Vertiflite May/June 2021

S

The vertical landing itself was made after the descent stage conducted what NASA called the “skycrane” maneuver. With about 12 seconds before touchdown, at about 66 ft (20 m) above the surface, the descent stage lowered the rover on a set of cables about 21 ft (6.4 m) long, while the rover unstowed its legs and wheels for landing. As soon as the rover sensed that its wheels had touched the surface, it cut the cables connecting it to the descent stage, which then flew off to crash a safe distance away from Perseverance. Thus, after traveling 293 million miles (471 million kilometers), the autonomous Ingenuity Mars helicopter, attached to the belly of the Perseverance rover, landed safely, at the 28-mile (45-km) wide Jezero Crater, just north of the Martian equator. The Perseverance Rover then conducted several days of checkouts, taking its first test drive on March 4. An important task for the team was finding an appropriate field from which to take off and land Ingenuity within a designated flight zone. Luckily, aerial photos showed a relatively flat field with few boulders near Perseverance’s landing site, according to Ingenuity chief pilot Håvard Grip during a post-landing press briefing. The 10-by-10-ft (3-by-3-m) “helipad,” within a 33-by-33-ft (10-by-10-m) airfield, is contained within a much larger flight zone. The next challenging step of the mission was releasing Ingenuity from underneath Perseverance and driving away without damaging the rotorcraft.The complexity of the task is noteworthy. First, the rover ejected the debris shield that protected the helicopter during the flight to Mars, the descent and landing. The rover then went through a series of steps that transitioned Ingenuity from its horizontal cocoon to a vertical position, followed by carefully depositing the drone on the surface. This deployment process took six Martian sols (six days and four hours on Earth). Following deployment, the rover drove to its observation area, its “twitcher’s point,” a safe 211 ft (64 m) away called “Van Zyl Overlook,” named after Jacob van Zyl, the team’s longtime colleague and JPL leader. Van Zyl, who joined JPL in 1986 and was instrumental on the Mars mission, died unexpectedly in August 2020. Sol 1: The team activated a bolt-breaking device, which released the locking mechanism that held Ingenuity firmly against the rover’s belly during launch and landing. Sol 2: The team fired a cable-cutting pyrotechnic device, which enabled the mechanized arm that held Ingenuity to begin rotating the craft from its horizontal to vertical position. During this task, Ingenuity deployed two of its four landing legs. Sol 3: A small electric motor finished rotating Ingenuity until it latched, which brought the rotorcraft to a full vertical, final configuration. At this point, Ingenuity was suspended 5 inches (13 cm) over the Martian surface, with only a single bolt and several tiny electrical contacts connecting it to the Perseverance. Below is the step-by-step process the team took to deploy Ingenuity to the surface.

Vertical landing of the NASA Perseverance Rover was via the descent stage performing a “skycrane” maneuver. At touchdown, the rover cut the cables and the descent stage flew off.

Underneath the rover, Ingenuity was exposed when Perseverance jettisoned its heat shield.

(WATSON) took “confirmation shots of Ingenuity as it incrementally unfolded into its flight configuration.”

Sol 5: Perseverance charged Ingenuity’s six battery cells.

Sol 6: The team confirmed that Ingenuity’s four legs were lowered and locked, and conducted final checks.

“This is the first time that Ingenuity has been on its own on the surface of Mars,” stated Aung. “We now have confirmation that we have the right insulation, the right heaters and enough energy in its battery to survive the cold night, which is a big win for the team. We’re excited to continue to prepare Ingenuity for its first flight test.” Ingenuity could only withstand one frigid Mars night if its solar panel didn’t charge properly, according to JPL. Martian night temperatures can drop as low as -130°F (-90°C).

May / June 2021

Sol 4: The final two legs were snapped into position. The Wide Angle Topographic Sensor for Operations and eNgineering

17