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The Ingenuity folks at NASA and lots of viewers on the internet I'm sure were pleased to see the first data from "the first flight of powered aircraft on another planet" (by humans at least); the output of the helicopter's altimeter.

Question: How does Ingenuity measure its altitude when flying? How does its altimeter work? Air pressure? Lidar? Laser displacement? Radar? Gamma rays? Something else?

Screenshot from the new NASA video First Flight of the Ingenuity Mars Helicopter: Live from Mission Control

enter image description here

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From multiple sites, but for the following quote, ScienceMag.org references a laser altimeter: (emphasis mine)

The data began to trickle in at 6:40 a.m. ET, relayed by the Perseverance rover to orbiters above and back to Earth. Cheers erupted 12 minutes later among Ingenuity’s small team of engineers and scientists when confirmation of a successful flight came, first from a laser altimeter showing that the helicopter had risen about 3 meters in the air. That data was followed by a picture from a camera on the helicopter's belly, showing its shadow directly below on the surface.

Additional research would indicate that the laser altimeter is a Garmin LIDAR-Lite V3. From the linked site:

So how is Garmin involved? Our technology — LIDAR-Lite v3 — will be measuring the distance from the helicopter to the ground. Ingenuity’s flight altitude goal is to get up to 15 feet (or 5 meters) from the surface of Mars for a flight lasting up to 90 seconds.

The link internal to the quote points to a purchase-related webpage: LIDAR-Lite v3 image

  • Weight: 22 g (0.77 oz)
  • Resolution: 1 cm
  • Accuracy: +/- 2.5 cm at distances greater than 1 meter. Refer to operating manual for complete operating specifications.
  • Range: 5 cm to 40 meters
  • Update rate: up to 500 Hz
  • Interface: I2C or PWM
  • Power (operating voltage): 4.75-5 VDC; 6 V Max
  • Current consumption: 105ma, idle; 130ma, continuous
  • Operating temperature: -20 to 60° C
  • Laser wave length/Peak power: 905 nm/1.3 watts
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  • $\begingroup$ Thanks for the edit, pretty cool! I hope you don't mind that I added a few of the relevant specifications, feel free to roll back or edit further. $\endgroup$ – uhoh Apr 19 at 22:57
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    $\begingroup$ I guess that's part of the "off-the-shelf" strategy. Makerspace NASA (or rather JPL). Pretty cool. $\endgroup$ – Peter - Reinstate Monica Apr 20 at 1:41
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    $\begingroup$ So this would be distance from the ground being measured, rather than distance above sea-level, as we're used to from typical earth-bound altimeters. (Makes sense since what would "sea-level" mean on Mars anyhow?) $\endgroup$ – Darrel Hoffman Apr 20 at 14:40
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    $\begingroup$ @DarrelHoffman Altitude above sea-level would depend on the distance between Earth and Mars. $\endgroup$ – Barmar Apr 20 at 15:04
  • $\begingroup$ @DarrelHoffman yes, it's referenced to the local surface, and they know the altitude of the local surface pretty well because Mars has been mapped and a reference surface or geoid has been defined. See How were Mars' zero elevation datum defined? What are their shapes? These days we usually use the WGS84 geoid on Earth rather than "sea level". The lat, lon and elevation reported by a GPS device is referenced to the WGS84 geoid I believe. $\endgroup$ – uhoh Apr 20 at 15:20

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