In other words, the position and velocity of the center of gravity at the start point may be the position and velocity of the center of gravity at {HEAD ~ the current time} as measured by {TAIL ~ sensors} 
as measured by
In other words , the position and velocity of the center of gravity at the start point may be the position and velocity of the center of gravity at { HEAD ~ the current time } as measured by { TAIL ~ sensors }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL