The Mars Surveyor '98 program is comprised of two spacecraft launched separately, the MCO (Mars Climate Orbiter, formerly the Mars Surveyor '98 Orbiter) and the MPL (Mars Polar Lander, formerly the Mars Surveyor '98 Lander). The two missions were to study the Martian weather, climate, and water and carbon dioxide budget, in order to understand the reservoirs, behavior, and atmospheric role of volatiles and to search for evidence of long-term and episodic climate changes. The Mars Climate Orbiter was destroyed when a navigation error caused it to miss its target altitude at Mars by 80 to 90 km, instead entering the Martian atmosphere at an altitude of 57 km during the orbit insertion maneuver.
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.