Procedure

     IRFROT ( Inertial reference frame rotation )

     ENTRY IRFROT ( REFA, REFB, ROTAB )

Abstract

     Compute the matrix needed to rotate vectors between two
     standard inertial reference frames.

Required_Reading

     FRAMES

Keywords

     CONVERSION
     COORDINATES
     EPHEMERIS
     FRAMES
     MATRIX
     ROTATION
     TRANSFORMATION
     VECTOR

Declarations

    INTEGER               REFA
    INTEGER               REFB
    DOUBLE PRECISION      ROTAB    ( 3, 3 )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     REFA,
     REFB       I   Indices of target reference frames (A,B).
     ROTAB      O   Rotation from frame A to frame B.

Detailed_Input

     REFA,
     REFB     are the indices of two standard inertial reference
              frames. The complete set of supported frames is shown
              below.

                 Index  Name      Description
                 -----  --------  --------------------------------
                  1    J2000      Earth mean equator, dynamical
                                  equinox of J2000

                  2    B1950      Earth mean equator, dynamical
                                  equinox of B1950

                  3    FK4        Fundamental Catalog (4)

                  4    DE-118     JPL Developmental Ephemeris (118)

                  5    DE-96      JPL Developmental Ephemeris ( 96)

                  6    DE-102     JPL Developmental Ephemeris (102)

                  7    DE-108     JPL Developmental Ephemeris (108)

                  8    DE-111     JPL Developmental Ephemeris (111)

                  9    DE-114     JPL Developmental Ephemeris (114)

                 10    DE-122     JPL Developmental Ephemeris (122)

                 11    DE-125     JPL Developmental Ephemeris (125)

                 12    DE-130     JPL Developmental Ephemeris (130)

                 13    GALACTIC   Galactic System II

                 14    DE-200     JPL Developmental Ephemeris (200)

                 15    DE-202     JPL Developmental Ephemeris (202)

                 16    MARSIAU    Mars Observer inertial frame
                                  defined relative to MARS.

                 17    ECLIPJ2000 Earth mean ecliptic and equinox
                                  of the epoch J2000

                 18    ECLIPB1950 Earth mean ecliptic and equinox
                                  of the Besselian date 1950.

                 19    DE-140    JPL Developmental Ephemeris (140)

                 20    DE-142    JPL Developmental Ephemeris (142)

                 21    DE-143    JPL Developmental Ephemeris (143)

Detailed_Output

     ROTAB    is the rotation which, when applied to a vector v
              in reference frame A,
                 _            _
                 v  = (ROTAB) v
                  B            A

              yields the same vector in reference frame B. The
              inverse rotation is performed by applying the
              transpose,
                 _           T _
                 v  = (ROTAB)  v
                  A             B

Parameters

     None.

Exceptions

     1)  If either REFA or REFB is outside the range [1,MAXF],
         where MAXF is the number of supported frames, the error
         SPICE(IRFNOTREC) is signaled.

Files

     None.

Particulars

     IRFROT exists primarily for use by the ephemeris and star
     catalog readers in the SPICELIB toolkit library.

Examples

     In the following code fragment, IRFROT is used to rotate
     vectors originally referenced to the DE-118 coordinate frame
     to equivalent vectors referenced to the IAU standard J2000
     reference frame.

        CALL IRFROT ( 4, 1, R )

        CALL MXV ( R, SC1950, SC2000 )
        CALL MXV ( R, MP1950, MP2000 )

Restrictions

     None.

Literature_References

     [1]  J. Lieske, "Precession Matrix Based on IAU (1976) System of
          Astronomical Constants," Astron. Astrophys. 73, 282-284,
          1979.

     [2]  E. M. Standish, Jr., "Orientation of the JPL Ephemerides,
          DE 200/LE 200, to the Dynamical Equinox of J2000," Astron.
          Astrophys. 114, 297-302, 1982.

     [3]  E. M. Standish, Jr., "Conversion of Ephemeris Coordinates
          from the B1950 System to the J2000 System," JPL IOM
          314.6-581, 24 June 1985.

     [4]  E. M. Standish, Jr., "The Equinox Offsets of the JPL
          Ephemeris," JPL IOM 314.6-929, 26 February 1988.

     [5]  J. Lieske, "Expressions for the Precession Quantities Based
          upon the IAU (1976) System of Astronomical Constants,"
          Astron. Astrophys. 58, 1-16, 1977.

     [6]  L. Bass and R. Cesarone, "Mars Observer Planetary Constants
          and Models," JPL D-3444, November 1990.

     [7]  P. Kenneth Seidelmann (Ed.), "Explanatory Supplement to the
          Astronomical Almanac," University Science Books, 1992.

Author_and_Institution

     J. Diaz del Rio    (ODC Space)
     B.V. Semenov       (JPL)
     W.L. Taber         (JPL)
     I.M. Underwood     (JPL)
     E.D. Wright        (JPL)

Version

    SPICELIB Version 4.4.0, 17-JUN-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard. Corrected
        argument name in $Brief_I/O section: ROTAB was MATRIX. Added
        $Literature_References.

    SPICELIB Version 4.3.0, 24-SEP-2013 (BVS)

        Updated to do discovery check-in/check-out.

    SPICELIB Version 4.2.1, 04-JAN-2002 (EDW)

        Added DE-143 to header description for IRFROT.

    SPICELIB Version 4.2.0, 10-APR-1997 (WLT)

        A descriptive diagnostic was added to the entry points
        IRFROT and IRFDEF. Before they simply signaled the error
        with no diagnostic.

    SPICELIB Version 4.1.0, 14-OCT-1996 (WLT)

        The number of inertial frames recognized is now stored
        in the include file ninert.inc.

    SPICELIB Version 4.0.0, 20-MAY-1996 (WLT)

        The inertial frame DE-143 was added to the list of recognized
        inertial frames.

    SPICELIB Version 3.0.0, 20-MAR-1995 (WLT)

        The inertial frames DE-140 and DE-142  were added to the
        list of recognized inertial frames.

    SPICELIB Version 2.0.0, 30-JUL-1993 (WLT)

        The transformation from J2000 to B1950 was upgraded
        so that the transformation matrix produced matches
        the matrix given in [1].

        The frame MARSIAU was added to the list
        of recognized frames. This is the standard mars
        referenced inertial frame used by the Mars Observer
        project.

        Values for the obliquity of the ecliptic were taken
        from the Explanatory Supplement [7] to the Astronomical
        Almanac (1992) at both the epochs J2000 and B1950 and
        used to define the mean ecliptic and equinox frames
        ECLIPJ2000 and ECLIPB1950.

    SPICELIB Version 1.0.1, 10-MAR-1992 (WLT)

        Comment section for permuted index source lines was added
        following the header.

    SPICELIB Version 1.0.0, 31-JAN-1990 (WLT) (IMU)