Tucked under the belly of the Perseverance rover that will be landing on Mars in just a few days is a little helicopter called Ingenuity. Its body is the size of a box of tissues, slung underneath a pair of 1.2m carbon fiber rotors on top of four spindly legs. It weighs just 1.8kg, but the importance of its mission is massive. If everything goes according to plan, Ingenuity will become the first aircraft to fly on Mars.
In order for this to work, Ingenuity has to survive frigid temperatures, manage merciless power constraints, and attempt a series of 90 second flights while separated from Earth by 10 light minutes. Which means that real-time communication or control is impossible. To understand how NASA is making this happen, below is our conversation with Tim Canham, Mars Helicopter Operations Lead at NASA's Jet Propulsion Laboratory (JPL).
It's important to keep the Mars Helicopter mission in context, because this is a technology demonstration. The primary goal here is to fly on Mars, full stop. Ingenuity won't be doing any of the same sort of science that the Perseverance rover is designed to do. If we're lucky, the helicopter will take a couple of in-flight pictures, but that's about it. The importance and the value of the mission is to show that flight on Mars is possible, and to collect data that will enable the next generation of Martian rotorcraft, which will be able to do more ambitious and exciting things.
[...] With all this in mind, getting Ingenuity to Mars in one piece and having it take off and land even once is a definite victory for NASA, JPL's Tim Canham tells us. Canham helped develop the software architecture that runs Ingenuity. As the Ingenuity operations lead, he's now focused on flight planning and coordinating with the Perseverance rover team. We spoke with Canham to get a better understanding of how Ingenuity will be relying on autonomy for its upcoming flights on Mars.
[...] With a technology demo, JPL is willing to try new ways of doing things. So we essentially went out and used a lot of off-the-shelf consumer hardware.
There are some avionics components that are very tough and radiation resistant, but much of the technology is commercial grade. The processor board that we used, for instance, is a Snapdragon 801, which is manufactured by Qualcomm. It's essentially a cell phone class processor, and the board is very small. But ironically, because it's relatively modern technology, it's vastly more powerful than the processors that are flying on the rover. We actually have a couple of orders of magnitude more computing power than the rover does, because we need it. Our guidance loops are running at 500 Hz in order to maintain control in the atmosphere that we're flying in. And on top of that, we're capturing images and analyzing features and tracking them from frame to frame at 30 Hz, and so there's some pretty serious computing power needed for that. And none of the avionics that NASA is currently flying are anywhere near powerful enough. In some cases we literally ordered parts from SparkFun [Electronics]. Our philosophy was, "this is commercial hardware, but we'll test it, and if it works well, we'll use it."
[...] We use a cellphone-grade IMU[*], a laser altimeter (from SparkFun), and a downward-pointing VGA camera for monocular feature tracking. A few dozen features are compared frame to frame to track relative position to figure out direction and speed, which is how the helicopter navigates. It's all done by estimates of position, as opposed to memorizing features or creating a map.
We also have an inclinometer that we use to establish the tilt of the ground just during takeoff, and we have a cellphone-grade 13 megapixel color camera that isn't used for navigation, but we're going to try to take some nice pictures while we're flying.
[...] This the first time we'll be flying Linux on Mars. We're actually running on a Linux operating system. The software framework that we're using is one that we developed at JPL for cubesats and instruments, and we open-sourced it a few years ago. So, you can get the software framework that's flying on the Mars helicopter, and use it on your own project. It's kind of an open-source victory, because we're flying an open-source operating system and an open-source flight software framework and flying commercial parts that you can buy off the shelf if you wanted to do this yourself someday. This is a new thing for JPL because they tend to like what's very safe and proven, but a lot of people are very excited about it, and we're really looking forward to doing it.
See, also, the NASA Mars Helicopter Ingenuity Animations on YouTube.
[*] IMU: Inertial measurement unit.
Salon has an article on Ingenuity.
In 1903, Orville and Wilbur Wright flew a plane for 12 seconds, 120 feet in the air, on what is now known as the first powered-controlled flight on Earth. Now, 118 years later, the first powered-controlled attempt at a flight on another planet is about to take place.
According to NASA, Ingenuity — the four-pound rotorcraft attached to Perseverance — is on its way to its "airfield" on Mars.
The space agency announced that its target for its first takeoff attempt will happen no earlier than April 8, 2021.
Ingenuity was designed as an experiment to see if it is possible to fly on Mars as we do here on Earth. And the process leading up to the takeoff is a very meticulous one. Consider how long it took humans to stick a powered-controlled flight on Earth; given Mars' thin atmosphere and a twenty-minute delay in communication, it is arguably more challenging on Mars.
"As with everything with the helicopter, this type of deployment has never been done before," Farah Alibay, Mars helicopter integration lead for the Perseverance rover, said in a press statement. "Once we start the deployment there is no turning back."
Every move for the next couple of weeks could make or break Ingenuity's success — starting with precisely positioning the rotorcraft in the middle of its 33-by-33-foot square airfield, which is actually a flat field on the Martian surface with no obstructions. From there, the entire deployment process from Perseverance will take about six Martian days, which are called sols. (The Martian sol is thirty-nine minutes longer than an Earth day.)
Good luck, little chopper!