5 ms·

Generally, these cameras are many years out of date. They don't load up the rovers with the latest gear from today, but with the latest gear from when the desig

Generally, these cameras are many years out of date. They don't load up the rovers with the latest gear from today, but with the latest gear from when the design review process was closed. I don't know when that was for Perseverance, but it would not surprise me if that was a decade ago. The cameras are also not specifically designed for image capture, but for scientific study. In that they take images at a wider range of wavelengths than what humans can see. It's a subtle difference, but an important one. Additionally, the cameras' chips are not what we have commercially. They are designed to withstand the vacuum, the solar radiation on the long transit, and for use on the Martian surface for many years. You can't swap them out, ever. As such, they are much more 'rugged', which may effect image quality as well.

reilly3000 6y ago
Yep, that’s the same reason why it runs on a PowerPC750 chip. They cost $200k+ for under 200Mhz on a 150-250 nm process, but can withstand up to 1,000,000 rads of radiation and function within extreme temperature ranges for decades. They have been proven to work in the harshest environments on prior missions, and the risk of an unproven processor is giant; a CPU failure could jeopardize the mission just as much as a crash landing. Design constrains are so very different when you shoot something 140M miles away!
- Cthulhu_ 6y ago
  Especially since hardware is generally designed for speed and performance instead of reliability. Didn't NASA use a lot of 486es for a long time for this same reason? But yeah. It's not a problem if a CPU gets buggy or dies in a datacenter with 10K similar ones, because of redundancy and a completely different approach to software workloads nowadays. I mean a lot of production systems barely even care what CPU they run on. And ~200 Mhz is still powerful enough for a LOT of applications.
  - darkr 6y ago
    > Didn't NASA use a lot of 486es for a long time for this same reason? They were also using Amigas until ~2006 for various duties, including launch control.
- wiz21c 6y ago
  Could you explain why such a processor is 1000x more expensive than a non-rugged one ? I mean, considering the future of earth, I'd certainly welcome a processor that could withstand a lifespan of decades (including the harsh "I'm going to unsolder it to put it in another device" environment).
  - ben_w 6y ago
    From this list, I assume the isotopic purity is the biggest contribution to the price, though I expect relative lack of mass production doesn’t help: https://en.m.wikipedia.org/wiki/Radiation_hardening https://en.m.wikipedia.org/wiki/Radiation_hardening
  - TeMPOraL 6y ago
    Part of it is low demand, so you don't benefit from economies of scale. Also the customers buying this type of equipment are able to bear such costs. They aren't gonna haggle over $100k on a critical component to a $3B mission.
    - dylan604 6y ago
      a $100k here, a $100k there, suddenly, we're talking real money.
      - reilly3000 6y ago
        Oh we're talking real money. JPL will destroy 78 production grade parachutes to find all the ways they can break. There is tremendous energy poured into eliminating risk, because launch is so expensive. As it becomes cheaper, perhaps these measures won't be as necessary.
        derekp7 6y ago
        With Spacex being able to launch a car out beyond the orbit of Mars, is their current capability being considered for future JPL missions? Or is everything waiting on Starship?
- velvetz 6y ago
  Maybe a stupid question, but couldn’t they put there something “cutting-edge” next to the existing system? Then if that fails then whatever, the rest of the system is still functional as expected, but at least they know that in the future what they would need to change to be able to use the new technologies in that environment. Although I can imagine that even the smallest weight increase could cause issues, so probably that’s the reason.
  - wongarsu 6y ago
    Ingenuity (the Mars helicopter) has a much more modern processor that isn't particularly radiation hardened, and instead just restarts within milliseconds on any fault (fast enough to recover if it happens in flight). If Ingenuity does well I wouldn't be surprised to see a similar design in a future rover.
  - grishka 6y ago
    They did this exact thing with the helicopter — it's using a Snapdragon SoC that runs Linux.
  - josho 6y ago
    But now you’ve added weight and need to remove something else. As a tangent, I remember a talk from Grady Booch where he put software cost in terms of mass that needed to be added to your rocket. So every new feature cost weight by requiring more chips and more fuel.
  - m4rtink 6y ago
    Scott Manley mentioned in one of his recent videos about Perserverance that they have an FPGA on board the rad hardened PPC main cpu can offload tasks to, such computer vision based navigation during landing. Not sure what the long term plan is for that hardware - I guess they can just do stuff more slowly on the main CPU if it gets fried by radiation. Or maybe being an FPGA the can just isolate the radiation affected regions over time and use the rest ?
    - reilly3000 6y ago

reilly3000 6y ago

Yep, that’s the same reason why it runs on a PowerPC750 chip. They cost $200k+ for under 200Mhz on a 150-250 nm process, but can withstand up to 1,000,000 rads of radiation and function within extreme temperature ranges for decades. They have been proven to work in the harshest environments on prior missions, and the risk of an unproven processor is giant; a CPU failure could jeopardize the mission just as much as a crash landing. Design constrains are so very different when you shoot something 140M miles away!

Cthulhu_ 6y ago
Especially since hardware is generally designed for speed and performance instead of reliability. Didn't NASA use a lot of 486es for a long time for this same reason? But yeah. It's not a problem if a CPU gets buggy or dies in a datacenter with 10K similar ones, because of redundancy and a completely different approach to software workloads nowadays. I mean a lot of production systems barely even care what CPU they run on. And ~200 Mhz is still powerful enough for a LOT of applications.
- darkr 6y ago
  > Didn't NASA use a lot of 486es for a long time for this same reason? They were also using Amigas until ~2006 for various duties, including launch control.
wiz21c 6y ago
Could you explain why such a processor is 1000x more expensive than a non-rugged one ? I mean, considering the future of earth, I'd certainly welcome a processor that could withstand a lifespan of decades (including the harsh "I'm going to unsolder it to put it in another device" environment).
- ben_w 6y ago
  From this list, I assume the isotopic purity is the biggest contribution to the price, though I expect relative lack of mass production doesn’t help: https://en.m.wikipedia.org/wiki/Radiation_hardening https://en.m.wikipedia.org/wiki/Radiation_hardening
- TeMPOraL 6y ago
  Part of it is low demand, so you don't benefit from economies of scale. Also the customers buying this type of equipment are able to bear such costs. They aren't gonna haggle over $100k on a critical component to a $3B mission.
  - dylan604 6y ago
    a $100k here, a $100k there, suddenly, we're talking real money.
    - reilly3000 6y ago
      Oh we're talking real money. JPL will destroy 78 production grade parachutes to find all the ways they can break. There is tremendous energy poured into eliminating risk, because launch is so expensive. As it becomes cheaper, perhaps these measures won't be as necessary.
      - derekp7 6y ago
        With Spacex being able to launch a car out beyond the orbit of Mars, is their current capability being considered for future JPL missions? Or is everything waiting on Starship?
velvetz 6y ago
Maybe a stupid question, but couldn’t they put there something “cutting-edge” next to the existing system? Then if that fails then whatever, the rest of the system is still functional as expected, but at least they know that in the future what they would need to change to be able to use the new technologies in that environment. Although I can imagine that even the smallest weight increase could cause issues, so probably that’s the reason.
- wongarsu 6y ago
  Ingenuity (the Mars helicopter) has a much more modern processor that isn't particularly radiation hardened, and instead just restarts within milliseconds on any fault (fast enough to recover if it happens in flight). If Ingenuity does well I wouldn't be surprised to see a similar design in a future rover.
- grishka 6y ago
  They did this exact thing with the helicopter — it's using a Snapdragon SoC that runs Linux.
- josho 6y ago
  But now you’ve added weight and need to remove something else. As a tangent, I remember a talk from Grady Booch where he put software cost in terms of mass that needed to be added to your rocket. So every new feature cost weight by requiring more chips and more fuel.
- m4rtink 6y ago
  Scott Manley mentioned in one of his recent videos about Perserverance that they have an FPGA on board the rad hardened PPC main cpu can offload tasks to, such computer vision based navigation during landing. Not sure what the long term plan is for that hardware - I guess they can just do stuff more slowly on the main CPU if it gets fried by radiation. Or maybe being an FPGA the can just isolate the radiation affected regions over time and use the rest ?
  - reilly3000 6y ago