Editing Proton (satellite program) (section)

===Proton 4===

After the end of the run of UR-500 test launches, the rocket (now designated Proton) and its successors were largely employed in the launch of the [[Zond program|Zond]] lunar spacecraft. However, on 16 November 1968 11:40&nbsp;UTC, the final and much larger Proton 4 was launched into orbit via [[Proton-K]] rocket from [[Baikonur Cosmodrome Site 81/24]] to continue the search for the quark and supplement the earlier Proton satellites' cosmic ray measurements.<ref name=sov/> This final Proton reentered Earth's atmosphere on 24 July 1969.<ref name=cat/>