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In all the downward-facing images from Ingenuity, I find it surprising that the rotor blades have a lighter shadow than the rest of the helicopter. I asked abou

In all the downward-facing images from Ingenuity, I find it surprising that the rotor blades have a lighter shadow than the rest of the helicopter. I asked about this on Twitter and was told the sensor for each pixel isn't fully shielded from light. The fast-moving rotor blades allow for latent light to enter into the sensor during the image scan, causing the rotor blade itself to appear slightly lighter. [1] [1]: https://twitter.com/sdamico/status/1384205372668350465 https://twitter.com/sdamico/status/1384205372668350465

Miraste 6y ago
> it’s identical to the Google Project Tango SLAM camera module That's fascinating, I would've guessed it had a special radiation-hardened camera like the processor.
- meepmorp 6y ago
  It’s using an off the shelf Snspdragon CPU. The whole helicopter is made with COTS parts.
  - Miraste 6y ago
    Oh, I meant on the rover. From googling, it seems the helicopter's design lifetime is too short for radiation damage to matter, and the cameras actually on the rover are rad-hardened to some degree.
    - ixfo 6y ago
      Generally cameras are reasonably rad-hard because the pixel size dictates a lot of the wiring size (and puts a lower bound on the process size). 3.5um pixels don't play well with 5nm features. Bigger features are generally more resistant to radiation fun.
    - kevin_thibedeau 6y ago
      Rad hard cameras intended for long term operation use CCDs with the drivers and ADCs off chip, implemented in a hardened process.
  - pkaye 6y ago
    This paper discusses the design of the helicopter. https://rotorcraft.arc.nasa.gov/Publications/files/Balaram_AIAA2018_0023.pdf https://rotorcraft.arc.nasa.gov/Publications/files/Balaram_A...
    - everybodyknows 6y ago
      Thanks! Fascinating hints at the complexities of working around radiation hazards: >MCU processor units operate redundantly, receiving and processing identical sensor data to perform the flight-control functions necessary to keep the vehicle flying in the air. At any given time, one of the MCU is active with the other waiting to be hot-swapped in case of a fault. >Each subsystem has a current monitor to detect possible latch-up current and can be power cycled to clear a SEL. In addition, current limiting is added to prevent a destructive SEL event and most devices are switched off when not in use to minimize their exposure to SEL. For the critical FPGA which is always on for the duration of the mission, the radiation tolerant ProASIC3 is chosen with the military temperature grade (-55 C to 125 C) and -1 speed grade to mitigate the degradation in the propagation delay caused by the total dose radiation.
      - meepmorp 6y ago
        I'm always amazed by the crazy crap people deal with in space, and how much protection the Earth affords us. Extreme temperatures, radiation, small bits of material traveling fast enough to go through structural metals like a knife; it's a thrill a second.
        martin_balsam 6y ago
        Don’t forget vacuum welding https://en.m.wikipedia.org/wiki/Cold_welding https://en.m.wikipedia.org/wiki/Cold_welding https://en.m.wikipedia.org/wiki/Vacuum_cementing https://en.m.wikipedia.org/wiki/Vacuum_cementing The first time it happened it must have been puzzling
        lisper 6y ago
        This is an important and highly under-appreciated point. We humans evolved under some very particular environmental conditions, ones which are radically different from space in almost every conceivable way. When people talk about colonizing Mars, I ask them to do the following thought experiment: imagine you are going to move to the Atacama desert. You have to live there for the rest of your life. You get to take one standard twenty-foot shipping container with you. You can pack that container however you like, but you have to live inside the container along with whatever stuff you pack it with for nine months before you can go out for the first time. Figuring out how to make that work is about 100 times easier than colonizing Mars.
hanoz 6y ago
Then shouldn't the circle swept by the blades look slightly darker than the surround?
- MontagFTB 6y ago
  Apparently the sweep circle is there but nearly indistinguishable from the ground.
  - ReactiveJelly 6y ago
    So the blades being lighter is a kind of motion blur? But instead of the typical envelope for exposure, it's got a long and low tail?

Miraste 6y ago

> it’s identical to the Google Project Tango SLAM camera module That's fascinating, I would've guessed it had a special radiation-hardened camera like the processor.

meepmorp 6y ago
It’s using an off the shelf Snspdragon CPU. The whole helicopter is made with COTS parts.
- Miraste 6y ago
  Oh, I meant on the rover. From googling, it seems the helicopter's design lifetime is too short for radiation damage to matter, and the cameras actually on the rover are rad-hardened to some degree.
  - ixfo 6y ago
    Generally cameras are reasonably rad-hard because the pixel size dictates a lot of the wiring size (and puts a lower bound on the process size). 3.5um pixels don't play well with 5nm features. Bigger features are generally more resistant to radiation fun.
  - kevin_thibedeau 6y ago
    Rad hard cameras intended for long term operation use CCDs with the drivers and ADCs off chip, implemented in a hardened process.
- pkaye 6y ago
  This paper discusses the design of the helicopter. https://rotorcraft.arc.nasa.gov/Publications/files/Balaram_AIAA2018_0023.pdf https://rotorcraft.arc.nasa.gov/Publications/files/Balaram_A...
  - everybodyknows 6y ago
    Thanks! Fascinating hints at the complexities of working around radiation hazards: >MCU processor units operate redundantly, receiving and processing identical sensor data to perform the flight-control functions necessary to keep the vehicle flying in the air. At any given time, one of the MCU is active with the other waiting to be hot-swapped in case of a fault. >Each subsystem has a current monitor to detect possible latch-up current and can be power cycled to clear a SEL. In addition, current limiting is added to prevent a destructive SEL event and most devices are switched off when not in use to minimize their exposure to SEL. For the critical FPGA which is always on for the duration of the mission, the radiation tolerant ProASIC3 is chosen with the military temperature grade (-55 C to 125 C) and -1 speed grade to mitigate the degradation in the propagation delay caused by the total dose radiation.
    - meepmorp 6y ago
      I'm always amazed by the crazy crap people deal with in space, and how much protection the Earth affords us. Extreme temperatures, radiation, small bits of material traveling fast enough to go through structural metals like a knife; it's a thrill a second.
      - martin_balsam 6y ago
        Don’t forget vacuum welding https://en.m.wikipedia.org/wiki/Cold_welding https://en.m.wikipedia.org/wiki/Cold_welding https://en.m.wikipedia.org/wiki/Vacuum_cementing https://en.m.wikipedia.org/wiki/Vacuum_cementing The first time it happened it must have been puzzling
      - lisper 6y ago
        This is an important and highly under-appreciated point. We humans evolved under some very particular environmental conditions, ones which are radically different from space in almost every conceivable way. When people talk about colonizing Mars, I ask them to do the following thought experiment: imagine you are going to move to the Atacama desert. You have to live there for the rest of your life. You get to take one standard twenty-foot shipping container with you. You can pack that container however you like, but you have to live inside the container along with whatever stuff you pack it with for nine months before you can go out for the first time. Figuring out how to make that work is about 100 times easier than colonizing Mars.

hanoz 6y ago

Then shouldn't the circle swept by the blades look slightly darker than the surround?

MontagFTB 6y ago
Apparently the sweep circle is there but nearly indistinguishable from the ground.
- ReactiveJelly 6y ago
  So the blades being lighter is a kind of motion blur? But instead of the typical envelope for exposure, it's got a long and low tail?