▁Space ▁Network . ▁ ▁Method s ▁ ▁Or bit ▁determ ination ▁must ▁take ▁into ▁account ▁that ▁the ▁apparent ▁cel est ial ▁motion ▁of ▁the ▁body ▁is ▁influenced ▁by ▁the ▁observer ' s ▁own ▁motion . ▁ ▁For ▁instance , ▁an ▁observer ▁on ▁Earth ▁tracking ▁an ▁astero id ▁must ▁take ▁into ▁account ▁the ▁motion ▁of ▁the ▁Earth ▁around ▁the ▁Sun , ▁the ▁rotation ▁of ▁the ▁Earth , ▁and ▁the ▁observer ' s ▁local ▁latitude ▁and ▁longitude , ▁as ▁these ▁affect ▁the ▁apparent ▁position ▁of ▁the ▁body . ▁ ▁A ▁key ▁observation ▁is ▁that ▁( to ▁a ▁close ▁approximation ) ▁all ▁objects ▁move ▁in ▁or bits ▁that ▁are ▁con ic ▁sections , ▁with ▁the ▁attract ing ▁body ▁( such ▁as ▁the ▁Sun ▁or ▁the ▁Earth ) ▁in ▁the ▁prime ▁focus , ▁and ▁that ▁the ▁orbit ▁lies ▁in ▁a ▁fixed ▁plane . ▁V ectors ▁drawn ▁from ▁the ▁attract ing ▁body ▁to ▁the ▁body ▁at ▁different ▁points ▁in ▁time ▁will ▁all ▁lie ▁in ▁the ▁orb ital ▁plane . ▁ ▁If ▁the ▁position ▁and ▁velocity ▁relative ▁to ▁the ▁observer ▁are ▁available ▁( as ▁is ▁the ▁case ▁with ▁rad ar ▁observations ), ▁these ▁observ ational ▁data ▁can ▁be ▁adjust ed ▁by ▁the ▁known ▁position ▁and ▁velocity ▁of ▁the ▁observer ▁relative ▁to ▁the ▁attract ing ▁body ▁at ▁the ▁times ▁of ▁observation . ▁This ▁yields ▁the ▁position ▁and ▁velocity ▁with ▁respect ▁to ▁the ▁attract ing ▁body . ▁If ▁two ▁such ▁observations ▁are ▁available , ▁along ▁with ▁the ▁time ▁difference ▁between ▁them , ▁the ▁orbit ▁can ▁be ▁determined ▁using ▁Lam bert '