Delta II was an expendable launch system, originally designed and built by McDonnell Douglas. Delta II was part of the Delta rocket family and entered service in 1989. Delta II vehicles included the Delta 6000, and the two later Delta 7000 variants ("Light" and "Heavy"). The rocket flew its final mission ICESat-2 on 15 September 2018, earning the launch vehicle a streak of 100 successful missions in a row, with the last failure being GPS IIR-1 in 1997.
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The objective of the ACE (Advanced Composition Explorer) is to collect observations of particles of solar, interplanetary, interstellar, and galactic origins, spanning the energy range from that of keV.solar wind ions to galactic cosmic ray nuclei up to 600 MeV/nucleon.
Heliocentric L1