NAME:
  rhosc
 PURPOSE:   (one line only)
  Compute rhosinp,rhocosp from observatory lat,alt
 DESCRIPTION:
  This is from a formalism used by Ted Bowell, the Minor Planet Center,
    Larry Wasserman and probably others to compute topcentric X, Y, Z.
 CATEGORY:
  Astronomy
 CALLING SEQUENCE:
  rhosc,lat,alt,rhosinp,rhocosp
 INPUTS:
  lat - observatory latitude in WGS84 datum [radians]        (scalar or vector)
  alt - observatory altitude above reference datum [meters]  (match lat)
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
 OUTPUTS:
  rhosinp - units and values as tabulated by MPC for observatories
  rhocosp - units and values as tabulated by MPC for observatories
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
  No protections on input for speed of computation
 PROCEDURE:
 MODIFICATION HISTORY:
  Written by Marc W. Buie, Southwest Research Institute, 2019/10/21