undefined | Better HN

0 pointscaconym_4y ago0 comments

> While I understand you're trying to point out hubris, you're swaying the other way and appealing to authority.

I'm appealing to the fact that they sent the thing to Mars and flew it. If you think "any hobbyist" could have trivially done a better job, which seems to be essentially what you're saying, there isn't much for me to say to you other than that I strongly disagree. And if I'm supposed to be the one who's appealing to authority here, I'm not sure what everybody else thinks they're doing.

I expect JPL tends toward having generalists working on projects like this, and I expect they do have things to learn. Nothing in my comment contradicts any of that. But the level of armchair quarterbacking in here is crazy and IMO largely unjustified.

0 comments

stevenhuang4y ago

They expected the camera not to drop frames. Their optical flow system tracked time independent of actual frame time. Anyone who've done optical flow or even anything with video recording on embedded devices knows these are known failure modes, and should be handled properly.

That is what's being discussed here, this is the failure mode in question. So yes, those experienced in optical flow and embedded control systems _would_ have handled this specific failure better.

But none of us are saying any hobbyist could have trivially sent it to Mars.

It should be obvious what we are specifically addressing: that this kind of error is not the sort that should happen in a properly thought out, bog standard real time system.

> JPL tends toward having generalists

And that's fine too, plus dumb mistakes always happen.

So it shouldn't be much surprise when the "armchair quarterback" responses show up, and rightly point out the issues. It would be more crazy not to be incredulous.

caconym_OP4y ago

> They expected the camera not to drop frames [...] That is what's being discussed here

It isn't, actually. The comment I responded to, and the one it linked to, are broadly criticizing the sensor fusion/control loop implementation--the thing that saved Ingenuity after the optical flow subsystem started returning bad data. That's what's being discussed here, in the context of this subthread where I entered it.

The dropped frame thing is much more cut and dried, and it's obviously a bonehead mistake. It's also the kind of thing that's always going to happen, as you say. Many of the commenters here seem to be generally at odds with that reality--I don't believe the state of the art in software development has yet achieved guaranteed bug-free implementation of diverse real world applications, but you wouldn't think that from reading some of these comments (e.g. the one you linked above).

j / k navigate · click thread line to collapse