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Scott Tilley 🇺🇦 Profile picture
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Feb 26 • 4 tweets • 2 min read
No signals from MERIDIAN 4 today. I suspect it has gone offline. We should be hearing about a replenishment soon.

This creates a gap in MERIDIAN Molniya coverage for ~8 hours each day. Much like when M3 went belly up.
Unlike when MERIDIAN 3 went down they still had MERIDIAN 2 stranded in the wrong orbit but still operational and filling in some of the gap from time to time.
MERIDIAN 2 re-entered early in 2020. But here's how it's sky tracked worked. Instead of being fixed and repeating daily it wandered around.
It takes some months to commission a MERIDIAN satellite based on my observations. M8 took many months before transponders appeared. M9 much less. Both were the newer generation of the spacecraft bus.

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More from @coastal8049

Scott Tilley 🇺🇦 Profile picture
Feb 26
This is the P-441 communication complex that the Russian military uses for MERIDIAN, RADUGA and maybe transponders on other assets. It uses C and X-band. On these bands a clear view of the satellite is needed. Many variants of this system exist. (1/n)
Tactically, you'd likely want to hid this thing as it's a critical asset and part of your command and control which limits your options to deploy it. MERIDIAN could give you the ability to hid it and use those satellites high elevation to advantage. From the operating manual...
So if your a commander in a tactically active environment not having a MERIDIAN for 8 hours could be a reason you need to take higher risk and expose the system for a view of a GEO satellite.
Read 6 tweets
Scott Tilley 🇺🇦 Profile picture
Feb 24
The world can observe Russian military activity on UHF, C and X-band via their communication satellites in GEO and HEO. Observers should scan 279 +/- 2MHz, 484MHz +/- 2MHz , 980-1000MHz, 3.4-3.7GHz and 7.5GHz +/- 100 MHz for activity from GEO and HEO assets. Reports to follow.
Search my profile @coastal8049 and use keywords like MERIDIAN to find details.
279MHz is expected to be fairly tactical communications. 484MHz tactical air et.al. 980-1000MHz major military bases and strategic air assets. 3.4-3.7 TT&C and tactical/strategic comms. 7.5GHz tactical and strategic comms.
Read 4 tweets
Scott Tilley 🇺🇦 Profile picture
Jan 13
The last observation before #Change5 'disappeared' after Dec 2nd, was 19 degrees from the Moon on the western side. Perhaps just before a burn!? This as you will see is significant to understand CE5's present trajectory and why I'm pretty much convinced it is in a DRO now. (1/n)
The geometry of Dec 2nd timing is curious to say the least. If you examine this plot you'll not there are a number of possible DROs. If you measure the elongation angles for the second closest to the Moon you get ~19 degrees. (2/n)
I'm not sure if it's required or just easier, but #NASA is using the elongation point to do their insertions to a DRO. It's referred to as a Distant Retrograde Insertion (DRI) of course!
Read 8 tweets
Scott Tilley 🇺🇦 Profile picture
Jan 12
What in tarnation is a Distant Retrograde Orbit (DRO)?

For those wondering what I'm waving my hands about these days about here's a THREAD about what a DRO is and why it may be something you hear a lot more of soon... (1/n) Image
A DRO is a long term STABLE orbit for a very small mass object around the smaller of two much larger bodies that are in a two-body orbital system. As the Earth has a Moon, one could place a spacecraft in a DRO of the Moon. (2/n) web.archive.org/web/2015011122… Image
The general parameters of a DRO are about +/- 70000km form the Moon along the axis to the Earth and between 70000-110000km on the perpendicular axis. The period is around 13-14 days. This is why it's call 'distant'.
Read 8 tweets
Scott Tilley 🇺🇦 Profile picture
Jan 9
#Change5 DRO state vector estimate with rationale.

Amateurs lost signal ~2021-12-03. About 3 integer periods of ~13 days, which is around the optimal DRO period. We appear to be seeing spacecraft at eastern elongation now. So... (1/n)
From what I understand of DRO insertion geometry one likes to enter DRO from one of the elongation points not the EM-L1 or EM-L2 points. This insertion burn occurred ~ 2021-12-03. SOURCE: ntrs.nasa.gov/api/citations/…
Location of #Change5 this evening is within error bars of rough location of a hacked together state vector estimate is. (2/n)
Read 4 tweets
Scott Tilley 🇺🇦 Profile picture
Jan 9
Could #Change5 be in a Distant Retrograde Orbit (DRO) of the Moon pulling off a space first?

CE5 is ~15deg east of the Moon suggesting it is ~100000km distant from the Moon. I made a model DRO in GMAT seeded it with a start from EM-L2 around 2021-12-01 00:00 UTC, Hmmm... (1/n)
Examining papers on the upcoming #NASA SLS EM-1 mission that will use a DRO reveals the geometry somewhat fits the limited observations we have of #Change5 since it was recovered a couple of days ago. (2/n) SOURCE: ntrs.nasa.gov/api/citations/…
Range estimates based on SNR of #Change5 X-band signal appear to be consistent with it being approximately at a lunar distance. If it is in a DRO this would be a first scoping the upcoming #NASA SLS EM-1 mission. (3/n)
Read 4 tweets

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