▁basic ▁methods ▁were ▁discovered ▁in ▁the ▁ 1 7 th ▁century ▁and ▁have ▁been ▁continu ously ▁ref ined . ▁ ▁Observ ations ▁are ▁the ▁raw ▁data ▁fed ▁into ▁orbit ▁determ ination ▁algorithms . ▁ ▁Observ ations ▁made ▁by ▁a ▁ground - based ▁observer ▁typically ▁consist ▁of ▁time - tag ged ▁az im uth , ▁elev ation , ▁range , ▁and / or ▁range - rate ▁values . ▁ ▁T eles cop es ▁or ▁rad ar ▁appar atus ▁are ▁used , ▁because ▁n aked - ey e ▁observations ▁are ▁in ade qu ate ▁for ▁precise ▁orbit ▁determ ination . ▁ ▁With ▁more ▁or ▁better ▁observations , ▁the ▁accuracy ▁of ▁the ▁orbit ▁determ ination ▁process ▁also ▁impro ves , ▁and ▁fewer ▁" false ▁al ar ms " ▁result . ▁ ▁After ▁or bits ▁are ▁determined , ▁mathematical ▁propag ation ▁techniques ▁can ▁be ▁used ▁to ▁predict ▁the ▁future ▁positions ▁of ▁orbit ing ▁objects . ▁ ▁As ▁time ▁goes ▁by , ▁the ▁actual ▁path ▁of ▁an ▁orbit ing ▁object ▁tends ▁to ▁diver ge ▁from ▁the ▁predicted ▁path ▁( es pecially ▁if ▁the ▁object ▁is ▁subject ▁to ▁difficult - to - predict ▁perturb ations ▁such ▁as ▁atmos pher ic ▁drag ), ▁and ▁a ▁new ▁orbit ▁determ ination ▁using ▁new ▁observations ▁serves ▁to ▁re - cal ibr ate ▁knowledge ▁of ▁the ▁orbit . ▁ ▁Sat ellite ▁tracking ▁is ▁another ▁major ▁application . ▁For ▁the ▁US ▁and ▁partner ▁countries , ▁to ▁the ▁extent ▁that ▁optical ▁and ▁rad ar ▁resources ▁allow , ▁the ▁J oint ▁Space ▁Oper ations ▁Center ▁g athers