Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

NASA's Perseverance rover sends stunning images

bbc.com

Post reply on HN
Print view View original

231–240 of 365 posts

Re: NASA's Perseverance rover sends stunning images

#231

Post by londons_explore »

jdmichal wrote: post #190
akg_67 wrote: post #168

Earlier quoted context omitted.

Reddit had AMA with engineers from this mission, IIRC last week. They provided good info on different aspects including how they were able to get video over low bandwith connection, including various mission site link for more info. You might want to check out AMA for your question. Edit: added following links This Q&A about storage https://www.reddit.com/r/IAmA/comments/lpzbzo/were_scientist... These Q&A about data…

Others have posted links to the Reddit thread overall, but I think this is the specific question being referred to: https://old.reddit.com/r/IAmA/comments/lpzbzo/were_scientist... EDIT: Apparently the rover has an antenna that can directly communicate with Earth at 10 bits per second! That's obviously not useful for pictures or anything, but it's an amazing capability for emergency comms.

Very low bandwidth, very low power, very long distance comms are really cool. The limiting factor tends to be the clock frequency precision - if you have precise enough clocks at both ends, there isn't anywhere in the universe you couldn't communicate with, as long as you're happy to go slow enough.

Re: NASA's Perseverance rover sends stunning images

#232

Post by berkes »

vasco wrote: post #192
berkes wrote: post #189

Looking at closeups of the Rover, I cannot help but think: are those screws, nuts and bolts? And if so, why? Why carry the weight or decreased stiffness of or by the notches, slits, threads etc. that makes screws be screwable. To a place where no-one ever will unscrew them?

I predict that the chances of someone ever unscrewing them are higher than not. Just not super soon. Plus during development its useful, and why would you change the platform you test when deploying to live?

My thoughts as well: the benefits during development outweigh any downsides during transport and deployment.

My other thought is that I simply saw it wrong and there are no screws in the rover, just things that look like screws, nuts or bolts.

Re: NASA's Perseverance rover sends stunning images

#233

Post by Symbiote »

gtm1260 wrote: post #87

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.

Is it simply dusty/hazy?

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

Re: NASA's Perseverance rover sends stunning images

#235

Post by magicalhippo »

londons_explore wrote: post #231
jdmichal wrote: post #190

Earlier quoted context omitted.

Others have posted links to the Reddit thread overall, but I think this is the specific question being referred to: https://old.reddit.com/r/IAmA/comments/lpzbzo/were_scientist... EDIT: Apparently the rover has an antenna that can directly communicate with Earth at 10 bits per second! That's obviously not useful for pictures or anything, but it's an amazing capability for emergency comms.

Very low bandwidth, very low power, very long distance comms are really cool. The limiting factor tends to be the clock frequency precision - if you have precise enough clocks at both ends, there isn't anywhere in the universe you couldn't communicate with, as long as you're happy to go slow enough.

Given self-clocking signalling[1] exists, why is clock frequency precision the limiting factor?

I would imagine signal-to-noise would be the limiting factor, ie how strong is your transmitter and how sensitive is your receiver.

[1]: https://en.wikipedia.org/wiki/Self-clocking_signal

Re: NASA's Perseverance rover sends stunning images

#236

Post by zaik »

TeMPOraL wrote: post #221
histriosum wrote: post #195

Earlier quoted context omitted.

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...

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.

Re: NASA's Perseverance rover sends stunning images

#237

Post by zimpenfish »

DrBazza wrote: post #228
dvfjsdhgfv wrote: post #225

Earlier quoted context omitted.

Incredible for me, too. The power of building the civilization, one generation after another, and of working together, sharing the knowledge.

But according to Ancient Aliens, the large stone Pyramids were built by aliens, but the TV cameras recording the show's hosts, with CCDs, and likely 10nm chips inside, were built by humans. In all seriousness, it's impressive what knowledge sharing and cooperation achieves.

[Ancient Aliens] Ah but the cameras and chips are only possible -because- the aliens built the pyramids and inspired humans technologically and a mere 4450 years later, voila! CCDs and computer chips!

Re: NASA's Perseverance rover sends stunning images

#238

Post by londons_explore »

magicalhippo wrote: post #235
londons_explore wrote: post #231

Earlier quoted context omitted.

Very low bandwidth, very low power, very long distance comms are really cool. The limiting factor tends to be the clock frequency precision - if you have precise enough clocks at both ends, there isn't anywhere in the universe you couldn't communicate with, as long as you're happy to go slow enough.

Given self-clocking signalling[1] exists, why is clock frequency precision the limiting factor? I would imagine signal-to-noise would be the limiting factor, ie how strong is your transmitter and how sensitive is your receiver. [1]: https://en.wikipedia.org/wiki/Self-clocking_signal

It is possible to send a signal weaker than the noise floor. The maximum information you can send is defined by shannon's channel capacity formula, which clearly says a signal can be weaker than the noise.

If you use a self-clocking signal, then effectively the information you are sending consists of both the clock timings and the information you're really trying to send. If your channel capacity is very low, you will find there is no channel capacity for even the clocking information, let alone the information you really want to send.

Re: NASA's Perseverance rover sends stunning images

#239

Post by tremon »

magicalhippo wrote: post #235
londons_explore wrote: post #231

Earlier quoted context omitted.

Very low bandwidth, very low power, very long distance comms are really cool. The limiting factor tends to be the clock frequency precision - if you have precise enough clocks at both ends, there isn't anywhere in the universe you couldn't communicate with, as long as you're happy to go slow enough.

Given self-clocking signalling[1] exists, why is clock frequency precision the limiting factor? I would imagine signal-to-noise would be the limiting factor, ie how strong is your transmitter and how sensitive is your receiver. [1]: https://en.wikipedia.org/wiki/Self-clocking_signal

Noise, by definition, doesn't have a qualifying characteristic. It just means "all signals we're not interested in". That means your ability to filter out noise is strongly dependent on having pre-existing knowledge about the shape of the signal you're interested in.

Self-clocking signals are useful when the ambient noise level is low with respect to the signal, but if your signal is just "these two droplets in an ocean" you will not be able to filter out enough of the signal to detect the edges of the original signal.

Having a very reliable clock frequency means you can apply a very exact filter to lock on to the signal you want, thereby making the transmission less sensitive to interference from other radio signals. Just having a sensitive receiver isn't enough, because a sensitive receiver will also pick up more of the other radio signals.

Re: NASA's Perseverance rover sends stunning images

#240

Post by athul7744 »

dmix wrote: post #181
gtm1260 wrote: post #87

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.

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.

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