocity) of the body at
                  time `et'. Components are x, y, z, dx/dt, dy/dt, dz/dt.
#### Parameters
       None.
#### Exceptions
       1) If the eccentricity supplied is less than 0, the error
          SPICE(BADECCENTRICITY) is signaled.

       2) If a non-positive periapse distance is supplied, the error
          SPICE(BADPERIAPSEVALUE) is signaled.

       3) If a non-positive value for the attracting mass is supplied,
          the error SPICE(BADGM),  is signaled.

       4) Errors such as an out of bounds value for `et' are diagnosed
          by routines in the call tree of this routine.
#### Files
       None.
#### Particulars
       None.
#### Examples
       Let vinit contain the initial state of a spacecraft relative to the
       center of a planet at epoch `et', and let `gm' be the gravitation
       parameter of the planet. The call

          oscelt_c ( vinit, et, gm, elts );

       produces a set of osculating elements describing the nominal
       orbit that the spacecraft would follow in the absence of all
       other bodies in the solar system and non-gravitational forces
       on the spacecraft.

       Now let `state' contain the state of the same spacecraft at some
       other, later epoch. The difference between this state and the
       state predicted by the nominal orbit at the same epoch can be
       computed as follows.

          conics_c ( elts,    later, nominal );
          vsubg_c  ( nominal, state, 6, diff );

          printf( "Perturbation in x, dx/dt = %f %f", diff[0], diff[3] );
          printf( "                y, dy/dt = %f %f", diff[1], diff[4] );
          printf( "                z, dz/dt = %f %f", diff[2], diff[5] );
#### Restrictions
       None.
#### Literature_References
       [1] Roger Bate, Fundamentals of Astrodynamics, Dover, 1971.
#### Author_and_Institution
       N.J. Bachman    (JPL)
       I.M. Underwood  (JPL)
       W.L. Taber      (JPL)
       E.D. Wright     (JPL)
#### Version
       -CSPICE Version 1.1.1, 29-JUL-2003   (NJB)

           Various header corrections were made.

       -CSPICE Version 1.1.0, 24-JUL-2001   (NJB)

           Changed protoype:  input elts is now type (ConstSpiceDouble *).
           Implemented interface macro for casting input array to const.

       -CSPICE Version 1.0.1, 08-FEB-1998   (EDW)

           Corrected and clarified header entries.

       -CSPICE Version 1.0.0, 10-NOV-1997   (EDW)
#### Index_Entries
       state from conic elements
#### Link to routine conics_c source file conics_c.c

    Thu Apr 16 08:57:33 2009