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Abstract
I/O
Examples
Particulars
Required Reading
Version
Index_Entries

Abstract


   CSPICE_PROP2B uses the two-body force model to propagate the
   state of a massless body orbiting a primary at time t0 to
   the body state at time t0 + dt.

   For important details concerning this module's function, please refer to
   the CSPICE routine prop2b_c.

I/O


   Given:

      gm       a scalar double precision defining the gravitational constant
               of the primary.

      pvinit   the double precision state 6-vector describing the initial
               state of the massless body (secondary) at some epoch.

      dt       the double precision scalar time step in TDB seconds from
               the epoch.

   the call:

      cspice_prop2b, gm, pvinit, dt, pvprop

   returns:

      pvprop   a double precision 6-vector defining the state of the body at a
               time 'dt' from the epoch as determined by the classical two-body
               force model.

Examples


   Any numerical results shown for this example may differ between
   platforms as the results depend on the SPICE kernels used as input
   and the machine specific arithmetic implementation.


      ;;
      ;; In circular two-body motion, the orbital speed 's' is
      ;; sqrt(mu/r), where mu is the central mass. After
      ;; tau/2 = pi*r/s seconds (half period), the state
      ;; should equal the negative of the original state.
      ;;
      mu    =  398600.45d
      r     =  1.d08
      speed =  sqrt( mu / r )
      t     =  cspice_pi()*r/speed

      pvinit= [  0.d, r/sqrt(2.d),      r/sqrt(2.d)   , $
                 0.d, -speed/sqrt(2.d), speed/sqrt(2.d) ]

      ;;
      ;; Calculate the state of the body at 0.5 period
      ;; after the epoch.
      ;;
      cspice_prop2b, mu, pvinit, t, state

      ;;
      ;; The 'state' vector should equal '-pvinit'
      ;;
      ;; Check position...
      ;;
      print, pvinit[0:2]
      print, state[0:2]

      ;;
      ;; ... and velocity.
      ;;
      print, pvinit[3:5]
      print, state[3:5]

   IDL outputs for pvinit[0:2], state[0:2]:

          0.0000000       70710678.       70710678.
          0.0000000      -70710678.      -70710678.

   IDL outputs for pvinit[3:5], state[3:5]:

          0.0000000    -0.044643054     0.044643054
          0.0000000     0.044643054    -0.044643054

Particulars


   None.

Required Reading


   ICY.REQ

Version


   -Icy Version 1.0.1, 15-AUG-2011, EDW (JPL)

      Edits to comply with NAIF standard for Icy headers.

   -Icy Version 1.0.0, 16-JUN-2003, EDW (JPL)

Index_Entries


    Propagate state vector using two-body force model




Wed Apr  5 17:58:02 2017