Wednesday, February 17, 2021

It's time to #Perseverance

Tomorrow is the big day: at about 21.55 (Italian time) the NASA rover Perseverance will land on the surface of the Red Planet! You can Watch it with us here.

Landing on Mars is not easy: you have to go from 20000 km/h to which the rover moves in space to 0 km/h when it touches the surface. All this then happens in just seven minutes. Considering that Mars is now 11 minutes light away from Earth the maneuver must be accomplished in a totally autonomous way by the onboard computer.

The landing maneuver is articulated in different phases.

The spacecraft begins to enter the Martian atmosphere with the heat shield correctly oriented to counteract the friction of the air. The Martian atmosphere is much rarefier than the terrestrial one but has very significant effects on the rover: two and a half minutes after the start of the maneuver the speed has been reduced to 4000 km/h, but the temperature on the thermal shield has gone up beyond 13000 degrees Celsius.

At 4 minutes and 30 seconds from entering the atmosphere and at a height of 12 km above the surface the on-board computer opens the parachute, which further slows down the descent speed. A few seconds later the heat shield is released, now useless, and the rover begins to collect the first data and images of the surface. These data are analyzed by the on-board computer in order to choose in real time the best landing site.

At 6 minutes from the entry into the atmosphere the spacecraft slowed to 300 km/h and is located 2000 meters above the surface. At this point the rover detaches from the parachute and the descent is now controlled by rockets installed on the descent module above the rover, which stabilize the speed up to 2.7 km/h.

At this point the final phases of the landing begin: the Sky Crane maneuvers. At 20 meters above the surface the rover is lowered slowly through cables from the descent module. As soon as the rover touches the surface, 7 minutes from entering the atmosphere, the cables are sheared and the descent module flies away, crashing to the surface away from the landing site.

Perseverance at this point will begin all control operations of his systems and his instrumentation, also releasing the small drone Ingenuity. After performing all the necessary checks the rover will be ready to begin its mission inside the Jezero Crater.

Credit: NASA, JPL.

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