anchor.diff:  		 :center :ssb
   		 :ref :eclipj2000
   		 :abcorr :none
  -		 :mu (with-kernel (ephemeris-path "gm_de431.tpc")
  +		 :mu (with-ephemeris "gm_de431.tpc"
   		       (body-vrd :sun :gm 1))))
   
   (defparameter *sun*
  
positive.code: 		 :center :ssb
  		 :ref :eclipj2000
  		 :abcorr :none
  		 :mu (with-kernel (ephemeris-path "gm_de431.tpc")
  		       (body-vrd :sun :gm 1))))
  
  ;;; Cartesian
  
negative.code: 		 :center :ssb
  		 :ref :eclipj2000
  		 :abcorr :none
  		 :mu (with-ephemeris "gm_de431.tpc"
  		       (body-vrd :sun :gm 1))
  		 :ls 1361.3477d0 ; solar luminosity in W/m^2 (same with km)
  		 :ls-du *au*))
  