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Perseverance Rover lands on Mars [video]

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Re: Perseverance Rover lands on Mars [video]

#231

Post by whatshisface »

gfiorav wrote: post #197
unanswered wrote: post #167

Something I don't understand: when they say "X is 1 minute from happening", does that mean it's really 1 minute from happening or does that mean "in 1 minute we'll receive the signal that X has happened"? Maybe my question makes more sense in the case of "X is happening right now", because then I should either understand "we infer that X should have happened right about now" or "we have confirmed via signal that X ha…

Waiting for the physicist in the room to point out: there is no such thing as simultaneity! :)

Simultaneity is at least as well defined as clock time. Both clock time and the velocity of your reference frame can have arbitrary constants added to them to yield equally valid coordinate systems. So "it's not really simultaneous" is analogous to "it's not really 6:30 PM."

Re: Perseverance Rover lands on Mars [video]

#232

Post by bluescrn »

joeyh wrote: post #198
bluescrn wrote: post #133

Earlier quoted context omitted.

Dust on the solar panel seems likely to be a problem after the first landing, unless it's got a clever way to keep it clean. And its got to be tough conditions for the battery, low temperatures and probably deep discharges to make the most of it.

It's powered by plutonium. Rovers with solar panels deal with the dust by waiting for a storm to blow it away.

Perseverance is powered by an RTG, but the Ingenuity, the helicopter, is powered by lithium-ion batteries recharged via a solar panel.

I'd expect it to kick up a fair bit of dust on landing. But I suppose that's something else that'll behave a bit differently on Mars to what we'd expect in Earth's atmosphere.

Re: Perseverance Rover lands on Mars [video]

#233

Post by ddingus »

kharak wrote: post #203
nwallin wrote: post #177

Earlier quoted context omitted.

Other posters have pointed out that it's the hazard avoidance camera, but they haven't said why the hazard avoidance camera is black and white. When you do computer vision, the first step you do is convert your color image into a black and white image, and run your CV algorithms on the black and white image. This is because when you're looking at objects and shapes and stuff, it's contrast that tells you where the bo…

Thank you for the explanation. That was highly interesting. Does anyone else know if the human eye does perceive color directly? Is this at all technically possible? And if yes, why aren't we doing it with cameras?

I believe in purple.

After you get done exploring how we perceive colors associated with different wave lengths of light, and how nobody really knows whether these are common somehow, or unique to each of us, that sentence should bring you both a chuckle and some wonder about perception.

Re: Perseverance Rover lands on Mars [video]

#234

Post by dmix »

tectonic wrote: post #14

You can also watch an EDL visualization in your browser: https://eyes.nasa.gov/apps/mars2020/#/home And read about how it will use Terrain Relative Navigation to find a safe landing spot: https://www.jpl.nasa.gov/news/a-neil-armstrong-for-mars-land... Perseverance is phenomenally complex, its Sample Caching System alone contains 3,000+ parts and two robotic arms. So exited for all the sciencing this nuclear-powered,…

> And read about how it will use Terrain Relative Navigation to find a safe landing spot:

So basically TERCOM from cruise missles but used on space crafts? All you need is a radar countour map of the area and it can automate it's way to the endzone.

https://en.wikipedia.org/wiki/TERCOM

Re: Perseverance Rover lands on Mars [video]

#235

Post by interestica »

themeiguoren wrote: post #206
ehsankia wrote: post #100

Earlier quoted context omitted.

Worth noting that these first pictures are sent in the first seconds after touchdown, you can even still see the dust in the air from the landing (even if it was craned down to reduce dust). It also explains the very low resolution in general, they want to get confirmation ASAP, no time for high quality high resolution images.

The low resolution and fuzz is also because they still have the lens caps on - they are of course transparent lens caps in case the explosive bolts that will release them fail. Redundancy!

This is one of the cooler things that I learned today. Could they go even further: make the caps themselves lenses+filters. Take photos. And then blow them off for new photos.

Re: Perseverance Rover lands on Mars [video]

#236

Post by spaetzleesser »

tectonic wrote: post #14

You can also watch an EDL visualization in your browser: https://eyes.nasa.gov/apps/mars2020/#/home And read about how it will use Terrain Relative Navigation to find a safe landing spot: https://www.jpl.nasa.gov/news/a-neil-armstrong-for-mars-land... Perseverance is phenomenally complex, its Sample Caching System alone contains 3,000+ parts and two robotic arms. So exited for all the sciencing this nuclear-powered,…

They should make km the default unit and not miles....

Re: Perseverance Rover lands on Mars [video]

#237

Post by dralley »

kibwen wrote: post #138
nelsonmandela wrote: post #117

Apparently the copter was made with off-the-shelf parts. I wonder if I can cop a replica somewhere, and how it would fly considering it is built for martian air

Here's a really excellent video that answers all your questions: https://m.youtube.com/watch?v=GhsZUZmJvaM TL;DW: Martian atmosphere is so sparse that it's equivalent to flying at 100,000 feet on Earth. (The altitude record on Earth is 85,000 feet, set by the SR-71.) In order to fly at all the blades have to spin at nearly the (Martian) speed of sound. The drone wouldn't fly on Earth because the atmosphere is so dens…

> (The altitude record on Earth is 85,000 feet, set by the SR-71.)

The A-12 Arkangel flew higher (95,000 feet) and faster, but was short-lived and so highly classified that it doesn't hold any "official" records.

And a MiG pilot flew up to 123,000 feet, but only on a ballistic trajectory, it wasn't a sustainable altitude.

Re: Perseverance Rover lands on Mars [video]

#238

Post by bregma »

whatshisface wrote: post #231
gfiorav wrote: post #197

Earlier quoted context omitted.

Waiting for the physicist in the room to point out: there is no such thing as simultaneity! :)

Simultaneity is at least as well defined as clock time. Both clock time and the velocity of your reference frame can have arbitrary constants added to them to yield equally valid coordinate systems. So "it's not really simultaneous" is analogous to "it's not really 6:30 PM."

Well, it's 6:30 PM somewhere.

lifts glass

Re: Perseverance Rover lands on Mars [video]

#239

Post by walrus01 »

gfiorav wrote: post #197
unanswered wrote: post #167

Something I don't understand: when they say "X is 1 minute from happening", does that mean it's really 1 minute from happening or does that mean "in 1 minute we'll receive the signal that X has happened"? Maybe my question makes more sense in the case of "X is happening right now", because then I should either understand "we infer that X should have happened right about now" or "we have confirmed via signal that X ha…

Waiting for the physicist in the room to point out: there is no such thing as simultaneity! :)

> simultaneity

not in the true accurate to the picosecond sense of the word, no, but the exact word simultaneity is used when discussing number and density of satellites about a given latitude/longitude in the starlink beta program. Since they're LEO and orbiting at only 550 km, the satellites above a given spot on the ground vary greatly in the not-yet-complete sparse network.

Usually related to discussions of whether a beta test customer terminal will briefly hiccup and lose connection to its default gateway, or if somebody is at a sufficiently high latitude that they can have full coverage for all 86400 seconds in a day.

https://satellitemap.space/ has a good animated visualization of this.

Re: Perseverance Rover lands on Mars [video]

#240

Post by interestica »

robinjfisher wrote: post #92
kaycebasques wrote: post #78

Earlier quoted context omitted.

N00b question: why is it black & white?

This was explained on the feed. It's from a lower-res safety camera mainly used for object avoidance on the ground. High definition images will be available later.

https://mars.nasa.gov/mars2020/multimedia/raw-images/

It seems that NASA is being awesome and making all raw images available as they get them. So far just the 2-ish.

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