Chandrayaan 3: Launch and Discussions

[Ashokk]

Chandrayaan-3 LIVE Updates: Vikram Lander separation to take place at 1 pm today

Chandrayaan-3 Live Updates: The lander module separation will take place between 1 pm to 1.30 pm, according to Business Today reports.

[SRajesh]

Hopefully everything is Naarmal!!
And a smooth Separation

[juvva]

is dilbu off duty today?

[dinesha]

BREAKING: Chandrayaan-3 lander module successfully separates from the propulsion module. The final phase of moon approach begins. Landing scheduled for August 23 at 5.45 pm. #GoVikram!

https://twitter.com/ShivAroor/status/16 ... 80005?s=20

[rahulm]

Chandrayaan-3 Mission:

‘Thanks for the ride, mate! ’
said the Lander Module (LM).

LM is successfully separated from the Propulsion Module (PM)

LM is set to descend to a slightly lower orbit upon a deboosting planned for tomorrow around 1600 Hrs., IST.

[dinesha]

Lander Module Successfully separates from Propulsion Module today (August 17, 2023).
The next Lander Module (Deorbit 1) maneuver is scheduled for tomorrow (August 18, 2023) around 1600 hrs IST.
https://twitter.com/chandrayaan_3/statu ... 06463?s=20

[juvva]

can we hope for a video of the seperation event ?

[juvva]

how are the two modules pushed apart ? springs? thrusters ?

[Dilbu]

Sorry couldn't make it in time. Congrats ISRO. Now on to 15 minutes of terror on 23rd.
Chandrayaan 3 will not successfully soft land onlee.

[SSSalvi]

No, this is only half dilbu.
Real dilbu is only in last sentence.

[rrao]

what is this dilbu sir, you are telling C3 landing will not be soft...i am hurt!!!
salvi sir, any chances that we may alter the schedule landing much earlier to beat those russians.

[Pratyush]

I can now breathe easy. Reverse jinx is done.

[Amber G.]

If you are looking at Sankara V's excellent orbit simulation The orbit updates include LBN5.
NASA/JPL tells us "158" will continue to be lander ID. 169 will be used for PM. Separation data not available yet but hope that it is there soon.



(If you have not tried, try "joy ride" feature from the above simulation .. to see how close to moon you are and how swiftly moon passes down there)




: Meanwhile, the PM will continues its journey in the current orbit for months/years.

The SHAPE payload onboard it would:
Perform spectroscopic study of the Earth’s atmosphere and
Measure the variations in polarization from the clouds on Earth
– to accumulate signatures of Exoplanets that would qualify for our habitability!

This payload is SHAPEd by U R Rao Satellite Centre/ISRO, Bengaluru

[Amber G.]

Sorry couldn't make it in time. Congrats ISRO. Now on to 15 minutes of terror on 23rd.
Chandrayaan 3 will not successfully soft land onlee.

Worry not sir.. As a kavi will say:

लक्ष्य की ओर चंद्रयान का नया पथ,
विक्रम ने प्रक्षेपण मोड़ किया आगमन साथ।
चंद्रमा पर शीतल लहर, विक्रम को अभिनन्दन,
प्रज्ञान के रंगीन घुमाने, सुखद चरण।

प्रगति से प्रस्थित, प्रग्यान का गान,
चंद्रमा के सदृश रहस्यों की खोज में उत्सुक ज्ञान।
चंद्रयान की कहानी, एक नई पहचान,

[fanne]

you guys are reversing Diblu's sir reverse Jinx. Please let it go!!

[Amber G.]

how are the two modules pushed apart ? springs? thrusters ?

Preparation: Once the CY3 is in the desired lunar orbit, the ISRO mission control would assess the conditions and confirm that all systems were functioning as expected. This is a crucial step.

Orbital Adjustment: CY3 trajectory/orbit (after LBN5) might be adjusted slightly to ensure the optimal conditions for separation. This adjustment might involve firing the spacecraft's thrusters to fine-tune its position.

De-coupling: The separation process would involve firing specific thrusters on the lander (Vikram) to gradually increase the distance between the lander and PM (the orbiter). The thrusters would be carefully controlled to ensure a controlled and stable separation.

(I put down basic formula for calculating delta-V in BRF , ISRO uses a little more sophisticated calculations and computers to get things exactly right )

Safe Separation: Once the lander was at a safe distance from the orbiter, it would continue on its trajectory .. Meanwhile, PM would continue its near circular lunar orbit, conducting scientific observations ...

After separation, the Vikram would carry out another burn to obtain a elliptical orbit - reduce its altitude to nearly 30 Km at perigee .. repeating the orbit every two hours or so ... and prepare for a soft landing it will have a further few more days to scan the surface below to find/confirm the right spot ...(Moon in the meanwhile would be rotating slowly and (day/nigh separating longitude line - or places where sun is just rising) This landing sequence would involve firing thrusters at precise moments to control the descent and ensure a safe landing.

It's important to note that the success of these operations relies heavily on precise calculations, careful planning, and the performance of the spacecraft's onboard systems. Any deviations or issues during the separation process could impact the mission's outcome.

Here is the screen shot put here before from the planning: (See Ashokk 's post)

[sanman]

Chandrayaan-3 lander has a drill:

[Amber G.]

Journey so far: For BRF quick reference:
Last edited August 18, 2023 by Amber G.

Earth Bound:

1 15 July 2023 — 41,762 km 173 km Success
2 17 July 2023 — 41,603 km 226 km Success
3 18 July 2023 — 51,400 km 228 km Success
4 20 July 2023 — 71,351 km 233 km Success
5 25 July 2023 — 127,603 km 236 km Success

Trans Lunar Injection:

31 July 2023 — 369,328 km 288 km Success

Lunar Bound

1 5 August 2023 -- 18,074 km 164 km Success (Orbit Time Approx. 21 h )
2 6 August 2023 — 4,313 km 170 km Success (Orbit Time Approx. 6.25 h)
3 9 August 2023 — 1,437 km 174 km Success (Orbit Time Approx 2.3 h )
4- 14 August 2023 - 151 km 179 km Success (Orbit Time Approx 2.07 h) (ISRO Figures: 7434 sec)
5 16 August 2023 - 163 Km 153 Km Success - (Orbit Time 2.05 h)

17 August 2023 Lander Module Separation PM Orbit Success- 163 Km - 153 Km (Orbit Time (2.05 h)

18 August 2023 Lander Deorbit Burn I Vikram - 113 km 157 km success - (Updated on August 18 by Amber G.
20 August 2023 Lander Deorbit Burn II (Planned)

23(?) August 2023 Vikram Landing. (Planned)

Click images below to see animation:

Earth Bound: (Click the image to see video)



To the Moon: (Click the image to see video)


Around the Moon: (Click the image to see video)

[Amber G.]

Doppler says: The PM and Lander are distinctly in separate orbit. The lander is leading with the gap increasing between revs. JPL Horizons' data hasn't been updated.

[Amber G.]

Meanwhile - I have not seen any other confirmation of Luna-25's orbit by others outside the official site...(Unlike CY3, the signals are weak - frequencies not that well-known ityadi)

But per Roscosmos - Luna-25 lander , snapped its first detailed photo of the moon's surface

[disha]

For that there is a separate fixed frequency beacon used exclusively by satellite operator in conjunction with Ranging equipment using Tx/Rx for accurate measurements )

Also, laser-ranging through laser retro-reflectors affixed on spacecraft. Don't know if CY3 carries any.

The laser-ranging through laser retro-reflectors on the CY3 lander (The LRR payload) is a passive instrument for Lunar laser ranging studies. This is a NASA payload which has been accomodated on the CY3 lander.

Think of Lunar RetroReflector Array (LRA) is a highly polished mirror stuck on the lander and NASA plans to send a laser pulse to it and measure its reflection to Lunar ranging studies.

NASA is contributing the retroreflector for LRA (This will be a big help for future missions - if all other things fail, this could still survive - as it requires no battery so it will remain for a long time)

The way above is worded, it appears that NASA is doing ISRO/India a favor. That is not the case. It is exactly reverse.

ISRO/India is contributing its lander for NASA to do its Lunar Ranging studies. Further the conjecture on all other things fail, this could still survive as it requires no battery - is a remarkable wrong conjecture.

Simple if things fail, the LRA will be out of alignment and will not help NASA do its studies. So there is no "could still survive as it requires no battery".

And again even ISRO chairman did not think much about LRA. Paraphrasing him: The LRA is just a mirror stuck on the lander. FWIW.

So to say NASA is contributing to ISRO's science is exactly reverse. It is ISRO/India that is contributing to NASA/USA science.

LUNA26 has 1 Targeted location and 2 standby locations.

It is interesting to see the spread of these locations on Moon surface.

First target is L25_A ( in subsequent video post I will show how these targets get illuminated with sunlight ), which will get twilight from 21st Aug, CH3 will get twilight on 22nd , L25_B will get twilight on 23rd and L25_C on 23rd.

So, Rus has kept some risk margin if 1st attempt is not executed and taking care that L25 will not clash with CH3 location.

Salvi'ji, I think you are being nice and charitable to Ruskies/Roscosmos.


1. For Roscosmos, C3 landing site and any kind of interference from Luna 25 was never under consideration. Even Roscosmos never acknowledged that it has taken into account any interference with C3. The "interference" part is a media play. The distances are so great that even a fraction of degree of separation makes kilometers of spatial difference. Take the case of the last stage of Apollo 12 which went into a long journey around Earth just because of miscalculation on few kms/sec.

This is a "hail mary" pass by Roscosmos. Since they do not want to be left behind in the "space race" and they have to make it. Or seen making a try. Even to gain credibility as a junior partner to Cheen.

2. Roscosmos chose the landing site with the following criteria to identify the landing site in the S. Pole (70*) region of the moon:

a. Identify a landing site that is quite large (30 x 15 km ellipse). Why? The Luna25 lander does not have an active maneuvering system during the landing phase [/list]
b. The slope of the surface within the landing ellipse cannot be more than 15*. [/list]
c. The surface must be sufficiently smooth
d. Must meet the lunar day criteria of at least 40% and radio interval visibility from the Earth be at least 50%

After setting up those engineering parameters, Roscosmos identified which craters will match the criteria that could do some science. And that's how they came up with the 69*S 43*E location which is north of Boguslavsky crater. Then the reserve points around Manzini and Pentland A crater.

Point is, Roscosmos went with engineering first approach as compared to science first approach of ISRO. This is a nuance that needs to be brought out.

Here is what I mentioned some days back:

Ruskie's first goal, "hey we reached first". Science, oh that is secondary. Let's do the engineering first.

Mission profile: just drop the Luna 25, it will slow down and it will slow down further. And then land, somewhere in the vicinity of where we intend to land. The Russian scientist says, but the crater is over there to study. Well, from the engineering perspective, that is the problem of the intertial navigation team. They were not precise enough.

Anyway, operation successful, even if the patient is dead

I might be adding more color in my subjective interpretation of Roscosmos, but it definitely is not far from the truth. How am I stating it? This is what Roscosmos states itself (discovered it after I made the above post)

https://iki.cosmos.ru/missions/luna-25 <-- Click on English version of the site if you do not know Russian.

[disha]

how are the two modules pushed apart ? springs? thrusters ?

It need not be springs. I think it is a cold gas thrust from the propulsion module to the lander module. The way lander is staged on the propulsion module a strong puff of gas (generally liquid nitrogen as generator) to safely push the lander module out.

I would not be surprised that the propulsion+lander combined module did a 180* turn and become a lander+propulsion and then push the lander out. This not just achieves a distance but also changes the orbit parameters of both the lander and propulsion. The propulsion module gains more energy and the lander module looses some energy (imparts some of its KE to the propulsion module).

This also orients the lander in the nozzle out position. That is subsequently, the lander will use its thrusters to slow further down, de-boost and go through its rough and fine braking phases before landing.

[Najunamar]

Dishaji, Thanks! I thought about the 180 degree orientation change of the LM also where the thrusters are facing the direction of motion in orbit! Only I was wondering how it was going to be accomished at such a high speed. Your explanations made it very clear.

Just a quick question it would still have taken a significant effort to reorient the PM+LM right? Though the larger PM engines would be better placed to accomplish that?

[Dilbu]

Chandrayaan 3 will not successfully soft land onlee.

[disha]

...
Just a quick question it would still have taken a significant effort to reorient the PM+LM right? Though the larger PM engines would be better placed to accomplish that?
...

Najunamar'ji, all satellites are falling bodies and hence are weightless. It does not take much energy to re-orient the falling object. For example if the object is oriented like this "--->", to re-orient it 180* into "<---" does not require much energy as long as it is in the same orbit and the same plane.

As an example, I found this SpaceX simulator (https://iss-sim.spacex.com/) for docking into ISS. You will notice that the alignment with ISS takes less then <0.1 m/s.

Now coming to your question on Propulsion module vs lander, and using the propulsion module to slow down the lander, that to me can be an experiment for some other day. I also wondered, if propulsion module has some spare fuel why not use it to slow down the lander and conserve fuel for the lander. But then the questions does arise, how much fuel is left? What happens if the fuel amount is miscalculated and the PM sputters? Or creates some other problem after going through Van Allen belt several times and firing for some 7-9 times?

So, why risk the mission now when the lander has been sufficiently fueled and PM has done its job? I feel that it is all about managing variables within certain margins. And not introduce new variables when all of the system with those variables and margins have been tested on ground and simulations as well run and the C3 is sticking to that plan. That is what I am surmising.

Also the energy required to slow down the lander is immense. That is why the lander has four 800N engines which will generate enormous amount of thrust (in this case reverse thrust). And comparatively the propulsion module has to just raise the orbit and an orbital plane change which requires lesser energy and hence is sized for that purpose. Again comparatively the energy required by Propulsion Module is lesser than the energy required by Lander to do a soft landing. This is attested in the IISc lecture by ISRO Chairman.

So all in all, the propulsion module has done its job and done its job well. Time to say good bye to PM and shift the focus on LM.

[juvva]

how are the two modules pushed apart ? springs? thrusters ?

It need not be springs. I think it is a cold gas thrust from the propulsion module to the lander module. The way lander is staged on the propulsion module a strong puff of gas (generally liquid nitrogen as generator) to safely push the lander module out.

---

how are the modules uncoupled mechanically ?
electro mechanical latches?
explosive bolts ?
??

[Ashokk]

Chandrayaan-3: As Vikram prepares for deboosting, here’s how it separated from spacecraft on Thursday

The cylindrical structure on top of the orbiter, the extension of the fuel tank, is where the lander with the rover inside it, was sitting. Both these modules were held together by clamps with two bolts.
Isro chairman S Somanath confirmed to TOI that the mechanism employed for separation on Thursday was the same as Chandrayaan-2. That is, two halves of a metal flat spring held the two modules. The springs were pre-loaded using two bolts. The bolts were sheared, releasing the lander.
On the reason behind employing this mechanism, a scientist associated with the previous lunar mission said it was simple, reliable and had extensive flight history.
Former Isro chairman K Sivan said: “If the same mechanism as Chandrayaan-2 was employed, then the systems are released by operation of a pyrotechnic bolt cutter to cut the bolts that hold the clamp. This system has high strength and stiffness when clamped and releases quickly, typically in less than 50 milliseconds, when command is given.”

[juvva]

^ thanks! ashok for the detailed info.

[juvva]

https://sankara.net/chandrayaan3.html

will it be possible for this kind of animations to include all the 3 craft of interest:
1. lm
2.pm
3.cy2 ( relay station )
of particular interest is the relative positions of lm and cy2 during the landing phase.

[juvva]

how is lm communicating with earth stations right now ( when in lunar orbit) ?
directly or through cy2 ?

i believe isro said pm cannot act as a radio relay for lm...

[putnanja]

From ISRO Facebook page, 1st deboosting operation of lander successful

Chandrayaan-3 Mission:
The Lander Module (LM) health is normal.

LM successfully underwent a deboosting operation that reduced its orbit to 113 km x 157 km.

The second deboosting operation is scheduled for August 20, 2023, around 0200 Hrs. IST

#Chandrayaan_3
#Ch3

[SSSalvi]

https://sankara.net/chandrayaan3.html

will it be possible for this kind of animations to include all the 3 craft of interest:
1. lm
2.pm
3.cy2 ( relay station )
of particular interest is the relative positions of lm and cy2 during the landing phase.

For CH2, orbiter,lander and ch2 were 3 separate bodies on Horizons.. same is expected for ch3

[Ashokk]

New video of the moon surface shared by ISRO.
https://twitter.com/isro/status/1692476417093890282

View from the Lander Imager (LI) Camera-1
on August 17, 2023
just after the separation of the Lander Module from the Propulsion Module

#Chandrayaan_3
#Ch3

[Ashokk]

One more video
https://twitter.com/isro/status/1692474762369626329

Chandrayaan-3 Mission:
as captured by the
Lander Position Detection Camera (LPDC)
on August 15, 2023

ISRO has added a link on its website for media persons to register for covering the landing event on 23rd, its in Google docs

[Ashokk]

Update from Roscosmos on Luna-25
https://www.roscosmos.ru/39645/
Translation:

Today at 09:20 Moscow time the propulsion system of the automatic station performed an orbit correction lasting 40 seconds. Its goal is to provide the best conditions for the subsequent creation of the pre-landing orbit.

The correction went smoothly, all onboard systems of Luna-25 are working normally, communication with it is stable.

[S_Madhukar]

Is it just me that I find CY3 photos a bit meh ? I would have hoped better quality this time around since CY1 and MoM … also a decent video would have been nice… I know ISRO’s priorities and all but kids would do a better job with visuals these days ! More funding is needed to make this a proper space faring project not a university science project

[Amber G.]

https://sankara.net/chandrayaan3.html

will it be possible for this kind of animations to include all the 3 craft of interest:
1. lm
2.pm
3.cy2 ( relay station )
of particular interest is the relative positions of lm and cy2 during the landing phase.

For CH2, orbiter,lander and ch2 were 3 separate bodies on Horizons.. same is expected for ch3

To add: As I posted here:
Per JPL: For CY3 158 will continue as the lander ID and -169 will be used for the PM. Separation data not yet available.

Plan is both, LM and PM will be animated in that animation as soon as data is posted (don't know if ISRO (or how quickly it) shares this data with JPL).

CY2's orbit is also well known - so it will not be difficult .. if there is interest..

[Amber G.]

After LM's successful deboosting operation that reduced its orbit to 113 km×157 km. I have updated the "Journey so far post" a few posts above. The 2nd deboosting oprtn is scheduled for Aug 20, 2023.
(Doppler is showing -most of this nicely )

[Amber G.]

how is lm communicating with earth stations right now ( when in lunar orbit) ?
directly or through cy2 ?

i believe isro said pm cannot act as a radio relay for lm...

Actually Apart from pushing the lander and rover closer to the Moon, PM will also act as a communication relay satellite. ( The propulsion module will continue to orbit for months or years - It also has SHAPE payload, which will analyse the spectral and polarimetric properties of light ityadi..)

[ramana]

you guys are reversing Diblu's sir reverse Jinx. Please let it go!!

What's the point o being on the forum for donkey's years when you don't know reverse jinx!