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Comment by gtm1260 | Hacker News Reader

Stupid question maybe but like is there a reason the picture quality seems worse than a decent dslr photo? I'm so curious what that photo would look like, taken with an everyday camera, without the bizarre 'scientific' look of these shots.

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Generally, these cameras are many years out of date.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.

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!

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.

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.

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.

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 ?

You got me curious and I found a product listing with a rather amazing explanation of what they're doing for radiation-proofing.

Radiation Performance

> RTG4 FPGAs are immune to radiation-induced changes in configuration, due to the robustness of the flash cells used to connect and configure logic resources and routing tracks. No background scrubbing or reconfiguration of the FPGA is needed in order to mitigate changes in configuration due to radiation effects. Data errors, due to radiation, are mitigated by hardwired SEU resistant flip-flops in the logic cells and in the mathblocks. Single Error Correct Double Error Detect (SECDED) protection is optional for the embedded SRAM (LSRAM and uSRAM) and the DDR memory controllers. This means that if a one-bit error is detected, it will be corrected. Errors of more than one bit are detected only and not corrected. SECDED error signals are brought to the FPGA fabric to allow the user to monitor the status of these protected internal memories.

https://www.microsemi.com/product-directory/rad-tolerant-fpg...

Wow, a rad hard FPGA! Now that's something I didn't expect - thanks for digging this up! :)

I know the camera image compression happens on a x86 processor. Not sure if it is rad hardened. It would be okay if the processor is not doing critical work and can be power cycled due to a rare SEU failure. Also the same with the helicopter uses a mobile phone processor.

Also some of the components are not rated for long term use. The microphones they installed will probably fail due to extreme temperature cycling. The helicopter is expected to last only 4 uses and anything beyond that is a bonus.

They did this exact thing with the helicopter — it's using a Snapdragon SoC that runs Linux.

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.

> 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.

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).

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.

a $100k here, a $100k there, suddenly, we're talking real money.

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.

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?

Thankfully, SpaceX isn't waiting for anyone. They are in the front with a machete wacking down the limbs leaving a trail for others to follow. Of course SpaceX is standing on the shoulders of those missions that lead the way before, but let's be honest, after Gemini, Mercury, Apollo, Shuttle, everything else has been a bit stagnant. Not taking anything away from all of the probes and rover missions. Those are the only things that make NASA relevant. Finally, we have a space agency actively working on humans in space again.

And it's not like people at JPL are clenching their fists and screaming, "Damn you, Shotwell! Begone, Mueller! SEC eat you, Musk!". NASA is fully on-board with what SpaceX is doing - cutting straight into and reversing the dreaded Space Mission Costs Spiral. They may be cautious now, but eventually, they'll just start putting scientific probes on SpaceX rockets too (and those of competitors). SLS notwithstanding, NASA is happy to outsource launches and focus on bleeding edge missions.

And if SpaceX blazes the trail? Expect more scientific missions to follow, as cheaper and more frequent launches - the Spiral put into reverse - cuts mission costs across the board. NASA will be able to do more cool stuff with their budget. And so will everyone else.

IIRC it’s a custom process using wide-bandgap silicon (part of the whole rad-hardening thing) that no-one else needs or wants, so you have to pay the full costs of a fab run for a relatively small number of chips. Hence the cost per chip is huge.

The low demand definitely leads to higher prices but the other aspect is all of the additional testing involved for every chip. There's standard testing at every level of the manufacturing process and there will be further environmental testing at the package level. They will even run radiation tests on the wafer to characterize any quirks.

Hopefully as more space & deep space stuff gets going there will be more demand and the unit cost will go down thanks to economies of scale. Or alternatively ways of computing are tried and found viable (massive shielding, standardized massive redundancy, etc.).

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

For radiation-hardened semiconductors sometimes you use specialized processes like silicon-on-insulator. Even if you're using a more conventional process, you're probably using specialized upset-resistant gate designs and layout. And even your gate-level or HDL-level design might have changes to make it possible to detect and recover from some kinds of bitflips. It really affects the whole technology stack.

Specs: https://en.wikipedia.org/wiki/RAD750

Scott Manley recently did a pretty good ELI5 on the topic: https://www.youtube.com/watch?v=Wah1DbFVFiY

It takes 15min but this plus the comment section on CMOS (can’t link directly) is excellent. The other comment about being made a decade ago is also relevant and accurate. They will certainly be better next time with evolutions in camera tech thanks to smartphones.

TLDR worth a listen

My question is why was the “sound of Mars” release only 18 seconds long?

Why not record hours of what it sounds like to be on another planet? Even the sound recordings from decades ago on (I think Titan) was only a short creepy clip.

I understand it’s mostly going to be wind and interspliced with the robots sounds but I still don’t get how we don’t have hours of Mars already.

My guess would be bandwidth. Every bit of bandwidth is precious, so they probably dont have the spare budget to send long audio files without obvious scientific value...

Yes, but you could record few minutes of sound in the same amount of data taken by one high res photo. I think the good question is why 18 seconds specifically.

It's just 18 seconds so far. I doubt they sent the microphone just so they could use it once, but then I doubt sending hours of audio was at the top of the priority list for the first few days of the mission.

Maybe after they complete their primary and secondary mission objectives, they'll find spare time and compute to stream a couple hours of Martian ambience. Does NASA have a suggestion box for after hours / extended program experiments?

I doubt a NASA suggestion box open to the internet will be very fruitful.

I for one look forward to Rover McRoverface in the 2022 launch window.

Marvin McMarsface is to take a close-up look at the Face On Mars in 2023 and then implant an Illudium Q-36 Explosive Space Modulator to eliminate Mars because it obstructs our view of Venus.

> I doubt a NASA suggestion box open to the internet will be very fruitful.

The two resectful and fun comments between 'this' comment and your comment.

I can imagine a Tumblr/Reddit re-post would be more fun, but-yes-not for the NASA suggestion box. They would have 1 diamond idea every 100k unusable ones.

I can imagine every gaming company would LOVE to have the original Mars sound in their games (e.g. "No Man's Sky").

In a world where the sounds of sports on TV is not even the true sound of what's happening in the stadium because it's boring, I highly doubt they would pay a single penny for what would probably be a highly disappointing wind-like monotonous sound.

One of the most beautiful and haunting things I've ever heard was a tape cassette that had EM signals recorded by Voyager transposed into human-audible sound domain somehow. It was like whale song of space.

I found it here (there's a series on other planets/moons as well in the recommendations):

https://www.youtube.com/watch?v=LIAZWb9_si4

And Cassini flying into Saturn https://www.youtube.com/watch?v=hWHLCHv4PiI

I wonder what it sounds like to leave the atomosphere now too, I guess this is as close as we can get in the near future. Even with probes going 15km/s.

Ah yeah, that's the kind of thing! Cheers! The tape was recorded much earlier though (I was listening to it in the late 90's IIRC) and a lot longer.

Perseverance is the first rover with microphones on Mars. This is why we don't have audios from prior missions.

Working microphones. They've sent microphones previously, which have either failed or been on missions that crashed.

IIRC the Mars Insight mission was able to reconstruct the sounds of wind in Mars from signals picked up by their super sensitive seismometter.

speculation, but it's probably compressed before transmission to earth... for obvious reasons.

It would surprise me if they used lossy compression. However I once read about a space probe using a custom image compression and transmission format which does not require 100% data integrity for proper decoding. So if the transmission is cut off after 60% NASA will still be able to view whatever they received. I assume such methods are still applied.

Is it simply dusty/hazy?

Some of the fuzzy photos remind me of the Sahara Desert when there was a little wind.

Dusty. Gives the sky a dull reddish color. Also makes Martian sunsets blue.

In some interviews with the mast cam engineers, they say they can capture higher resolution images later on. Maybe they were reducing the image size to get then transmitted quicker.

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