void rav2xf_c ( ConstSpiceDouble rot ,
ConstSpiceDouble av ,
SpiceDouble xform  )
This routine determines a state transformation matrix
from a rotation matrix and the angular velocity of the
VARIABLE I/O DESCRIPTION
-------- --- --------------------------------------------------
rot I Rotation matrix.
av I Angular velocity vector.
xform O State transformation associated with rot and av.
rot is a rotation that gives the transformation from
some frame frame1 to another frame frame2.
av is the angular velocity of the transformation.
In other words, if p is the position of a fixed
point in frame2, then from the point of view of
frame1, p rotates (in a right handed sense) about
an axis parallel to av. Moreover the rate of rotation
in radians per unit time is given by the length of
More formally, the velocity v of p in frame1 is
v = av x ( rot * p )
xform is a state transformation matrix associated
with rot and av. If s1 is the state of an object
with respect to frame1, then the state s2 of the
object with respect to frame2 is given by
s2 = xform * s1
where "*" denotes matrix-vector multiplication.
1) No checks are performed on ROT to ensure that it is indeed
a rotation matrix.
This routine is essentially a macro routine for converting
a rotation and angular velocity of the rotation to the
equivalent state transformation matrix.
This routine is an inverse of xf2rav_c.
Suppose that you wanted to determine state transformation
matrix from a platform frame to the J2000 frame.
The following call obtains the J2000-to-platform transformation
matrix and platform angular velocity at the time of interest.
The time value is expressed as encoded SCLK.
ckgpav_c ( ckid, time, tol, "J2000", rot, av, &clkout, &fnd );
Recall that rot and av are the rotation and angular velocity
of the transformation from J2000 to the platform frame.
if ( fnd )
First get the state transformation from J2000 to the platform
rav2xf_c ( rot, av, j2plt );
Invert the state transformation matrix (using invstm_c) to
the desired state transformation matrix.
invstm_c ( j2plt, xform );
N.J. Bachman (JPL)
W.L. Taber (JPL)
-CSPICE Version 1.0.1, 12-APR-2007 (EDW)
Edit to abstract.
-CSPICE Version 1.0.0, 18-JUN-1999 (WLT) (NJB)
State transformation to rotation and angular velocity