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Athena landed in a dark crater where the temperature was -280° F / -173° C

arstechnica.com

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Re: Athena landed in a dark crater where the temperature was -280° F / -173° C

#201

Post by kryogen1c »

jmmcd wrote: post #198

> The Athena spacecraft was not exactly flying blind as it approached the lunar surface one week ago. The software on board did a credible job of recognizing nearby craters, even with elongated shadows over the terrain. However, the lander's altimeter had failed. > So while Athena knew where it was relative to the surface of the Moon, the lander did not know how far it was above the surface. This is really crappy wri…

> That second paragraph sounds like a self-contradiction

Aside from the point you made, it actually IS a contradiction. Paraphrased:

>> Athena knew where it was relative to the surface of the Moon, but Athena did not know how far it was above the surface of the moon.

Relative position includes height/altitude? One understands from context, but this sentence does not carry meaning itself.

Re: Athena landed in a dark crater where the temperature was -280° F / -173° C

#202

Post by JonChesterfield »

Waterluvian wrote: post #146
ghostly_s wrote: post #139

This company's PR team is doing incredible work getting all this type of coverage out of a 0/2 track record with a design everyone else seems to think is obviously flawed.

What’s the prevailing criticism? High COG?

It's tall and narrow and falls over when it hits the ground moving fast. Irritating for intuitive machines whose stance is that mass is not uniformly distributed and center of mass is already low enough to make flight control somewhat challenging.

The criticism should perhaps be that the laser range finders are clearly a liability and a robust/workable backup for telling how far away the ground is needs to be brought along.

Re: Athena landed in a dark crater where the temperature was -280° F / -173° C

#203

Post by pclmulqdq »

scarab92 wrote: post #191
smolder wrote: post #180

Earlier quoted context omitted.

Ars has been one of the best publications across my whole experience with the internet, going on 20+ years. Without them I wouldn't have been clued into how broken the internet is.

The articles (except for the syndicated Wired articles) are great, but the comment section is Reddit-level degeneracy.

The articles often have good style, but redditor-level insight.

Re: Athena landed in a dark crater where the temperature was -280° F / -173° C

#204

Post by lionkor »

JonChesterfield wrote: post #199
lionkor wrote: post #188

the altimeter? Surely you would put three on there?

Had two. One showed so much measurement noise they couldn't trust it, other kept cutting out. Not great.

So three ones, two different models, one in a different location. These are like... basics, no?

Re: Athena landed in a dark crater where the temperature was -280° F / -173° C

#205

Post by chrisweekly »

TylerE wrote: post #143
Seanambers wrote: post #99

Earlier quoted context omitted.

Multiple sea landings, but I guess you'd argue those don't count since the vehicles tip over in water and explode. Moving barges in the sea should qualify though.

They also have the atmosphere, with drag that will make all velocities trend towards zero. Don’t have that on the moon, gotta do it all with fuel. More than half of the energy she’s by the returning falcon is aerobraking. Yes, the moon has substantially less gravity but it’s also exponentially harder to get the fuel there.

"the atmosphere, with drag that will make all velocities trend towards zero"

Did you forget about gravity? Terminal velocity in free-fall is not zero!

Re: Athena landed in a dark crater where the temperature was -280° F / -173° C

#206

Post by randallsquared »

jmmcd wrote: post #198

> The Athena spacecraft was not exactly flying blind as it approached the lunar surface one week ago. The software on board did a credible job of recognizing nearby craters, even with elongated shadows over the terrain. However, the lander's altimeter had failed. > So while Athena knew where it was relative to the surface of the Moon, the lander did not know how far it was above the surface. This is really crappy wri…

It knew where it was selenographically, which is what the author means by "relative to the surface of the moon", I think.

Re: Athena landed in a dark crater where the temperature was -280° F / -173° C

#207

Post by Tyr42 »

wruza wrote: post #186
someothherguyy wrote: post #171

Earlier quoted context omitted.

Does anyone know an extension that strips this tracking information and normalizes YouTube URLs?

Just in case, I’m using my own violentmonkey scripts rather than hoping for extensions, and everyone can do that too (now only on firefox, I guess, and maybe brave). For example, I remove &t= from urls that youtube added recently in addition to regular watch position restoration. This broke it for me and they don’t seem to plan a revert.

That is also used if you want to share a video at a particular timestamp with someone. E.g. check this out it happens 40s in. YouTube.com....&t=40s

Re: Athena landed in a dark crater where the temperature was -280° F / -173° C

#208

Post by HenryBemis »

kryogen1c wrote: post #201
jmmcd wrote: post #198

> The Athena spacecraft was not exactly flying blind as it approached the lunar surface one week ago. The software on board did a credible job of recognizing nearby craters, even with elongated shadows over the terrain. However, the lander's altimeter had failed. > So while Athena knew where it was relative to the surface of the Moon, the lander did not know how far it was above the surface. This is really crappy wri…

> That second paragraph sounds like a self-contradiction Aside from the point you made, it actually IS a contradiction. Paraphrased: >> Athena knew where it was relative to the surface of the Moon, but Athena did not know how far it was above the surface of the moon. Relative position includes height/altitude? One understands from context, but this sentence does not carry meaning itself.

I read this and I thought it was a bad writing, and I assumed (right or wrong) that (metaphor ensues):

The airplane's pilot could see where the ground was and he estimated it was 1000m-1200m below. But the instrument of the airplane were malfunctioning and reported that the ground was at 500m (or 5000m). This caused the plane to override/resist the pilot's manual landing efforts causing the plane to ultimately crash but not allowing the wheels to come down and the flaps to do turn.

So two different mechanisms, providing contradicting evidence, and the lack of a 'higher' deciding authority to use 'judgment' and/or other inputs to 'decide' which reported measurements are more accurate, and thus make the viable decision/take the viable action.

I get that for such devices every-gram-counts, and perhaps from now on some devices/mechanisms that are truly single-points-of-failure, will get 2x or 3x for redundancy/contingencies. If your ABC-camera fails, it's 'ok' you can still get images from your DEF and GHI will give you some data, reducing to 80% the output of the mission, but still not making it 5%. Your 'landing equipment' fails, and you get out only 5% of the value (flying/trajectory/telemetry of flight/perhaps some eclipse photos).

Re: Athena landed in a dark crater where the temperature was -280° F / -173° C

#209

Post by ivanjermakov »

TimByte wrote: post #182
ivanjermakov wrote: post #151

Why people make temperature in space a big deal? It's mostly vacuum and has no heat capacity. Sun radiation is the real threat, but the concept of temperature can't even be applied to vacuum.

The problem here isn't the vacuum itself, but that surfaces facing away from the sun radiate heat rapidly into space, causing extremely low temperatures on lander components. That's why temperature still matters practically, even if it's a bit counterintuitive.

Does it matter, if vacuum does not conduct heat? Lander would not experience conductive heat unless it has a great contact with the ground.

Re: Athena landed in a dark crater where the temperature was -280° F / -173° C

#210

Post by [deleted] »

jmmcd wrote: post #198

> The Athena spacecraft was not exactly flying blind as it approached the lunar surface one week ago. The software on board did a credible job of recognizing nearby craters, even with elongated shadows over the terrain. However, the lander's altimeter had failed. > So while Athena knew where it was relative to the surface of the Moon, the lander did not know how far it was above the surface. This is really crappy wri…

[deleted]
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