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Scott Tilley 🇺🇦 Profile picture
@coastal8049
Sep 16, 2019 • 14 tweets • 5 min read • Read on X
As we gear up for observations tonight, it appears #Chandrayaan2 may have made a slight orbital adjustment lower its nominal altitude to ~92km. Observations from @VK5EI, @df2mz and myself support this.
Let's have a little fun with this and try the Twitter poll feature.

Why do you think the orbit of #Chandrayaan2 is changing?
Hey Guys the 'are they nuts!' answer was a joke OK?!
Feel free to make comments on this thread to state your argument to sway the vote!
The moon is almost over the trees... Peeking through now. Image
@LRO_NASA is coming in now... Not long before we can get going on this night's session.... Image
Will DSN24 transmit tonight?
Only an hour to vote...
What's that bright object in the sky? Been so rainy here lately I forget what the moon looks like! Almost clear of trees.... Image
#Chandrayaan2 gracing us with another great signal, nice start to the tracking session. Image
Looks like the optimists have it here!
#Chandrayaan2 loudest I've heard with data sidebands appearing on the signal. The orbit is still fully visible as predicted and the period is roughly 7089 seconds which about 104Km altitude on the first complete orbit measured tonight.
Here's a look at the Doppler data from that first measured orbit of #Chandrayaan2 this night. Off to bed all. Fingers crossed @LRO_NASA gets some more info for us tomorrow. Image
Only an hours left. vote!

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More from @coastal8049

Scott Tilley 🇺🇦 Profile picture
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. ⬇️
Image
Image
Read 8 tweets
Scott Tilley 🇺🇦 Profile picture
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
Russian controllers now need to troubleshoot and fix the issue. This is complicated by their lack of a global deep space communications network. So recovery efforts will be limited to when the Moon is visible over Russia due to their geopolitical misadventures... ⬇️ Image
Read 8 tweets
Scott Tilley 🇺🇦 Profile picture
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
Read 10 tweets
Scott Tilley 🇺🇦 Profile picture
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
Scott Tilley 🇺🇦 Profile picture
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
Scott Tilley 🇺🇦 Profile picture
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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