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The wheels of the Curiosity rover have hole patterns spelling J-P-L in Morse code. The reason why these existed in the first place was to help vision-based odometry and distance measurements, especially when driving over barren/featureless terrain. The Mars 2020 Perseverance rover wheels do not have such markers. Why is that?

Did the markers on Curiosity’s wheels turned out to not be that useful? Or are the new cameras onboard Perseverance so good that they can pick up the markings left by the (many) wavy grousers, without the need for distinct markers?

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  • $\begingroup$ It seemed like the most beneficial location for this more code was on “featureless plains”. Is Perseverance expected to cross a lot of this terrain, or is it exploring something totally different? $\endgroup$
    – IronEagle
    Feb 1, 2021 at 3:13
  • $\begingroup$ Good point! When looking at orbital maps, Jezero Crater looks like a feature-rich place, but I’m not sure about local features that will be visible from the rover’s perspective. $\endgroup$
    – olamarre
    Feb 1, 2021 at 16:00

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Perseverance's LCAM can image 1024x1024 pixels at 1 Hz, possibly faster. That's the camera used for visual odometry (after landing). I haven't found hard numbers for the camera that Curiosity used for this, but over nine years one would expect that both the camera and the software improved. Faster image processing would reduce the need for the relatively widely spaced image features created by the Morse code holes.

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  • $\begingroup$ Thanks for the reply! I however think that like Curiosity, Perseverance will be using its Navcams for visual odometry. Curiosity’s navcams only had a resolution of 1024x1024 px, and Perseverance’s are much better (and are colour). Also, the paper you linked mentions that the LCAM will not be used after landing for imaging purposes: “After landing, LCAM image acquisition will not be possible because the camera interface FPGA will be reconfigured to support stereo vision and visual odometry processing tasks.” $\endgroup$
    – olamarre
    Feb 1, 2021 at 15:56
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    $\begingroup$ Oops, I had misread that as "the LCAM won't be used in the way it was during landing... because odometry instead." You're right, it means, "after landing, the changed FPGA will disable the LCAM." The linked paper remains useful, but my answer is now mere speculation. $\endgroup$
    – Camille Goudeseune
    Feb 1, 2021 at 16:30

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