DESIGNATE STELLAR

Syntax

Fixed

   DESIGNATE @int(1001:10099)
      CENTER @body
      REFERENCE STELLAR
      (0:1){ FRAME @name }
      (2:3){ DECLINATION      @number
           | RIGHT ASCENSION  @number
           | @options
           | RANGE            @number }
      (0:3){ FROM  @calendar
           | TO    @calendar
           | EPOCH @calendar }

Moving

   DESIGNATE @int(1001:10099)
      CENTER @body
      REFERENCE STELLAR
      (0:1){ FRAME @name }
      (2:3){ DECLINATION     (1:2)@number
           | RIGHT ASCENSION (1:2)@number
           | @options
           | RANGE           (1:2)@number }
      EPOCH @calendar
      (0:2){ FROM @calendar
           | TO   @calendar }

Description

When creating a designated object in this system, you must specify the right ascension and declination of the object. The range to the object is optional, and defaults to 10,000,000,000,000,000 kilometers (approximately 1000 light years). You may specify the right ascension and declination relative to any reference frame supported by the SPICE system. While not required, this command has been designed under the assumption that you will choose an inertial reference frame if you specify a reference frame.

Definition

If not supplied explicitly, the stellar reference frame is identical to the IAU standard J2000 inertial reference frame.

Examples

If the proper motion of a stellar object is negligible, constant values for right ascension and declination are normally supplied,

   DEFINE RIGEL 1001;
 
   DESIGNATE RIGEL
        CENTER 0
        REFERENCE STELLAR
        RIGHT ASCENSION  78.03319881 DEGREES
        DECLINATION     - 8.25794522 DEGREES ;

On the other hand,

   DEFINE SIRIUS 1002;
 
   DESIGNATE SIRIUS
        CENTER 0
        REFERENCE STELLAR
        RIGHT ASCENSION  100.7362138     DEGREES
                          -0.00015794559 DEGREES/YEAR
        DECLINATION      -16.6462019     DEGREES
                          -0.00033649029 DEGREES/YEAR
        EPOCH 1 JAN 1900 ;

Note that in these examples, the origin of the stellar frame is placed at the solar system barycenter (CENTER 0). By default, the range to the designated object is 1000 light years, so moving the origin to the Earth (CENTER 399) would generate a parallax of about 0.003 arc seconds.