NASA said Thursday that the Perseverance rover had touched down on the surface of Mars after successfully overcoming a risky landing phase known as the “seven minutes of terror.”
“Touchdown confirmed,” said operations lead Swati Mohan at around 3:55 p.m. Eastern Time (2055 GMT) as mission control at NASA’s Jet Propulsion Laboratory headquarters erupted in cheers.
The autonomously-guided procedure was completed more than 11 minutes earlier, which is how long it takes for radio signals to return to Earth.
“WOW!!” tweeted NASA Associate Administrator Thomas Zurburchen as he posted the Perseverance’s first black and white image from the Jezero Crater in Mars’ northern hemisphere.
— Thomas Zurbuchen (@Dr_ThomasZ) February 18, 2021
The rover is only the fifth ever to set its wheels down on Mars. The feat was first accomplished in 1997 and all so far have been American.
It is part of an epic quest to bring back rocks that could answer whether life ever existed on the red planet.
Weather conditions were favorable in the Martian northern hemisphere spring, but nothing is taken for granted.
“This is one of the most difficult maneuvers that we do in this business, and almost 50 percent of the spacecraft that had been sent to the surface of Mars have failed,” Matt Wallace, the mission’s deputy project manager said.
Ten minutes before entering the Martian atmosphere, the spacecraft shed its cruise stage that supplied the fuel tanks, radios and solar panels on the voyage.
It was left with just a protective aeroshell, carrying the rover and descent stage, and it fired thrusters to make sure its heat shield was forward-facing.
At about 80 miles (130 kilometers) altitude, it careened into the atmosphere and things started to get hot: Peak heating occured about 80 seconds in, when the heat shield surface reached 2,370 degrees Fahrenheit (about 1,300 degrees Celsius).
Perseverance was tucked away safely in the aeroshell, only experiencing room temperature.
Once the spacecraft slowed down to less than 1,000 miles (1,600 kilometers) an hour, it wa time to deploy the 70.5 feet (21.5 meters) wide supersonic parachute at an altitude of seven miles (11 kilometers).
Perseverance deployed a new technology called Range Trigger that decides the precise moment to deploy, based on the craft’s position relative to the landing site.
Asked to name the single most critical event, NASA’s EDL lead Allen Chen said: “Obviously there’s a lot of concentrated risk in supersonic parachute opening.”
To try out its new design, NASA had to carry out extensive supersonic parachute testing from high altitudes here on Earth, a field of research that had been dormant since the 1970s.
Heat shield separation
Next, the spacecraft jettisoned its heat shield, around 20 seconds after the parachute was deployed. The rover was exposed to the atmosphere for the first time, and used a landing radar to bounce signals off the surface and calculate its precise altitude.
The mission also saw another technology deployed for the first time: The “Terrain Relative Navigation” (TRN) system that uses a special camera to identify surface features and compare them to an onboard map where engineers pre-programmed the safest landing sites.
“That gives our vehicle eyes, and the ability to really see where she’s going and figure out where she is,” said Chen.
In the thin atmosphere of Mars, the parachute only got the vehicle down to 200 miles (300 kilometers) per hour — so Perseverance had to cut the chute loose, dispense with its back shell, and use rocket thrusters to ease itself down.
It did this using an eight-engined jetpack that’s installed directly above the rover and fired up at around 6,900 feet (2,100 meters) above the surface.
The vehicle had to tilt right away in order to avoid the falling parachute and back shell, then used its sophisticated systems to continue its descent.
With 12 seconds to go, at a height of 66 feet (20 meters), the rocket-powered descent stage lowered the rover down to the ground using long cables in a maneuver called “skycrane.”
The rover locked its legs and wheels into a landing position and touched the ground at a little less than two miles (1.2 kilometers) an hour, as the descent stage flew off and made its own controlled landing.
Perseverance is now set for its mission as Earth’s fifth rover on Mars.
In this illustration of its descent to Mars, the spacecraft containing NASA’s Perseverance rover slows down using the drag generated by its motion in the Martian atmosphere. Hundreds of critical events must execute perfectly and exactly on time for the rover to land on Mars safely on Feb. 18, 2021.
Entry, Descent, and Landing, or “EDL,” begins when the spacecraft reaches the top of the Martian atmosphere, travelling nearly 12,500 mph (20,000 kph).
The cruise stage separates about 10 minutes before entering into the atmosphere, leaving the aeroshell, which encloses the rover and descent stage, to make the trip to the surface. The vehicle fires small thrusters on the backshell to reorient itself and make sure the heat shield is facing forward as it plunges into the atmosphere. As it descends through the atmosphere, the spacecraft fires these thrusters on its backshell to guide itself. The spacecraft uses the Martian atmosphere to brake, causing it to heat up dramatically. Peak heating occurs about 80 seconds after atmospheric entry, when the temperature at the external surface of the heat shield reaches about 2,370 degrees Fahrenheit (about 1,300 degrees Celsius). The rover is safe in the aeroshell, and reaches only about room temperature. Peak deceleration occurs about 10 seconds later (~90 seconds after atmospheric entry). The heat shield slows the spacecraft to under 1,000 mph (1,600 kph).
NASA’s Jet Propulsion Laboratory in Southern California built and will manage operations of the Mars 2020 Perseverance rover for NASA.
For more information about the mission, go to: https://mars.nasa.gov/mars2020.