subroutine PLCMS - J.F.Chandler - 1977 December 1
Set up for planet center of mass correction to system center
or for solar-system barycenter offset with "star" observations.
Called from CMPAR3.  Subsequently, PLCMC is called from PLTRP
or from SOTRP.
JCT(55) is a packed bits indicator for the planet center of mass
computations
JCT(55)=0  no center of mass corrections
1 bit = 1: get satellite coordinates from interpolation if possible
2 bit = 1: get satellite coordinates from elliptic if necessary
4 bit = 1: use only satellites that are on s-body tape
8 bit = 1: for elliptic method, obtain elements from s-body tape
(if possible).  Warning: this option should normally
be set because the initial conditions in /EMPCND/ are
likely to have been overwritten from tape anyway and
may not match the epoch in CON1(1).
16 bit = 1: allow calculation of barycenter of planet+observed
satellite instead of planet
32 bit = 1: use precessing elliptic orbit instead of stationary

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Get total mass of solar system for the purposes of calculating
barycenter position.  Include the conglomerate of perturbing
asteroids from the external file, if any.  Note: if the
observations are of a "star", also include any individual
asteroids specified for this run.

Mascnt = Prmter(50)
do i = 45,46
Mascnt = Mascnt + Prmter(i)
end do