Editing Mars Science Laboratory (section)

=== EDL spacecraft system ===
{{See also|Timeline of Mars Science Laboratory}}
Landing a large mass on Mars is particularly challenging as the [[Atmosphere of Mars|atmosphere]] is too thin for [[parachute]]s and [[aerobraking]] alone to be effective,<ref name="landing-approach"/> while remaining thick enough to create stability and impingement problems when decelerating with [[retrorocket]]s.<ref name="landing-approach"/> Although some previous missions have used [[Airbag#Aerospace and military applications|airbags]] to cushion the shock of landing, the ''Curiosity'' rover is too heavy for this to be an option. Instead, ''Curiosity'' was set down on the Martian surface using a new high-accuracy entry, descent, and landing (EDL) system that was part of the MSL spacecraft descent stage. The mass of this EDL system, including parachute, sky crane, fuel and [[aeroshell]], is {{convert|2401|kg|abbr=on}}.<ref>{{cite web |url=https://mars.nasa.gov/msl/mission/spacecraft/ |title=Mission: Spacecraft |publisher=NASA |access-date=June 12, 2018}}</ref> The novel EDL system placed ''Curiosity'' within a {{convert|20|by|7|km|abbr=on}} landing ellipse,<ref name="ellipse"/> in contrast to the {{convert|150|by|20|km|abbr=on}} landing ellipse of the landing systems used by the Mars Exploration Rovers.<ref name="Mission Timeline: Entry, Descent, and Landing"/>

The entry-descent-landing (EDL) system differs from those used for other missions in that it does not require an interactive, ground-generated mission plan. During the entire landing phase, the vehicle acts autonomously, based on pre-loaded software and parameters.<ref name="DESCANSO"/> The EDL system was based on a [[Viking program|Viking-derived]] aeroshell structure and propulsion system for a precision guided entry and soft landing, in contrasts with the airbag landings that were used in the mid-1990s by the [[Mars Pathfinder]] and [[Mars Exploration Rover]] missions. The spacecraft employed several systems in a precise order, with the entry, descent and landing sequence broken down into four parts<ref name="Mission Timeline: Entry, Descent, and Landing"/><ref name="Mars Science Laboratory Entry, Descent, and Landing Triggers"/>—described below as the spaceflight events unfolded on August 6, 2012.