# Most recents (10)

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!
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)
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…
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'.
#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)
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)
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.
Here's a plot of an estimated ground track for the #Change5 re-entry.
- Evidence supporting this ground track,
- Alternatives that have been excluded,
- 'Skip' re-entry profile visibility characteristics,
- State vector confirmation of timings/position.
Two possible re-entry ground tracks have been explored. The one presented is favoured because the tracking ship Yuan Wang 3 is now presently at the 'skip re-entry perigee'. Using AIS data dug up by @steffanwatkins the ship has been loitering in the area for a day or so now.
@Cosmic_Penguin noted the following graphics posted during pre-launch coverage of training efforts which showed the location of Yuan Wang 3 and the major re-entry event locations. Despite some oddness in the presented data the plan looks solid.
I consulted with Astrogator Mike and we are getting closer to a ground track estimate for #Change5 during re-entry. The s/c will skip off the atmosphere over Yemen. The timing of this is directly related to TCM corrections and the accuracy of our model so should improve. THREAD
#Change5 like the Apollo capsules will use the atmosphere to steer itself. Thus creating a lot of complexity and uncertainty in modelling the actual ground track to aid observers. We are looking at a few ways to spit ball a ground track for those living in the general area.
As it will be night time over this part of the world it should be a spectacular show for those lucky enough to see it.
01/12 > Déchiffrer le code énergétique des cellules pour améliorer les thérapies anticancéreuses bit.ly/3g0vsdW via @CNRS #LaMethSci
[L’étude à découvrir] 01/12 > SCENITH : Une méthode basée sur la cytométrie en flux pour profiler fonctionnellement le métabolisme énergétique avec une résolution monocellulaire bit.ly/39z0vfV via @CellPressNews #LaMethSci
02/12 > Le #RoyaumeUni approuve le #vaccin contre le coronavirus #Pfizer / #BioNTech pour le déploiement la semaine prochaine bit.ly/3lvJs0G via @newscientist #LaMethSci
23/11 > Lancement réussi pour la mission chinoise qui vise à décrocher un morceau de #Lune bit.ly/33chyjU via @lemondefr #Change5 #LaMethSci
24/11 > Malgré les confinements lié au #CoVid19, les gaz à effet de serre sont toujours à des niveaux records prévient l’#ONU bit.ly/2USDkEK via @ScienceAlert #LaMethSci
23/11 > Découverte d’une “galaxie fossile” enfouie dans la #VoieLactée bit.ly/33cSPfe via @Trust_My_Science #LaMethSci
[Lancement] - 🇨🇳 Longue Marche 5 (CASC), Chang'e 5

Allez il est temps de débuter ce thread du lancement de Chang'e 5 vers la Lune! Le décollage est prévu vers 22h heure de Paris, mais le direct depuis Wenchang a déjà débuté...

Allez la Chine, Allez Chang'e !

#Change5
Le direct est pour l'instant disponible sur Weibo, à cette adresse:

#Change5

live.media.weibo.com/show?id=104215…
Pour l'instant, la nuit tombe doucement sur la base de lancement de Wenchang. Le portique de lancement est encore fermé, le lanceur se cache encore dedans...