NASA officials have an expression for what it’s like to land a rover on Mars: seven minutes of terror. A million things could go wrong as the spacecraft enters the Martian atmosphere and attempts to make it to the surface safely. The drama is made all the more stressful by the 11-minute lag in communications between the planets. On February 18, when the Perseverance rover descends toward the Martian surface, mission control will have no clue whether it succeeded or failed until after the fact.

“There are no guarantees in this business,” Jennifer Trosper, the deputy project manager for the Mars Perseverance mission, told reporters on Tuesday. “But I’m feeling great.” She is an old hand at this nerve-racking experience, having gone through it with Perseverance’s predecessors Curiosity, Spirit, and Opportunity.

Should it succeed, Perseverance will explore Jezero crater, a former Martian lake bed that may be home to fossilized remains of ancient life. But it has to stick the landing first.

The landing

The technical terms for the seven minutes of terror is “entry, descent, and landing,” or EDL. It starts when the spacecraft enters the Martian upper atmosphere at around 20,000 kilometers per hour (12,500 miles per hour) and faces rapidly increasing temperatures. Perseverance is protected by a heat shield and shell, as well as a suite of 28 sensors that monitor hot gases and winds. Temperatures peak at a punishing 13,00 °C (2,400 °F).

About four minutes into EDL—roughly 11 kilometers (seven miles) above the surface and still hurtling to the ground at about 1,500 km/h (940 mph)—the rover deploys a 21-meter parachute The spacecraft will get rid of its heat shield soon. Underneath are a slew of other radar instruments and cameras that will be used to set the spacecraft down in a safe spot. Software called Terrain-Relative Navigation processes images taken by the cameras and compares them with an onboard topographical map to figure out where the spacecraft is and which potential safe spots it should head for.

At a little less than six minutes into EDL and around two kilometers in the air, the outer shell and parachute separate from the rover, and Perseverance heads directly for the ground. The descent stage (attached on top of the rover) uses its thrusters to find a safe spot within 10 to 100 meters of its current drop location, and slows down to around 2.7 km/h (1.7 mph). Nylon cords on the descent stage lower the rover to the ground from 20 meters (66 feet) in the air. Once the rover touches the ground, the cords are severed and the descent stage flies away to crash into the ground from a safe distance. Perseverance is now at its new home.

jezero crater
A view of Jezero

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By: Neel Patel
Title: NASA’s Perseverance rover is about to start searching for life on Mars
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Published Date: Wed, 17 Feb 2021 18:35:13 +0000




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