Martian helicopter ‘muscles through’ navigation issue on sixth flight – astronomy now

One of the cameras on the Perseverance rover’s Mastcam-Z instrument took this photo of the Ingenuity helicopter on April 9. Credit: NASA / JPL-Caltech / ASU

NASA’s Ingenuity helicopter landed safely after wobbling, suffering from power surges and speed fluctuations on its sixth flight to Mars.

The helicopter took off on May 22 for its sixth automated flight and completed the first leg of a planned 215-meter (705-foot) excursion without a hitch. But Ingenuity began to tilt back and forth in an oscillating pattern, encountering roll and pitch excursions of over 20 degrees, registering large control inputs, and suffered spikes in power consumption, according to HÃ¥vard Grip, chief helicopter pilot at NASA’s Jet Propulsion Laboratory in California.

Ingenuity overcame the problem, which engineers attributed to part of the helicopter’s navigation system. The helicopter limped for the remainder of its flight and landed safely about 5 meters (16 feet) from its intended landing location, NASA said.

The 49-centimeter-high rotorcraft, delivered to Mars in February by NASA’s Perseverance rover, made the first flight in the atmosphere of another planet on April 19. Since then, Ingenuity has flown four more times, reaching higher altitudes, traveling at higher speeds and covering longer distances with each take off.

NASA said a problem in the helicopter’s navigation system caused Ingenuity to start swaying about 54 seconds after an expected 140-second flight last week.

The helicopter navigates using an inertial measurement unit, which measures the acceleration and the rate of rotation of the craft. The data helps Ingenuity determine where it is, how fast it is moving, and its orientation in flight. But the unit of measurement is subject to errors over time.

Ingenuity uses a downward-facing navigation camera to track its flight path against features such as rocks and sand ripples on the Martian surface. The camera takes pictures 30 times per second, and each image is accompanied by a time stamp allowing the helicopter’s navigation system to compare sets of images to estimate the movement of the rotorcraft.

“Approximately 54 seconds after the start of the flight, there was a problem in the pipeline of images provided by the navigation camera,” said Grip. written in an article on the NASA website. “This issue resulted in the loss of only one image, but more importantly, all subsequent navigation images came with inaccurate timestamps.

“From that point on, whenever the navigation algorithm made a correction based on a navigation image, it worked based on incorrect information about when the image was taken,” Grip wrote. “The resulting inconsistencies significantly degraded the information used to fly the helicopter, leading to estimates that are constantly ‘corrected’ to account for phantom errors. Great oscillations ensued. “

The video below, released by NASA, shows the last 29 seconds of the May 22 flight. The helicopter is designed to ignore navigation camera footage upon landing and instead descends straight to the surface of Mars.

The helicopter had performed perfectly until the sixth flight last week. Grip, who led the development of Ingenuity’s flight control system, wrote that the sixth flight problem gives engineers valuable data on the helicopter’s design limitations.

“Flight Six ended with Ingenuity safely on the ground as a number of subsystems – the rotor system, actuators, and power system – responded to increasing demands to keep the helicopter running. flight, ”Grip wrote. “In a very real sense, ingenuity built up through the situation, and while theft discovered a timing vulnerability that will now need to be addressed, it also confirmed the robustness of the system in multiple ways.

Driven by counter-rotating 1.2 meter (4 foot) rotor blades, Ingenuity continued in flight despite the navigation error. The purpose of the May 22 flight was to demonstrate the helicopter’s aerial imagery capabilities, while staying in flight longer and moving at higher speeds than previous flights.

The maximum speed of the May 22 flight was 4 meters per second (9 mph) as the helicopter headed for a new base of operations, or “airfield,” at a location that had not yet been spotted by Ingenuity or the Perseverance rover.

Perseverance did not imagine the helicopter during the May 22 flight, which was Ingenuity’s first excursion of an extended mission phase intended to demonstrate the rotorcraft’s utility in aerial reconnaissance and exploration. The helicopter’s first five flights were aimed at demonstrating the craft’s design and proving that a rotorcraft could take off and land safely on another world.

The Martian atmosphere is less than 1% of Earth’s density at sea level, and Ingenuity’s rovers must spin at around 2,500 rpm to generate lift in thin air.

NASA has added the $ 85 million Mars helicopter technology experience to the $ 2.7 billion Perseverance rover mission, which has the primary objective of identifying, collecting and sealing Martian rock samples. for the return to Earth by a future spacecraft. With the first phase of the Ingenuity helicopter technical demonstration completed, Perseverance is now preparing for its own scientific mission.

The rover continues to serve as a communication relay between Ingenuity and the ground teams on Earth.

This latest Ingenuity flight began with an ascent to an elevation of 10 meters (33 feet) before heading southwest for about 150 meters (492 feet). The next move was to translate 15 meters (49 feet) to the south while a side-facing color camera took pictures towards the western horizon. The helicopter was then supposed to fly another 50 meters (164 feet) northeast and land at its new airfield, an area shown by orbital imagery to be relatively flat and free from major surface hazards.

In the end, the helicopter ended up just 4.8 meters (16 feet) from its intended location, despite the navigation issue, NASA said.

“While we didn’t intentionally plan such a stressful flight, NASA now has flight data probing the outer limits of the helicopter’s performance envelope,” Grip wrote. “This data will be carefully analyzed in the years to come, thus expanding our knowledge base on helicopter flight on Mars.”

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Follow Stephen Clark on Twitter: @ StephenClark1.


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