NAME: platlon PURPOSE: (one line only) Compute viewing and illumination geometry for Pluto DESCRIPTION: CATEGORY: Astronomy CALLING SEQUENCE: platlon,jd,elat,elon,slat,slon,polang,phang,earth,sun,elong INPUTS: jd - Julian date for the geometry calculation (double precision, scalar or vector) OPTIONAL INPUT PARAMETERS: KEYWORD INPUT PARAMETERS: ORBIT - String with name of Charon orbit solution to use, the default is to use the most recent orbit. This default can change as new orbits are added. Currently supported: '2012' - From AJ, 144, 15 (2012) '2008' - From AJ, 135, 777 (2008) '1997' - From Icarus, 125, 245 (1997) EPH - Optionally, you can provide the ephemeris information. The default is to compute geocentric circumstants at the input time. This information should be a vector as would be returned from a code=22 request: [ra,dec,xobj,yobj,zobj,xsun,ysun,zsun]. The positions should all be in units of AU. The ra,dec should be in radians. The positions are relative to the observer. OUTPUTS: elat - Latitude of the sub-earth point [radians] elon - East longitude of the sub-earth point [radians] slat - Latitude of the sub-solar point [radians] slon - East longitude of the sub-solar point [radians] polang - Position angle of Pluto's north pole, measured eastward from north [radians] phang - Solar phase angle (Sun-Pluto-Earth angle) [radians] earth - Geocentric distance [AU] sun - Heliocentric distance [AU] elong - Solar elongation [radians] KEYWORD OUTPUT PARAMETERS: COMMON BLOCKS: SIDE EFFECTS: This is a slow routine for vector calls. Some of the supporting routines cannot handle vectorized input so each output value is computed in an explicit loop. RESTRICTIONS: PROCEDURE: MODIFICATION HISTORY: 2011/12/30 - Written by Marc W. Buie, Southwest Research Institute code based on fortran routines written by David Tholen 2012/06/04 - MWB, fixed typo on 2012 orbit. 2013/06/06 - MWB, added elong output. 2015/05/25 - MWB, added EPH input keyword.