Index Page tisbod_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 tisbod_c ( ConstSpiceChar   * ref,
                       SpiceInt           body,
                       SpiceDouble        et,
                       SpiceDouble        tsipm[6][6] )

#### Abstract

       Return a 6x6 matrix that transforms states in inertial coordinates to
       states in body-equator-and-prime-meridian coordinates.

#### Required_Reading

       PCK
       NAIF_IDS
       ROTATION
       TIME

#### Keywords

       None.

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       ref        I   ID of inertial reference frame to transform from
       body       I   ID code of body
       et         I   Epoch of transformation
       tsipm      O   Transformation (state), inertial to prime meridian

#### Detailed_Input

       ref         is the NAIF name for an inertial reference frame.
                   Acceptable names include:

                      Name       Description
                      --------   --------------------------------
                      "J2000"    Earth mean equator, dynamical
                                 equinox of J2000

                      "B1950"    Earth mean equator, dynamical
                                 equinox of B1950

                      "FK4"      Fundamental Catalog (4)

                      "DE-118"   JPL Developmental Ephemeris (118)

                      "DE-96"    JPL Developmental Ephemeris ( 96)

                      "DE-102"   JPL Developmental Ephemeris (102)

                      "DE-108"   JPL Developmental Ephemeris (108)

                      "DE-111"   JPL Developmental Ephemeris (111)

                      "DE-114"   JPL Developmental Ephemeris (114)

                      "DE-122"   JPL Developmental Ephemeris (122)

                      "DE-125"   JPL Developmental Ephemeris (125)

                      "DE-130"   JPL Developmental Ephemeris (130)

                      "GALACTIC" Galactic System II

                      "DE-200"   JPL Developmental Ephemeris (200)

                      "DE-202"   JPL Developmental Ephemeris (202)

                   (See the routine chgirf_c for a full list of names.)

                   The output tipm will give the transformation
                   from this frame to the bodyfixed frame specified by
                   body at the epoch specified by et.

       body        is the integer ID code of the body for which the
                   state transformation matrix is requested. Bodies
                   are numbered according to the standard NAIF
                   numbering scheme.  The numbering scheme is
                   explained in the NAIF_IDS required reading file.

       et          is the epoch at which the state transformation
                   matrix is requested. (This is typically the
                   epoch of observation minus the one-way light time
                   from the observer to the body at the epoch of
                   observation.)

#### Detailed_Output

       tsipm       is a 6x6 transformation matrix.  It is used to
                   transform states from inertial coordinates to body
                   fixed (also called equator and prime meridian --- PM)

                   Given a state s in the inertial reference frame
                   specified by ref, the corresponding bodyfixed state
                   is given by the matrix vector product:

                      tsipm * s

                   The X axis of the PM system is directed  to the
                   intersection of the equator and prime meridian.
                   The Z axis points along  the spin axis and points
                   towards the same side of the invariable plane of
                   the solar system as does earth's north pole.

                   NOTE: The inverse of tsipm is NOT its transpose.
                   The matrix tsipm has the structure shown below:

                        -            -
                       |       :      |
                       |   r   :  0   |
                       | ......:......|
                       |       :      |
                       | dr_dt :  r   |
                       |       :      |
                        -            -

                   where r is a time varying rotation matrix and
                   dr_dt is its derivative.  The inverse of this
                   matrix is:

                        -              -
                       |     T  :       |
                       |    r   :  0    |
                       | .......:.......|
                       |        :       |
                       |      T :   T   |
                       | dr_dt  :  r    |
                       |        :       |
                        -              -

                   The CSPICE routine invstm_c is available for
                   producing this inverse.

#### Parameters

       None.

#### Exceptions

       1) If the kernel pool does not contain all of the data required
          for computing the transformation matrix, tsipm, the error
          SPICE(INSUFFICIENTANGLES) is signalled.

       2) If the reference frame ref is not recognized, a routine
          called by tisbod_c will diagnose the condition and invoke the
          SPICE error handling system.

       3) If the specified ID code body is not recognized, the
          error is diagnosed by a routine called by tisbod_c.

#### Files

       None.

#### Particulars

       The matrix for transforming inertial states to bodyfixed
       states is the 6x6 matrix shown below as a block structured
       matrix.

                  -            -
                 |       :      |
                 | tipm  :  0   |
                 | ......:......|
                 |       :      |
                 | dtipm : tipm |
                 |       :      |
                  -            -

      This can also be expressed in terms of Euler angles
      phi, delta and w.  The transformation from inertial to
      bodyfixed coordinates is represented in the SPICE kernel
      pool as:

             tipm =   [w] [delta] [phi]
                         3       1     3
       Thus

            dtipm =   D[w] /Dt   [delta]       [phi]
                          3             1           3

                    +  [w]      D[delta] /Dt   [phi]
                          3             1           3

                    +  [w]       [delta]      D[phi] /Dt
                          3             1           3

       If a binary PCK file record can be used for the time and
       body requested, it will be used.  The most recently loaded
       binary PCK file has first priority, followed by previously
       loaded binary PCK files in backward time order.  If no
       binary PCK file has been loaded, the text P_constants
       kernel file is used.

       If there is only text PCK kernel information, it is
       expressed in terms of ra, dec and w (same w as above), where

         ra    = phi  - pi/2
         dec   = pi/2 - delta

       The angles ra, dec, and w are defined as follows in the
       text PCK file:

                                          2      ____
                                     ra2*t       \
             ra  = ra0  + ra1*t/T  + ------   +  /     a  sin theta
                                        2        ----   i          i
                                       T           i

                                           2     ____
                                     dec2*t      \
             dec = dec0 + dec1*t/T + -------  +  /    d  cos theta
                                         2       ----  i          i
                                        T          i

                                         2      ____
                                     w2*t       \
             w   = w0   + w1*t/d   + -----   +  /     w  sin theta
                                        2       ----   i          i
                                       d          i

       where:

             d = seconds/day

             T = seconds/Julian century

             a , d , and w  arrays apply to satellites only.
              i   i       i

             theta  = THETA0(i) + THETA1(i)*t/T are specific to each
                  i

             planet.

         These angles -- typically nodal rates -- vary in number and
         definition from one planetary system to the next.

         Thus
                                          ____
                              2*ra2*t     \
           dra/dt  = ra1/T  + -------   + /   a THETA1(i)/T cos theta
                                  2       ---- i                     i
                                 T          i

                                          ____
                              2*dec2*t    \
           ddec/dt = dec1/T + --------  - /    d  THETA1(i)/T sin theta
                                  2       ----  i                      i
                                 T          i

                                          ____
                              2*w2*t      \
           dw/dt   = w1/d   + ------    + /    w  THETA1(i)/T cos theta
                                  2       ----  i                      i
                                 d          i

#### Examples

       Note that the data needed to compute the output state transition
       matrix must have been made available to your program by having
       loaded an appropriate binary or text PCK file via furnsh_c.

       Example 1.

          In the following code fragment, tisbod_c is used to transform
          a state in J2000 inertial coordinates to a state in bodyfixed
          coordinates.

          The 6-vector eulang represents the inertial state (position and
          velocity) of an object with respect to the center of the body
          at time et.

             #include "SpiceUsr.h"
                   .
                   .
                   .

             /.
             First load the kernel pool.
             ./
             furnsh_c ( "planetary_constants.ker" );

             /.
             Next get the transformation and its derivative.
             ./
             tisbod_c ( "J2000", body, et, tsipm );

             /.
             Convert position to bodyfixed coordinates.
             ./
             mxvg_c   ( tsipm, eulang, 6, 6, bdstat );

       Example 2.

          In the example below, tisbod_c is used to compute the angular
          velocity vector (with respect to an inertial frame) of the
          specified body at time et.

             #include "SpiceUsr.h"
                   .
                   .
                   .
             /.
             First get the state transformation matrix.
             ./
             tisbod_c ( body,  et,  tsipm );

             /.
             This matrix has the form:

                 -            -
                |       :      |
                | tipm  :  0   |
                | ......:......|
                |       :      |
                | dtipm : tipm |
                |       :      |
                 -            -

             We extract tipm and dtipm:
             ./

             for ( i = 0;  i<3;  i++ )
             {
                for ( j = 0;  j<3;  j++ )
                {
                   tipm  [i][j] = tsipm[i  ][j];
                   dtipm [i][j] = tsipm[i+3][j];
                }
             }

             /.

             The transposes of tipm and dtipm, (tpmi and dtpmi), give
             the transformation from bodyfixed coordinates to inertial
             coordinates and its time derivative.

             Here is a fact about the relationship between angular
             velocity associated with a time varying rotation matrix
             that gives the orientation of a body with respect to
             an inertial frame:

             The angular velocity vector can be read from the off
             diagonal components of the matrix product:

                                     t
             omega =     dtpmi * tpmi

                              t
                   =     dtipm * tipm

             the components of the angular velocity v will appear
             in this matrix as:

                  _                   _
                 |                     |
                 |   0    -v(3)  v(2)  |
                 |                     |
                 |  v(3)    0   -v(1)  |
                 |                     |
                 | -v(2)   v(1)   0    |
                 |_                   _|

             Pick off the angular velocity components from omega.

            ./

             mtxm_c ( dtipm, tipm, omega );

             v[0] = omega [2][1];
             v[1] = omega [0][2];
             v[2] = omega [1][0];

#### Restrictions

       The kernel pool must be loaded with the appropriate coefficients
       (from the P_constants kernel or binary PCK file) prior to calling
       this routine.

#### Literature_References

       None.

#### Author_and_Institution

       N. J. Bachman   (JPL)
       W. L. Taber     (JPL)
       K. S. Zukor     (JPL)

#### Version

       -CSPICE Version 1.0.3, 16-JAN-2008   (EDW)

          Corrected typos in header titles:

          Detailed Input to Detailed_Input
          Detailed Output to Detailed_Output

       -CSPICE Version 1.0.2, 10-NOV-2006   (EDW)

          Replace mention of ldpool_c and pcklof_c with furnsh_c.
          Added Keywords and Parameters section headers.
          Reordered section headers.

       -CSPICE Version 1.0.1, 02-JUL-2003 (EDW)

           Corrected trivial typo in the Version 1.0.0 line.
           The typo caused an integrity check script to fail.

       -CSPICE Version 1.0.0, 20-JUN-1999 (NJB) (WLT) (KSZ)

           Initial release, based on SPICELIB Version 3.3.0, 29-MAR-1995

#### Index_Entries

       transformation from inertial state to bodyfixed

#### Link to routine tisbod_c source file tisbod_c.c

    Wed Apr  5 17:54:45 2017