We Can Still Persevere
In the middle of this challenging time of pandemic and politics, a group of dedicated scientists on February 18, 2021 landed a car-sized rover designed to explore the crater Jezero on the surface of Mars. The picture above might look like one of NASA’s animations depicting the event. But it is not. The picture is real, taken by the HiRISE high resolution camera on the Mars Reconnaissance Orbiter, which has been circling the planet since March 10, 2006. The photo clearly shows the rover, named Perseverance, beneath its huge parachute. To take this photo, the crew directing the Orbiter had to calculate in advance the precise timing and position so they could instruct the Orbiter to aim its camera and catch Perseverance in flight.
The Entry, Descent and Landing phase of the mission is nicknamed the “seven minutes of terror.” It started when Perseverance entered the thin Mars atmosphere, travelling at almost 12,500 miles per hour. It ended seven minutes later when the rover, executing a Rube Goldberg machine-like series of maneuvers, touched down at a speed of less than two miles per hour. Anything faster and Perseverance would have been shattered into a collection of worthless parts spread across the Martian surface.
The graphic below shows all the steps required. The engineers test, simulate, experience and test again but as the day for landing approaches they must load the instructions into the computers on Perseverance and then stand back and simply watch. That’s because even at the speed with which radio transmissions travel a signal from Mars took 11 minutes to reach Earth, then about 127 million miles distant. With a time lag like that, you couldn’t have a human controlling the landing with a joystick. Perseverance was on its own.
This is actually the fifth time NASA has landed a rover on Mars. Their names are: Sojourner, Spirit and Opportunity, Curiosity, and now Perseverance. Curiosity also used this complicated landing sequence when it reached Mars on August 5, 2012. And the Orbiter caught a similar picture of the actual landing at that time. But Perseverance is larger and heavier than Curiosity. It includes several new technologies and experiments. And while Curiosity was set to land in a largely flat area, Perseverance was directed to a rockier and far more hazardous landing site where planetary scientists hope they will have a better chance of finding evidence of microbial life.
To make that precision landing, the scientists had the Orbiter take high resolution pictures of potential landing sites. They then selected one, and loaded that high resolution image into the Perseverance computers. One of its new technologies is called “Terrain Relative Navigation,” a technique in which the rover compares images of the surface taken during its descent with the reference images, allowing it to make last minute adjustments to its course. The rover also uses the images to select a safe landing site at the last minute, allowing it to land in relatively unhazardous terrain. This enables it to land much closer to its science objectives than previous missions, which all had to use a landing zone free of hazards.
It took Perseverance almost seven months to get from Earth to Mars. It was launched from the Cape Canaveral Air Force Station on July 30, 2020, and its route to Mars made for a 292.5 million-mile journey to touchdown. It was within 15 meters of the bullseye. That’s a fraction of a mile.
The rover is essentially a 2,263-pound laboratory on wheels. For the next several years, Perseverance will cross Mars’ Jezero Crater to collect soil samples for a future retrieval mission, analyze the makeup of Martian rocks with a laser-beaming camera system, and deploy a helicopter named Ingenuity, a four-foot-wide rotorcraft that will demonstrate the first powered flight on another planet. You read that right. Yes, it carries a helicopter. Yes, is will collect samples to be picked up by subsequent missions.
Though initially hesitant to commit to an ambitious sample-caching capability (and subsequent follow-on missions), a NASA-convened science definition team for the Mars 2020 project released a report in July 2013 that the mission should “select and store a compelling suite of samples in a returnable cache.” The budget for Perseverance is $2.7 billion. That’s development, construction, launch, landing and several years of science on the surface.
Yes, we will someday send humans to Mars. And we will, someday, send humans back to the Moon. We will do that, not because it necessarily makes sense, but because personally exploring is something humans just do. But humans are fragile. We break easily. And the cost of protecting us on our extraterrestrial journeys is great and the risk is greater. For now, let us cheer on our robotic emissaries like Perseverance, and applaud the work of the men and women who design these vehicles and direct them on their missions.
And while we are tipping our hats to space exploration, note that the 60th Anniversary of Yuri Gagarin’s Space Flight is April 12. This is the UN’s International Day of Human Space Flight. Officially celebrated in Russia as Cosmonautics Day, in 2021 it marks 60 years since Yuri Gagarin became the first man in space.