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Abstract
I/O
Examples
Particulars
Required Reading
Version
Index_Entries

Abstract


   CSPICE_LTIME computes the transmit (or receive) time of 
   a signal at a specified target, given the receive (or transmit) 
   time at a specified observer. The elapsed time between transmit 
   and receive is also returned.

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

I/O

   
   Given:
   
      etobs   a double precision scalar defining the epoch 
              in ephemeris seconds (TDB) of a signal at some observer 

      obs     the scalar integer NAIF ID code of the observer 

      dir     a character string pictograph defining the 
              direction the signal travels, to target
              from observer "->", or from the target to the 
              observer "<-" 

      targ    the scalar integer NAIF ID code of the target  
   
   the call:
   
      cspice_ltime, etobs, obs, dir, targ, ettarg, elapsd
   
   returns:
   
      ettarg  the double precision scalar value defining the
              epoch at which the electromagnetic signal is "at" the 
              target body, expressed in ephemeris seconds (TDB) 
   
                 Note ettarg is computed using only Newtonian 
                 assumptions about the propagation of light. 
   
      elapsd  the double precision scalar defining the number
              interval of ephemeris seconds (TDB) between 
              transmission and receipt of the signal 
   
                    elapsd = abs( etobs - ettarg )
   

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.

   
      ;;
      ;; Load an SPK, PCK, and leapseconds kernel
      ;;
      cspice_furnsh, 'standard.tm'
   
      ;;
      ;; Suppose a signal originates from Earth towards the
      ;; the Jupiter system barycenter. Define the NAIF IDs
      ;; for the observer, Earth (399), the target, Jupiter
      ;; barycenter (5), and time of interest. 
      ;;
      OBS      = 399
      TARGET   = 5
      TIME_STR = 'July 4, 2004'
   
      ;; 
      ;; Convert the transmission time to ET.
      ;;
      cspice_str2et, TIME_STR, et
   
      ;;
      ;; Determine the arrival time and the time for propagation.
      ;;
      cspice_ltime, et, OBS, "->", TARGET, arrive, ltime
   
      ;;
      ;; Convert the arrival time (ET) to UTC.
      ;;
      cspice_et2utc, arrive, 'C', 3, arrive_utc
   
      ;;
      ;; Output the results.
      ;;
      print, 'Transmission at (UTC)       : ', TIME_STR
      print, 'The signal arrived at (UTC) : ', arrive_utc
      print, 'Time for propagation (secs) : ', ltime
      print
   
      ;;
      ;; Now assume the signal originated at Jupiter barycenter,
      ;; received by Earth at TIME_STR. Determine the transmission
      ;; time and the time for propagation.
      ;;
      cspice_ltime, et, OBS, "<-", TARGET, receive, ltime
   
      ;;
      ;; Convert the reception time (ET) to UTC.
      ;;
      cspice_et2utc, receive, 'C', 3, receive_utc
   
      ;;
      ;; Output the results.
      ;;
      print, 'Reception at (UTC)          : ', TIME_STR
      print, 'The signal sent at (UTC)    : ', receive_utc
      print, 'Time for propagation (secs) : ', ltime
   
   IDL outputs for the transmission '->' case:
   
      Transmission at (UTC)       : July 4, 2004
      The signal arrived at (UTC) : 2004 JUL 04 00:48:38.717
      Time for propagation (secs) :        2918.7170
   
   IDL outputs for the reception '<-' case:
   
      Reception at (UTC)          : July 4, 2004
      The signal sent at (UTC)    : 2004 JUL 03 23:11:21.248
      Time for propagation (secs) :        2918.7524

Particulars


   None.

Required Reading


   ICY.REQ

Version


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

Index_Entries

 
   Compute uplink and downlink light time 
 



Wed Apr  5 17:58:02 2017