Luna 25 lander mission, Russian lander following on from the Soviet-era lunar program Options

[Phil Stooke]

I am starting a new thread for this mission which should fly this year.

Phil

[Thorsten Denk]

Launch is to my knowledge on July 22, 23:21:45 UTC.
Arrival at the lunar orbit on July 28.

Thorsten

[kymani76]

Two possible landing ellipses for Luna 25 from Hiesinger et al..

[Paolo]

my photo of a model of Luna 25 on top of its Fregat stage
https://flic.kr/p/2ggQAdM

[Phil Stooke]

https://selena.sai.msu.ru/Rod/Publications/...sites_final.pdf

Paolo's reference to the landing sites is quite old, and the sites have now moved out of Bugaevsky crater to the north. This link is to a paper about mapping the landing sites for hazards. Ellipse 6 in this paper is the primary site, just north of the crater. Meanwhile, the Chandrayaan 3 site seems to be in the southern floor of Bugaevsky very near the old Luna 25 ellipses.

Phil

[kymani76]

Phil it is my fault, not Paolo's. I dug into the matter deeper and in addition to Phil's article also found this paper.
The list of sites is almost the same between the 2 sources, one lists 11 sites, the other has 12 (apparently old Boguslawsky crater site), one has coordinates down to 3 decimals, the other rounds it up to 2.
These ellipses were meant for 2019 or 2020 landings so they might have changed further since the papers were published.
I couldn't find much on Chandrayaan 3 site, but what i found says the plan to land at more or less same spot as at the last attempt.
Here is update map with ellipse 6 marked as landing spot:

[Phil Stooke]

Yes, sorry, Paolo, I should have known better.

Phil

[Paolo]

Yes, sorry, Paolo,

no problem

[Huguet]

Russia sets date for historic space mission
“Taking into consideration the astronomical ‘window,’ the launch of ‘Luna-25’ spacecraft is planned for 13.07.2023.”

We got a new date.

https://www.rt.com/russia/571964-roscosmos-...-lunar-mission/

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[Phil Stooke]

If this mission lands successfully it is supposed to operate for about a year. During the first lunar day it will study its landing site with various remote sensing instruments and map its workspace. On each subsequent lunar day its arm will collect a sample from the workspace and deliver it to analytical instruments inside the spacecraft. Samples from different locations and depths will explore the variations in volatile content (and basic mineral composition) in the workspace.

Phil

[Phil Stooke]

https://twitter.com/katlinegrey/status/1663597591613919233

A one month delay. Now it is possible that Luna 25 and Chandrayaan 3 will land at almost the same date and only about 100 km apart.

Phil

[Holder of the Tw...]

Rumor has it that the launch will occur August 11th, just a few more days.

Update: 23:10 pm GMT on August 10th (which is August 11th Moscow time).

Launch on a Soyuz with a Fregat upper stage from Vostochny Cosmodrome.

This according to a Russian news agency, not otherwise confirmed.

[nogal]

Anyone wanting to see the launch can do so via the YouTube channel of Roscosmos at:

https://www.youtube.com/watch?v=cgi2pIFrnW4

As I post this it will be live in about 70 minutes.

Luna 25's landing site seems to be the Boguslawsky crater, which is centered on 72.9°S 43.2°E. Source: Wikipedia page on Luna 25

Fernando

[Phil Stooke]

Wikipedia is a bit out of date on that point. The current target is north of the crater, not in it.

This map shows a large set of ellipses considered for the mission and the three ellipses preferred, with number 6 actually being the target. a white outline inside the ellipse is the most hazard-free region which will presumably form the actual target within the ellipse.

Phil

[nprev]

Successfully launched into parking orbit. There will apparently be two burns required for translunar injection, but live coverage seems to have ended.

[Ron Hobbs]

I found a post on twitter (or X) that has what looks like a release from Roscosmos that says that TLI has been performed and Luna 25 has separated from the Fregat stage.

https://twitter.com/TitaniumSV5/status/1689...9728000/photo/1

It says the landing is now scheduled for August 21.

[Phil Stooke]

https://iki.cosmos.ru/news/ot-zemli-uleteli-letim-k-lune

IKI (Institute for Cosmic Research) news page for Luna 25 with some early images.

This is the mission website:

https://iki.cosmos.ru/missions/luna-25

Phil

[Toma B]

There is this quite detailed site about Luna-25 and its instruments.
It is written in Russian so you should open it in some browser that enables translation like Google Chrome. It works just fine for me. Takes some time to load.

Luna-25 site

[Hungry4info]

From Anatoly Zak - possible LOI success.

According to unofficial reports, the Luna-25 (Luna-Glob) spacecraft was expected to enter an initial orbit around the Moon at noon Moscow Time (5 a.m. EDT) on Aug. 16, 2023. According to an unofficial report on the Novosti Kosmonavtiki web forum, posted around 1.5 hour after the expected lunar orbit insertion maneuver and citing available telemetry, the probe's engine fired as scheduled and the spacecraft maintained correct attitude during the maneuver.

[Hungry4info]

And it's official. From the Roscosmos Telegram post:

This was ensured by two switching on of the propulsion system of the automatic station. The first activation was performed at 11:57 Moscow time by a corrective braking engine and lasted 243 seconds, the second - by soft landing engines and lasted 76 seconds.

For the first time in the modern history of Russia, at 12:03 Moscow time, an automatic station was launched into the orbit of an artificial satellite of the Moon!

All Luna-25 systems are functioning normally, communication with it is stable. Sessions are being taken to measure the current navigational parameters.

[Phil Stooke]

https://iki.cosmos.ru/news/kosmicheskiy-app...-sputnikom-luny

update with a colour version of the spacecraft image seen earlier in monochrome.

Phil

[Hungry4info]

Zeeman crater from Luna 25.
(source)

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[kenny]

The text issued with above picture.

Luna-25" took the first picture of the lunar surface

An automatic station flying in a circular orbit of an artificial satellite of the Moon took pictures of the lunar surface with television cameras of the STS-L complex.
The picture shows the south polar crater Zeeman on the far side of the Moon. The coordinates of the center of the crater correspond to 75 degrees south latitude and 135 degrees west longitude.
Invisible from Earth, the Zeeman crater is a unique object on the lunar surface and is of great interest to researchers - the height of the shaft surrounding it reaches 8 kilometers above the surface of a relatively flat bottom.
The resulting images significantly complement the currently available information about this crater. The world's first image of the far side of the moon was obtained in October 1959 by the Soviet automatic station "Luna-3".
"Luna-25" carried out observations with the help of ADRON-LR and PmL, ARIES-L instruments. Fluxes of gamma rays and neutrons from the lunar surface are measured, and the parameters of the circumlunar space plasma and gas and dust exosphere in the circumlunar orbit are also obtained.

[Hungry4info]

The manoeuvre to lower to a pre-landing orbit failed.

Today at 11:10 UTC, an impulse was given to transfer the spacecraft to a pre-landing orbit. During the operation, an emergency situation occurred, which didn't allow the maneuver to be performed as planned. Currently, the specialists are analyzing the situation.

[Phil Stooke]

We don't have anything official as I write this but the suggestion floating around various Russian online forums (Astroforum, Novosti Kosmonavtiki) is that a braking burn lasted about 60% longer than intended, causing excessive braking and an impact on the surface. Mare Tranquillitatis has been suggested as an impact area. This is NOT official.

Phil

[abalone]

Russian spacecraft has crashed into the Moon after it spun into an uncontrolled orbit, Russia's national space agency Roskosmos says.
https://www.abc.net.au/news/2023-08-20/russ...-moon/102753294

[rlorenz]

Space is hard. Landings especially so.

I put this table together a few years ago for a paper on evaluating risk and payoff of planetary missions (in part to show the advantage of mobility, and of reconnaissance, to note that without at least the latter, a single, fixed Europa lander would be unlikely to realize the claims being made for it...)

It shows that the empirical historical record for landings is something like 25-83% reliable (which is in stark contrast to the 99% reliability sought, and used in e.g. landing ellipse specification). I havent run the numbers, but I suspect the Chandrayaan2-Beresheet-Hakuto-Luna25 set of losses is consistent with the lower end of that. We'll see what happens later in the week....

The paper is at https://www.sciencedirect.com/science/artic...273117719303539 (may be paywalled, tho. email me if you need it and cant get it)

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[stevesliva]

Always tell us the odds, Ralph.

[fredk]

And presumably the "expected success probability" for something like ESA Mars landings needs to be taken with a healthy grain of salt, since there have been no successes...

[kenny]

And the Soviet moon landings had a lot more than 1 failure, and a lot more than 5 attempts (if that is what "trials" means).

[Phil Stooke]

The impact site has been calculated now: 57.910° S, 61.450° E. (From the NK forum)

Phil

[rlorenz]

And presumably the "expected success probability" for something like ESA Mars landings needs to be taken with a healthy grain of salt, since there have been no successes...

You miss the whole point of the Cromwell-Laplace estimate (discussed in the supplement to the paper -
the success probability estimator of most use may be informally termed the
Cromwell‐Laplace estimate, equal to (k+1)/(n+2) where k is the number of successes out of n trials. It
essentially encodes the idea that one can never be 100% certain (from Oliver Cromwell’s appeal “I
beseech you, in the bowels of Christ, think it possible that you may be mistaken” to the Church of
Scotland in 1650). Equivalently, it introduces the possibility that one’s luck could run out and the next
trial may fail, even in an otherwise unblemished record so far.)

In effect k+1/n+2 dilutes the track record by the prospect that the next attempt could go either way. It embodies the prior that
no system is 100% reliable or 100% unreliable, and starts with a 50:50 guess if there is no track record, then asymptotically
tends as data accumulate to the frequentist probability k/n. So 'the grain of salt' is baked into the method via Bayes rule.

[rlorenz]

And the Soviet moon landings had a lot more than 1 failure, and a lot more than 5 attempts (if that is what "trials" means).

You're quite right. The supplement notes
Data in this section are drawn from a variety of sources, principally Wilson (1987), Ball et al. (2006) and
Harland and Lorenz (2006) together with contemporary internet sources (Wikipedia entries for Soyuz,
Falcon 9, Luna Program, Cromwell's Rule, downloaded November 2018). Various judgements are made
regarding the accounting of specific examples which could lead to small adjustments in estimated
probabilities. The principal message, that probabilities of success are not (and are sometimes far from)
unity, is robust to the subjective component of these assessments
.....
.....
The Soviet lunar exploration program featured 2 successful semi‐hard landings (Luna‐9 and ‐13), two
successful landers with Lunokhod rovers (Luna‐17 and ‐21) and one rover that failed to depart Earth.
This set of 4 successful landers yields PL~0.83, although adding sample return landers to the set brings
this probability rather lower. Soviet Mars landing attempts Mars‐2, ‐3, ‐6 and ‐7 yielded only 20
seconds of transmission from the surface from Mars‐3 – depending whether that is considered a success
or not, we have 0.17<PL<0.33, although factors contributing to this particularly dismaying performance
were known at the time (e.g. Perminov, 1999).


I forget why I excluded the sample return landers. Note that missions lost on launch would have been rolled up
into the launch success number (i.e. PL is conditional on getting delivered to a landing trajectory, although I
forget why I included Lunokhod-0....) Anyway, I maintain the remark above, that the overall conclusion (that
loss probability on landing attempts is ten to tens of per cent, and not just a few per cent as the Challenger-like
risk assessments always seem to say) is robust...

[fredk]

In effect k+1/n+2 dilutes the track record by the prospect that the next attempt could go either way. It embodies the prior that no system is 100% reliable or 100% unreliable, and starts with a 50:50 guess if there is no track record, then asymptotically tends as data accumulate to the frequentist probability k/n. So 'the grain of salt' is baked into the method via Bayes rule.

I agree that the Cromwell‐Laplace estimate (aka the "rule of succession") gives the best estimate (expectation of the posterior) of the probability, P, of success for independent trials when we assume a uniform prior on P.

My point instead was simply that the variance of the posterior for P gets large for small n. Eg, for ESA Mars landings (k = 0, n = 2) we have mean P = 0.25 but standard deviation of 0.19 (for the beta distribution posterior). In other words, we really can't say much about P in that case except that it's vaguely somewhere between maybe 0.06 and 0.44. That's what I meant by taking P = 0.25 with a grain of salt.

Of course the variance gets smaller as n gets larger, so when there are many launches the value of the expectation P is more meaningful.

[rlorenz]

I agree that the Cromwell‐Laplace estimate (aka the "rule of succession") gives the best estimate (expectation of the posterior) of the probability, P, of success for independent trials when we assume a uniform prior on P.

My point instead was simply that the variance of the posterior for P gets large for small n. Eg, for ESA Mars landings (k = 0, n = 2) we have mean P = 0.25 but standard deviation of 0.19 (for the beta distribution posterior). In other words, we really can't say much about P in that case except that it's vaguely somewhere between maybe 0.06 and 0.44. That's what I meant by taking P = 0.25 with a grain of salt.

Of course the variance gets smaller as n gets larger, so when there are many launches the value of the expectation P is more meaningful.

Sure. To put it another way that avoids people having to mess with Beta distributions, you can get an idea of the size of the required salt grain (i.e. some measure of the uncertainty) from the difference between (k/n) and (k+1/n+2), here 0/2 vs 1/4, or 0.25

[Thorsten Denk]

...you can get an idea of the size of the required salt grain...

Haha, I like this way to express uncertainty.
Thorsten

[kenny]

The French News Agency AFP reports the following, repeated by Moscow Times:

Kremlin vows to pursue Moon race after Luna-25 crash
by AFP Staff Writers
Moscow (AFP) Aug 29, 2023

The Kremlin said Tuesday that Russia would not give up its ambitions to land a craft on the Moon after its first lunar mission in nearly 50 years failed this month.
The Luna-25 module crashed on the Moon's surface after an incident during pre-landing manoeuvres. An Indian mission days later successfully landed near the Moon's south pole.

"We know that the way to the stars is through thorns. The main thing is to continue the Russian programme," Kremlin spokesman Dmitry Peskov told reporters.

"The plans are quite ambitious and they will be realised," he said, adding that the failed mission was not a reason to "tear your hair out".

Moscow Times - Luna program to continue

[Phil Stooke]

https://www.nasa.gov/feature/goddard/2023/lro-luna-25-impact

Luna 25 impact crater - very probably. The story is cautious but I think the faint downrange spray of bright ejecta is pretty conclusive. Dark markings near the impact are also seen at other anthropogenic impacts. Difference image attached.

Phil

[kenny]

NASA Goddard has released an alternating GIF that shows the candidate site for Luna 25, before and after the presumed impact.


Luna 25 impact site before and after