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Scott Tilley 🇺🇦

@coastal8049

Sep 14, 2020 • 9 tweets • 4 min read • Read on X

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Following the penumbral eclipse of LES-5 on 2020-09-05 I've been able to identify all of the data words that are sensitive to solar illumination. Interesting patterns noted may help gain some insight into the present operation of the attitude control system. [THREAD]

36 of 128 data words responded to the penumbral eclipse(PE). A PE is the only way to know which data words are sensitive to solar illumination as LES-5 switches off during umbral eclipses. PEs only occur twice during each equinox and it may not be visible to me. So I got lucky.

Now I was able to see what appeared as relatively undynamic data words reveal they were sensitive to solar illumination. Frame1 word23 and frame3 word23 jumped out as they appeared to respond to something relating to the period of the LES-5.

Now overlay F1 W23 and F3 W23 with two words suspected from the beginning of our monitoring efforts as being Sun or Earth sensor data and related that to LES-5's angle to the Sun and some magic jumps out as this plot of pass 2's data shows.

I've added in some references to make reading the plot easier. The green line is the Sun angle from LES-5's perspective. 0 is noon, 180 midnight and 90 and 270, 6am and 6pm respectively from the satellite's perspective. What's going on at ~3pm LES-5 time (45 degrees)?

It turns out LES-5 was designed to make attitude control measurement at the 9am and 3pm points in its orbit. Or +/- 45 degrees from noon from it's perspective.

The Sun/Earth sensing system acts like a real time clock on LES-5 and doesn't send real time telemetry as it operates during each rotation of the satellite ~10 seconds. But I suspect based on the results above that it sends a summary of the data.

I then examined the timing of noon on LES-5 to the change in frame3 word23 over all of the passes I have received data from and as you can see this angle remains close to 45 degrees. I also looked at the total data copied and plotted to see if there is a correlation.

If you look at the F0 W27 and F1 W23 you see a strong correlation between the two. F1 28 also correlates with the 3pm behaviour. I suspect the system has degraded and we are not seeing all the sensor's operating but this analysis thus far seems ID meaning in these words

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More from @coastal8049

Scott Tilley 🇺🇦

@coastal8049

Dec 22, 2023

https://twitter.com/coastal8049/status/1736517007154303168

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. 🧵⬇️

https://twitter.com/coastal8049/status/1736517007154303168

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. ⬇️

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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Scott Tilley 🇺🇦

@coastal8049

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. 🧵⬇️

A telegram post by @roscosmos provides limited information of the status of #Luna25. Apparently, the spacecraft failed to adjust its orbit as planned.⬇️

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... ⬇️

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Scott Tilley 🇺🇦

@coastal8049

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? 🧵⬇️

#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. ⬇️

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...⬇️

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Scott Tilley 🇺🇦

@coastal8049

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. ⬇️

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Scott Tilley 🇺🇦

@coastal8049

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. 🧵⬇️

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⬇️

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Scott Tilley 🇺🇦

@coastal8049

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. 🧵⬇️

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. ⬇️