m.e.ash    april 1973    subroutine chncne
Transform orbital elements to mean equatorial frame of epoch if
necessary.  Change initial orbital elements of type 'incnd' to type
'icnd' (possibly by way of Cartesian).

NPLNT    = planet number
NCENTR   = central body number
LCND = 0 nothing
LCND = 1 input adbarv cond(4) is velocity and not difference between
velocity and circular orbit velocity  (units au & au/day)
change to difference velocity

JTYPE specifies the coordinate frame of input elements - to be
converted to mean equinox and equator of reference epoch.
JTYPE = 0 mean equinox and equator of input date
= 1 true equinox and equator of input date
= 2 mean equinox and ecliptic of input date
= 4 mean lunar plane of date (x axis along intersection of mean
lunar and ecliptic planes of date)
= 5 mean equinox and true equator of input date

INCND=-1 input initial conditions are cartesian
= 0 input initial conditions are elliptic elements
= 1 input initial conditions are elliptic with angle sums
= 2 input initial conditions are adbarv
ICND =   same logic as incnd: specifies output initial conditions
Both INCND and ICND are ignored for rotation i.c.'s.

transform rotation i.c.'s (Euler angles)
psi   = cond(1)
theta = cond(2)
phi   = cond(3)
dpsi  = cond(4)
dth   = cond(5)
dphi  = cond(6)