r. goldstein     april, 1976
interpolations are now done by calls to mntrp,emtrp,
pltrp, and sbtrp.
polynomial extrapolations are now done by dguess

sept. 1976...derivative of sbdldp (sbbg)
this routine handles radar to a natural satellite of a
planet other than the earth or to a spacecraft treated as
a natural satellite
required flags:
ncodf=1, nspot=0, klanb.gt.0
oct. 1976...large sections of code replaced by calls to
subroutines propco and radrel
may 1978... converted to implicit real*8  and unit vector code
made compatible with rest of 'new code'

xslcns(1-6,j) = position and velocity (not used) of the center
of mass of the solar system relative to the sun
at receive time (j=1), reflection time (j=2)
and send time (j=3)