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# '''Guided entry:''' The rover is folded up within an [[aeroshell]] that protects it during the travel through space and during the [[atmospheric entry]] at Mars. Ten minutes before atmospheric entry the aeroshell separates from the cruise stage that provided power, communications and propulsion during the long flight to Mars. One minute after separation from the cruise stage thrusters on the aeroshell fire to cancel out the spacecraft's 2-rpm rotation and achieve an orientation with the heat shield facing Mars in preparation for [[Atmospheric entry]].<ref name="spaceflightnow.com_1">{{cite news | title = Curiosity relies on untried 'sky crane' for Mars descent | date = July 31, 2012 | publisher = Spaceflight Now | url = http://spaceflightnow.com/mars/msl/120731skycrane/ | accessdate =August 1, 2012}}</ref> The heat shield is made of [[phenolic impregnated carbon ablator]]. The {{convert|4.5|m|abbr=on}} diameter heat shield, which is the largest heat shield ever flown in space,<ref>NASA, [http://www.nasa.gov/mission_pages/msl/msl-20090710.html Large Heat Shield for Mars Science Laboratory], July 10, 2009 (Retrieved March 26, 2010)</ref> reduces the velocity of the spacecraft by [[Atmospheric entry#Ablative|ablation against the Martian atmosphere]], from the atmospheric interface velocity of approximately {{convert|5.8|km/s|abbr=on}} down to approximately {{convert|470|m/s|abbr=on}}, where parachute deployment is possible about four minutes later. One minute and 15 seconds after entry the heat shield will experience peak temperatures of up to {{convert|3800|F|C|abbr=on}} as atmospheric pressure converts kinetic energy into heat. Ten seconds after peak heating, that deceleration will max out at 15 [[g-force|g]].<ref name="spaceflightnow.com_1"/> Much of the reduction of the landing precision error is accomplished by an entry guidance algorithm, derived from the algorithm used for guidance of the [[Apollo Command Module]]s returning to Earth in the [[Apollo space program]].<ref name="spaceflightnow.com_1"/> This guidance uses the lifting force experienced by the aeroshell to "fly out" any detected error in range and thereby arrive at the targeted landing site. In order for the aeroshell to have lift, its center of mass is offset from the axial centerline that results in an off-center trim angle in atmospheric flight. This is accomplished by a series of ejectable ballast masses consisting of two 165 pound (75 kg) [[tungsten]] weights that are jettisoned minutes before atmospheric entry.<ref name="spaceflightnow.com_1"/> The lift vector is controlled by four sets of two [[Reaction Control System]] (RCS) thrusters that produce approximately {{convert|500|N|lbf|abbr=on}} of thrust per pair. This ability to change the pointing of the direction of lift allows the spacecraft to react to the ambient environment, and steer toward the landing zone. Prior to parachute deployment the entry vehicle must eject more ballast mass consisting of six {{convert|55|lbs|kg|abbr=on}} tungsten weights such that the [[center of gravity]] offset is removed.<ref name="spaceflightnow.com_1"/> [[File:20090422MSLtestparachute.jpg|thumb|100px|MSL's parachute is {{convert|51|ft|abbr=on}} in diameter.]]
# '''Parachute descent:''' When the entry phase is complete and the capsule has slowed to Mach 1.7 or {{convert|578|m/s|abbr=on}} and at about {{convert|10|km|mi|abbr=on}} the supersonic [[parachute]] will deploy,<ref name="EntryDescentLanding"/><ref name="ParaTest">{{cite web |url=http://marsprogram.jpl.nasa.gov/msl/news/index.cfm?FuseAction=ShowNews&NewsID=90 |title=Mars Science Laboratory Parachute Qualification Testing |publisher=NASA/JPL |accessdate=April 15, 2009 }}</ref> as was done by previous landers such as [[Viking program|Viking]], [[Mars Pathfinder]] and the [[Mars Exploration Rover]]s. The parachute has 80 suspension lines, is over {{convert|50|m|ft|abbr=on}} long, and is about {{convert|16|m|ft|abbr=on}} in diameter.<ref name="ParaTest"/> The parachute is capable of being deployed at Mach 2.2 and can generate up to {{convert|289|kN|lbf|abbr=on}} of [[drag force]] in the Martian atmosphere.<ref name="ParaTest"/> After the parachute has deployed, the heat shield will separate and fall away. A camera beneath the rover will acquire about 5 frames per second (with resolution of 1600×1200 pixels) below {{convert|3.7|km|mi|abbr=on}} during a period of about 2 minutes until the rover sensors confirms successful landing.<ref>{{cite web |url=http://msl-scicorner.jpl.nasa.gov/Instruments/MARDI/ |title=Mars Descent Imager (MARDI) |publisher=NASA/JPL |accessdate=December 2, 2009 }}</ref>
# '''Powered descent:''' Following the parachute braking, at about {{convert|1.8|km|mi|abbr=on}} altitude, still travelling at about {{convert|100|m/s|mph|abbr=on}}, the rover and descent stage drop out of the aeroshell.<ref name="EntryDescentLanding"/> The descent stage is a platform above the rover with 8 variable thrust mono propellant [[hydrazine]] rocket thrusters on arms extending around this platform to slow the descent. Each rocket thruster, called a Mars Lander Engine (MLE),<ref>{{cite web|title=Mars Science Laboratory: Entry, Descent, and Landing System Performance|url=http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090007730_2009006430.pdf|publisher=[[NASA]]|date=March 2006|page=7}}</ref> produces {{convert|400|N|lbf|abbr=on}} to {{convert|3,100|N|lbf|abbr=on}} of thrust and were derived from those used on the [[Viking program|Viking landers]].<ref name="aerojetMSLengines">{{cite web |url=http://aerojet.com/news2.php?action=fullnews&id=135 |title=Aerojet Ships Propulsion for Mars Science Laboratory |publisher=Aerojet |accessdate=December 18, 2010 }}</ref> Meanwhile, the rover will transform from its stowed flight configuration to a landing configuration while being lowered beneath the descent stage by the "sky crane" system. [[File:593484main pia14839 full Curiosity's Sky Crane Maneuver, Artist's Concept.jpg|thumb|
# '''Sky crane:''' For several reasons a different landing system was chosen for MSL compared to previous Mars landers and rovers. ''Curiosity'' was considered too heavy to use the airbag landing system as used on the [[Mars Pathfinder]] and [[Mars Exploration Rover|Mars Exploration]]. A legged lander approach would have caused several design problems.<ref name="spaceflightnow.com_1"/> It would have needed to have engines high enough above the ground when landing to not form a dust cloud that could damage the rover's instruments. This would have required long landing legs that would need to have significant width to keep the center of gravity low. A legged Lander would have also required ramps so the rover could drive down to the surface, which would incurred extra risk to the mission on the chance rocks or tilt would prevent ''Curiosity'' from being able to drive off the lander successfully. Faced with these challenges, the MSL engineers came up with a novel alternative solution: the sky crane.<ref name="spaceflightnow.com_1"/> The sky crane system will lower the rover with a {{convert|25|foot|m|abbr=on}}<ref name="spaceflightnow.com_1"/> tether to a soft landing—wheels down—on the surface of Mars.<ref name="EntryDescentLanding"/><ref>[http://blogs.scientificamerican.com/guest-blog/2011/11/28/sky-crane-how-to-land-curiosity-on-the-surface-of-mars/ Sky Crane – how to land Curiosity on the surface of Mars] by Amal Shira Teitel.</ref><ref> {{cite news | first = Mike Snider | title = Mars rover lands on Xbox Live | date = July 17, 2012 | url = http://www.usatoday.com/tech/science/space/story/2012-07-16/nasa-mars-rover-game/56253212/1 | work = USA Today | accessdate =July 27, 2012}}</ref> This system consists of 3 bridles lowering the rover and an umbilical cable carrying electrical signals between the descent stage and rover. As the support and data cables unreel, the rover's six motorized wheels will snap into position. At roughly {{convert|7.5|m|abbr=on}} below the descent stage the sky crane system slows to a halt and the rover touches down. After the rover touches down it waits 2 seconds to confirm that it is on solid ground by detecting the weight on the wheels and fires several [[pyrotechnic fastener|pyros]] (small explosive devices) activating cable cutters on the bridle and umbilical cords to free itself from the descent stage. The descent stage flies away to a crash landing at least {{convert|500|foot|m|abbr=on}} away, and possibly twice that far. The sky crane powered descent landing system had never been used in missions before.<ref>[http://www.youtube.com/watch?v=noy8o0lN1fE&feature=related Sky crane concept video]</ref>
<gallery widths="300" heights="200" title="Mars Science Laboratory (Curiosity)'s landing system">
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