Hi all!

Cháng'é-4 is now in the final 15x100km orbit!

https://gbtimes.com/change-4-lowers-orbit-r...ide-of-the-moonVery nice video there!

I herewith dare to predict the landing time:

**02 January, 00:00 UTC (midnight) at 178.1° East.**How do I get there?

Quite simple calculations with the publicly available data:

*First looking at the orbital plane:*Lunar orbit insertion (LOI) was on 12Dec at 08:39 (all times UTC)

in (- assumption! -) a plane

*exactly perpendicular to the earth vector*, this means "face-on" and over the poles.

Furthermore: Landing site: Between 176.4° and 178.7° East. (This is from

here.)

The orbital plane therefore has to rotate between LOI and landing between 271.3° and 273.6°.

Or, more precisely, the Moon under it.

Since a sidereal lunar rotation lasts 27.3217 days,

this corresponds to a time from LOI to landing of 20.590 and 20.764 days.

That falls between 01Jan 22:48 and 02Jan 02:59 (as said, UTC).

That's a period of just over 4 hours, enough for two passes.

*And now, when exactly?*The insertion into the final orbit of 15x100km was early today (30Dec) at 0:55 UTC.

This injection occurs in the aposelene, this means

*half an orbit* from periselene!

And the periselene is logically (almost) over the landing site.

The orbital period can be calculated (113.68min), so you just have to look

when a

*multiple-plus-zero-point-five of the orbit period* falls into the the time frame calculated above.

This is the case (UTC) on 01 Jan at 23:58 (37.5rev) and on 02 Jan at 01:51 (38.5rev).

With uncertainty in the minute range and a bit of time for the final (slow) approach,

it will be midnight UTC on January 2nd.

And the backup opportunity at 177.0° East just before 2h UTC.

To all this also fits that on that day, the Moon in Beijing rises at 03:45 (Beijing time).

The landing would be at 07:58, the backup landing at 09:51, and the moonset at 14:23.

Perfect timing for the ground stations.

Some (dis-)agreement here?

Best

Thorsten