▁ 1 5 , ▁ 3 0 ▁and ▁ 6 0 ▁i ps ▁from ▁N ems ▁Clark ▁ 1 4 3 2 ▁receiver . ▁ ▁The ▁ac quisition ▁director , ▁which ▁compr ised ▁the ▁R AD AP - C ▁Computer ▁together ▁with ▁associated ▁input ▁and ▁output ▁devices , ▁served ▁as ▁an ▁ac quisition ▁aid , ▁as ▁means ▁for ▁checkout ▁and ▁cal ibration ▁of ▁associated ▁electronic ▁equipment , ▁and , ▁in ▁the ▁TR AN S IT ▁mode , ▁as ▁an ▁aid ▁to ▁the ▁navigation ▁of ▁the ▁D AMP ▁ship . ▁ ▁The ▁Trans it ▁system ▁of ▁navigation ▁consisted ▁of ▁the ▁Trans it ▁satellite , ▁a ▁world wide ▁network ▁of ▁tracking ▁stations ▁to ▁observe ▁and ▁determine ▁the ▁orb ital ▁elements ▁of ▁the ▁satellite , ▁and ▁suitable ▁rece ivers ▁and ▁Aut on et ics ▁Re comp ▁computers ▁ab o ard ▁the ▁navig ating ▁vessel ▁to ▁receive ▁the ▁stable ▁frequency ▁radio ▁signals ▁broadcast ▁by ▁the ▁satellite , ▁to ▁observe ▁the ▁Do pp ler ▁frequency ▁shift , ▁and ▁from ▁this ▁information , ▁plus ▁the ▁approximate ▁location ▁of ▁the ▁vessel , ▁compute ▁to ▁within ▁one ▁mile ▁( 1 . 6   km ) ▁the ▁exact ▁location ▁of ▁the ▁vessel . ▁ ▁The ▁quart z ▁Reference ▁O sc ill ator ▁was ▁the ▁heart ▁of ▁the ▁ship board ▁system , ▁and ▁operated ▁at ▁ 1   M Hz ▁and ▁ 1 0 0 ▁K C ▁with ▁a ▁short ▁term ▁stability ▁of ▁ 5 ▁parts ▁in ▁ 1 0 ▁to ▁the ▁t enth ▁aver aged ▁over ▁a ▁one - second ▁interval ,