How Close Did Perseverance Land to Its Target?

NASA’s mission to Mars in 2020 was a feat that had never been attempted before: getting their spacecraft, Perseverance, to make a more precise landing on the Red Planet than ever before. It was an ambitious task, and Perseverance certainly lived up to its name. But the question remains, how close did the spacecraft land to its target?

The Mission of Perseverance

Perseverance was the fifth mission sent to Mars by NASA in the last decade. The mission was part of the Mars Exploration Program and was designed to search for evidence of fossilized microbial life in the martian environment and collect samples for future return to Earth. The mission also included executing the first aerial reconnaissance of Mars with the Ingenuity Helicopter, the first powered flight on another planet and the first extraction of a rock sample from the Martian surface.

The Planning and Preparation

Getting to the Red Planet is no easy feat, and with precision landings, even more careful planning and preparation was required. First, the Perseverance team had to determine the perfect flight path to reach the planet. The chosen path was an elliptical trajectory that took the spacecraft around the sun, swing it in close around the Earth for a gravity assist and send it sailing to its final destination.

Next, the team had to pinpoint the landing spot, which required knowledge of the terrain, topography, land cover, and resources on Mars — including the landing site’s proximity to the science objectives. This meant pinpointing an area within the landing ellipses that was smooth, flat, and offered all the resources necessary to support the mission.

The Landing

On February 18, 2021, Perseverance, otherwise known as the Mars 2020 mission, successfully arrived at Mars. Shortly after, the craft made its descent and entered the Martian atmosphere careening at speeds upwards of 12,000 miles per hour.

The intricate process lasted seven intense minutes as the entry, descent, and landing (EDL) team members carefully monitored Perseverance’s position, velocity, orientation and thrust performance to control its descent. At the moment of landing, a reaction control system or thrusters fired and slowed the spacecraft to a gentle touchdown on the surface of Mars at a velocity of about one mile per hour.

How Close Was It?

The margin of error for the Perseverance EDL had been no more than 2.2 miles from the target location. Therefore, the exact spot of Perseverance’s landing was significant. The landing team had to perform calculations near immediately when the EDL began to determine the touchdown location.

And remarkably, Perseverance only missed its target by about 1.2 miles, wildly exceeding expectations and proving that the preparations for the mission had paid off. This made Perseverance’s landing the first potential human mission-level precision landing, with an accuracy of nearly a X-band or three football fields, making it the most precise landing ever attempted on Mars.

Why Was It So Accurate?

The success of Perseverance’s landing was due in part to the upgrades to its orbiter, Descent Element (DE), Autonomous Flight Management System (AFMS), and upgraded parachute design.

The DE comprised an advanced guidance system and new terrain relative navigation technology that utilized high-resolution terrain maps to successfully guide the spacecraft. The advanced guidance system leveraged advanced imaging and sensing capabilities, including a high-resolution stereo camera, a 24/7 active vision system, and advanced terrain-relative navigation to steer the craft during its descent.

The Autonomous Flight Management System (AFMS) was an advanced onboard navigation system that was developed for this mission, and it provided an alternative solution to the tedious process of precisely pointing the craft toward the objective coordinates. The system ensured the trajectory of the spacecraft was accurately controlled and allowed for autonomous landing.

Finally, the upgraded, sturdier parachute was composed of Kevlar fibers, providing the 18-meter, 4-ringed parachute with a durability that effectively countered the martian wind.

As NASA’s most precise mission to date, the successful arrival of Perseverance at the Red Planet proves that the planning, engineering, and technology are up to the challenge of space exploration. Its incredibly precise landing, only 1.2 miles off target, clearly demonstrates the upgrades and technology used, and sets a high expectation for future exploration missions.