; docformat = 'rst'
;+
; This function gets the spacecraft position at a certain time.
; 
; :Examples:
;   position = scpos(gps_time, ecef=ecef, dr=dr)
;-
;+
; :Params:
;   Time : in, required, type=double
;     Time in question in GPS microseconds. Must be scalar.
;     
; :Keywords:
;   ecef : in, optional, type=boolean
;     Set to get the result in ECEF coordinates, defaults to ECI.
;   dr : out, optional, type=double
;     1 sigma of uncertainty in each coordinate, in km.
;     
; :Returns:
;   Returns the position vector of the spcecraft, in km.
;-
function scpos,Time,ecef=ecef,dr=dr, native_toggle=toggle

  if ~real_numeric_type(Time) then begin
    doc_library, 'scpos'
    return, -1
  endif

  JD=usec2jd(Time)
  
  if keyword_set(toggle) then $
    spacecraft_pv,!SC_NUMBER,JD,pv,pv_uncertainty=dpv,tle_path=!tle_path,status=status $
  ; Using Chris Jeppesen's IDL replacement of Barry Knapp's astron library
  else $
    spacecraft_pv_msgp4,!SC_NUMBER, jd, pv,pv_uncertainty=dpv,status=status, tle_path=!tle_path
    
  if status gt 0 then message,"spacecraft_pv didn't work... returned with status: " + string(status, format='(i0)')
  r=pv[0:2]
  dr=dpv[0:2]
  if keyword_set(ecef) then begin
    dr=transformgrid(eci_to_ecef(time),dr)
    return,transformgrid(eci_to_ecef(time),r)
  end else begin
    return,r;
  end

end