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posted by janrinok on Wednesday May 31 2023, @07:53AM   Printer-friendly

Mars Helicopter went silent for six sols, risked rover:

NASA has revealed a six-day stretch during which it could not contact its Ingenuity Mars helicopter.

In a lengthy post, chief engineer Travis Brown explained that after the copter's 49th flight, radio contact was lost for six sols – just short of six days and six hours of terrestrial time.

Initially, NASA's Mars boffins weren't unduly concerned. The Perseverance Rover had moved behind a rocky outcrop that created a "communication shadow." Brown wrote that since Sol 685 the helicopter "had unfortunately been drifting in and out of night-time survival mode" which made daily contact with the craft difficult. So a day or two without contact wasn't worrying.

But once Perseverance moved to another location and Ingenuity still could not be found, Brown wrote "the situation began to generate some unease."

"Poor telecom performance was seen as a plausible explanation, but there were reasons to doubt it," he wrote. "In more than 700 sols operating the helicopter on Mars, not once had we ever experienced a total radio blackout. Even in the worst communications environments, we had always seen some indication of activity."

But the signal received on that day, sol 761, was just a simple ACK (acknowledgement). The next day, the copter again acknowledged a command, but did little else.

Mission staff determined that the ridge separating Ingenuity and Perseverance was a challenge for the copter's radio. It didn't help that Perseverance's helicopter base station (HBS) antenna is mounted low on the vehicle's right and is subject to occlusion effects.

While NASA folk figured that out, Perseverance moved towards its next goal – but that created new problems.

"It is extremely important for Ingenuity to stay ahead of Perseverance while moving through the narrow channels of the Jezero delta," Brown wrote, as the rotorcraft's job is to scout ahead for the wheeled rover. And NASA operates a no-fly zone around Perseverance.

With the rover on the move, and the helicopter stopped, it became imperative to get Ingenuity moving.

"Relying on the helicopter's onboard pre-flight checks to ensure vehicle safety and banking on solid communications from the rover's imminent proximity, the team uplinked the flight plan," Brown wrote.

Ingenuity did more than just ACK that upload. It ingested and executed it, resulting in its 50th flight and an altitude record of 18 meters.

"It would be an understatement to say that the helicopter team was relieved to see the successful flight telemetry in the Sol 763 downlink the following morning," Brown wrote.

[...] Ingenuity last flew on April 22, when it made a 188-meter hop at an altitude of 12 meters. The craft was designed to fly just five times, so has already vastly exceeded expectations.


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  • (Score: 1) by H_Fisher on Wednesday May 31 2023, @12:21PM (1 child)

    by H_Fisher (29782) on Wednesday May 31 2023, @12:21PM (#1309037)

    I'm sure NASA intentionally sets the bar for these things fairly low to manage expectations - i.e. the "designed to fly just five times" stat that's often repeated - but it's still great to see the team able to use the Mars-copter after all this time. Hopefully we'll get some more flights out of her.

    Heck, the one radio-controlled helicopter I owned (this was before we called 'em "drones," kids) was lucky to have flown about seven times before it succumbed to an excess of kinetic energy ... although that was largely due to user error.

    --
    "Life is pain, highness. Anyone who tells you differently is selling something." -William Goldman
  • (Score: 4, Interesting) by Immerman on Wednesday May 31 2023, @01:19PM (1 child)

    by Immerman (3985) on Wednesday May 31 2023, @01:19PM (#1309047)

    So, where exactly does the headline's "risked rover" come into play? Had they landed it in such a narrow choke point in the terrain that the rover wouldn't be able to maneuver around it if it failed to respond? That's the only risk I can think of, and it seems *extremely* unlikely that mission control would have done such a thing - NASA is normally extremely risk-averse, and it seems like they've been operating on the assumption that every flight might be its last.

    As useful as the helicopter has proven to be, it's original role was only to provide a few proof-of-concept flight tests. Worst case scenario if it becomes unresponsive, Perseverance drives past it and continues the mission as originally planned. And if they regained communication in the future, they fly it in a nice big arc around the rover to get out in front of it again while maintaining a safe distance.

    • (Score: 3, Interesting) by janrinok on Wednesday May 31 2023, @03:27PM

      by janrinok (52) Subscriber Badge on Wednesday May 31 2023, @03:27PM (#1309065) Journal

      The Rover is vulnerable to certain types of terrain. The helo is used to plan routes in advance of the Rover, which in this case it couldn't do.

      The current route was chosen because the helo had worked far more than had been expected of it so it was thought to be a risk worth taking. I hope it can continue to contribute to the mission and identify hazards for the Rover to avoid.

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