“The mission has 314 million miles of interplanetary space and seven minutes of terror to get safely onto the surface of Mars,” said Lori Glaze, director of NASA’s planetary science division, in a statement. “When we see the landscape at Jezero Crater for the first time and we truly begin to realize the scientific bounty before us, the fun really begins.”
Perseverance and the Ingenuity helicopter are safely tucked inside a protective aeroshell capsule. The descent stage that will help land the rover is also located in this aeroshell, which is attached to the cruise stage, or the mission’s spacecraft.
The cruise stage is shaped like a disk and solar powered. It will travel more than 300 million miles to reach Mars.
While it’s cruising to Mars, engineers on Earth will tell the spacecraft when to execute correction maneuvers to keep it on the right path to Mars, as well as its landing target. The ground team will also perform checks on the instruments and subsystems in the spacecraft.
About 45 days before landing on Mars, the spacecraft will enter the approach phase, with more correction maneuvers to its trajectory.
During what is hopefully a quiet journey to Mars, Perseverance’s teams will be preparing and training for when the rover lands on Mars. The science team will prepare the instructions it wants to send to the rover as it uses its instruments on Mars.
The rover’s drivers will also work with a model of the rover on Earth to prepare for Perseverance’s journey across the Martian surface.
This includes using a twin of Perseverance on Earth to test hardware, drive it through the Mars Yard at NASA’s Jet Propulsion Laboratory in Pasadena, California, and make sure the auto-navigation algorithms work, said Heather Justice, robotic operation downlink lead and one of the rover drivers at JPL.
‘Seven minutes of terror’
The one-way light time it takes for radio signals to travel from Earth to Mars is about 10.5 minutes, which means the seven minutes it takes for the spacecraft to land on Mars will occur without any help or intervention from NASA teams on Earth.
NASA team members refer to this as the “seven minutes of terror.” They tell the spacecraft when to begin EDL, (entry, descent and landing), and the spacecraft takes over from there.
The spacecraft hits the top of the Martian atmosphere moving at 12,000 miles per hour and has to slow down to zero miles per hour seven minutes later when the rover softly lands on the surface.
About 10 minutes before entering the thin Martian atmosphere, the cruise stage is shed and the spacecraft prepares for a guided entry, where small thrusters on the aeroshell help adjust its angle.
The spacecraft’s heat shield will endure peak heating of 2,370 degrees Fahrenheit 75 seconds after entering the atmosphere.
Perseverance is targeting a 28-mile-wide ancient lake bed and river delta, the most challenging site yet for a NASA spacecraft landing on Mars. Rather than being flat and smooth, the small landing site is littered with sand dunes, steep cliffs, boulders and small craters.
The spacecraft has two upgrades — called Range Trigger and Terrain-Relative Navigation — to navigate this difficult and hazardous site.
Range Trigger will tell the 70.5-foot-wide parachute when to deploy based on the spacecraft’s position 240 seconds after entering the atmosphere. After the parachute deploys, the heat shield will detach.
Terrain-Relative Navigation acts like a second brain for the rover, using cameras to take pictures of the ground as it rapidly approaches and determines the safest spot to land. It can shift the landing spot by up to 2,000 feet, according to NASA.
The back shell and parachute separate after the heat shield is discarded when the spacecraft is 1.3 miles above the Martian surface. The Mars landing engines, which include eight retrorockets, will fire to slow the descent from 190 miles per hour to about 1.7 miles per hour.
Then, the famed sky crane maneuver that landed the Curiosity rover will occur. Nylon cords will lower the rover 25 feet below the descent stage. After the rover touches down on the Martian surface, the cords will detach and the descent stage will fly away and land at a safe distance.
On the surface of Mars
Once the rover has landed, Perseverance’s two-year mission will begin and it will go through a “checkout” period to make sure it’s ready.
The rover will deploy its mast and antenna, image its landing sight, conduct a “health check” for its instruments, test movement and “flex” its arm and conduct a short test drive. Perseverance will also release its belly pan, which provided a safe haven for the Ingenuity helicopter stowed there during cruising and landing.
The rover will also find a nice, flat surface to drop the Ingenuity helicopter so it has a place to use as a helipad for its potential five test flights during a 30-day period. This will occur within the first 50 to 90 sols, or Martian days, of the mission.
Once Ingenuity is settled on the surface, Perseverance will drive to a safe spot at a distance and use its cameras to watch Ingenuity’s flight.
After those flights, Perseverance will begin searching for evidence of ancient life, study Mars’ climate and geology and collect samples that will eventually be returned to Earth via planned future missions.