Chandrayaan 3: Launch and Discussions

[Ashokk]

S Somnath stated at the IISC presentation that the CY2 orbiter will be as the relay for CY3 lander, while the CY3 PM will only be used for the SHAPE experiment. The RF links from the lander are shown in the screenshot below, it clearly says Propulsion Module - NIL.

[ramana]

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

Every new gadget increases reliability risk.
The objective of CY3 is to land Vikram and it functions for one lunar day.
Let me assure you no uty in the world can execute this 'science' project.

[Ashokk]

Clearer screenshot of the lander velocity profile during the touchdown phase on the 23rd.

[SriKumar]

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.
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.”

Thanks for this post. So it is springs with pyrotechnic bolts. Good to get confirmation.

I am assuming that pyrotechnic bolts are probably used for stage separation as well i.e. in releasing the clamping mechanism (I am not talking pushback here just unclamping) in the numerous rockets fired by ISRO, so it must be mature technology. On a related note, normally, rockets are clamped/bolted to the ground before lift-off and lift-off is permitted only after a pre-determined minimum thrust is generated (or else rockets can fall off or other bad things can happen). It is possible pyrotechnic bolts might be the clamp-and-release mechanism here as well to hold the rocket on to the launch pad. NASA has videos on youtube of the space shuttle pyrotechnic bolts exploding and releasing the shuttle (specifically I think the SRB which are released after the SMEs also reach full thrust). No such videos of ISRO rockets, so one must conjecture....based on what little is known. The above report is a possible data point.

[juvva]

Clearer screenshot of the lander velocity profile during the touchdown phase on the 23rd.

unable to understand how vertical velocity Vv can be zero at 800m/1300m altitude.

also what is the meaning of the T=xx [s] , in the final phase of the landing shown in this diagram?

[juvva]

S Somnath stated at the IISC presentation that the CY2 orbiter will be as the relay for CY3 lander, while the CY3 PM will only be used for the SHAPE experiment. The RF links from the lander are shown in the screenshot below, it clearly says Propulsion Module - NIL.

looks like the lander is also capable of direct communication with earth stations.
(for all three - telemetry, telecommand and data ).

data link between rover and lander is not shown here (?)
but telemetry and telecomand links are shown.

[SriKumar]

>>>>juvva wrote: why is vertical velocity at 800m/1300m 0?

...mis understood the question in my earlier response.

Added later: It appears that ISRO has changed strategy and decided to bring it to a complete stop 800/1300 m above the lunar surface using thrusters. And then bring it down gradually from there. Seems like a good strategy. If the lander does not come to a complete stop then (i.e. if something goes wrong) the craft has 800 m of altitude to recover. (Not sure if the slide is from S.Somnath's IISc presentation but if it is, then there might be a more detailed explanation in the video).

Added laterer:
Per the slides at Somnath's IISc presentation, the same approach was used for CY2 as well, except that the height at which it comes to a complete stop was set to 400m. They've increased it to 800m (or 1300m) for this mission. SO the stragegy is not new. Only the safety margin has been increased.

[Ashokk]

looks like the lander is also capable of direct communication with earth stations.
(for all three - telemetry, telecommand and data ).

The lander can communicate directly with IDSN or via the CY2 orbiter.

data link between rover and lander is not shown here (?)
but telemetry and telecomand links are shown.

The data link with the rover is shown on the right hand side - ISM-Band TC & ISM-Band TM.

[Ashokk]

(Not sure if the slide is from S.Somnath's IISc presentation but if it is, then there might be a more detailed explanation in the video).

The slide is from another presentation done by S Somnath, where the recording quality is better

[juvva]

----
The data link with the rover is shown on the right hand side - ISM-Band TC & ISM-Band TM.

yes telecommand and telemetry but not data(from camera and instruments on rover) link

[juvva]

---
The slide is from another presentation done by S Somnath, where the recording quality is better

link to this presentation please

[Ashokk]

---
The slide is from another presentation done by S Somnath, where the recording quality is better

link to this presentation please

https://www.facebook.com/DishaBharat/vi ... 3631401782

[Tanaji]

What is 2nd and 3rd order poly guidance? I understand in the mathematical sense what the orders are but not with respect to guidance…

[disha]

Thanks Ashokk'ji for the link and more clear presentation recording. And yes, the slides are better now. Pulling this up in the top page shortly.

Link to this presentation on C3 by ISRO chairman

https://www.facebook.com/DishaBharat/vi ... 3631401782

[Ashokk]

What is 2nd and 3rd order poly guidance? I understand in the mathematical sense what the orders are but not with respect to guidance…

Not a control theory expert but my understanding is that the transfer function for the system is a 2nd or 3rd order polynomial. I am sure gurus on the forum will be able to shed more light.

[Tanaji]

You are probably right Ashokkji. I vaguely remember doing Bode plots in my control theory class many years ago with first order and second order functions…

[SSSalvi]

^^^
Only for non engineers -- Order of control system

I want to go to some destination.
If my vehicle can move with a fixed speed.. and I only have clutch to move or stop.
if I press clutch after Reaching destination then I will go ahead or stop before the destination.
That is type 1 system.. called position control system.

To reduce the overshoot I will add accelerater to control speed and reduce speed near destination avoiding overshoot and then apply clutch to stop.
That is type 2 or velocity control system.

If inertia ( if more people are in vehicle ) is more then I will have to start reducing speed from longer distance which in some cases may not be possible ( Ch3 if you try to stop from greater height then before coming to halt it may crash in destination due to gravity ), then I will have to have an extra control to increase the efficacy of accelerate, that will be type 3 control and so on...

That is the explanation from a geology grad who was thrust into communication antennas and antenna control system by those old ISRO bosses.

Added later: No, not ISRO, the culprit was Deptt of Atomic energy, which gave birth to ISRO through INCOSPAR, a short liven entity.

[juvva]

link to this presentation please

https://www.facebook.com/DishaBharat/vi ... 3631401782

thank you! ashok
this is a treasure.

[SSSalvi]

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

The pictures of Moon are taken by the Lander Horizontal Velocity Camera (LVHC) on the Vikram Lander on #Chandrayaan3.
This is the camera used for navigation during descent and not for regular imaging during operation.
ISRO has world class cameras proven operationally in various Remote Sensing applications and there is no reason why they will not use best cameras for this prestigious mission.

[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.

CY2 - is quite active ..and doppler can be measured. LM, PM, CY2 are/could be dopplered. (Luna- 25 is still a sort of mystery unless one has good dish antenna)...


LM and PM are drifting apart .. going out of phase .. phase difference will increase..

Horizon/JPL figures - CY2 id is "CH2-152"
(it is equipped with advanced communication equipment)
( Perigee = 1827 Km, Apogee = 1864 Km, a = (semi-major-axis) = 1844 Km which gives (see my post for such calculation) period of 7168 seconds)
Measured by doppler time period of LM(CH3) fits very nicely with 113x157 Km orbit.

Both, CH2 and CH3-PM are in nearly circular polar orbit (Inclination within 1/2 a degree to 90).. and their nodal points are pretty close (270 deg vs 268 degrees)... so if any one wants to estimate/calculate/exactly_knwo) where they are at any particular point of time.. all you need is a simple calculator and it's position at any particular time. ...

CY1, BTW is still there .. quiet .. a=1900 Km, still nearly polar,.. with a period of 7700 seconds... (according to elements of some times back)

[Ashokk]

Seems something went wrong with Luna-25 during the latest engine firing.

https://www.roscosmos.ru/39649/

Translation

About the flight of the automatic station "Luna-25"

19.08.2023 18:25

Today, in accordance with the flight program, the automatic station "Luna-25" at 14:10 Moscow time issued an impulse for transition to the pre-landing orbit.

During the operation, an abnormal situation occurred onboard the automatic station, which prevented it from performing the maneuver with the specified parameters.

At present, the specialists of the control group are analyzing the situation.

[Amber G.]

^^^
>>Russian controllers now need to troubleshoot and fix the issue. This is complicated by their lack of a global deep space communications network. So recovery efforts will be limited to when the Moon is visible over Russia


(The Moon's orbit is inclined to the Earth and causes it to appear high in the sky in northern latitudes for half the month and the very low in the sky the other part of the month. So the timing is such that this will further reduce Russia's time to fix the issue..(Assuming they do not have access to other places on the globe)
(The Moon is still rotating under Luna25 and the Russian controllers have (looks like ) only one communications window left before they planned to land. So the clock is ticking...Otherwise they need to delay and pick an secondary landing site..Now if they turn on their beacon so others (even amature astronomers) can locate it's position etc..

[Amber G.]

^^^ (this post.. shows basics..

This also means - the Moon's *maximum* possible declination (position above or below equatorial plane) can vary from 18.5 to about 28.5 degrees (with in time span of 18,6 years).. at present this inclination is about 28 degrees.
(This means, at present (this whole year) one can see Moon at zenith at its highest point in the sky at some time of the month from any latitude below 28 degrees - say from Florida or Jaipur India. For Sun, you have to be lower than 23.5 degree lattitude, About 9 years from now, the situation will change and you have to go below 18 degrees to see moon at zenith)

This is the time of the month, that Moon is very low on the horizon (especially from high northern latitude - Even in Ohio it is going only about 22 degrees above horizon at maximum -).... (This is like in winter, Sun is very low in northern latitudes)

They tell me that Russia does have one deep sea tracking ship called the 'Marshal Krylov' which serves in the Pacific Ocean. So it could be out there now providing coverage...

(So ESA stopping its involvement in Luna programs is being noticed -- glad that along with ISRO, - NASA, ESA Kourou and Goonhilly (GES Ltd)' are also supporting Chandrayaan3)...

----
This looks like --- *serious* ...
According to Zakryty Kosmos TG channel (unofficial): Luna-Glob (#Luna25) broke communications with ground control during today's orbit correction but Roskosmos continues its attempts to contact the spacecraft.

[Amber G.]

^^^^ News is now being picked up by major news outlets..
Luna-25 malfunctions during lunar orbit maneuver

[SriKumar]

So, the thrust needed for this orbit change was initiated, but it did not work out the intended way. I hope this new trajectory does not interfere with CY'3 trajectory. (I suppose different news outlets can report on this but all the factual information known as of now is still contained in that one original tweet. Unless we believe the unofficial tweet reporting on a communications breakdown.).
PS: IMHO I expect it would be serious (and perhaps detectable by the world space community) otherwise I think Russia wouldn't have announced this.

[Ashokk]

There was a new item from earlier today on the Roscosmos website on the results from the scientific payloads on board Luna-25. Interestingly, it mentions that Luna-25 flew through the Perseid meteor shower and one of its instruments registered micro-particles from it. Maybe some of the particles damaged to the probe.

https://www.roscosmos.ru/39648/

Translation:

The first results of the scientific instruments of the Luna-25 automatic station in circular orbit

The Luna-25 automatic station, created at the Lavochkin Research and Production Association (part of Roscosmos State Corporation), continues its flight along the circular orbit of the Moon's artificial satellite. During the flight, several activations of the scientific equipment created at the Space Research Institute of the Russian Academy of Sciences were carried out.

Analyzing their data, IKI RAS specialists obtained the following results:

* In the energy spectrum of gamma rays, the neutron and gamma-ray spectrometer ADRON-LR registered the most intense lines of chemical elements of the lunar soil.

* For the first time, the ion energy-mass analyzer ARIES-L, designed to study the near-surface ion exosphere in the circumpolar region of the Moon, was included in the near-lunar orbit. The data obtained made it possible to select the optimal mode of operation of the instrument on the lunar surface to measure the energy spectra of particles in the energy range from 10 to 3000 eV.

* The PML instrument, designed to record micro-particles levitating near the Moon's surface and to determine the parameters of the surrounding plasma, has registered a micrometeorite impact event. Most likely, this micro-meteoroid belongs to the Perseid meteor stream, which the automatic station "Luna-25" managed to successfully cross during the flight to the Moon.

* Based on the results of processing of two frames of the Moon imagery taken on August 17 by the landing cameras of the STS-L system, specialists of IKI RAS and the Moscow State University of Geodesy and Cartography geo-referenced the digital elevation model. This technology will allow in the future to significantly increase the accuracy of knowledge of the spacecraft orbit.

These images show the Zeeman crater, named in honor of the Dutch physicist, Nobel Prize winner Peter Zeeman. This crater is truly unique. In the list of the twenty deepest craters in the southern hemisphere of the Moon, it is in third place. It has an unusual size ratio: diameter - about 190 km, depth - about 8 km. Its formation is attributed to a very strong impact, which is possible if the speed of the impactor is very high or its substance is very dense.

Detailed photographs show that the bottom of the crater is mottled with smaller ones. This happens if some of the material ejected during the impact fell back and created numerous small "potholes". Such formations are very interesting from the point of view of lunar geology.

[Tanaji]

The western media may exult at this news but it is a sad state of affairs. A science experiment is going to fail because of politics - it’s a loss for everyone.

[Ashokk]

https://twitter.com/isro/status/1692995757413192015

Chandrayaan-3 Mission:

The second and final deboosting operation has successfully reduced the LM orbit to 25 km x 134 km.

The module would undergo internal checks and await the sun-rise at the designated landing site.

The powered descent is expected to commence on August 23, 2023, around 1745 Hrs. IST

[Jayram]

Re Luna -25
Around the same time, another Telegram channel Yura Prosti claimed that a computational error led to the final engine firing to be 1.5 times longer than required and thus resulting in deorbiting and crash of the spacecraft on the Moon.
from here
https://www.russianspaceweb.com/luna-gl ... .html#0816

[Amber G.]

Last update before Landing!
Journey so far: For BRF quick reference:
Last edited August 20, 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 -
20 August 2023 Lander Deorbit Burn II Vikram 25 Km 134 km Success


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)

[/quote]

[Dilbu]

Chandrayaan 3 will not successfully soft land onlee.

[rrao]

Dilbu saar aap ka moo mein bhooth jalokia

[sajaym]

Re Luna -25
Around the same time, another Telegram channel Yura Prosti claimed that a computational error led to the final engine firing to be 1.5 times longer than required and thus resulting in deorbiting and crash of the spacecraft on the Moon.
from here
https://www.russianspaceweb.com/luna-gl ... .html#0816

When the CY2 crashed into the moon, the project head cried and our PM hugged him. But knowing Putin, I just have one word of advice for the Luna-25 project head..."RUN!!"

[drnayar]

Re Luna -25
Around the same time, another Telegram channel Yura Prosti claimed that a computational error led to the final engine firing to be 1.5 times longer than required and thus resulting in deorbiting and crash of the spacecraft on the Moon.
from here
https://www.russianspaceweb.com/luna-gl ... .html#0816

When the CY2 crashed into the moon, the project head cried and our PM hugged him. But knowing Putin, I just have one word of advice for the Luna-25 project head..."RUN!!"

a crash would still be a "landing " ...maybe thats what they want., as long as its before Ch 3

[Ashokk]

Roscosmos confirms that Luna-25 crashed on the surface of the moon.

https://www.roscosmos.ru/39650/

Translation:

About the automatic station "Luna-25"
20.08.2023 11:50

According to the flight program of the automatic station "Luna-25", on August 19, it was envisaged to issue an impulse for the formation of its pre-launch elliptical orbit.

At about 14:57 Moscow time, communication with the automatic station was interrupted.

Measures implemented on August 19 and 20 to search for Luna-25 and communicate with it did not yield any results.

According to the results of preliminary analysis, due to the deviation of the actual pulse parameters from the calculated ones, the automatic station entered a non-calculated orbit and ceased to exist as a result of collision with the Moon surface.

A specially formed interdepartmental commission will investigate the reasons for the loss of Luna-25.

[Narad]

Chandrayaan 3 will not successfully soft land onlee.

Thank you Mulla Dilbullah.. I can now sleep peacefully !
Your Anti-Jinx mechanism is battle tested.

[Mort Walker]

Roscosmos confirms that Luna-25 crashed on the surface of the moon.

https://www.roscosmos.ru/39650/

Translation:

About the automatic station "Luna-25"
20.08.2023 11:50

According to the flight program of the automatic station "Luna-25", on August 19, it was envisaged to issue an impulse for the formation of its pre-launch elliptical orbit.

At about 14:57 Moscow time, communication with the automatic station was interrupted.

Measures implemented on August 19 and 20 to search for Luna-25 and communicate with it did not yield any results.

According to the results of preliminary analysis, due to the deviation of the actual pulse parameters from the calculated ones, the automatic station entered a non-calculated orbit and ceased to exist as a result of collision with the Moon surface.

A specially formed interdepartmental commission will investigate the reasons for the loss of Luna-25.

Communication problem. Although difficult, if signals were weak, I wouldn't put it past the US regime to jam communications.

[arvin]

Regarding Luna 25, hope Kremlin acts professionally and supports Roscosmos to investigate, rectify and relaunch.
Kinzhal aftermath treason incidents shouldn't be repeated.

[putnanja]

Dilbu saar aap ka moo mein bhooth jalokia

I don't think you have been on the forum long enough to understand the legendary anti-jinx power of Dilbu-ji! So ignore if you don't know or understand it

[rrao]

putnanja sir, i know some ppl are blessed with such supernatural reverse powers...Dilbu sir is one such may be....