Entry, Descent, And Landing Technologies for Perseverance

Key takeaways

This initiative aims to find evidence of life on Mars and go even beyond that to have a better understanding of the continuously expanding universe.
It is the point where it travels nearly 12,100 miles per hour (19500 kilometers per hour).
Consequently, the Perseverance Rover operates with an accuracy of 40 meters or 130 feet.

In February 2021, Perseverance Rover landed on Mars and was set to explore the red planet and uncover traces of ancient life (microbial).

The Perseverance Rover happens to be the most expensive and upgraded mobile laboratory sent on a Mars mission ever. This initiative aims to find evidence of life on Mars and go even beyond that to have a better understanding of the continuously expanding universe. Also, the Rover is supposed to throw light on the future of both manned and unmanned missions to the red planet.

The Rover is expected to begin the drilling work during the summer months. It has been programmed to explore the delta first, move across the lakeshore, and then go for the crater’s edges.

Let us now explore the technological aspects of the Perseverance Rover.

Searching for Clues #

The first thing the Perseverance Rover is expected to do is search for microscopic life forms that may be millions of years old. For this purpose, scientists and engineers have fitted the Rover with a PIXL (Planetary Instrument for X-ray Lithochemistry). It is a precision x-ray device that runs on AI (Artificial Intelligence). The PIXL has a superior ability to scan rocks through a focussed x-ray beam. In addition, the device can detect chemicals along with their quantity and distribution.

Ingenuity Mars Helicopter #

It is attached to the belly of the Rover and has a lot of autonomy while flying through waypoints since it is not controlled from Earth. In fact, it happens to be the first helicopter that would be flying outside Earth. Commands are sent beforehand, and accordingly, the helicopter executes the flight. The most interesting aspect of the Ingenuity Mars Helicopter is accessing terrain off-limits for the Rover.

Data Collection for Future Flights and Landings #

Scientists have designed MEDLI (MSL Entry, Descent, and Landing Instrumentation) which helps to detect the pressure and temperature of the Rover.

The next-gen sensor suite MEDLI2 assists in collecting data from both the backshell and heat shield. It combines the pressure and temperature of the Rover along with the data collected from the Rover’s weather station to extract insights and help scientists decide entry, descent, and landing techniques in the future, thereby mitigating risks.

The AI-controlled terrain navigation system ensures that the Rover can safely descend on the surface, like Mars. The terrain relative navigation ensures that the Rover can calculate its position and location with respect to the ground. The accuracy limit is about 40 meters.

While descending, the Rover, with the help of LiDAR or similar technology, can create a map of the landing site. The map is then compared with the images of the Rover while approaching the surface, thereby allowing it to redirect if needed. That way, the Rover can figure out and land in the safest spot possible.

Fittings #

The other fittings of the Rover include MOXIE that can demonstrate how oxygen is produced from the Martian atmosphere. The MEDA analyzes and measures the dust with the help of sensors. RIMFAX uses radar waves to scan the surface below the Rover. SuperCam combines camera, laser, and spectrometers to analyze the soil and rocks.

How The Perseverance Rover Works #

The entry, descent, and landing (EDL) of the Rover took only seven minutes in February 2021. Then, it touched down on the surface of Mars, which is now termed as the ‘Seven Minutes Of Terror’ sequence. The entire process and steps involved precise and careful maneuvering and control.

The Mars 2020 mission, the Perseverance Rover, and The Ingenuity Mars Helicopter were given the green signal in July 2020. The objective was to attempt to land on the Jezero Crater, almost 45 kilometers (28 miles) wide. It took nearly six and a half months to reach Mars. The Rover has been programmed to search for evidence of previous microbes and, if possible liveable environments and conditions on the red planet. Samples would be collected from the planet that would be analyzed back on Earth for designing future mission campaigns.

The journey and operation of Perseverance Rover to Mars are more or less similar to what Curiosity Rover did in 2012. As the air vehicle cruised towards Mars, the Perseverance Rover, along with the descent stages, were well protected in a capsule called an ‘aeroshell’. It is attached to the ring structured cruise phase.

The cruise phase comprises eight thrusters that give power at specific times so that the spacecraft is on its designated course. In addition, the spacecraft is fitted with solar arrays that help to power the craft. Also, it has antennas for communicating with the control center on Earth.

Given below is an account of how the various components work together to assist in the landing of the craft on Mars:

The Over was 2.40 million miles (3.90 kilometers) away from Mars in February. At that time, it was buzzing through space at a speed of 49290 miles per hour (79330 kilometers per hour).
In the last three weeks before landing, the mission control focussed on the navigational aspects, like whether the craft was following the correct trajectory or not, along with activities related to the preparation of the vehicle for EDL.
During the cruise stage, solar arrays could be seen that help to provide extra power to the craft apart from the main power source. It is referred to as the Mufti-Mission Radioisotope Thermoelectric Generator.

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Aeroshell Separation #

Almost 10 minutes before entering the Martian atmosphere in 2020, the aeroshell separated from the cruise stage. Thereafter, the aeroshell having the Perseverance Rover and descent stage would descent to the Martian soil on its own.

The aeroshell measures nearly 15 feet (4.50 meters) in diameter. It consists of two parts, namely the backshell and the heat shield. Both protect the craft from getting burned when extreme heat is generated at the initial descent through Mar’s atmosphere. The aerodynamic design and property of the heat shield also function as a stopping mechanism that helps slow the craft’s pace.

Entering The Martian Atmosphere #

The EDL phase starts when the craft reaches the top of the Martian atmosphere. It is the point where it travels nearly 12,100 miles per hour (19500 kilometers per hour). Then, roughly after 90 seconds after entering the atmosphere, the peak acceleration occurs. During this time, the spacecraft slows to less than 1000 miles per hour (1600 kilometers per hour).

While descending to the surface of Mars, the speed of the Rover decreases because of the drag generated by the motion in the Martian atmosphere. The aeroshell also releases small thrusters on the backshell. It helps in reorienting and ensures that the heat shield faces the Red Planet as the Rover descends through the atmosphere.

Seven Minutes of Nailbiting #

EDL will last for approximately seven minutes. Once the EDL phase starts, the craft uses a technique referred to as the guided entry. It takes around 14 minutes or so for radio signals to travel from Earth to the Rover and vice verse. It implies that the spacecraft will land on the red planet without any assistance or intervention from the ground team on Earth. It is why the landing of the craft has been referred to as the Seven Minutes Of Terror.

The spacecraft’s heat shield that faces Mars endures peak heating when it enters the Martian atmosphere. This is because the friction of the Mar’s atmosphere decreases the rate of descent, thereby increasing the temperature of the heat shield.

The Parachute #

After about four minutes post entering the Martian atmosphere, the craft deploys a supersonic parachute that comes out from the aeroshell. The diameter of the chute is 70.50 feet (21.50 meters), and it gets deployed at an altitude of 11 km or 7 miles above the surface of the red planet. The craft’s velocity at that point is close to 940 miles per hour, equivalent to 1512 kilometers per hour. The chute helps to slow down the craft’s motion to almost 200 miles per hour or 320 kilometers per hour.

The chute is deployed using the latest technology called Range Trigger. It helps to narrow down on the intended landing area. According to the engineers who designed the system, the Range Trigger technology can significantly reduce the size of the landing ellipse, which is an oval area around the target landing, by almost 50 per cent. As a result, it implies that it will take the Rover less time to get to its location than previous missions that have landed on Mars. In addition, the Range Trigger will autonomously adjust the timing of the parachute deployment with respect to the position of the craft and distance from the landing target.

Rover in the Backshell #

The Heat Shield separates and drops away from the backshell about 20 seconds post deployment of the parachute. The descent stage and Rover remain tucked in the backshell of the craft as the whole thing slows the dive towards the surface of Mars.

When the Rover is exposed to the Martian atmosphere for the first time. As part of the landing system of the craft, the Terrain Relative Navigation System, along with the landing radar of the craft, starts accessing the velocity, position, and altitude to help guide the Rover to a safe landing on Mars.

The navigation technology is a new approach and comes with a Lander Vision System. It is equipped with a down-facing camera that can take images when the craft descends. The inboard computers work on the images and accordingly calculate the approximate position of the craft with respect to the ground on a fine-scale as compared to previously available systems. Using this data, the new navigation system can adjust the touchdown of the Rover, thereby averting any unsafe landing.

The navigation technologies and the range trigger allow landing on the floor of the Jazero Crater possible. The area has a complicated terrain since it includes sand dunes, cliffs, boulder areas, and small impact craters.

Powered Decent Phase #

When the Rover is at the height of 2.10 kilometers (1.30 miles), the Rover and the descent stage separate from the backshell and parachute. The descent phase consists of eight throttleable retro-rockets, also called landing engines. They help to decrease the pace of the spacecraft while preparing for a touchdown on the Martian surface.

During the descent stage, the engine fires up at the final moment before Rover lands on Mars. At this point, the craft travels at almost 306 kilometers per hour or 190 miles per hour. The landing engines assist in guiding the craft to the designated landing spot. It first levels out and then decreases the vehicle’s speed to the final landing speed of 2.70 kilometers per hour or 1.70 miles per hour.

Touchdown #

At about 20 meters above the ground (65 feet) or about 12 seconds before touchdown, the Rover is safely lowered to the ground by a sky crane. Three nylon cables are extended almost 25 feet (7.60 meters) below the descent stage, bringing the Rover to the ground. In the meantime, the Rover stretches its legs, bringing the wheels for the final landing.

Once the Rover senses that it has touched the ground, the cables are released automatically, linking the craft to the descent stage. The cables then fly off safely from the Rover. If everything goes as per plan, nothing can stop the Rover from completing its two years mission of exploring the Jezero crater.

Interplanetary Helicopter (First of its Kind) #

The Ingenuity Mars Helicopter is attached to the belly of the Perseverance. It will detach after 30 - 90 post touchdown of the craft on the Red Planet. Thereafter, the helicopter will perform some test flights to demonstrate that robotic flights are no big deal on another planet.

Overall, to improve the entry, descent, and landing of the Rover, two key factors need to be taken into account. The first is to know where the craft is headed and, secondly, to divert to a safe place in case the terrain seems hazardous.

The most crucial component of the Rover happens to be the navigation system that allows the Rover to make accurate estimates of the position with respect to the ground below. The Rover can know its exact position while descending the Martian atmosphere. Consequently, the Perseverance Rover operates with an accuracy of 40 meters or 130 feet.

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