▁and ▁objects ▁reaching ▁orbit : ▁sat ell ites , ▁protect ive ▁shield s ▁and ▁upper - st ages ▁of ▁launch ▁vehicles . ▁NASA ▁later ▁published ▁modified ▁versions ▁of ▁the ▁database ▁in ▁two - line ▁element ▁set , ▁and ▁beginning ▁in ▁the ▁early ▁ 1 9 8 0 s ▁the ▁C eles T rak ▁bullet in ▁board ▁system ▁re - pub lished ▁them . ▁ ▁The ▁track ers ▁who ▁fed ▁the ▁database ▁were ▁aware ▁of ▁other ▁objects ▁in ▁orbit , ▁many ▁of ▁which ▁were ▁the ▁result ▁of ▁in - or bit ▁explos ions . ▁Some ▁were ▁deliber ately ▁caused ▁during ▁the ▁ 1 9 6 0 s ▁anti - s at ellite ▁weapon ▁( AS AT ) ▁testing , ▁and ▁others ▁were ▁the ▁result ▁of ▁ro cket ▁stages ▁blow ing ▁up ▁in ▁orbit ▁as ▁le f to ver ▁prop ell ant ▁expanded ▁and ▁ru pt ured ▁their ▁t anks . ▁To ▁improve ▁tracking , ▁N OR AD ▁employee ▁John ▁G abb ard ▁kept ▁a ▁separate ▁database . ▁Stud ying ▁the ▁explos ions , ▁G abb ard ▁developed ▁a ▁technique ▁for ▁predict ing ▁the ▁orb ital ▁paths ▁of ▁their ▁products , ▁and ▁G abb ard ▁diag rams ▁( or ▁plots ) ▁are ▁now ▁widely ▁used . ▁These ▁studies ▁were ▁used ▁to ▁improve ▁the ▁model ing ▁of ▁orb ital ▁evolution ▁and ▁decay . ▁ ▁When ▁the ▁N OR AD ▁database ▁became ▁public ly ▁available ▁during ▁the ▁ 1 9 7 0 s , ▁techniques ▁developed ▁for ▁the ▁astero id - b elt ▁were ▁applied ▁to ▁the