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!
#Change5 was recovered on January 6th and it was noted to be very close to the Moon at that time. With Edgar and Jean-Luc noting it pass just below it. Some grace for measurement errors should be allowed as radio positional techniques were used... (3/n)
Later observations by amateurs observed the eastern elongation from the Moon at about 15 degrees. Afterwards #Change5 has been getting closer to the Moon angularly. A DRO of this size would have a period 12-14 days... (4/n)
We are seeing ~7 days for #Change5 to transit from its last angular close approach to the one that is setting up now. This matches half the DRO orbital period of this class of DRO. I'm calling it, CE5 is in a DRO. We only need to determine just how DRO it is... (5/n)
Please recall, a DRO is a chaotic orbit in the sense that it is highly sensitive to initial and on going very small condition changes. While it is stable it is only predictable within a certain defined realm for a fairly finite period of time. (6/n)
Thanks to @df2mz and @LucMilette for sharing their data.

• • •

Missing some Tweet in this thread? You can try to force a refresh

Keep Current with Scott Tilley

Scott Tilley Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!


Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @coastal8049

12 Jan
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)… 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
9 Jan
#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:…
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
9 Jan
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:…
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
9 Oct 21
March 2021 - 18SPCS reported that YUNHAI 1-02 [44547, 2019-063A] had broken up. Since the breakup report, amateurs have monitored radio emissions on 1704MHz. As the spacecraft straddles the terminator it was lost in the glare of daylight until now...
@18SPCS reported that YUNHAI 1-02 broke up and amateurs noticed it continued to emit. The following thread should catch you up on some of these facts.
@planet4589 later noted an anomolly in the @SpaceTrackOrg catalogue with a report indicating 48078, 1996-051Q: "Collided with satellite". See this great thread to learn more about his analysis and the tie to YUNHAI 1-02.
Read 7 tweets
16 Jan 21
Well well well, the mystery of what the signal on ~992.4MHz/~1000.44MHz and FM audio on ~998.94MHz from the Meridian satellites is resolved. It's SECAM TV channels from Turkmenistan. SECAM channel spacing is 8MHz and video carrier to audio carrier is 6.5MHz which matches.
I mused a few weeks about about the curious nature of the 15.625MHz sub-carriers around the primary.
Here you can find some info on the SECAM channel frequencies. Look up France, Eastern Europe, Former Soviet Union, French overseas territories and former French colonies in Africa, North Korea, Vietnam...…
Read 7 tweets
15 Dec 20
Steffan Watkins provided a wealth of AIS data from MarineTraffic about the journey of Yuan Wang 3 to the #Change5 re-entry skip point in the Arabian Sea. The data reveals that the ship did some interesting stop and goes prior to arriving on station to look at what? THREAD.
2020-12-10 UTC between 18:30 & 22:30, Mars was at the zenith when they stopped and set just before they got underway again. Perhaps providing support for TIANWEN-1 on the way to Mars?
2020-12-11 UTC between 14:20 & 22:05 more TIANWEN-1 watching at the zenith again it appears. The Mars bound probe has a big signal on X-band which is also used by #Change5.
Read 8 tweets

Did Thread Reader help you today?

Support us! We are indie developers!

This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal

Or Donate anonymously using crypto!


0xfe58350B80634f60Fa6Dc149a72b4DFbc17D341E copy


3ATGMxNzCUFzxpMCHL5sWSt4DVtS8UqXpi copy

Thank you for your support!

Follow Us on Twitter!