Chandrayaan 3: Launch and Discussions

[dnivas]

2 more days. I am soo excited!!!!.. Great posts everybody

[Amber G.]

Okay, decided to some fun calculation and put some basic figures to show/understand the orbits of CY3 PM (Propulation Module), CY3 (Lander, Vikram) and CY2(orbiter).

Most people use ecliptic coordinates, or Earth's equatorial coordinates, but for following I am using Moon as the point of origin - How things will look from Moon:

Basic Math (and may be some trigonometry) is all you need to calculate relative position of CY3PM, CY3, CY2, Earth, Sun from the point of view of the Moon.

Origin: Moon Center. (Radius of Moon = Center radii 1737.4 km (To calculate altitude, subtract this from distance)
XY plane - Moon's Equator (This is within 1.5 degrees of ecliptic - so if you use figures from my previous post, will be almost ok)
X- Axis - points towards vernal equinox (Moon slowly spins -- 27.33 days for 1 rev -- so wrt to Moon's surface, this direction is not fixed)


Epoch: August 21, 2023, 00:00:00 UTC

Orbital Plane:

Inclination of CY3PM = 89.4 deg of CY3 = 89.3 deg , CY2 = 90.0 degrees ==> All orbits are almost polar.
Ascending Node: CY3 (PM and CY3) = 270 degrees, CY2 = 268 Degrees.
(Both orbits are almost in the same plane - within 2 degrees)
e (eccentricity) : CY3PM = .004 CY3 =.002 , CY2 = .0015 ==> All orbits are nearly circular ( Easy for calculation)

Perigee CY3PM -> 1888, CY3 ->1769 CY2 -> 1818 Km (To find altitude subtract r= 1737.4)
Apogee CY3PM -->1901 CY3 -> 1864 , CY2 -> 1871 Km

Semimajor Axis = a = CY3PM -> 1894.5, CY3 -> 1816.8 , CY2 --> 1871 Km.

This gives period in seconds CY3PM -> 7402, CY3 -> 6949, CY2 --> 7111 seconds. (1 Hr = 3600 seconds)

(IOW: CY3-PM period is 123 Minutes, CY2 is 118 Minutes, while CY3 lander is 115 minutes.)

(This is useful in calculating velocity at any point in the orbit.
𝑣²=μ(2/𝑟 −1/𝑎)
𝑇=2π √(𝑎³/μ)
μ for moon = 4.905×10¹² ... in SI units)

(So you can calculate velocity of CY3 at any given altitude)

---

Location of the primary landing site: 69.367621 deg. S, 32.348126 deg East

This means: Earth is almost fixed: About 20 degrees from horizon -- will move about 6 degrees above or below this number within 14 days (or 1 Moon day - On August 21, this angle is about 14 degrees from horizon.)
Sun will rise and set within these 14 days - Sun never going higher than 20 degrees above the horizon (at "noon" at Moon - 7 days after landing)
Position of CY3PM and CY2 orbiter can be calculated knowing both space-crafts are moving in almost circular polar orbits,

(One thing I calculated and noticed: CH2 and CH3PM are orbiting in such a way at least one of them will be in visible/radio range from CH3 around most of the time during those 14 days.. at time of landing both of them..)

Hope this is useful.

[suryag]

SSS and other gurus, i was looking at dry mass and wet mass of CY-3, looks like there might be fuel left in PM, how i wish ISRO surprises us with Vikram taking off mating with PM and coming back to earth and crash burning. Hope CY-4 is already being planned for to-fro trip

[Amber G.]

^^^FWIW this was posted here:

Per ISRO, PM has left with about 150 Kg of fuel "way beyond our expectations" .. all orbit burns worked perfectly ityadi .. so life of PM would be now in years.

"There’s a lot of fuel left as everything was very nominal on the way to Moon and there were no contingencies requiring corrections (for which fuel would have been expended). We’re left with almost all the margin, that’s around 150+kg,” he said.
The propulsion module was loaded with 1,696.4 kg of fuel at the time of the launch on July 14, and did all the heavy lifting — five Earth-bound manoeuvres and five lunar-bound manoeuvres before separating from the landing module — between July 15 and Aug 17. (Each of these manoeuvres that were part of the mission profile and some minor corrections in between would have consumed some fuel..which was saved).

[krithivas]

We must absolutely name the areas of Moon where Chandrayaan lands with pioneering/peer-less historical Indian astronomers - Aryabhatta, Varaahamihira etc. Tired of seeing Greek names.

[rahulm]

Over 3,000 wind tunnel tests of Chandrayaan-3 launch vehicle done at Bengaluru facility

“Based on these wind tunnel tests, the configuration underwent major design changes in 2014-2015. All stages of LVM3 with Chandrayaan-3 payload fairing were acoustically characterised in this facility and cleared for launch, which was crucial for the mission,” the official added.

[arvin]

SSS and other gurus, i was looking at dry mass and wet mass of CY-3, looks like there might be fuel left in PM, how i wish ISRO surprises us with Vikram taking off mating with PM and coming back to earth and crash burning. Hope CY-4 is already being planned for to-fro trip

I think the PM alone can be bought back.
The Propulsion module (PM) in orbit around moon at 100 km is having velocity of 1.6 km/ sec.(Assumption).
To escape lunar gravity PM would need velocity of 2.38 km/ sec.
It has currently excess of 150 kg of feul as per reports which is more than 10% of the feul loaded during launch that is 1696 kg.
With that kind of feul and no overhead of lander, I think PM engines can easily break free from lunar gravity.
I think we should seriously consider this option of bringing back PM, post SHAPE experiments are over.
We can test lunar sample return trajectory with this mission itself.

[Najunamar]

Question to Gurus: there’s a TOI(let) article saying it is possible that the Lander and Rover could survive the lunar night. If we want to prepare for such a possibility is it better to try to get rover back into lander? Is that even possible to go up the ramp?

[arvin]

Even more feul would have been left over, if we allowed the cryogenic stage to burn to depletion as was done during CY2.

From Wikipedia

Finally Chandrayaan-2 was launched on board the LVM3 M1 launch vehicle on 22 July 2019 at 09:13:12 UTC (14:43:12 IST) with a better-than-expected apogee as a result of the cryogenic upper stage being burned to depletion, which later eliminated the need for one of the apogee-raising burns during the geocentric phase of mission.[43][125][126] This also resulted in the saving of around 40 kg fuel on board the spacecraft.

[Amber G.]

We must absolutely name the areas of Moon where Chandrayaan lands with pioneering/peer-less historical Indian astronomers - Aryabhatta, Varaahamihira etc. Tired of seeing Greek names.

Just a few famous ones:
Chandrasekhar Crater: Named after Subrahmanyan Chandrasekhar, (Nobel Prize in Physics for his work on the structure and evolution of stars).
Bhabha Crater: Named after Homi J. Bhabha, ( nuclear physicist who played a crucial role in the development of India's nuclear program.
Raman Crater: Named after C. V. Raman, (Nobel Prize in Physics for his work on the scattering of light, which came to be known as the "Raman Effect."
Saha Crater: Named after Meghnad Saha (astrophysicist who formulated the Saha ionization equation, which explains the physical and chemical conditions in stars.)
Ramanujan Crater: Named after Srinivasa Ramanujan,
Aryabhata Crater: Named after Aryabhata
Tagore Crater: Named after Rabindranath Tagore,
Of course, if you were following BRF ... recent ones like Sisir Kumar Mitra On the far side
And one named after VIKRAM ( Vikram of CY3 is also named after the same guy) Vikram Sarabhai ...

And (also Jawahar Point - Point of Impact of CY1 probe which happened on his Birthday Nov 14)

There may be more... but these I know..
(I have known/interacted/learned_from / with Chandrasekhar, His uncle, CV Raman, Bhabha.. )

[Dilbu]

Chandrayaan 3 will not successfully soft land onlee.

[nits]

Question to Gurus: there’s a TOI(let) article saying it is possible that the Lander and Rover could survive the lunar night. If we want to prepare for such a possibility is it better to try to get rover back into lander? Is that even possible to go up the ramp?

Not a Guru - but what will that serve; if it survive more - scientific advantage will be that we get more area covered by Rover then planned. infact rover has imprints of ISRO and National Emblem ( <-- Click)- good to put it on larger area of moon so that after 500 years when there is fight for moon we have a advantage

[Ashokk]

Latest update from ISRO including video from the Lander Position Detection Camera (LPDC)

https://twitter.com/isro/status/1693879632481935555

Chandrayaan-3 Mission:
The mission is on schedule.
Systems are undergoing regular checks.
Smooth sailing is continuing.

The Mission Operations Complex (MOX) is buzzed with energy & excitement!

The live telecast of the landing operations at MOX/ISTRAC begins at 17:20 Hrs. IST on August 23, 2023.

Here are the images of the moon captured by the Lander Position Detection Camera (LPDC) from an altitude of about 70 km, on August 19, 2023.

LPDC images assist the Lander Module in determining its position (latitude and longitude) by matching them against an onboard moon reference map.

[juvva]

SSS and other gurus, i was looking at dry mass and wet mass of CY-3, looks like there might be fuel left in PM, how i wish ISRO surprises us with Vikram taking off mating with PM and coming back to earth and crash burning. Hope CY-4 is already being planned for to-fro trip

I think the PM alone can be bought back.
The Propulsion module (PM) in orbit around moon at 100 km is having velocity of 1.6 km/ sec.(Assumption).
To escape lunar gravity PM would need velocity of 2.38 km/ sec.
It has currently excess of 150 kg of feul as per reports which is more than 10% of the feul loaded during launch that is 1696 kg.
With that kind of feul and no overhead of lander, I think PM engines can easily break free from lunar gravity.
I think we should seriously consider this option of bringing back PM, post SHAPE experiments are over.
We can test lunar sample return trajectory with this mission itself.

or a venus fly by / orbital adventure voyage.

[Tanaji]

Why would we want the PM to come back? It cant survive re-entry as it has no heat shields. It cant go out as it does not have enough solar sails to power itself when solar output reduces as it goes further away from earth. It cant go close to inner planets as it does not have a heat shield.

[Ashokk]

One more video, great to see frequent updates from ISRO

https://twitter.com/isro/status/1693911595720823129

.... and
The moon as captured by the
Lander Imager Camera 4
on August 20, 2023.

[Cyrano]

Birathers,
Where on the internet can we pravasis get the best possible live telecast of the touch down phase?
Dhanya waad !

[Cyrano]

Ok DD news live seems to be covering the landing, in Hindi or English on YT. Thats good enough for me.

[Ashokk]

ISRO will stream it on youtube https://www.youtube.com/watch?v=DLA_64yz8Ss

I am sure many channels will be covering it as well.

[Dilbu]

I hope they wont postpone and go for plan B. The tension is unbearable.

[SSSalvi]

I hope they wont postpone and go for plan B. The tension is unbearable.

If what you mean by Plan B is the last option of alternate location while touching down, then no tension.. only a few minutes of hold your breath.

[Dilbu]

There are reports about postponing the date also.
'Chandrayaan-3 landing will be postponed to Aug 27 if...': ISRO reveals ‘Plan B’ for Vikram Lander

[sanman]

ISRO chief talks about CY-3 and other aspects of Indian space program:

[Amber G.]

Decided to point my telescope from the resting point of Vikram-1 (CY2)... I heard that they are sending Vikram-2 on CY3 from that blue planet... Not too long to wait...
(Image AmberG - Star positions are mathematically correct at the time specified - as I post this post..)

[Amber G.]

Question to Gurus: there’s a TOI(let) article saying it is possible that the Lander and Rover could survive the lunar night. If we want to prepare for such a possibility is it better to try to get rover back into lander? Is that even possible to go up the ramp?

Main use of RTG (radioisotope thermoelectric generator - like Pu298) is to keep things warm so electronics do not freeze and survive lunar night..Putting Pragyan inside Lander is not going to make much difference over such a long time. There is hope (but no one in ISRO etc will say it openly/publicly as the hope is quite slight - and no one knows for sure) that the electronics might survive and after 14 days night, things may power up...but we will see..

[Amber G.]

Some comments on the ISRO's recent video/photos: (Points highlighted)

Mare Maginis: lies on the very edge of the lunar nearside
Mare Smythii: located along equator on easternmost edge of Moon's near side.
Ibn Yunus: remains of a flooded lunar impact crater
Craters visible from the side from Earth :Jansky F & Goddard: Crater, also visible from side of Earth
Hirayama: large lunar impact crater that is located on the far side of the Moon
Brunner: crater is located close to Mare Smythii.

[Amber G.]

As posted here before , Live broadcast is here:


For family and friends I will do some live commentary...So sharing..

In Ohio, (and in California).. Moon would be below horizon (About 33 degree where I live).. but in India..train your telescopes/ radio telescopes at around 6:30 PM tomorrow.. Moon's RA will be around 15Hr,05 Minutes and Dec = -20.15 degree... that's about 43 degree above horizon in Udaipur, Rajasthan and 198 degree Azimuth)

So if you look towards Sun (From my home-town Udaipur) or Moon , here are the sky maps:



Of course, if you look from the moon, All Brf posters location would look something like < (I posted the image before)

[Amber G.]

As I post this (August 22, Time: 8:42 UTC) Vikram is 43.5 Km away from the surface moving at 1.67 Km/Sec wrt to the Moon.
This is 387,976 Km from earth (Velocity 1.01 Km wrt to Earth)>

Here, From Sankara's Animation, Orbits in XY, YZ and ZX Planes, to understand the past orbits at the time of Landing.. Then the distance from the moon is 1734 Km - giving altitude = 0, Velocity wrt the moon = 0, All went well.

XY - Plane - Z axis is coming towards you from the screen.


YZ Plane:


Z-X Plane:

[KL Dubey]

Amber G - whatever the outcome of CY3 (may it be a total and complete success for Bharat), the scientifically rich yet engaging coverage you (and a few others) have provided is absolutely terrific.

[Ashokk]

Good info from Scott Tilley.

https://twitter.com/coastal8049/status/ ... 6243188209

#Chandrayaan3 (and family) trajectory update for 2023-08-21.

Landing is over a day away. Doppler modelling to the orbits of CH2 and CH3_LM is very good now.

Let's look at the details of the landing based on the orbits and see how it all comes together.

#Chandrayaan3 lander's orbit is very well described by the Doppler data. The residuals are very low and the wobbles you see in the residual plot are artificial and introduced by the ground station. The final orbit is precisely known now allowing landing timing estimates.

Propagating the orbital state vector for #Chandrayaan3 until the perilune before the landing places us here vs. the landing site at about 2023-08-23T12:13:41 UTC. The lander needs a little over 14.5 minutes from beginning the sequence to land. So it looks about right.

Meanwhile what is #Chandrayaan2 up to? How will it help?

It will be positioned antipodal to CH3 at the time of the landing attempt. It's role in the mission appears to be support after landing as it will pass over the site just after the landing is completed. Makes sense.

[SriKumar]

Naming of craters....methinks it high time they consider naming craters after regular people. I vote for the following names: Ramkumar, Kishan, Rakesh, Suresh and Venkateswaran. You get the idea. Just imagine the level of motivation all these (thousands or lakhs of people with these names) will have when they find out there is a crater on moon named after them. Kids with these names may become motivated/energized to get into science and engineering, some will want to visit the crater named after them. Very motivating...irrespective of the outcome.

To even things out genderwise, I propose: Leela, Sheela, Sunita, Anita and GajaLakshmi. Not kidding here. I guarantee you a lot more people will point their telescopes at the moon just to locate the crater named after them/their friend/girl-friend/boy-friend. And this will likely continue years after Chandrayaan 3 rover has done its roving for however long it roves. These names would be more meaningful to the rest of us without these names, since most of us may personally know many people with above names. Also, many of the above-named people paid taxes which funds ISRO, and paid for the Chandrayaan 1, 2, 3 and other missions. High time that the taxpayer is recognized in the naming process.

[S_Madhukar]

Naming of craters....methinks it high time they consider naming craters after regular people. I vote for the following names: Ramkumar, Kishan, Rakesh, Suresh and Venkateswaran.

Reminds me of the Aap ki Farmaish program on AIR …

[sanman]

Naming of craters....methinks it high time they consider naming craters after regular people. I vote for the following names: Ramkumar, Kishan, Rakesh, Suresh and Venkateswaran. You get the idea. Just imagine the level of motivation all these (thousands or lakhs of people with these names) will have when they find out there is a crater on moon named after them. Kids with these names may become motivated/energized to get into science and engineering, some will want to visit the crater named after them. Very motivating...irrespective of the outcome.

To even things out genderwise, I propose: Leela, Sheela, Sunita, Anita and GajaLakshmi. Not kidding here. I guarantee you a lot more people will point their telescopes at the moon just to locate the crater named after them/their children/parents. And this will likely continue years after Chandrayaan 3 rover has done its roving for however long it roves. These names would be more meaningful to the rest of us without these names, since most of us may personally know many people with above names. Also, many of the above-named people paid taxes which funds ISRO, and paid for the Chandrayaan 1, 2, 3 and other missions. High time that the taxpayer is recognized in the naming process.

I don't agree. Craters and other features should be named after those who've accomplished something in the field of astronomy.

[ricky_v]

Some images from Reuters






https://www.reuters.com/science/why-are ... 023-08-22/

[Roop]

Craters and other features should be named after those who've accomplished something in the field of astronomy.

I agree completely. From the list of names suggested by Amberji, my two favourites are "Raman Crater" and "Saha Crater". Meghnad Saha is famous for the directly-related field of astrophysics; CV Raman, while not involved with astronomy, is hugely respected in physics (the "Raman Effect" re. the scattering of light)

[Amber G.]

Naming of craters....methinks it high time they consider naming craters after regular people....

Well.. While naming of Craters on the Moon at present are after Famous Scientists and Explorers, some after Artists and Authors Poets,(who have created works related to the Moon or space) and a few after Mythology and Astronomy , and even after geographical features on Earth...

Names of Minor planets (asteroids etc) could be named to honor for those young ones who are good in Math and such things.. Well there is one named Amber... (And this person is my family member -- )

[disha]

First of all thanks Ashok'ji for the informative links that confirmed the separation of C3PM from Lander was enabled by a spring and a latch. Something like this bolt cutters https://psemc.com/products/pyrotechnic-bolt-rod-cutter/

Thanks everyone for posting photos from various sites like ISRO's X/Twitter account and other channels.

Please attribute those links upfront instead of hiding them below.

---

In several ways, it is sad and disheartening to see Luna-25 crash into Moon. This is a major setback to the Russian capability of launching deep space missions.. There are several reasons why it ended up like that and hopefully we will be able to explore the mis-steps Roscosmos took and hopefully learn from them. Anyway, C3 is a far larger and more sophisticated mission than Luna 25. And this was their first mission after several years., success was not guaranteed. Also Roscosmos has a new challenge to build up the space program beyond launching satellites. For example, the inertial unit in Luna25 was 10x heavier than what Airbus offers for sale. C3 carried Indian made inertial unit and they are sophisticated.

All eyes are on ISRO/India now. This is a different kind of pressure. But make no mistake, while the larger space community is saddened and disheartened, no such empathy will come for ISRO/India. Never. Our own resident-non-indians like Bakwas Kaj will be part of the derision. Leave alone the types of WaPo or WSJ or NYTs or PeePeeChee. Particularly when we are successful.

This needs to be discussed as well. Exploration of science and development of technology is never linear. At the end of the day, what sacrifices we make as a country reflects on the success or failure of future generations.

What we must not miss is that we are standing at an epochal movement. A major transition is happening right in front of our eyes. And a massive generational shift. We are witnessing history in making and getting a ring side view of it. Some of us may not even be able to recognize what is happening, but at the end of the week, ISRO/India will transition from an imminent space power to an eminent space power.

We have to learn to accept the fact that India of 2023s is not the same as India of 1960s. And Indian space capability has made a major leapfrog forward. From the sounding rockets carried out on cycles to a cycle of deep space missions.

That means more responsibility. We need to start planning deep space missions to Mars, including landing on Mars, Moons of Mars (Phobos/Deimos), missions to asteroids & comets and a mission to vision. And we need to start looking at planning a mission to Jupiter and another to Saturn. And of course sample returns from Moon. Apart from that we need to start putting AstroSats and Aditya's, maybe at Lagrange points.

And of course the human space flight program with the goal to set up a moon base by 2040. And a asteroid mining mission by 2050.

This will require continuous development of new launch vehicles and more powerful boosters and extended upper stages and more launches. Basically the entire space sector is going to heat up and we have to start looking at an enormously expanded space program.

More importantly this will require bold decisions to go into uncharted and sometimes dangerous territories and an even more courage to absorb grave losses. The pertinent question is, do we have the will? And will we open up the budget? Or just brag how cheap our missions are compared to Hollywood or Bollywood movies?
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But only thing Propulsion Module has is the SHAPE instrument. It's not clear how much the SHAPE experiment will benefit from this longer operating life. It doesn't even have much of a communications array to supplement other missions.

I hope there are young ISRO scientists sharpening their pencils and wondering what they can do with the fuel that has been saved by excellent science and engineering by ISRO. Here are my recommendations:

1. Use the moon's gravity to slingshot the C3-Propulsion Module to a Lagrange point. And observe earth from there. And bring it back into Moon orbit.
2. Use it to do orbit studies around moon. Moon's gravity is not even. It is more muddled than Earth's gravity. So try different calculations and orbits around Moon and tabulate it. It will help future missions.

[disha]

SSS and other gurus, i was looking at dry mass and wet mass of CY-3, looks like there might be fuel left in PM, how i wish ISRO surprises us with Vikram taking off mating with PM and coming back to earth and crash burning. Hope CY-4 is already being planned for to-fro trip

Vikram cannot mate back with PM even if it can get off the moon's surface and approach PM. Reason is the bolt cutters cannot be welded back

Though is this a possibility? That is if the lander survives the moon night and several such nights, and has lots of fuel, can the Vikram lander be commanded to launch itself few metres high and target another landing site? That is go crater to crater jumping? That would be an awesome engineering and science feat. Yes, more fuel is expended this way, but the primary science is over and it can target "juicy" craters (pun on craters with ice).

[disha]

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

I think Ashok'ji or someone posted the information on how C3 separates. It is spring based, the lander is latched to the propulsion module and are cut using bolt cutters.

I was wrong in my initial assessment that it would be gas based thrusters. Coming to think of it, spring based thrusters are more effective, once the latches are opened up via a cut or the anchoring bolts are cut. To see the exact mechanism will be interesting.

[Amber G.]

Craters and other features should be named after those who've accomplished something in the field of astronomy.

I agree completely. From the list of names suggested by Amberji, my two favourites are "Raman Crater" and "Saha Crater". Meghnad Saha is famous for the directly-related field of astrophysics; CV Raman, while not involved with astronomy, is hugely respected in physics (the "Raman Effect" re. the scattering of light)

Just to be clear: These are not *suggested* (by me) but are already there...(The naming of craters on the Moon is typically done according to established naming conventions set by various organizations, eg .. International Astronomical Union (IAU) . The IAU has a specific task group, the Working Group for Planetary System Nomenclature (WGPSN), that oversees the naming of features on all planets and their moons. (You could see locate these in any moon atlas). (Mitra, Vikaram are relatively recent one added after CY1/2)

----
Also normally it is after historical figures (Not after living person).. Among astronauts/Cosmonauts/vyomanauts I know are following craters:
vyomanauts:
Armstrong: Named after Neil Armstrong, the first person to walk on the Moon
Aldrin: Named after Buzz Aldrin, the second person to walk on the Moon
Collins: Named after Michael Collins, the command module pilot of the Apollo 11 mission.
Russian (Soviet) Cosmonauts:

Gagarin: Named after Yuri Gagarin, the first human to travel into space and orbit the Earth.
Lev: Named after Alexei Arkhipovich Leonov, a Soviet cosmonaut who conducted the first spacewalk.
Chinese Astronauts (Taikonauts):

---- Minor (non-craters) point of interest there is more flexibility...To encourage schools/Parents many of winners/finalists of International exams .. points of interest are named after that (which are accepted etc..)..

Chang'e: Named after the Chinese moon goddess, this name has been used for various lunar features including craters, landing sites, and lunar missions.

Japanese Astronauts:

Yamamoto: Named after Mamoru Mohri,