Chandrayaan 3: Launch and Discussions

[sanman]

Here's another picture before deployment of solar panel:

[hanumadu]

Rover's solar panel is deployed and upright:

---snip image--

(that happened hours ago, but I was so busy surfing I forgot to post it)

Looks like the solar panel was deployed while still on the ramp. There are some stones right after the off ramp. The rover's dimensions are 3 feet x 2.5 feet x 2.8 feet and a velocity of 1 cm /sec. What is it's ground clearance? Hope it's enough to clear the rocks.

How does the rover control it's speed on the ramp as its quite steep. The gravity on the moon is less, so that helps. Are there any other mechanisms that will slow it down while it gets down the ramp?

[Roop]

Viking 1 and 2 were Mars landers. Roopji was that sarcasm?

Unfortunately not, it was a blunder.

@disha:

Please do a simple google search.

Okay boss, my bad.

[rahulm]

Rover's solar panel is deployed and upright:

---snip image--

(that happened hours ago, but I was so busy surfing I forgot to post it)

Looks like the solar panel was deployed while still on the ramp. There are some stones right after the off ramp. The rover's dimensions are 3 feet x 2.5 feet x 2.8 feet and a velocity of 1 cm /sec. What is it's ground clearance? Hope it's enough to clear the rocks.

How does the rover control it's speed on the ramp as its quite steep. The gravity on the moon is less, so that helps. Are there any other mechanisms that will slow it down while it gets down the ramp?

I think PRAGYAN is tethered to VIKRAM as it drives off the ramp onto the lunar surface. Once on the lunar surface (i.e. off the ramp) PRAGYAN ditches the tether and is free. I am quoting from memory from some Brochure/article I read and happy to stand corrected.

[RCase]

I came across this video about the landing gear on CY3. Pretty cool stuff.

https://www.youtube.com/shorts/PV8Qa3poB2s

1. The wires on the legs are touch sensors placed on the bottom of the landing pads.
2. There is a layer of Aluminium webbing crush zone that crumples and absorbs the kinetic energy.
3. Was designed to absorb a much higher impact speed!

[Pratyush]

How does the rover control it's speed on the ramp as its quite steep. The gravity on the moon is less, so that helps. Are there any other mechanisms that will slow it down while it gets down the ramp?

Dry lubricated Mechanical disk breaks are the simplest way to control the speed of the rover.

[SSSalvi]

BTW, who makes our camera optics ? ISRO? DRDO? Pvt Co?
thanks.

Fully ISRO product

[SSSalvi]

How does the rover control it's speed on the ramp as its quite steep. The gravity on the moon is less, so that helps. Are there any other mechanisms that will slow it down while it gets down the ramp?

Dry lubricated Mechanical disk breaks are the simplest way to control the speed of the rover.

I doubt whether you require brakes.at all if the wheels are directly driven by motor.

[rahulm]

BTW, who makes our camera optics ? ISRO? DRDO? Pvt Co?
thanks.

Fully ISRO product

I thought the lens is normally procured from Zeiss (Germany) but the rest of the camera is indigenous or am I wrong?

[RCase]

Ignore - if not interested in nerdy science - Trying to give some scientific insights in answering the questions:
(Comments are scientifically accurate -- figures etc are not 'official' etc)

Communication Challenges:
One of the primary difficulties in landing on the far side of the Moon is that direct communication with Earth is blocked by the Moon itself. To overcome this challenge, China utilized a relay satellite named Queqiao, positioned at the Earth-Moon Lagrange Point 2 (L2), which provides a line of sight to both the far side of the Moon and Earth. This relay satellite receives signals from the lander and rover and then relays them to Earth.

Q. Will a satellite in a large elliptical orbit around the earth be within line of sight of the far side of the moon (even a partial amount of the far side) or is the Langrange point the only spot that can provide line of sight to both the earth and moon?

Thanks. Appreciate your knowledge sharing across various posts.

[juvva]

Rover's solar panel is deployed and upright:



(that happened hours ago, but I was so busy surfing I forgot to post it)

yes it has been quiet a while since the rover solar panel deployment event.
i am guessing they are waiting for the sun to come up further, for a more optimum solar power generation and/or waiting for the electronics and mechanicals to warm up before moving on to the surface.

in any case: i hope dilbu comes back on the forum with his reverse black magic powers

[rahulm]

President of India tweeted Pragyan deployed

I once again congratulate the ISRO team and all fellow citizens for successful deployment of Pragyan-rover from inside Vikram-lander. Its rolling out a few hours after the landing of Vikram marked the success of yet another stage of Chandrayan 3. I look forward with excitement, alongside my fellow citizens and scientists to the information and analyses that Pragyan will acquire and enrich our understanding of the moon.

So did ISRO a few mins ago

The Ch-3 Rover ramped down from the Lander and
India took a walk on the moon !

More updates soon.

[nitzter]

I think the coolest bit was it reselecting the target landing spot after the initial one was deemed not good enough.

Need more details on this, should be an interesting anecdote

As Disha ji pointed out - fully automated.

May be the rough braking could be done manually, sitting here on Earth, even with the 3s relay latency. But the fine braking phase (especially the final descent) have to be autonomous. If there were a human in the lander, everything could have been manual - this happened with Apollo 11, where automated systems starting failing)

The selection of landing spot in CY3 is based on image processing. Here's my take on this -
1. A wide 4x2.4 sq km area was pre selected for landing.
2. The above rectangle was divided into 3900 sub-sets of smaller rectangles. Each of these subsets were pre-fed into the software with their own bucketing (Unsafe, Safe, Very safe, etc.). Another bucketing would have been (Bad, Good, Better, Best) on the basis of possibility of finding good scientific data about water, minerals etc.
3. At 150 m altitude, CY3 took images of the surface exactly below it and the image processor started over laying the input onto the existing database of 3900 subsets to identify where it actually was.
4. If the current subset was identified to be unsafe, it would try to move to the next safe one. Similarly, if current subset is safe, it would still try to move to a very safe one if possible.

Since CY3 had to match up a few images with an existing set of 3900, it was doable with a limited powered computer on board (instead of giving the lander a free run over too much high quality CY2 data and failing to achieve anything).

ISRO has conducted a highly sophisticated exercise here and became fully aware about the lander's current terrain, possibility of getting better sunlight, which direction to go search for water, etc. At 150m altitude before the landing happened...

[sanman]

[SSSalvi]

https://twitter.com/isro/status/1694545322251571687

Lander on surface

[Amber G.]

AmberG and team Kudos for high level discussions and explaining intricacies.
Ramana

Ramana and others ..Thanks.
---

Let me comment on few of the items discussed here .mainly to provide some insight into basic math/physics/science of orbital mechanics.. again ignore if you wish. (will answer honest questions to clarify but for basic concepts see any good text book)..

Few questions/discussion are centered on the extra fuel - can that be used to bring PM to Earth etc..

1. With lunar gravity very low, returning to earth should consume much less thrust. What would be the ratio , is it 1:100?
2. Entering back to earth, how much thrust ratio needed compared to escaping the earth's gravity, my understanding is huge thrust is used for escaping the earth's gravity.
3. How easy it would be to launch rocket from moon to outer space compared to launching from earth, with moons low gravity advantage, provided we can generate rocket fuel from moon's water/gas/elements.
4. In case we make moon habitable, does building international space station become redundant?

First, let's cover some fundamental concepts. Honestly, some of the comments provided are not entirely accurate (and some, in my opinion, are quite peculiar) when it comes to basic physics.

The speed of the spacecraft in its current orbit around the Moon is approximately 1.6 km/s. This orbit is polar, meaning it is nearly perpendicular to the ecliptic plane (at around 90 degrees) and also nearly perpendicular (within 5 degrees) to the Moon's orbit around the Earth.

It's important to note that this velocity is a vector quantity. You cannot simply "add" a value of x to get "1.6 + x" in any direction.

The often-mentioned "escape velocity" (around 2.4 km/s) allows a spacecraft to break free from the Moon's gravitational pull. However, it's worth mentioning that even after escaping, the spacecraft would still follow an orbit around the Sun that is quite similar to Earth's and the Moon's orbit. In other words:

To travel to other planets, such as Mars, a spacecraft would still require a velocity of nearly 30 km/s. So, for interplanetary travel, a significant amount of fuel is still necessary.

If the intention is to return to Earth, thinking that a certain amount of fuel is needed to transition from 1.6 km/s to 2.4 km/s misses a crucial point.

This analogy is akin to saying that all you need is a certain amount of energy to hit a six in cricket. You actually need precise timing (just as in scoring a hole in one in golf).

(Not only is an adequate change in velocity (delta-v) necessary, but the spacecraft must be launched in the correct orbital plane. Even more importantly, the timing has to be impeccable, ensuring that when the spacecraft reaches its highest point (apogee), it encounters Earth. This is incredibly difficult to achieve – hence why many of us refer to ISRO's orbit calculations as "magic," as timing is exceptionally complex.)

Regarding the CH3PM's rockets, I'm not well-versed enough to calculate fuel requirements accurately, but I can calculate delta-v. As for timing calculations, those are exceedingly challenging. I would venture to guess that the practical chances of achieving the required timing are less than one in a million. (While ISRO might surprise me, I remain skeptical.)

Lastly, just as with Lunar Orbit Insertion (LOI), there must be a burn close to Earth. This maneuver comes with its own challenges – if the angle is too shallow, Earth's atmosphere could send the spacecraft back into space, akin to a pebble skipping on a lake's surface. Conversely, if the angle is too steep and there isn't a reliable heat shield, the spacecraft could burn up upon reentry.

--- Just for perspective:

TEI (Trans Earth Injection) burn for Apollo 11 lasted almost 6 minutes on 45,000 N engines using nearly 1200 Kg of fuel.

(And I am not counting mid course correction and breaking near earth fuel)

And for making the timing right ..( all that calculations *literally* took months of computer time (and all timing was predetermined) in 1960's when computers were not very fast and on-board computers had only 4K of RAM

Now ISRO can do magic, gravity can assist to save fuel, but WHY?

IMO we should be delighted that CH3PM will be there for years to come -- doing its SHAPE thingie... May be some time in future ...it could be moved to a safer orbit or join a moon space station in the museum section .. who knows..



Now ISRO can do magic

3. How easy it would be to launch rocket from moon to outer space compared to launching from earth, with moons low gravity advantage, provided we can generate rocket fuel from moon's water/gas/elements.b][/b]

We will still need delta-V of about 30 Km/sec to, say go to Mars (unless, we do gravity assist with Moon or Earth etc) .. but from earth we need around 8 km/sec just to get to a space -station.. so savings are tremendous... besides since there is no air on moon, it is possible to have ground based shooting guns type launch to provide more efficiency than rockets. (On earth, you can not shoot with high velocity as the friction from air there ... so you need 2 or 3 stages...))

[hanumadu]

Rover's solar panel is deployed and upright:

(that happened hours ago, but I was so busy surfing I forgot to post it)

yes it has been quiet a while since the rover solar panel deployment event.
i am guessing they are waiting for the sun to come up further, for a more optimum solar power generation and/or waiting for the electronics and mechanicals to warm up before moving on to the surface.

in any case: i hope dilbu comes back on the forum with his reverse black magic powers

The lunar day is 14 days and it just started. So, the sun was already up when the lander touched down on the moon.

[SSSalvi]

Q. Will a satellite in a large elliptical orbit around the earth be within line of sight of the far side of the moon (even a partial amount of the far side) or is the Langrange point the only spot that can provide line of sight to both the earth and moon?

Thanks. Appreciate your knowledge sharing across various posts.

Earthbound orbits are possible upto 1.5 million kilometres apogee. ( That is Lagrange1 point distance ... beyond it Sun will gobble the craft as its orbit slave )

You find whether this is beyond moon or not

[hanumadu]

Landing co ordinates

It began its powered descent towards the surface at 12:14 UT on 23 August and landed in the south polar region of the Moon, near 69.37 S, 32.35 E, 19 minutes later at 12:33 UT (6:03 p.m. India Standard Time).

https://nssdc.gsfc.nasa.gov/nmc/spacecr ... d%20Time).
Added later:

The landing occurred between Manzinus C and Simpelius N craters on the lunar nearside at 12:34 Universal Time (UT) (6:34 a.m. Eastern Daylight Time, or EDT) on Wednesday, August 23rd.

The craters themselves are much smaller compared to other craters and the small plateau between them seems to have other features like hills.

[Najunamar]

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?

[SSSalvi]

Rover has started to roam around:

https://twitter.com/sdhrthmp/status/169 ... D59189.220

[tandav]

A comparison of the mission profiles of ISRO Chandrayaan and CNSA Chang-E missions

ISRO CY3 2023 : Launch Weight of 3900 Kg Orbitor Lander Rover
https://en.wikipedia.org/wiki/Chandrayaan-3
ISRO missions are limited by the smaller launch weights of the LVM3 launcher which is 4000 KG to GSO
https://en.wikipedia.org/wiki/LVM3


CNSA CE5 (2019) The CE5 is an impressive mission: Launch weight of 8100KG, Orbitor+Lander+RoverwithCoreSampler+Returner). The CE5 currently is still in orbit in a DRO orbit of the Earth Moon System
https://en.wikipedia.org/wiki/Chang%27e_5
https://en.wikipedia.org/wiki/Distant_retrograde_orbit
CNSA LM5 launchers are rated at 14000 KG to GSO
https://en.wikipedia.org/wiki/Long_March_5

[SSSalvi]

^^^
DD thinks that it HAS TO use its camera.

When you are in control room, can you not CONNECT one terminal as a feed?

[chetak]

and this too

[Ashokk]

^^^
DD thinks that it HAS TO use its camera.

When you are in control room, can you not CONNECT one terminal as a feed?

SSSalvi ji, unfortunately, ISRO is the producer of the video feed and the commentary, not DD. Sadly, they dont seem to care about the production quality and camera work.

DD does not have copyright over rocket launch broadcast: ISRO

Chennai, Dec 6 : The Indian space agency has said it is the producer of all its rocket/satellite launch broadcast/telecast by Doordarshan (DD) and the latter does not have any copyright.

[sanman]

I love listening to the current ISRO Chairman S Somanath talk, and really have high confidence in his character and abilities:

[sanman]

Mr Unnikrishnan Nair -- I feel he'll likely be the next ISRO Chairman after S Somnath:

[hanumadu]

Saved some screenshots of yesterday’s CH-3 Landing live event...............
Posting it here for records..........(Screenshot Lot_1)

Why go all through all this trouble saar? There are videos on youtube.

I got carpal tunnel scrolling through them all.

[Mollick.R]

Saved some screenshots of yesterday’s CH-3 Landing live event...............
Posting it here for records..........(Screenshot Lot_1)

Why go all through all this trouble saar? There are videos on youtube.

I got carpal tunnel scrolling through them all.

point noted....
will try to delete them
sorry.

[SriKumar]

No, please keep them. They are all technical pictures with good technical data .

[sanman]

https://twitter.com/ANI/status/16945859 ... 69/photo/1

Someone got photo-op with ISRO people, and in the backdrop we can see the system health monitoring screen for Pragyan Rover:



The forward part of the rover is the blue-tinted sections, the back part of the rover has gray-tinted sections.

[juvva]

i hope they are not waiting for some vip to release rover pics.

[chetak]

https://twitter.com/ANI/status/16945859 ... 69/photo/1

Someone got photo-op with ISRO people, and in the backdrop we can see the system health monitoring screen for Pragyan Rover:

[img]https://pbs.twimg.com/media/F4RghEAa4AA ... medium[img]

The forward part of the rover is the blue-tinted sections, the back part of the rover has gray-tinted sections.

sanman ji,


didn't take these termites very long to come crawling out of the woodwork

The @isro dreamt of by Pandit Nehru, nurtured by Indira Gandhi ji, and taken to great heights by Rajiv Gandhi ji and Dr. Manmohan Singh ji achieves a new milestone!

A proud moment for all, as we excitedly watch the #Chandrayan3 take off to conquer the moon!

Jai Hind pic.twitter.com/xXkMWwLKwG

— K C Venugopal (@kcvenugopalmp) July 14, 2023

India's voyage to the moon and beyond is a tale of pride, determination & vision.

It was independent India’s first Prime Minister, Jawaharlal Nehru, whose scientific outlook and vision laid the foundation of Indian space research.

Today, the success of Chandrayaan-III is a… pic.twitter.com/Uc1PiIIesl

— Congress (@INCIndia) August 23, 2023

[AdityaM]

A whatif scenario:
Assuming that there is water in ice form in and under the soil close to the poles, won't it melt under the landers engine heat and form a slush at time of impact.
Also how does orbiter photography and laser mapping determine that the soil can take the weight of the lander?
Would be odd if any craft lands in an alien world and sinks into quicksand

[SriKumar]

OK, so the rover is out and it moved on the surface of the moon per a statement from K. Sivan. The interview is on Twitter (ANI) and linked in an article in NDTV website.

Not sure why no pics yet but I don’t want to see any surreptitiously recorded videos leaked from the Mission Control either. ISRO people in the room too have to follow security and protocol.

[nits]

As pr buzz on twitter ( not sure if to be believed) - Rover is out of charge and is being charged up using solar panel and may move by tomorrow

[Ashokk]

https://twitter.com/isro/status/1694699791505322117

Chandrayaan-3 Mission:
All activities are on schedule.
All systems are normal.

- Lander Module payloads ILSA, RAMBHA and ChaSTE are turned ON today.

- Rover mobility operations have commenced.

- SHAPE payload on the Propulsion Module was turned ON on Sunday.

[rahulm]

Gold mine interview with Somnath (even though title says Sivan but Somnath interview in the second half). No redundancies were required or used by VIKRAM, Landing was handled by the inertial unit. The LXXXX cameras were not used is what I understood which is a bit odd because VIKRAM did re-target.

[Ashokk]

https://twitter.com/isro/status/1694713817916473530

Lander Imager camera video from ISRO

[nitzter]

Q. Will a satellite in a large elliptical orbit around the earth be within line of sight of the far side of the moon (even a partial amount of the far side) or is the Langrange point the only spot that can provide line of sight to both the earth and moon?

Thanks. Appreciate your knowledge sharing across various posts.

Highly elliptical orbit around Earth will not be the best approach -
1. As you pointed out, it will at best provide a partial visibility to the far side even if the craft is placed perpendicular to the Earth-Moon plane.
2. This type of earth bound relay craft would limit the opportunities available to us for far side landing due to its own position in orbit. We would preferably want to wait for it to be at apogee for best lander-antenna-direction management.
3. Along with this relay craft, a moon bound relay would still be needed for regular connectivity and data transfer.

Having orbiters at Lagrange points solves this without worrying about the above three matters. Alternately, you can also put multiple orbiters on the moon to achieve this... One in a circular orbit and other in a high elliptical - the first ensuring general command relay and data transfer after touchdown whereas the second contributing towards the soft landing / other experiments.