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Congrats to all of the team at ISRO. Assuming the software development for these is non trivial; Its interesting that with the last mission(per Scott Manly) was
by itissid 3y ago
Congrats to all of the team at ISRO. Assuming the software development for these is non trivial; Its interesting that with the last mission(per Scott Manly) was designed to always select a spot(or more precisely a trajectory) and try hit it.
What made them make that decision? Was it like "lets be as precise as we can because we want to get to the spot X because X is special" and thus "Lets let the software always compensate for any errors to get to X". I am assuming that even at this point they tested the software for extreme conditions. It is most likely that once this assumption was made the Software was built that way, i.e: "Lets test the Software can always correct for any issues to get to X with feedback(like thrust)". It trades off Safety for Accuracy(to hit X).
This time the idea was "Lets select a trajectory to X" but this time "We will let the software prioritize safety(altitude, speed and heading) to be within norm once we start descending towards X". And additionally "Not make any corrections if we are somehow too far off X if it exceeds safety limits". It trades off Accuracy(to hit X) for Safety.
- kensai 3y agoLink to Manly's video?
- gourabmi 3y agoIf you understand Hindi, Gareeb Scientist has an amazing video about the landing algorithm issues of Chandrayaan-2 https://youtu.be/4oUdD_QSgRs https://youtu.be/4oUdD_QSgRs
- mandeepj 3y ago> If you understand Hindi Video has captions
- justinclift 3y agoThe English captions are pretty decent too. :)
- mandeepj 3y agoThat's what I meant! I thought it was clear, at least to me.
- itake 3y agoIs there a TLDW?
- ggop 3y agoIIUC, the salient points are: - target area was very small (500m x 500m) for CY2. With CY3 they've made it bigger at 4km x 4km, allows for larger margin of error. - CY2 lander had limited leeway in fixing issues, by design. CY3 has more and has landed itself, no assistance from base. - CY2 lander had limited time to fix itself, apparently it was just a few seconds short of making it fine
- erbdex 3y ago+ Software limited the upper limits of thrust correction/per second to 10% of what was possible. In other words, it could perhaps correct itself in those many seconds but was allowed only small degrees of change.
- OrangeMusic 3y agoI asked Kagi's Universal Summarizer, and it said this: The video provides an explanation for why India's Chandrayaan 2 lunar landing mission failed in 2019. The landing craft Vikram experienced issues during the camera coasting phase where instruments were being calibrated. Specifically, the engine thrust was higher than expected and thrust control couldn't be adjusted to correct the trajectory. As a result, errors accumulated and Vikram's trajectory deviated significantly from the planned path. For Chandrayaan 3, ISRO has implemented changes like adding instantaneous thrust control, increasing the allowed attitude change rate, and enlarging the landing zone to make the mission more robust to errors. The video offers an insightful technical look into what went wrong and how ISRO is addressing it for the next lunar mission.
- yencabulator 3y agoComplete wild-ass guess: safe landing spots are hard to find, they knew X to be a larger region safe to land in (so small errors wouldn't matter), and didn't at the time have the more complex subsystem to find safe landing spots (!= X) on the fly based on where the lander happens to go.
- 7_hours_ago 3y agoI don't understand why you keep referring to the company formerly known as Twitter.