A NASA decided to continue flying with the small helicopter Ingenuity, the first to fly on Mars. The Martian flying vehicle had a recent failure in its navigation system, preventing very long and far flights from the Perseverance rover.
According to the agency's engineers, the Ingenuity helicopter faced temperature amplitude conditions, facing several cold nights on Mars, with temperatures down to -80º C. This condition caused damage to the systems of the small Martian flying vehicle, and for this reason a sensor that measures the slope is completely inactive.
The inclinometer is responsible for providing Ingenuity's flight software with gravimetric data prior to takeoff.
These data allow the Ingenuity determines its position relative to the downward force of gravity on Mars and allows calculations of the rover's roll and pitch before liftoff, Ingenuity's chief pilot Håvard Grip of JPL explained in the status update.
Without this initial data, the vehicle's software cannot determine Ingenuity's proper orientation during flight. But NASA engineers have already thought about this condition before, and even before the rover and helicopter took off from Earth, a software update package was prepared to cover failures in sensors, including the “inclinometer”.
Through a command from the Jet Propulsion Laboratory (JPL), the helicopter's software was updated, using the Perseverance rover, and Ingenuity is now ready to resume flights on Mars, a milestone for humanity reached in 2021, considering the inhospitable conditions and the lower gravity of the neighboring planet.
When Ingenuity is flying, the onboard flight control system closely monitors the helicopter's current position, speed and orientation. It does this with the help of a set of sensors consisting of:
- An inertial measurement unit (IMU), which measures accelerations and angular rates in three directions.
- A laser rangefinder, which measures the distance to the ground.
- A navigation camera, which takes pictures of the ground below.
Data from these sensors is processed by a set of algorithms implemented in Ingenuity's navigation computer. For the algorithms to work correctly, they must be initialized before takeoff with an estimate of Ingenuity's roll and pitch attitude. That's where the inclinometer comes in.
The inclinometer is composed of two accelerometers, whose sole purpose is to measure gravity before turning and taking off; the sensed gravity direction is used to determine how Ingenuity is oriented relative to the downward direction.
The inclinometer isn't used during the flight itself, but without it NASA engineers are forced to find a new way to initialize the navigation algorithms before liftoff. Now Ingenuity is pulling that data from another system, which also has accelerometers but wasn't designed specifically for that function.
Ingenuity made its first flight in April 2021, and has already carried out 28 missions on Mars, exceeding the expectations of NASA scientists.
