Designing Curiosity's Perfect Landing on Mars
The Curiosity rover's precision touchdown on Mars was calculated with help from high-performance computers at NASA's Jet Propulsion Lab.
She's cute, she packs a laser, and with 1.2 million Twitter followers, NASA's Mars Science Laboratory Curiosity rover has captured the world's imagination. When Curiosity landed on August 5, 2012, NASA websites streaming video of the event served eight million hits in less than a minute. Now, as Curiosity roams Gale Crater conducting field experiments and relays images back to Earth, we are all going along for the ride.
Every Mars landing requires years of preparation and builds on technology developed for previous missions. When the Mars Exploration rovers Spirit and Opportunity successfully bounced to the Martian surface in 2004, they advanced the methods used by the Mars Pathfinder mission seven years before. However, at 2,000-pounds, it was clear that Curiosity was too heavy to rely on the airbags used by the earlier rovers, and that the precision landing crucial to the scientific aims of the mission would depend on the development of an innovative guided entry system.
Before the most comprehensive robotic geologist ever developed could begin her scientific mission on the Red Planet, she first had to get there.
"NASA's supercomputing resources dramatically reduced the risk involved in landing at Gale Crater," said Timofey Ovcharenko, system administrator at NASA's Jet Propulsion Laboratory (JPL). "This gave us confidence in the design and helped to bring into reality the extraordinary landing sequence that some initially thought was impossible."
To steer itself through the Martian atmosphere, the spacecraft needed to use a series of S-curve maneuvers similar to those used by space shuttle pilots. Like the astronauts, Curiosity's computer had to make fast, critical decisions based on the conditions it encountered during entry, descent, and landing (EDL). To ensure that Curiosity would be ready for anything, researchers ran millions of simulated landing scenarios on two high-performance computing clusters, named Nebula and Galaxy, at JPL.
Working with JPL's supercomputing team for 16 months–beginning a full seven months before launch–Curiosity's EDL team created a fully customized supercomputing environment capable of handling high-fidelity simulations and computing the probability of each outcome. Based on these results, engineers programmed Curiosity's software to navigate appropriately as it decelerated from 13,000 mph on entry to a complete stop on the surface of Mars in just seven minutes.
The highly complex landing simulations performed on the Nebula and Galaxy clusters had to account for the following new capabilities:
- Guided entry and powered descent – Small rockets enabled the spacecraft to steer itself through the Martian atmosphere, and to avoid hazards such as large rocks on touchdown. Retrorockets stabilized the vehicle, protecting it from sudden wind gusts.
- Bigger parachute – Curiosity's parachute, deployed when the spacecraft had slowed to about 900 mph at an altitude of approximately 12 kilometers, was 10% larger than previous versions used for Spirit and Opportunity and was designed to withstand 65,000 pounds of force.
- Sky crane – As rocket thrusters reduced velocity to nearly zero, the rover was released from the descent stage and the sky crane lowered Curiosity to the planet's surface.
After a nine-month journey, Curiosity landed with her wheels down, ready to investigate the possibility that Mars might ever have supported microbial life. Already, scientists are elated with the discovery of an ancient streambed, new data showing specific mineral content of Martian soil, clues to changes in Mars' atmosphere, and other exciting revelations provided by Curiosity's ten scientific instruments.
"NASA always builds upon its past experience," said Ovcharenko. "Curiosity's landing is by far the most complex and challenging landing that the agency has undertaken, and future missions will, in turn, use this experience to produce spectacular results."
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Contact Information:
Timofey Ovcharenko
System Administrator, OCIO Supercomputing Group, NASA Jet Propulsion Laboratory/California Institute of Technology
timofey.ovcharenko@jpl.nasa.gov
(818) 393-5181
Contact Information:
John Grotzinger
Project Scientist, Mars Science Laboratory NASA Jet Propulsion Laboratory/California Institute of Technology
grotz@gps.caltech.edu
More Information:
"Curiosity's landing is by far the most complex and challenging landing that the agency has undertaken, and future missions will, in turn, use this experience to produce spectacular results." Timofey Ovcharenko, NASA Jet Propulsion Laboratory/California Institute of Technology
