Chandrayaan 3: Launch and Discussions

[sanman]

Curiously ,ISRO Tweeted but withdrew this

Image of CH3 Lander by CH2 Orbiter camera

<snip>

They withdrew it because they re-posted it again under their different account:

https://twitter.com/chandrayaan_3/statu ... 3744214340

[Jayram]

Finally
Rover movement down the ramp
https://twitter.com/isro/status/1694945669721776263
from ISRO

[Prem Kumar]

Amazing!

You can see the ISRO symbol embossed on the left wheel of the Rover

Also, with a 50 cm resolution, the clarity of the CY-3 picture taken from CY-2 could be better. Are they purposely not releasing high-res imagery?

[RCase]

Is this because of the size of the earth being bigger?

It is same why we see only one side of Moon.
This side will always face Earth, although it will see Earth in rotation and all equatorial surface will be seen over about 1 earth day.

Added later: After posting I found that AmberG had already explained it .. but as usual he adds his simple math/numeric masala making it more spicy.

I understand that since the face of the moon is always facing the earth while it is spinning around the earth, a person on the moon surface will be seeing the earth and the rotation of the earth about its axis 14 times during a lunar day.

Maybe I should have been a little more specific in my question -
Q. Will the earth 'rise' and 'set' be the equivalent of waxing and waning of the earth, but will always be overhead (for a person on the moon's equator)?

Q. Also during a lunar day, will the person on the moon will be (primarily) seeing places on the earth that are night?

Q. Please correct me if I am wrong in my thought process. The middle of the lunar day would correspond to our full moon, with the beginning and end of the day being the half moon phases on earth?
(I tried to put this as a schematic below).

Legend:
m -> moon
E -> Earth
>-o observer on equator of moon

Situation:
(1). { full moon on earth, mid lunar day on moon}

(m)>-o ------------(E) ---------------------------------[Sun]

(2). { new moon on earth, mid lunar night on moon}

(E) -------------o-<(m)---------------------------------[Sun]

(3). { Begin Lunar Day}

(m)
v
o
|
|
(E)--------------------------------------------------[Sun}


(4). { End Lunar Day}

(E) ---------------------------------------------------[Sun}
|
|
o
^
(m)

[sanman]

Pragyan Rover Travels Down Ramp to Lunar Surface




which also means that Indian emblem of Asoka lions, as well as ISRO's logo, are now imprinted onto the lunar surface too

[RCase]

Even though I can't understand half of Dishaji and AmberGs posts on math, space and medicine, I propose....

Can we just appoint AmberG as BRs Bill Nye, the Science Guy ( or should it be, gal?).

AmberG, is BR's Scienceji. There. That's proper desi and even rhymes. Screw Bill Nye.

To rejig Modiji's quote - Even the 'Sky' is not the limit with our AmberG!

[Cyrano]

May the AmberG Force be with us.

[Ashokk]

Sushant Sareen gives it back to the UK

[SSridhar]

Sushant Sareen, hat tip.

[nitzter]

Maybe I should have been a little more specific in my question -
Q. Will the earth 'rise' and 'set' be the equivalent of waxing and waning of the earth, but will always be overhead (for a person on the moon's equator)?

Q. Also during a lunar day, will the person on the moon will be (primarily) seeing places on the earth that are night?

Q. Please correct me if I am wrong in my thought process. The middle of the lunar day would correspond to our full moon, with the beginning and end of the day being the half moon phases on earth?
(I tried to put this as a schematic below).

Q. Will the earth 'rise' and 'set' be the equivalent of waxing and waning of the earth, but will always be overhead (for a person on the moon's equator)? Yes, exactly.

Q. Also during a lunar day, will the person on the moon will be (primarily) seeing places on the earth that are night? Yes, increasingly as they reach mid-day and decreaingly as they reach mid-night. Well, referencing the previous images we have of Earth from moon they won't actually see anything for the night side of the earth - not sure about city lights or atmospheric impacts.

Q. Please correct me if I am wrong in my thought process. The middle of the lunar day would correspond to our full moon, with the beginning and end of the day being the half moon phases on earth? Yes.

[juvva]

Curiously ,ISRO Tweeted but withdrew this

Image of CH3 Lander by CH2 Orbiter camera

note the long shadows at dawn.
imagine india ( virtually ) standing on a alien landscape , with the sun low on the horizon.

[Ashokk]

New video from ISRO showing ramp & rover solar panel deployment

https://twitter.com/isro/status/1695026969807929460

A two-segment ramp facilitated the roll-down of the rover. A solar panel enabled the rover to generate power.

Here is how the rapid deployment of the ramp and solar panel took place, prior to the rolldown of the rover.

The deployment mechanisms, totalling 26 in the Ch-3 mission, were developed at U R Rao Satellite Centre (URSC)/ISRO, Bengaluru.

[SSSalvi]

Q. Will the earth 'rise' and 'set' be the equivalent of waxing and waning of the earth, but will always be overhead (for a person on the moon's equator)?

Q. Also during a lunar day, will the person on the moon will be (primarily) seeing places on the earth that are night?

Q. Please correct me if I am wrong in my thought process. The middle of the lunar day would correspond to our full moon, with the beginning and end of the day being the half moon phases on earth?

Picture is worth 100 words.

Attempting with real simulation ( Removed Sunlight/shadow effect for clarity )

Position of Moon and Earth as on 30th Aug 14:00 Hrs... White line joining the two bodies at theor respective South Poles.




Similar situation at 4 instants separated by 3 hrs interval. Moon removed.

Earth on Left of each set, while on Right image the view as seen by a Moon-vasi.

Notice the rotation of Earth seen from Moon.

( OK OK OK, before someone points out .. Actually Moon-vasi will NOT see this , because it is nearly a amavasya for him ... Sun is behind so he will see a black bob surrounded by a thin bright circle ... Earth is significantly Large and has Atmosphere for dispersion of light.



Will post a 14 day cycle pic-story later

[nitzter]

Mass differs from weight; a 100 kg mass on Earth remains a 100 kg mass on the Moon. (Hint: In orbit, everything is weightless, but that doesn't mean you can carry an unlimited payload.) Newton's laws deal with mass, and for a given change in velocity (delta-V), the energy (fuel) required depends hardly on whether you're on the Moon or not (assuming you're beyond the gravitational "potential well" of local body ).

You have to do work against Sun's gravity to go to Mars..

Whether you're near the Moon or Earth, the delta-V needed to reach Mars (or other outer planets) is approximately 42 km/s. Since Earth (or the Moon) is already moving at around 30 km/s, you might opt to wait for the right orbital alignment. This way, you'd only need about 12 km/s at the optimal time. (For this, you might need to wait for a year or a few, aligning Earth's or the Moon's trajectory with that of Mars.)

Moon's g is 1/6th of earth etc doesn't significantly alter flight time .. Forget about getting faster/slower due to this-- the flight time is mainly dictated by Newton's laws. (assuming you have limited fuel).

While gravity assists, mechanics, and planetary alignments can conserve fuel, apart from the fuel needed to escape Earth's (or the Moon's gravity well - where it has some advantage), the "one-sixth factor" doesn't hold much significance.

Hope this is useful.

Beautifully explained Amber ji!

If I put it together, there are three key steps - escaping your home celestial object, work to reach the destination object and, lastly, the insertion.

1. Work done to overcome the gravitational potential can be lowered if we start at moon's surface (which is at higher potential than Earth's surface). We will really benefit with launching from Moon if an in situ production of parts, fuel and life sustaining resources is done - else taking everything from Earth is counter intuitive. (additional benefit of no atmosphere is a plus)

2. Work done to displace the spacecraft to the destination object can be lowered if we start at the right planetary orientation. However, we already do that to conserve fuel - so nothing save there.

3. Work done to insert into an orbit of lower potential can be lessened if we ensure just enough transfer velocity and better line of approach. We already do that... - again no saving here.

[Amber G.]

I understand that since the face of the moon is always facing the earth while it is spinning around the earth, a person on the moon surface will be seeing the earth and the rotation of the earth about its axis 14 times during a lunar day.

Maybe I should have been a little more specific in my question -
Q. Will the earth 'rise' and 'set' be the equivalent of waxing and waning of the earth, but will always be overhead (for a person on the moon's equator)?

Q. Also during a lunar day, will the person on the moon will be (primarily) seeing places on the earth that are night?

Q. Please correct me if I am wrong in my thought process. The middle of the lunar day would correspond to our full moon, with the beginning and end of the day being the half moon phases on earth?
(I tried to put this as a schematic below).

Let me add: (Just to be clear):

ON Moon: If you look in the sky from a given point (Say CY3 Vikram)..

The stars will rise on East (exactly), set on west -- perion 27.3 days. (On Earth this time is 23 Hours 56 Minutes)
The Sun will rise on East (almost exactly within 1.5 degrees) and set on West - (Period 29.53 days)... making "day' and 'night' each of about 14.7 earth days. (On earth this time is 24 Hours)
(ON earth sunrise and sunset are on East-West direction (exactly) only on March 23 and Sept 22)

The earth (you can only see it from near side) will be a fixed point in the sky (wrt to horizon and local N/S direction).... like a fixed balloon)..
--- You will see it going through all the nakshatras (fixed stars in the background) in around 27.3 days (Just like we see Moon from Earth).. but position wrt to ground is not going to change much.
--- From Vikram viewpoint - it will be about 20 degrees above the horizon.
---- The angle above horizon could vary by 5 degrees over the course of 27.3 days... (So wrt to horizon - angle varies between 15 and 25)
--- Earth will be spinning (You can only see half of this at any given time --- This is why antenas all over the world help to provide 24 hour coverage -- the time period here is 24 hours 48 minutes -- (Why it is not exactly 24 hours ? - not difficult answer..)
--- The waning and waxing of earth period is still 29.53 days.... (going from 'full earth' to 'new earth' to 'full earth' again ) -- In other words, the brightness will also change.... (The bright part of the earth -- there will be 'day time' on earth ityadi)..


(You can simulate all this with various app - JPL/Horizon tools etc - I being an old fashioned just use pen/pencil and a calculator to calculate )

Q. Please correct me if I am wrong in my thought process. The middle of the lunar day would correspond to our full moon, with the beginning and end of the day being the half moon phases on earth?

Vikram has landed at 32E longitude. Moon's prime meridian passe right in the center of the moon when we observe at any time. So if vikram landed at 0 degree longitude, then "noon" will correspond to what you say... As it is it is only 32 degrees away , we know sun was just rising on August 23.... Next full moon is on August 30 (Interestingly it is 'blue moon') so it is will be approximately 'noon' there.

[juvva]

how often , will the earth eclipse the sun as seen from the moon ?
will such eclipses come in all the varieties - full, partial, annular - and depend on the location of the observer on the moon?

[Ashokk]

https://twitter.com/chandrayaan_3/statu ... 7682628884

Chandrayaan-3 Mission update:

All planned Rover movements have been verified. The Rover has successfully traversed a distance of about 8 meters.

Rover payloads LIBS and APXS are turned ON.

All payloads on the propulsion module, lander module, and rover are performing nominally.

[Amber G.]

^^^ When we have solar eclipse, Moon will have "earth' eclipse.,... when we have lunar eclipse Moon will have solar eclipse (it will last a little longer as earth is bigger and visible from much wider area)..

From Earth, both sun and moon (a big coincidence) has same angular diameter (about 1/2 degree).. due to orbits being ellipse moon can be bigger or smaller... hence one can have total (very rare) or annular eclipse. From Moon, apparent size of earth is much bigger than sun ,,, so there will be more total solar eclipses visible from wider area.. (and no chances of annular)

[Amber G.]

https://twitter.com/chandrayaan_3/statu ... 7682628884

Chandrayaan-3 Mission update:

All planned Rover movements have been verified. The Rover has successfully traversed a distance of about 8 meters.

Rover payloads LIBS and APXS are turned ON.

All payloads on the propulsion module, lander module, and rover are performing nominally.

Yay!

[juvva]

amber:

^^i suppose an earth eclipse, would be just a round dot traversing a path on the fully sunlit earth(?).

[juvva]

https://twitter.com/chandrayaan_3/statu ... 7682628884

Chandrayaan-3 Mission update:

All planned Rover movements have been verified. The Rover has successfully traversed a distance of about 8 meters.

Rover payloads LIBS and APXS are turned ON.

All payloads on the propulsion module, lander module, and rover are performing nominally.

wow great!
ashokk as usual brings the good news first to this forum

[vijayk]

https://twitter.com/MeghUpdates/status/ ... 4542328161
The times are changing. We are recognizing our true heroes- ISRO scientist Parvathi returns home to a hero's welcome at her society after the success of #Chandrayaan3. Proud feeling

[Amber G.]

amber:

^^i suppose an earth eclipse, would be just a round dot traversing a path on the fully sunlit earth(?).

- For those who are curious, if you are on the moon -
These solar eclipses are only seen in the near side portion (and a very small part of the far side - librations) Eclipses there are seen during the lunar sunrise and sunset and extend to the furthermost areas of the near side but mainly not in the polar areas of the Moon. While the Moon orbits Earth, Earth rotates once in nearly 24 hours, but its position at the sky is only in one position, as it never changes.

The last solar eclipse on the Moon was a total eclipse on 8 November 2022, with the entire near side and tiny surroundings of the far side seeing totality. The next total eclipse won't be until March 2025.

The longest eclipse that can be viewed in one area on the Moon lasts for up to five and a half hours. (Earth sees its eclipse for up to two and a half hours)

Some eclipses are longer when the Earth is slightly closer to the Moon. During such on eclipses, the Moon is seen on Earth with its apparent diameter larger than the Sun's. Meanwhile, some eclipses are shorter when the Earth is slightly further away from the Moon.
Unlike the Earth, where its eclipses start and end at a different place, all of the Moon's solar eclipses begin in the westernmost parts of the near side and end in the easternmost parts of the near side.

Solar eclipses starting near poles are always partial, while solar eclipses starting at or within the equator are always total.

---
An "Earth eclipse" as viewed from the Moon, as you described is correct - ..(When there is a solar eclipse on earth)

[disha]

Would we be able to repurpose the SHAPE instrument for analyzing any other planet if all of the habitable planet earth planned experiments are completed as someone else asked? In other words what advantages can be derived from the extended life of the PM? Also if you have both CH-2 and PM in large enough orbits would it be sufficient to communicate with a lander on the far side of course with its PM also kind of like a 3 satellite moon GPS?

All good questions to unpack:

1. The SHAPE instrument and how it observes Earth is described here: https://www.ursc.gov.in/shape.jsp

In very simple terms, Earth is the only known planet with life (and hopefully some sentient life) and observing Earth in infrared forms a baseline to identify Earth like exo-planets. If you identify earth like exo-planets, since they will have a similar signature like earth, for which we have a baseline using SHAPE, we can confidently say that those exo-planets can host life and hopefully sentient life (which is speculated to exist on earth).

2. The mission parameters called for propulsion module was singular:
2a. Take the lander from earth bound orbit to lunar bound orbit
2b. And while hanging around observe Earth.

Nowhere the mission parameters calls for it to be another communication relay. C2 is already around moon and acting as a communications relay. And as a backup from lander. So a backup to backup when C2 is operating well (and including on the far side of the moon) maybe an overkill.

Also setting up communications relay on C3 PM changes the mission parameters. Now one has to do power management and account for risks when C3 PM goes through van allen radiation belts around earth. This van allen belts radiation belts are highly charged energetic particles that poses great risk to electronics and humans.

In fact while C3 was doing its Oberth maneuvers, there was concern in this very pages on the health of C3 given the higher solar activity around that time.

[disha]

Engines cutoff a meter of two above the surface seems excessive in my opinion especially if there is a possibility of a bounce( in low lunar gravity) with uneven time of touchdown (due to uneven weight distribution of the LM) of the each of the four legs.

Thx for doing the calculations. The engines were cutoff at ~2m and C3 dropped like a stone for a good reason.

^^^
1, Engine shutoff earlier ... to avoid large dust settling on solar panels??
...

Juvva'ji, Please pay attention to above post by Salvi'ji.

...
iirc the engines cut off only after the sensors in the pads of the legs , signal contact with the lunar surface.
there is no possibility of free fall.

The free fall of C3 on Moon from ~2 meters above moon surface was engineered. And for a good reason.

1. On moon there is no atmosphere, so the lunar regolith (or moon dust) does not go through the weathering process that earth's dust goes through. If one goes to deserts of Earth, the rounded weathered silica grains still mess up any system and gets into places where it does not need to be. The lunar regolith is not even nice and well-rounded. It is just sharp with fine edges. Gets into everything and starts cutting up things.

2. The lander's rockets kick up quite a storm of dust. That is why in C2, they added a central motor to kick off the dust to sideways and that created additional algorithm challenges. This time, the mission said, let it free fall from a certain height. That way the dust kicked off has time to get off the way and *no new dust* is kicked off.

---

So all the nanha-mujahids who have not been halal'ed yet, please do not say that we will get moon dust for you to win some brownie points. First of all the moon dust is very sharp and if applied as makeup, will *not* shine the face of your beau but will scratch and cut the skin and make it like a face from one of those horror movies.

[disha]

Even though I can't understand half of Dishaji and AmberGs posts on math, space and medicine, I propose....

Can we just appoint AmberG as BRs Bill Nye, the Science Guy ( or should it be, gal?).

AmberG, is BR's Scienceji. There. That's proper desi and even rhymes. Screw Bill Nye.

Hey CainJi, thanks. But what about me, that is what desi name you propose?

[disha]

Sushant Sareen gives it back to the UK

^Excellent response by Sushant Sareen. I am forwarding that clip to some of my ex-colleagues.

[juvva]

Engines cutoff a meter of two above the surface seems excessive in my opinion especially if there is a possibility of a bounce( in low lunar gravity) with uneven time of touchdown (due to uneven weight distribution of the LM) of the each of the four legs.

Thx for doing the calculations. The engines were cutoff at ~2m and C3 dropped like a stone for a good reason.

^^^
1, Engine shutoff earlier ... to avoid large dust settling on solar panels??
...

Juvva'ji, Please pay attention to above post by Salvi'ji.

...
iirc the engines cut off only after the sensors in the pads of the legs , signal contact with the lunar surface.
there is no possibility of free fall.

The free fall of C3 on Moon from ~2 meters above moon surface was engineered. And for a good reason.

1. On moon there is no atmosphere, so the lunar regolith (or moon dust) does not go through the weathering process that earth's dust goes through. If one goes to deserts of Earth, the rounded weathered silica grains still mess up any system and gets into places where it does not need to be. The lunar regolith is not even nice and well-rounded. It is just sharp with fine edges. Gets into everything and starts cutting up things.

2. The lander's rockets kick up quite a storm of dust. That is why in C2, they added a central motor to kick off the dust to sideways and that created additional algorithm challenges. This time, the mission said, let it free fall from a certain height. That way the dust kicked off has time to get off the way and *no new dust* is kicked off.

---

So all the nanha-mujahids who have not been halal'ed yet, please do not say that we will get moon dust for you to win some brownie points. First of all the moon dust is very sharp and if applied as makeup, will *not* shine the face of your beau but will scratch and cut the skin and make it like a face from one of those horror movies.

https://www.google.com/amp/s/www.scient ... 3famp=true

Finally, on touchdown, sensors on the lander’s legs triggered the shutdown of its main engines. Chandrayaan-3 now stands tall on the moon.

the above is from a scientific american article.

[juvva]

i revisited landing video was unable to make out any sudden drop of lander in the animation of lander at touch down, after engine cut off.

same was the case in the footage of lander camera, no definitive sudden drop evident.

[juvva]

wiring visible at landing pads maybe related to the sensors.

[disha]

https://www.google.com/amp/s/www.scient ... 3famp=true

Finally, on touchdown, sensors on the lander’s legs triggered the shutdown of its main engines. Chandrayaan-3 now stands tall on the moon.

the above is from a scientific american article.

I think, Scientific American got it wrong. Some of this articles are written prior to the event and they do copy paste from past articles and their own thinking of what should happen. Basically a stock article that they need to publish the moment event happens.

ISRO PR messes up the telemetry and currently my day job is not allowing me to piece it all together. Jayaram'ji with his calculations.is onto something.

Juvvaji' what will be your take if we prove scientific american wrong?

[disha]

i revisited landing video was unable to make out any sudden drop of lander in the animation of lander at touch down, after engine cut off.

same was the case in the footage of lander camera, no definitive sudden drop evident.

The drop on moon will be gentler. 1/6th "slower". To perceive from a remote non-high fidelity camera first time & interpreting based on your senses tuned on Earth will lead to errors in perception.

[juvva]

Juvvaji' what will be your take if we prove scientific american wrong?

i will stop reading scientific american

[juvva]

to me it ( intuitively) feels a safer strategy to shut off engines after confirming physical contact with the surface ,rather than depend on a altimeter to indicate almost there signal.

i think isro basically said damn the dust, we dont care , when they removed the central engine - we want to land safely period.

[Amber G.]

Also if you have both CH-2 and PM in large enough orbits would it be sufficient to communicate with a lander on the far side of course with its PM also kind of like a 3 satellite moon GPS?

Not exactly --- here are some basics to make everything clear ..
1 - Both CH2 and CH3PM are almost in polar orbit (Moon's north pole/south pole)..and are almost in the same plane.
This plane is fixed wrt to stars - this means:
- Both are revolving with time period of about 2.1 hours. Both are about 100 Km above the surface. Going around the moon in almost circular orbit.
- Meanwhile moon below spins so geographical point on the moon, directly below the orbit when, say CH2 is over the equator, changes from day to day in each orbit ... takes around 27.3 days for this cycle..
- Just below, if there is 'day' or 'night' also changes -- This cycle is about 29.53 days.
- Relative position between PM and CH2 (although they share almost the same orbit) changes.. since there time-period is slightly different the phase difference changes from day to day. (For example at the time of the touchdown PM was visible from Vikram but CH2 was not.
- Vikram is always in sight from (some point) on earth.
- Both CH2 and PM are out from earth's view for about half the time of their orbit (of 2.1 hours)
Their height over the surface is only about 100 Km - so they do not see all of the moon (or even half of the surface) at the same time.

For GPS type system ... you would need 3 or more sats in *equatorial* orbit to cover the whole moon.

CH2 has the bandwidth to transmit high quality data -- both PM (about 50% of the time in the orbit) and Vikram (all the time) is "visible" (talk with earth's large radio antennas) from earth.

[SriKumar]

The Laser altimeter is about halfway up the Lander, so about 0.6m above the 'feet' or landing pads of Vikram. That leaves it still 3.46-0.6 = 2.86m above the surface with a velocity of -0.983 ms. If indeed that velocity is -0.983 m/s at 3.46 m altitude, then perhaps the engines cut off at this point but if they do, the free-fall would give it a touch-down velocity of sqrt( 0.983^2 + 2*(9.81/6)*2.86) = 3.21 m/s (going by v^2 = u^2 + 2 *g*s and taking lunar gravity into account). I recall hearing somewhere that the engines would cut off a meter or two above lunar surface.

Not an expert but we may be overthinking this . two points - LDV (Laser Doppler velocimetry) reads 0.0 - no motion detected ie touch down and the this time is then frozen at 1193.573 -consistent over on the left and right side of the picture. So at that point all the rest of the sensor data is frozen and is what we see in the picture. After all if all the sensor data was reset at touch down the usefulness of that data at that point would be diminished and would not allow for any troubleshooting.
Engines cutoff a meter of two above the surface seems excessive in my opinion especially if there is a possibility of a bounce( in low lunar gravity) with uneven time of touchdown (due to uneven weight distribution of the LM) of the each of the four legs.

Well, the two velocities shown in the sceenshot are non-zero (-.981 m/s and 0.0053 m/s or something close), clearly the velocity of the lander is not zero. LDV update counter is not velocity- units are not mentioned. This screenshot was taken while the lander was still above the surface of the moon and not landed yet. This squares with the non-zero and non-trivial value of vertical velocity. The lander is moving at 0.983 m/s and still at 3.46 m altitude when the screenshot was taken. I believe the touchdown was not complete at this point.

(As for what cuts off the engines, I'll try to look for a video that had some info on this (interview with S.Somnath iirc)

[sanman]

to me it ( intuitively) feels a safer strategy to shut off engines after confirming physical contact with the surface ,rather than depend on a altimeter to indicate almost there signal.

i think isro basically said damn the dust, we dont care , when they removed the central engine - we want to land safely period.

You could poll multiple sensors (legs, accelerometer, LDV, etc) and get a majority verdict.

Somnath himself replied that while system was able to verify through multiple sensors, the accelerometers worked so well on their own that there was no need to even turn to additional inputs for validation.

[rahulm]

Today M's address at ISRO will be telecast live at 11:30 "Chandrayaan-3 Addressing by Honorable Prime Minister-Live Event"

[Najunamar]

Thanks AmberGji, I think (way into the future) we will need to set up such a navigational set up for the moon too!

[Amber G.]

Thanks AmberGji, I think (way into the future) we will need to set up such a navigational set up for the moon too!

As I posted before, for Moon, setting up a relay station at L2 as China did works very well.

(The "Queqiao" relay satellite, launched as part of China's Chang'e 4 mission, is at a strategic position at the Earth-Moon L2 Lagrangian point, which is about 65,000 kilometers beyond the Moon from Earth. This satellite serves as a crucial communication link between Earth and the far side of the Moon, where direct communication is challenging due to the Moon blocking radio signals.

Queqiao enables real-time communication with the Chang'e 4 lander and rover stationed on the lunar far side. The satellite's position at L2 allows it to have a continuous line of sight to both Earth and the far side of the Moon, making it an essential element in advancing lunar exploration and expanding our understanding of this enigmatic celestial neighbor.

Beyond its primary mission Queqiao has contributed to space science research by studying the Earth's ionosphere and magnetic fields, as well as enabling observations of celestial phenomena from its vantage point beyond the Moon.. Apart for showing some photos ....AFAIK China has not publicly offered the use of its relay satellite to others.