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Chandrayaan-3 Soft-landing [video]

isro.gov.in

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Re: Chandrayaan-3 Soft-landing [video]

#151

Post by shri_krishna »

seatac76 wrote: post #146
mathieuh wrote: post #77

Wait did it land while they were showing us Modi's face? Why didn't they show the camera feed?

The speech after had a weird order I was expecting ISRO to speak first, thought that was not needed but idk

Because: https://news.ycombinator.com/item?id=37235089

Re: Chandrayaan-3 Soft-landing [video]

#152

Post by ansible »

m0llusk wrote: post #86
jvm___ wrote: post #12

Scott Manly has a video on why he thinks the last one failed. It sounds like their landing software didn't have "oh crap, we're way off course, just land wherever". It only had the happy path of "fly to here and land", so when it switched to the landing phase it tried valiently (including flying upside down) to try to fly back to the landing zone, but the landing zone was much further than fuel supplies allowed. Hope…

If anything they seem to have overcorrected for this. This landing path stopped with a near hover at around 800m, then a prolonged hover at 150m while the lander scoped the situation, then an extremely slow descent that allowed for corrections the whole way down. Very impressive.

Yes, it was a very conservative landing trajectory. But it is very, very difficult to get a hoverslam right the first time, or the second, or the third...

I did like seeing the live images captured during descent, I also hope those get made into a video and posted online.

Looking forward to the rover deployment too.

Re: Chandrayaan-3 Soft-landing [video]

#154

Post by b800h »

0xcafecafe wrote: post #150
b800h wrote: post #140

[flagged]

The aid is not sent to the government but some chosen NGOs. India has said aid is not needed: https://icai.independent.gov.uk/html-version/uk-aid-to-india... .

Yes, I think they described it as 'peanuts'. It's in the form of investment as well, but if they don't want it and we can't afford it, it's odd that it carries on. I'm sure it's a complex matter.

Re: Chandrayaan-3 Soft-landing [video]

#157

Post by distcs »

Can someone help me understand this Wikipedia article section: https://en.wikipedia.org/wiki/Chandrayaan_programme#List_of_...

Check the row for Chandrayaan-2. Why does it say Unsuccessful landing but main mission success and extended missing ongoing?

What exactly are main mission and extended mission and how can they succeed or be ongoing when the landing has been unsuccessful?

Re: Chandrayaan-3 Soft-landing [video]

#159

Post by fidotron »

taneq wrote: post #113
delta_p_delta_x wrote: post #38

Earlier quoted context omitted.

> seems like such a gross omission. Almost all space mission code only ever has the so-called 'happy path'. We rely on extremely tight mechanical and aerospace engineering tolerances to achieve that happy path. The Hubble Space Telescope's primary mirror grinding was off by a matter of micrometres, and resulted in blurry images. Consider all the Mars rovers. Imagine some wind gust threw the descending module off cour…

That can't still be the case these days, can it? Extremely tight mechanical and engineering tolerances are very expensive compared with merely 'very very' tight tolerances, and I'd imagine the difference between the two can be bridged with more intelligent software in place of "gyroscope + clock + maybe PID loop"?

Yeah, this reads like two people defining happy path subtly differently: one is saying the happy path is anything within acceptable strictly defined mission parameters and tolerances, the other thinks it is the sequence of steps that is expected to successfully execute the mission without ever encountering an exceptional situation (which is the conventional software view of the term), but there are exceptional situations which may be covered in the specification of the mission and so “on the happy path”.

In the case the system strays outside mission success parameters then aborting could make sense. The question there looks to be if the success parameters were defined too narrowly - it sounds like an error in specification that prioritizes landing in the required area over the possibility of landing at all.

Re: Chandrayaan-3 Soft-landing [video]

#160

Post by mryall »

distcs wrote: post #157

Can someone help me understand this Wikipedia article section: https://en.wikipedia.org/wiki/Chandrayaan_programme#List_of_... Check the row for Chandrayaan-2. Why does it say Unsuccessful landing but main mission success and extended missing ongoing? What exactly are main mission and extended mission and how can they succeed or be ongoing when the landing has been unsuccessful?

The Chandrayaan-2 mission had an orbiter, which is still operational, as well as the lander which crashed.
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