DESIGNATE GREAT CIRCLE

Syntax

   DESIGNATE @int(1001:1099)
      CENTER @body
      REFERENCE GREAT CIRCLE
      (0:1){ FRAME @name }
      (6:7){ FIRST  EPOCH @calendar
           | FIRST  RIGHT ASCENSION @number
           | FIRST  DECLINATION @number
           | SECOND EPOCH @calendar
           | SECOND RIGHT ASCENSION @number
           | SECOND DECLINATION @number
           | @options
           | RANGE @number(1:) }

Description

When creating a designated object in this system, you must specify the position (R.A. and Dec.) of the object as observed from the center of the reference frame at two distinct epochs. The reference frame and range are optional. Their default values are J2000 and 1000 astronomical units respectively.

Definition

The position and velocity of the designated object are defined by two observations (`great circle elements'), each consisting of an apparent position (right ascension and declination) and an epoch.

Examples

In the following example, the DESIGNATE GREAT CIRCLE command is used to create an a body orbiting earth whose position is roughly approximated by uniform motion along a great circle on the celestial sphere.

   DESIGNATE 1001
   CENTER 399
   REFERENCE GREAT CIRCLE
   FIRST  RIGHT ASCENSION 114.219 DEGREES
   FIRST  DECLINATION      21.927 DEGREES
   FIRST  EPOCH           22 APR 1991 21:11:34
   SECOND RIGHT ASCENSION 117.627 DEGREES
   SECOND DECLINATION      19.536 DEGREES
   SECOND EPOCH           26 APR 1991 20:31:52;