conics_c |

Table of contents## Procedureconics_c ( Determine state from conic elements ) void conics_c ( ConstSpiceDouble elts[8], SpiceDouble et, SpiceDouble state[6] ) ## AbstractDetermine the state (position, velocity) of an orbiting body from a set of elliptic, hyperbolic, or parabolic orbital elements. ## Required_ReadingNone. ## KeywordsCONIC EPHEMERIS ## Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- elts I Conic elements. et I Input time. state O State of orbiting body at et. ## Detailed_Inputelts are conic osculating elements describing the orbit of a body around a primary. The elements are, in order: RP Perifocal distance. ECC Eccentricity. INC Inclination. LNODE Longitude of the ascending node. ARGP Argument of periapse. M0 Mean anomaly at epoch. T0 Epoch. MU Gravitational parameter. Units are km, rad, rad/sec, km**3/sec**2. The epoch T0 is given in ephemeris seconds past J2000. T0 is the instant at which the state of the body is specified by the elements. The same elements are used to describe all three types (elliptic, hyperbolic, and parabolic) of conic orbit. et is the time at which the state of the orbiting body is to be determined, in ephemeris seconds J2000. ## Detailed_Outputstate is the state (position and velocity) of the body at time `et'. Components are x, y, z, dx/dt, dy/dt, dz/dt. ## ParametersNone. ## Exceptions1) If the eccentricity supplied is less than 0, the error SPICE(BADECCENTRICITY) is signaled by a routine in the call tree of this routine. 2) If a non-positive periapse distance is supplied, the error SPICE(BADPERIAPSEVALUE) is signaled by a routine in the call tree of this routine. 3) If a non-positive value for the attracting mass is supplied, the error SPICE(BADGM) is signaled by a routine in the call tree of this routine. 4) If `elts' is such that the resulting orbit at periapsis has either its position or velocity equal to zero, or the square of the resulting specific angular momentum's magnitude is zero, an error is signaled by a routine in the call tree of this routine. This is an indication of invalid `elts' elements. 5) If `et' is such that the offset in time from periapsis, at which the state is to be determined, is so large that there is a danger of floating point overflow during computation, an error is signaled by a routine in the call tree of this routine. ## FilesNone. ## ParticularsNone. ## ExamplesLet `vinit' contain the initial state of a spacecraft relative to the center of a planet at epoch `et', and let `gm' be the gravitation parameter of the planet. The call oscelt_c ( vinit, et, gm, elts ); produces a set of osculating elements describing the nominal orbit that the spacecraft would follow in the absence of all other bodies in the solar system and non-gravitational forces on the spacecraft. Now let `state' contain the state of the same spacecraft at some other, later epoch. The difference between this state and the state predicted by the nominal orbit at the same epoch can be computed as follows. ## RestrictionsNone. ## Literature_References[1] R. Bate, D. Mueller, and J. White, "Fundamentals of Astrodynamics," Dover Publications Inc., 1971. ## Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) E.D. Wright (JPL) ## Version-CSPICE Version 1.1.2, 02-JUL-2021 (JDR) Edited the header to comply with NAIF standard. Added entry #4 and updated entry #5 in -Exceptions section. -CSPICE Version 1.1.1, 29-JUL-2003 (NJB) Various header corrections were made. -CSPICE Version 1.1.0, 24-JUL-2001 (NJB) Changed protoype: input elts is now type (ConstSpiceDouble *). Implemented interface macro for casting input array to const. -CSPICE Version 1.0.1, 08-FEB-1998 (EDW) Corrected and clarified header entries. -CSPICE Version 1.0.0, 10-NOV-1997 (EDW) ## Index_Entriesstate from conic elements |

Fri Dec 31 18:41:03 2021