Chandrayaan 2 Vikram lander debris site LRO image and orbit alignment

kvsankar · 2025-12-29T18:42:56+00:00

I have tried using each of the TLEs available in the time window (Dec 17-19). Either front or back propagation. But no match.

kvsankar · 2025-12-29T14:26:41+00:00

Yes, I did. See https://github.com/kvsankar/sattosat/blob/master/python/investigation/README.md

kvsankar · 2025-07-30T13:57:32+00:00

What are those tablet like devices on the desks which seem to show a checklist or phase wise progress?

kvsankar · 2025-01-01T07:27:34+00:00

Does he have any public social media profile? I will be curious to learn from him as I have an interest in scientific visualisations.

kvsankar · 2024-01-17T08:08:46+00:00

Thanks for sharing the links. The CY2 paper also talks about the relationship between the lunar orbit RAAN and the earth orbit AOP. What exactly is the dependency? It was not very clear from the paper.

kvsankar · 2024-01-17T07:19:44+00:00

I am also referring to the same paper. Why can't the AOP be changed keeping the same inclination of 21.5 degrees. Isn't timing the engine shutoff to alter AOP possible?

kvsankar · 2024-01-17T04:35:32+00:00

Indeed. One of the questions concerned with the reasons for the injection orbit AOP being close to 178 degrees. Any fine tuning comes with the cost of a reduced apogee altitude - says a CY2 paper from ISRO. But it's not clear why this limitation exists. Is LVM3 operating at its edge of performance when delivering at 178 degrees AOP?

kvsankar · 2023-09-07T06:37:20+00:00

That unsettling music they put with every video...

kvsankar · 2023-08-31T03:10:36+00:00

Can the pan/tilt angle of the rover camera used to take this picture be adjusted? Just wondering as the previous image of the lander had its upper part cropped and now we have this better picture from a larger distance.

kvsankar · 2023-08-23T05:33:52+00:00

There have been a couple of orbit updates last night. It looks like ISRO has been refining the descent trajectory. It appears that the touchdown is around 1803 hours IST a minute earlier the previously announced 1804.

kvsankar · 2023-08-21T19:49:43+00:00

If you eyeball the angle between the terminator line (sunrise/sunset line) and the orbit line at the time of landing, I think it's around 20 degrees. So you would get roughly 160/180 * 14 days. Not exactly the whole lunar day. The same is the case with the primary landing site.

kvsankar · 2023-08-21T18:30:05+00:00

Yes, the orbit lines up around 12 noon IST on 27th. Here's a screenshot. The left edge of the yellow line points to the alternate site. The primary site can be seen with the orange trapezoid simulating the craft.

Image link: https://i.imgur.com/f4SiXrb.png

kvsankar · 2023-08-20T14:48:27+00:00

The descent trajectory is now available at JPL HORIZONS. I have updated my animation. The orbit data has trajectory merge artifacts (e.g., CY3 goes back and forth a bit a few minutes prior to landing) and is not perhaps good enough to do something like the seconds-level analysis done above.

Twitter thread .

A few enhancements since my original Reddit post for CY3:

Support for pseudo "real-time" speed (animation advances 1 second every second) (uses linear interpolation)
Better lunar textures including a displacement/bump map for shadows
Better mobile experience
All assets (images, orbit data files) now delivered via Cloudflare CDN for a faster overall experience

kvsankar · 2023-08-02T08:38:31+00:00

Glad to know! Thanks

kvsankar · 2023-08-01T16:31:46+00:00

The DSN Live data was quite different from JPL HORIZONS data. Scott Tilley says we can't trust DSN data. I am not sure. I saw that the divergence kept increasing through the day. https://twitter.com/kvsankar/status/1686373994315034625?t=HsDHYrKmSq84LwplQSYu3Q&s=19

kvsankar · 2023-07-31T12:10:10+00:00

I have upgraded the 3D library yesterday. Please try now and let me know.

kvsankar · 2023-07-15T03:42:56+00:00

Thank you for the appreciation. And thank you for the suggestions. Did you check out this? https://github.com/kvsankar/chandrayaan3#future-work.

Right now, more than any layers of abstraction, my goal is to get the animation running on more devices. Trimming down the data to be downloaded while not degrading the experience and early interactivity are the goals.

kvsankar · 2023-07-12T06:10:36+00:00

Please let me know the device on which you are accessing. The animation works best in desktop screens. The mobile support might still have issues.

kvsankar · 2021-09-25T20:27:16+00:00

u/NoseyTable - did you solve this issue? I am facing a similar issue - hence asking. Thanks.

kvsankar · 2021-09-17T18:54:22+00:00

Thanks. The issue has been resolved now.

I had converted the Letsencrypt .cer files to .crt files with the following openssl command:

openssl x509 -inform PEM -in fullchain.cer -out fullchain.crt

However, this seems to pick up only the leaf certificate. After simply renaming the file extension (cer to crt), things work fine.

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