Scott Tilley 🇺🇦 Profile picture
Sep 13, 2019 20 tweets 11 min read Read on X
Many new followers from India have asked many great questions about the #Chandrayaan2 orbiter and the fate of the #VikramLander. The following thread will provide some plain English answers about what I know about the present status of the mission.
#ISRO has not released any further official updates on the mission since Sept. 10th. Which indicated the orbiter had located the lander on the surface of the #Moon. Many rumours but there is no new official reports about #VikramLander or #Chandrayaan2 orbiter since this report.
No radio signals have been copied from #VirkamLander since the landing anomaly occurred.
#Chandrayaan2 orbiter continues to orbit the #Moon and is emitting strong radio signals that are currently being tracked and analyzed by amateur observers. The orbit appears to be around 100km and nearly circular and is stable.
There is some minor disagreement about the exact period of the orbit and we are working together to understand the discrepancy. However, we do agree the orbit is stable and the discrepancy is assumed to be related to our amateur measurement methods.
#NASA reported today that the LRO will be tasked to attempt to image the #VikramLander site this coming Monday, Sept. 17th. LRO is in a lunar polar orbit and well suited to image the Vikram landing site every 14 days if lighting conditions permit. spaceflightnow.com/2019/09/12/nas…
My station will continue to monitor for #VikramLander signals as long as the #DSN continues to search for it. However, the chances of my amateur station hearing a potential signal from Vikram are very slim.
The best hope we have is that an #ISRO and/or #NSAS DSN stations will hear a faint whisper from #VikramLander in response to high power beacon signals before lunar night descends and freezes the lander.
As #NASA #DSN operator @nascom1 mentioned yesterday on Twitter, the effort being made to communicate is standard procedure after an anomalous mission event like this. While there is always hope and that drives the search the prognosis of hearing from #VikramLander is not good.
Now lets sit back and enjoy an evening (my time) of satellite tracking and see if the universe reveals anything to us.
@scott23192 do you have AOS of Madrid on 2103.7? You'd earn another grid square 😉
#DSN Now shows that Madrid is signally for #VikramLander presently. Goldstone is just about to have #Moon rise and DSN 26 is tuning up for communication with #Chandrayaan2 orbiter. DSN24 is idle. Image
#DSN 26 at Goldstone, California appears to have started tracking and copying the #Chandrayaan2 orbiter as the #moon clears the local horizon there.
DSN 54 in Madrid still has the ball. I may actually get to hear the signal from there if it keeps up for a bit and the moon clears the trees... Here's the communication path geometry from Madrid->Moon->Vancouver Image
So far nothing on uplink on S-band directed at #VikramLander from Goldstone. I have clear view of Moon now and would expect signals if DSN26 was active. So DSN Now is not inaccurate.
DSN24 just changed status... Inactive.
DSN24 just switched to #VikramLander! Await tune up and tracking to start now.
Here we go folks, #Chandrayaan2 orbiter signal is loud and clear now. #Queqiao seen just above it. DSN24 is warming up so looks like they are still trying for #VikramLander lander. Image
#Chandrayaan2 orbiter returns to the Earth facing side of the Moon. Still no emissions for Goldstone towards #VikramLander. Image
I'm off to bed. The system is running on auto pilot and if anything interesting happens you'll all know tomorrow!

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More from @coastal8049

Dec 22, 2023
Update on the Chinese 'spaceplane' monitoring effort. @plugger_lockett observed possible emissions from objects from the 2023-195 launch. Despite using the same modulations it turns out these emissions are from other secret Chinese military sats, raising more questions. 🧵⬇️
Upon fixing a minor timing issue with his ground station @plugger_lockett sent me data from a pass yesterday & I was able to determine that the object being tracked yesterday was in fact YAOGAN-30 X the track of which passed over one of 2023-195. ⬇️ Image
I went back and looked at the erroneously timestamped data from the passes we thought detected OBJECT D and E finding that if I adjusted the timing YAOGAN-30 AA and YAOGAN-30 R passed closely to the track of these objects. ⬇️
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Aug 19, 2023
Moon rise here at the station. As the Moon clears the trees, an "Emergency" was declared by @roscosmos for #Luna25 as it failed to perform an orbital adjustment burn. Lets discuss how this could affect the mission. 🧵⬇️ Image
A telegram post by @roscosmos provides limited information of the status of #Luna25. Apparently, the spacecraft failed to adjust its orbit as planned.⬇️ https://t.me/roscosmos_gk/10535
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Aug 13, 2023
I have been asked repeatedly about #Luna25.

Thus far I have no independent observations of the mission to share. That is not without extensive trying to observe it.

So why am I not detecting anything? 🧵⬇️ Image
#Luna25 was launched into a trajectory that is largely only visible on Earth in daylight. Secondly, that trajectory is not exactly known. I have calculated one based on the launch timing and the scant public info shared and used GMAT to find a good direct trajectory. ⬇️ Image
The trajectory isn't arbitrary. You need to carefully line things up to the extreme to get anywhere close to the Moon. So it constrains where to look. As we're looking into the glare of the Sun, we need radio. ITU records report two bands, X and Ku-band. But wait...⬇️ Image
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Aug 13, 2023
A follower asked if #Chandrayaan3 could land on the Moon before #Luna25. The short answer is maybe.

As we'll see in this thread changing a plan as complex as landing on the Moon is not a great idea.🧵⬇️
#Chandrayaan3 is presently largely locked into an orbital plane above the Moon. What that means is that it needs to wait for the Moon to rotate under-neigh it to reach the primary landing site that @isro has painstakingly planned to land at. ⬇️
Therefore, if you want to rush to get to the landing site it's too late. Therefore, you need to pick a new landing site under up coming terrain that may be suitable and also change the mission plan. Recalculate, adjust and then execute. ⬇️
Read 6 tweets
Aug 3, 2023
#Chandrayaan3 trajectory update 2023-08-02 #2.

Despite my better judgement, I did a TLE update on the Doppler data. The problem with TLEs in these types of orbits is they degenerate fast as the model is not designed to deal with long periods et. al. 🧵⬇️
Image
Image
Small changes in the data or the fit has profound effects on the TLE and the orbital model. But they are convenient. So I offer a couple of TLEs to aid anyone wishing to hunt for #Chandrayaan3. NO WARRANTY offered 😉, look with WIDE field... ⬇️
Data fit to released orbital parameters:
1 57320U 23213.95526600 .00000000 00000-0 00000-0 0 04
2 57320 21.4000 180.4625 9648325 12.6358 39.3505 0.10345282 04
# 20230801.30-20230802.61, 53466 measurements, 0.005 kHz rms⬇️
Read 4 tweets
Jan 12, 2023
I've recently renewed an observing campaign on #TIANWEN1. The orbit hasn't changed so an aerobrake test claimed for late 2022 has not occurred yet. In preparation for observing an aerobraking manoeuvre I thought it would be interesting to study past missions that did one. 🧵⬇️ By NASA/JPL/Corby Waste - https://solarsystem.nasa.gov/multi
First a bit a reference of why we believe #TIANWEN1 will conduct an aerobraking test. This all relates to the #TIANWEN3 Mars sample return mission.
spacenews.com/china-aims-to-…
Aerobraking is used to allow a spacecraft to lower its apopasis by using a planet's atmosphere to decelerate the spacecraft as it passes through the tenuous upper atmosphere of the planet at periapsis at just the right altitude as not to cook the spacecraft and max. drag. ⬇️
Read 13 tweets

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