| tipbod_c |
|
Table of contents
Procedure
tipbod_c ( Transformation, inertial position to bodyfixed )
void tipbod_c ( ConstSpiceChar * ref,
SpiceInt body,
SpiceDouble et,
SpiceDouble tipm[3][3] )
AbstractReturn a 3x3 matrix that transforms positions in inertial coordinates to positions in body-equator-and-prime-meridian coordinates. Required_ReadingFRAMES PCK NAIF_IDS ROTATION TIME KeywordsROTATION TRANSFORMATION 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.
tipm O Position transformation matrix, 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 Frames Required Reading frames.req for a full
list of inertial reference frame names built into
SPICE.
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
position 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 naif_ids.req.
et is the epoch at which the position 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
tipm is a 3x3 coordinate transformation matrix. It is
used to transform positions from inertial
coordinates to body fixed (also called equator and
prime meridian --- PM) coordinates.
Given a position P in the inertial reference frame
specified by `ref', the corresponding bodyfixed
position is given by the matrix vector product:
tipm * 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.
ParametersNone. Exceptions
1) If the kernel pool does not contain all of the data required
for computing the transformation matrix, `tipm', the error
SPICE(INSUFFICIENTANGLES) is signaled by a routine in the call
tree of this routine.
2) If the reference frame, `ref', is not recognized, an error is
signaled by a routine in the call tree of this routine.
3) If the specified body code, `body', is not recognized, an error
is signaled by a routine in the call tree of this routine.
4) If the `ref' input string pointer is null, the error
SPICE(NULLPOINTER) is signaled.
5) If the `ref' input string has zero length, the error
SPICE(EMPTYSTRING) is signaled.
FilesNone. Particulars
tipbod_c takes PCK information as input, either in the form of a
binary or text PCK file. If the data required to compute tipm are
available in a binary PCK, these data will take precedence over data
from a text PCK. If there are multiple binary PCKs containing data
from which tipm can be computed, the last loaded PCK takes
precedence. If binary PCK data are available for the requested body
and time, the Euler angles giving the body's orientation are
evaluated, and the transformation matrix tipm is calculated from
them. Using the Euler angles PHI, DELTA and W we compute
TIPM = [W] [DELTA] [PHI]
3 1 3
If no appropriate binary PCK files have been loaded, text PCK data
are used. Here information is found as RA, DEC and W (with the
possible addition of nutation and libration terms for satellites).
Again, the Euler angles are found, and the transformation matrix is
calculated from them. The transformation from inertial to
bodyfixed coordinates is represented as:
TIPM = [W] [HALFPI-DEC] [RA+HALFPI]
3 1 3
These Euler angles RA, DEC and W are related to PHI, DELTA and W
by the equations
RA = PHI - pi/2
DEC = pi/2 - DELTA
W = W
In the text file, RA, DEC, and W are defined as follows:
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.
Examples
The numerical results shown for this example may differ across
platforms. The results depend on the SPICE kernels used as
input, the compiler and supporting libraries, and the machine
specific arithmetic implementation.
1) Calculate the matrix to rotate a position vector from the
J2000 frame to the Saturn fixed frame at a specified
time, and use it to compute the position of Titan in
Saturn's body-fixed frame.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: tipbod_ex1.tm
This meta-kernel is intended to support operation of SPICE
example programs. The kernels shown here should not be
assumed to contain adequate or correct versions of data
required by SPICE-based user applications.
In order for an application to use this meta-kernel, the
kernels referenced here must be present in the user's
current working directory.
The names and contents of the kernels referenced
by this meta-kernel are as follows:
File name Contents
--------- --------
sat375.bsp Saturn satellite ephemeris
pck00010.tpc Planet orientation and
radii
naif0012.tls Leapseconds
\begindata
KERNELS_TO_LOAD = ( 'sat375.bsp',
'pck00010.tpc',
'naif0012.tls' )
\begintext
End of meta-kernel
Example code begins here.
/.
Program tipbod_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local variables
./
SpiceDouble et;
SpiceDouble lt;
SpiceDouble pos [3];
SpiceDouble satvec [3];
SpiceDouble tipm [3][3];
SpiceInt satid;
/.
Load the kernels.
./
furnsh_c ( "tipbod_ex1.tm" );
/.
The body ID for Saturn.
./
satid = 699;
/.
Retrieve the transformation matrix at some time.
./
str2et_c ( "Jan 1 2005", &et );
tipbod_c ( "J2000", satid, et, tipm );
/.
Retrieve the position of Titan as seen from Saturn
in the J2000 frame at `et'.
./
spkpos_c ( "TITAN", et, "J2000", "NONE", "SATURN", pos, < );
printf( "Titan as seen from Saturn:\n" );
printf( " in J2000 frame : %12.3f %12.3f %12.3f\n",
pos[0], pos[1], pos[2] );
/.
Rotate the position 3-vector `pos' into the
Saturn body-fixed reference frame.
./
mxv_c ( tipm, pos, satvec );
printf( " in IAU_SATURN frame: %12.3f %12.3f %12.3f\n",
satvec[0], satvec[1], satvec[2] );
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:
Titan as seen from Saturn:
in J2000 frame : 1071928.661 -505781.970 -60383.976
in IAU_SATURN frame: 401063.338 -1116965.364 -5408.806
Note that the complete example could be replaced by a single
spkpos_c call:
spkpos_c ( "TITAN", et, "IAU_SATURN", "NONE", "SATURN", pos, < );
Restrictions
1) The kernel pool must be loaded with the appropriate
coefficients (from a text or binary PCK file) prior to
calling this routine.
Literature_ReferencesNone. Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) E.D. Wright (JPL) Version
-CSPICE Version 1.0.3, 05-AUG-2021 (JDR)
Edited the header to comply with NAIF standard. Added complete
code example.
Added frames.req to -Required_Reading. Updated -Exceptions
section.
-CSPICE Version 1.0.2, 14-AUG-2006 (EDW)
Replace mention of ldpool_c with furnsh_c.
-CSPICE Version 1.0.1, 13-APR-2000 (NJB)
Made some minor updates and corrections in the code example.
-CSPICE Version 1.0.0, 08-FEB-1998 (NJB)
Based on SPICELIB Version 1.0.3, 10-MAR-1994 (KSZ).
Index_Entriestransformation from inertial position to bodyfixed |
Fri Dec 31 18:41:14 2021