bodeul |

Table of contents## ProcedureBODEUL ( Return Euler angles for a body ) SUBROUTINE BODEUL ( BODY, ET, RA, DEC, W, LAMBDA ) ## AbstractReturn the Euler angles needed to compute the transformation from inertial to body-fixed coordinates for any body in the kernel pool. ## Required_ReadingPCK NAIF_IDS TIME ## KeywordsCONSTANTS ROTATION TRANSFORMATION ## DeclarationsIMPLICIT NONE INTEGER BODY DOUBLE PRECISION ET DOUBLE PRECISION RA DOUBLE PRECISION DEC DOUBLE PRECISION W DOUBLE PRECISION LAMBDA ## Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- BODY I ID code of body. ET I Epoch of transformation. RA O Right ascension of the (IAU) north pole. DEC O Declination of the (IAU) north pole of the body. W O Prime meridian rotation angle. LAMBDA O Angle between the prime meridian and longitude of longest axis. ## Detailed_InputBODY is the integer ID code of the body for which the transformation is requested. Bodies are numbered according to the standard NAIF numbering scheme. ET is the epoch at which the transformation is requested. ## Detailed_OutputRA, DEC are the right ascension and declination of the (IAU) north pole of the body at the epoch of transformation. RA and DEC are given in radians. W is the angle between the ascending node of the body-fixed equatorial plane on the inertial equatorial plane and the prime meridian of the body. The node is the cross product of the inertial frame's Z-axis with the Z-axis of the body-fixed frame. The angle is measured in the positive (counterclockwise) sense about the body-fixed Z-axis, from the node to the prime meridian. W is given in radians. LAMBDA is the angle between the prime meridian and the longest axis of the tri-axial ellipsoid which models the body. LAMBDA is given in radians. See the $Particulars section below for further discussion. ## ParametersNone. ## Exceptions1) If any of the PCK keywords required to compute the angles are not available in the kernel pool, an error is signaled by a routine in the call tree of this routine. 2) If the number of phase terms is insufficient, the error SPICE(INSUFFICIENTANGLES) is signaled. 3) If, for a given body, both forms of the kernel variable names BODY<body ID>_CONSTANTS_JED_EPOCH BODY<body ID>_CONSTS_JED_EPOCH are found in the kernel pool, the error SPICE(COMPETINGEPOCHSPEC) is signaled. This is done regardless of whether the values assigned to the kernel variable names match. 4) If, for a given body, both forms of the kernel variable names BODY<body ID>_CONSTANTS_REF_FRAME BODY<body ID>_CONSTS_REF_FRAME are found in the kernel pool, the error SPICE(COMPETINGFRAMESPEC) is signaled. This is done regardless of whether the values assigned to the kernel variable names match. 5) If the central body associated with the input BODY, whether a system barycenter or BODY itself, has associated phase angles (aka nutation precession angles), and the kernel variable BODY<body ID>_MAX_PHASE_DEGREE for the central body is present but has a value outside the range 1:3, the error SPICE(DEGREEOUTOFRANGE) is signaled. ## FilesA text or binary PCK containing orientation data for the body designated by BODY must be loaded at the time this routine is called. Normally PCK files are loaded during program initialization; they need not be re-loaded prior to each call to this routine. ## ParticularsApplications that need to compute the transformation between body-fixed and inertial frames usually can call the higher-level routine PXFORM instead of this routine. If there exists high-precision binary PCK kernel information for the body at the requested time, the angles, W, DELTA and PHI are computed directly from that file. These angles are then used to compute RA, DEC and W. 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 (PCK) 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 - HALFPI() DEC = HALFPI() - DELTA RA, DEC, and W are defined as follows in the text PCK file: RA = RA0 + RA1*T + RA2*T*T + a sin theta i i DEC = DEC0 + DEC1*T + DEC2*T*T + d cos theta i i W = W0 + W1*d + W2*d*d + w sin theta i i where: d = days past J2000. T = Julian centuries past J2000. a , d , and w arrays apply to satellites only. i i i theta = THETA0 * THETA1*T are specific to each planet. i These angles -- typically nodal rates -- vary in number and definition from one planetary system to the next. The prime meridian offset LAMBDA ================================ The offset LAMBDA is the value specified by the kernel variable BODYnnn_LONG_AXIS if such a variable is defined. The offset LAMBDA is a constant for a given body. LAMBDA serves to distinguish between the planetocentric prime meridian, which is provided in the PCK file, and the meridian that passes through the +X axis of a reference frame aligned with the axes of the body's reference ellipsoid. However, SPICE Toolkit makes no use of LAMBDA. In order to perform geometry computations using a reference ellipsoid not aligned with a body's planetocentric reference frame, a fixed-offset (aka "TK") reference frame aligned with the ellipsoid's axes should be specified in a frames kernel. Note that a fixed-offset frame may be rotated from the planetocentric frame about an arbitrary axis, not just the polar axis. See the Frames Required Reading frames.req for details on constructing a fixed-offset frame specification. ## ExamplesIn the following code fragment, ## RestrictionsNone. ## Literature_ReferencesNone. ## Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) B.V. Semenov (JPL) W.L. Taber (JPL) I.M. Underwood (JPL) K.S. Zukor (JPL) ## VersionSPICELIB Version 5.0.0, 14-APR-2021 (NJB) (JDR) The routine was updated to support user-defined maximum phase angle degrees. The additional text kernel kernel variable name BODYnnn_MAX_PHASE_DEGREE must be used when the phase angle polynomials have degree higher than 1. The maximum allowed degree is 3. The kernel variable names BODY#_CONSTS_REF_FRAME BODY#_CONSTS_JED_EPOCH are now recognized. Error handling was upgraded to check FAILED() between kernel data lookups and computations. Now SAVEs all local variables. Edited the header to comply with NAIF standard. Moved NAIF_IDS required reading from $Literature_References to $Required_Reading section. SPICELIB Version 4.2.0, 02-MAR-2016 (BVS) BUG FIX: changed available room in the BODVCD call fetching 'NUT_PREC_ANGLES' from MAXANG to MAXANG*2. Fixed indention in some header sections. Removed |

Fri Dec 31 18:35:59 2021