After a journey of almost seven months, NASA’s Mars 2020 mission, with the Perseverance rover on board, will land on Mars next Thursday with the ambitious goal of searching for remains of ancient life for the first time. With the countdown running, tension is at its highest at the US space agency’s control center. Engineers and researchers finalize the details of the final stretch and assess a possible correction of the trajectory of the spacecraft to choose the optimal atmospheric entry point. From there, the vehicle will begin the descent and will face the so-called ‘seven minutes of terror’, the short but dizzying time that it will take to perform complex maneuvers until it lands on the ground. Hundreds of things can go wrong and Perseverance will have to do them completely autonomously, without the teams on the ground knowing if it has succeeded until eleven and a half minutes later.
Also, it will test two new technologies never before used on the red planet. Landing on Mars is quite a feat. Only 40 percent of the missions sent by any space agency have succeeded. The site was chosen for the Perseverance, the size of a small car and similar to its predecessor Curiosity is Jezero Crater. The extension, about 50 km in diameter, has great scientific value since it is believed that it was covered by rivers and a lake 3.5 billion years ago and, therefore, has the best conditions to find traces of microorganisms, if at all. they ever lived there. But Jezero is a poisoned gift for the rover. “It is fantastic for science, but it is full of dangers: rocks, slopes, cliffs”, warns Fernando Abilleira, deputy director of Flight Operations at Mars 2020.
Parachute and a crane, Responsible for ensuring that all planned operations from launch to landing are carried out successfully, this Spanish engineer based in California is already on his third landing on Mars after Curiosity (2012) and the InSight platform (2018) that studies the interior of the planet. “We will enter the atmosphere at about 20,000 km per hour and in less than seven minutes the vehicle will have to decelerate to less than 3 km per hour when it reaches the surface,” he describes. He knows that a slight mistake could derail the mission as soon as it begins. Everything has to work exactly as we planned. For example, the vehicle has more than 70 pyrotechnic charges that are used to deploy or eject devices. If one of them did not work, the descent would not be completed, “he explains.
The sequence is measured to the millimeter. About 80 seconds after entering the atmosphere, the outside temperature will reach 1,300ºC, but the rover will withstand it thanks to its protective heat shield. As the descent occurs and to avoid veering off course, it will fire small thrusters. The heat shield will slow the craft to less than 1,600 km per hour. At that moment, 240 seconds after entry, at an altitude of 11 km and a speed of 1,512 km per hour, a supersonic parachute of more than 21 meters in diameter will open. For this, Perseverance will use a new technology (Range Trigger) that calculates the distance to the landing target instead of the navigation speed, as it was done with Curiosity. “It will make it possible to reduce landing errors by more than 50%,” Abilleira points out.
Twenty seconds later, the heat shield will detach and fall. The rover will be exposed to the atmosphere of Mars for the first time. As your landing radar bounces signals off the surface to calculate your altitude, another new technology, ground-relative navigation, will be activated. “This system uses cameras that will take images of the surface. The rover will compare them with an onboard map to determine exactly where it is during the descent and to maneuver fully autonomously towards a place that is safe for landing, ”explains the engineer. At that point, Perseverance will fall to 320 km per hour and will have to get rid of the parachute and go the rest of the way using rockets of different stages. When it reaches about 2.7 km per hour, 12 seconds from touching the ground and about 20 meters high, an ‘aerial crane’ maneuver will begin, by which the rover will be suspended by cables of about 6.4 meters long.
Meanwhile, it will arrange its legs and wheels for the landing position. As soon as the rover detects that its wheels have touched the ground, it will cut the cables that connect it to the descent stage, which will be released to fall to a safe distance. The teams on the ground will receive the reassuring signal that everything has gone well with eleven minutes of delay. A series of parameters will confirm the success and shortly after a low-resolution image will arrive. Sounds will also be recorded. Then Perseverance will become the fifth NASA rover to roam Mars. With seven magnificent scientific instruments, it will search for remnants of ancient microbial life and collect rock samples to be brought to Earth on future missions. Furthermore, his work will pave the way for humanity to explore other worlds beyond the Moon.
