Delta II

Delta II was an expendable launch system designed and built by McDonnell Douglas, sometimes known as the Thorad Delta 1. Delta II was part of the Delta rocket family, derived from the Delta 3000, and entered service in 1989. There were two main variants, the Delta 6000 and Delta 7000, with the latter also having "Light" and "Heavy" subvariants. During its career, Delta II flew several payloads, including 24 Global Positioning System (GPS) Block II satellites, several dozen NASA payloads, and 60 Iridium communication satellites. The rocket flew its final mission, ICESat-2, on 15 September 2018, earning a streak of 100 consecutive successful missions, with the last failure being GPS IIR-1 in 1997. In the late 1990s, Delta II was developed into the unsuccessful Delta III, which was in turn developed into the more capable and successful Delta IV, though the latter shares little heritage with the original Thor and Delta rockets.