Within segments, {HEAD ~ terrestrial interfaces} 143 exist between {TAIL ~ ground stations} 119 and the control center 135 
Within segments , { HEAD ~ terrestrial interfaces } 143 exist between { TAIL ~ ground stations } 119 and the control center 135
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH