Chandrayaan 3: Launch and Discussions

[rahulm]

Modi looks visibly emotional addressing ISRO staff.

[rahulm]

VIKRAM lander point on moon named "SHIV SHAKTI"

[fanne]

wow thank you Modi ji, we are proudly proclaiming/declaring our spiritual truth. No holding back.

[rahulm]

CY2 lander impact point named "TIRANGA"

[bala]

PM Modi has named the point where Chandrayaan-3's lander Vikram touched down on the moon's south pole area is called "ShivaShakti". Where the old Chandrayaan-2 crashed landed on the moon will be called Triranga point.

National Space Day is August 23.

[rahulm]

23 August from now on will be celebrated as "National Space Day"

[bala]

PM Modi has a new challenge: National Governance transparency - a national hackathon with the youth - ISRO (including the retired folks) to help with Nation's central governance to come up with a system which is brand new and innovative. Space sector funding to grow to $16B in coming years.

[sanman]

[sanman]

Modi declares Chandrayaan-3's landing site will henceforth be known as 'Shiv Shakti'

[sanman]

Warning: PM gets tearful @ 2:16 - I guess Sivan must have rubbed off on him

[sanman]

[bala]

ISRO Nari Shakti (women scientists) involved in Chandrayaan-3 lunar mission.

[SBajwa]

VIKRAM lander point on moon named "SHIV SHAKTI"

Very good and apt name!

[sanman]

[juvva]

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



the above is from a scientific american article.

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

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

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

https://www.youtube.com/watch?v=fZ2sNRP1opY

somnath's talk at iisc: 1:13:43s on wards.
he explains how the engines will be cut off after getting signal from the "touch sensors" in the landing pads of the lander legs.....

[Ashokk]

New video of Pragyan moving and making a turn
https://twitter.com/chandrayaan_3/statu ... 8111133110

Chandrayaan-3 Mission update:
Pragyan rover roams in pursuit of lunar secrets at the South Pole!

[SSSalvi]

^^^
Reversed probably for photo op of Mom( Lander).

[hanumadu]

New video of Pragyan moving and making a turn
https://twitter.com/chandrayaan_3/statu ... 8111133110

Chandrayaan-3 Mission update:
Pragyan rover roams in pursuit of lunar secrets at the South Pole!

Wow, it went right through the gadda (pot hole). I thought they will steer the rover around it.

[sanman]

[SriKumar]

I like these names a lot better: ShivaShakti and Tiranga. Tiranga, while meaning the tricolor flag, is an indirect reference to the people of the country rather than one person. These are names that lakhs and crores can directly relate to on a personal basis.

On a technical note, it appears that the rover was attached to ramp of the lander all through the flight. The moment the ramp deployed, the rover being attached to it, was already out of Vikram, without its wheels moving an inch. The dust of the moon is very interesting. Soft/compactble dust at this location is seen. The rover at 26 kg could make imprints on lunar soil. I estimate the pressure exerted by the rover to be about 26 kg/ ( 10 cm wide x 5 cm long footprint)/6 wheels ~ 0.08 kg/cm^2. Compare this with the pressure by the footprint left by Apollo astronauts: At ~ 150 kg (body + space suit) pressure from one foot (taang) = 150 kg /(30 cm long x10 cm wide)/2 (this is a space suit footprint , not the human) gives us = 0.25 kg/cm^2. The depth of compaction is difficult to estimate but they are comparable, with Pragyaan's imprints seeming to be less deep than the astronaut footprints by about 2-3 times. 0.08x 3 = 0.24 which is close to the pressure exerted by one wheel of the rover.

Surprisingly, no streak-lines from blown-off dust is seen at the landing site in the latest video. One would have expected to see atleast some trace of a tiny regolith carving a scour mark as it got blown away by the rocket blast. Same thing most pictures from the many Apollo moon landing sites. This lack of scour marks is surprising and perhaps speaks to the properties of lunar soil. The dust particles and tiny regoliths are probably very rough and rigid; and have high friction that inter-locks them with each other preventing them from being blown away but the overall soil is porous enough to compact under minimal pressure of a light rover. Obviously this is guesswork based on pictures, but all pictures tell a story.

[sudarshan]

Obviously this is guesswork based on pictures, but all pictures tell a story.

Yes they do. In fact, the lack of an atmosphere on the moon makes it easier to infer more of that story.

For example - the shadow of the rover wheel is roughly 2 to 2.5 times longer than the wheel itself. So - assuming level ground - the angle of the sun is between 22 deg. to 27 deg. in the sky.

Albedo of the moon is 0.12 (reflecting roughly 1/8th of incident light - being about the same as worn asphalt). So roughly 85% absorptivity. With an incident solar flux of ~1200 W/m^2 (same as in the upper atmosphere of the earth), and with the incidence angle as above, the temperature at that point (assuming equilibrium) is around 15 to 30 deg. C.

One can't make these same inferences just by looking at a similar picture of the earth, because the atmosphere greatly complicates the picture. The moon on the other hand is essentially driven by radiative transport.

[SSSalvi]

^^^
Reversed probably for photo op of Mom( Lander).

No, facing Sun for charging.

[sudarshan]

See how bright it is at the top right of the video. That's with a 12% reflectivity, essentially looks the same shade of white as the moon itself from earth. That's the level of incident solar flux on the earth/ moon, the atmosphere essentially protects us from a lot of that. Without the atmosphere, the lit side of the earth would hit 100 to 120 C. And as soon as the lit side of the earth slipped into shadow, it would cool far below freezing.

[juvva]

Obviously this is guesswork based on pictures, but all pictures tell a story.

Yes they do. In fact, the lack of an atmosphere on the moon makes it easier to infer more of that story.

For example - the shadow of the rover wheel is roughly 2 to 2.5 times longer than the wheel itself. So - assuming level ground - the angle of the sun is between 22 deg. to 27 deg. in the sky.

Albedo of the moon is 0.12 (reflecting roughly 1/8th of incident light - being about the same as worn asphalt). So roughly 85% absorptivity. With an incident solar flux of ~1200 W/m^2 (same as in the upper atmosphere of the earth), and with the incidence angle as above, the temperature at that point (assuming equilibrium) is around 15 to 30 deg. C.

One can't make these same inferences just by looking at a similar picture of the earth, because the atmosphere greatly complicates the picture. The moon on the other hand is essentially driven by radiative transport.

thanks! sudarshan for this analysis.
what would be the maximum day time temperature at this location?
and the minimum night time temperature?

[juvva]

did isro say explicitly at any time that vikram landed in nominal orientation?

[Ashokk]

https://twitter.com/chandrayaan_3/statu ... 1856520282

Chandrayaan-3 Mission update:
Of the 3 mission objectives,

* Demonstration of a Safe and Soft Landing on the Lunar Surface is accomplished

* Demonstration of Rover roving on the moon is accomplished

* Conducting in-situ scientific experiments is underway. All payloads are performing normally.

[Amber G.]

Obviously this is guesswork based on pictures, but all pictures tell a story.

Yes they do. In fact, the lack of an atmosphere on the moon makes it easier to infer more of that story.

For example - the shadow of the rover wheel is roughly 2 to 2.5 times longer than the wheel itself. So - assuming level ground - the angle of the sun is between 22 deg. to 27 deg. in the sky.

Around this time of posting, Sun is about 15 degree above horizon -- (Sun rose just a few days ago..about 7 days later it will reach it's maximum height about 22 degrees - simple math)..

This is the sky will look like (if we could see all the stars in the days) -- sun is very close to 'simbha rashi (मघा (नक्षत्र))..

[sanman]

So I 'm sorry, but I feel I must digress into a small personal peeve of mine in regards to this mission.

I wanted our PROPER TRICOLOUR FLAG to be PROPERLY VISIBLE on this mission.

While traveling to the Moon, we could see camera pics of our solar panels and surrounding gold foil-wrapped structures. We saw no TRICOLOUR FLAG.

We're told that Pragyan rover has wheels which will imprint Asoka Lions emblem and ISRO's own logo onto the lunar soil. Come on, we'll never be able to see that stuff -- and we're thus forced to just take ISRO's word for it.
What's the advantage of this clever-by-half stuff over seeing our TRICOLOUR FLAG?

I would have liked to see our TRICOLOUR FLAG visible on both rover and lander.

When we sail a naval ship, when we fly a fighter jet, when our tanks are rolling, our flag is displayed.
On our govt office buildings, on our overseas embassies, our flag is displayed.
Somebody at some point taught us to do this.

We claim to want to promote "Brand India" and want to establish ourselves in the growing space market.
Who doesn't understand that your National Flag is part of your brand in this global space marketplace?
People on BR especially should understand what I'm talking about in regards to our flag.

Now I can understand if scientists who stay cooped up in their labs don't know much about the significance of flags in the bigger picture of things.
But someone overseeing this program should have known to get the needful done by getting our flag properly displayed on our space hardware.
The images and video from missions like this get preserved for the history books. Having our flag in these pictures and videos serves as a powerful reminder to ourselves and others on our national identity and character.

I'm not talking about displaying some classical cloth flag, which cannot wave in the non-existent breeze in the vacuum of space.
It can just be a painted/decal thing, even just a few inches wide, just as long as it properly displays our tricolour on the hardware.
I would have even settled for just the Chakra.

American spacecraft & landers proudly display their national flag, so do Russian and Chinese counterparts.
Chinese may drop boosters on their rural towns and villages -- but at least they have their flag on them.

Please nobody feed me any claptrap about how the micrograms of paint required would completely throw out of balance the precisely calibrated hardware and precisely calculated orbital mechanics.
Please nobody argue to me that displaying our Chakra would've created unwanted electromagnetic resonances that would short out the antennas and collapse the spacetime continuum.
Please don't tell me that 50 paise worth of paint/decals would have put the entire project over budget.

Just put our TRICOLOUR FLAG on the damn hardware, and when testing the cameras, make sure that flag is properly visible.

[SriKumar]

did isro say explicitly at any time that vikram landed in nominal orientation?

From the point of view of solar energy capture, it is pretty close. If you notice the opening of the solar panel of the rover, it is almost (but not quite) normal/orthogonal to the direction of sunlight, even while on the ramp itself. You can see the sunlight as the rover hits the lunar surface. This suggests that the lander would likely have been oriented so as to capture the maximum solar radiation early in the day, one presumes.
Pragyaan itself can be rotated, so it is not a big concern for it, but Pragyaan's orientation as it comes off Vikram indicates the orientation of Vikram lander relative to the sun.

[bala]

ISRO Chief, S. Somnath (Lord of the moon!) talks about ancient Sanskrit texts (Surya Siddhanta, etc) which describes concepts which are today accepted worldwide and form the basis of modern science. Things like the earth as a sphere with north/south pole depressions, revolving around the sun, moon revolving the earth, the wobbling of the Earth's axis is calculated very precisely in the Surya Siddhanta, in Pancha Siddhantika Varahamihira estimated diameters of the planets, like Mercury, Venus, Mars, Saturn and Jupiter and so on. Till recently, the orthodox church and I might add even Islam believed that the earth was stationary and the sun revolved, etc. S. Somanath said that the principles of science originated in the Vedas but were repackaged as western discoveries later. Many Indians lauded the ISRO chief for shedding light on the timeless brilliance of Vedic knowledge.

[Amber G.]

Yes they do. In fact, the lack of an atmosphere on the moon makes it easier to infer more of that story.

For example - the shadow of the rover wheel is roughly 2 to 2.5 times longer than the wheel itself. So - assuming level ground - the angle of the sun is between 22 deg. to 27 deg. in the sky.

thanks! sudarshan for this analysis.
what would be the maximum day time temperature at this location?
and the minimum night time temperature?

FWIW: Simple math (see my posts about moon's tilt with ecliptic and knowing the lattitude of Vikram's landing point)
will give maximum Sun's angle above the horizon about 22 degrees.)

Longitude/Lattitude : 32.35 E, -69.37 ==> gives (90- 69.4 = 20.6).
MAX angle between Moon's equator and Sun (ecliptic) 1.5 degree.
(Max possible at any 'noon' for the current year etc -- the maximum possible elevation on any particular noon may vary by +- 1.5 degree from 20.6)

(With simple trigonometry, you can calculate/estimate Azimuth, and Elevation at any date (of sun or Earth or any other star which one is familiar with)

The daytime temperatures can soar to about 120 degrees Celsius while nighttime temperatures can plummet to as low as -173 degrees Celsius. As there is no air, rise and fall are much sharper. (Shade etc makes quite a bit of difference in daytime temperature )

[sudarshan]

thanks! sudarshan for this analysis.
what would be the maximum day time temperature at this location?
and the minimum night time temperature?

Actually, the lengths of the shadows provide great corroboration for the fact that the lander is at around 70 deg. (South - but could also be North) latitude on the moon. So the sun would be expected to reach a maximum altitude of 90 deg. - (70 deg. +/- 6.7 deg.) = 13.3 degrees to 26.7 deg. Basically, at this latitude, the tilt of the axis of the moon with respect to the sun can vary from 13.3 degrees to 26.7 degrees.

6.7 degrees is the tilt of the moon's axis with respect to the earth's ecliptic. So the shadow being ~2 to 2.5 times the length of the object (assuming level ground) already corroborates this:

cot(13.3 deg) = 1/tan(13.3 deg) = 4.2 : this would be one extreme - the shadow would be 4.2 times the length of the object
cot(20 deg) = 2.75 : this would be the median
cot(26.7 deg) = 2 : this would be the other extreme - the shadow would be twice the length of the object

AmberG can confirm, but I think the maximum temperature, being determined by latitude (and thus - maximum altitude of sun) and by the absorptivity (~85%) is roughly -15 to +30 degrees C (corresponding to 13.3 deg tilt and 26.7 deg tilt respectively). If you want the exact calculations, I can post that.

As for minimum temperature, that would be determined by the length of time that the area was in the night. It also depends on the specific heat of the rock/ soil, how quickly they lose heat through radiation (no convection without an atmosphere). Looking online, it seems that the night time temperature can plunge to -130 C. This should be relatively independent of latitude, since this is the case with zero solar influx (again - AmberG can confirm).

So any water at that location is going to go through freeze-thaw cycles every rotational period (29.5 days relative to the sun).

EDIT: I see AmberG has already replied, please refer to AmberG's posts instead.

[sudarshan]

The daytime temperatures can soar to about 120 degrees Celsius while nighttime temperatures can plummet to as low as -173 degrees Celsius. As there is no air, rise and fall are much sharper. (Shade etc makes quite a bit of difference in daytime temperature )

AmberG ji, the daytime temperatures can soar to 120 deg. C at the equator, but not at 70 deg. N or S latitude on the moon. At 70 deg. latitude (N or S), it seems to be more like 30 deg. C maximum.

[Amber G.]

ISRO Chief, S. Somnath (Lord of the moon!) talks about ancient Sanskrit texts (Surya Siddhanta, etc) which describes concepts which are today accepted worldwide and form the basis of modern science.

FWIW: The reason of my learning Sanskrit well was to read Surya Siddhanta in original (English Translation - especially many British scholars do not translate the text well - misses many important points.... (I know enough sanskrit to read math texts - and also Prakrit to read lot of Jain (Brahamagupts etc) texts.. (Many in math dhaga may have noticed that point.. ..

[drnayar]

So I 'm sorry, but I feel I must digress into a small personal peeve of mine in regards to this mission.

I wanted our PROPER TRICOLOUR FLAG to be PROPERLY VISIBLE on this mission.

Just put our TRICOLOUR FLAG on the damn hardware, and when testing the cameras, make sure that flag is properly visible.

Totally agree..what beats seeing the Indian tricolour on the moon ?!!

[Amber G.]

thanks! sudarshan for this analysis.
what would be the maximum day time temperature at this location?
and the minimum night time temperature?

Actually, the lengths of the shadows provide great corroboration for the fact that the lander is at around 70 deg. (South - but could also be North) latitude on the moon. So the sun would be expected to reach a maximum altitude of 90 deg. - (70 deg. +/- 6.7 deg.) = 13.3 degrees to 26.7 deg. Basically, at this latitude, the tilt of the axis of the moon with respect to the sun can vary from 13.3 degrees to 26.7 degrees.

6.7 degrees is the tilt of the moon's axis with respect to the earth's ecliptic. So the shadow being ~2 to 2.5 times the length of the object (assuming level ground) already corroborates this:

cot(13.3 deg) = 1/tan(13.3 deg) = 4.2 : this would be one extreme - the shadow would be 4.2 times the length of the object
cot(20 deg) = 2.75 : this would be the median
cot(26.7 deg) = 2 : this would be the other extreme - the shadow would be twice the length of the object

AmberG can confirm, but I think the maximum temperature, being determined by latitude (and thus - maximum altitude of sun) and by the absorptivity (~85%) is roughly -15 to +30 degrees C (corresponding to 13.3 deg tilt and 26.7 deg tilt respectively). If you want the exact calculations, I can post that.

As for minimum temperature, that would be determined by the length of time that the area was in the night. It also depends on the specific heat of the rock/ soil, how quickly they lose heat through radiation (no convection without an atmosphere). Looking online, it seems that the night time temperature can plunge to -130 C. This should be relatively independent of latitude, since this is the case with zero solar influx (again - AmberG can confirm).

So any water at that location is going to go through freeze-thaw cycles every rotational period (29.5 days relative to the sun).

EDIT: I see AmberG has already replied, please refer to AmberG's posts instead.

Sudarshanji - As to sun's Azimuth (measured eastward from the north point of the horizon, and altitude (the angle above the horizon) at any point on the Moon is *much* easier to calculate than earth due to the fact that moon's equator is tilted *only* about 1.5 degrees from the ecliptic.

Just to be clear:

Earth's axis (line joining N-S pole) is tilted about 23.5 degrees with respect to ecliptic.
Moon's axis (Line joining N-S pole of Moon) is tilted about 1.5 degrees with respect to ecliptic.

Ecliptic is the plane in which Earth (or Moon) goes around the sun. (Moon's motion around earth is quite a small wobble around this plane)

Moon's Orbit *around earth* is tilted about 5.14 deg from the ecliptic. (From Earth's equatorial plane the angle varies between 18.3 to 28.6 degrees).

Moon's Axis is tilted about 6.7 degrees (around now) *with respect' to plane of Moon's orbit around earth.

(To calculate Sun's elevation etc is *much* simpler... at "noon" (maximum elevation is 90 - lattitude +- 1.5 degrees)

[Amber G.]

The daytime temperatures can soar to about 120 degrees Celsius while nighttime temperatures can plummet to as low as -173 degrees Celsius. As there is no air, rise and fall are much sharper. (Shade etc makes quite a bit of difference in daytime temperature )

AmberG ji, the daytime temperatures can soar to 120 deg. C at the equator, but not at 70 deg. N or S latitude on the moon. At 70 deg. latitude (N or S), it seems to be more like 30 deg. C maximum.

You are correct that those figures are for equator. At higher lattitude the temperatures vary quite significantly due to local topography and long shadows.. As you say, at very high lattitude (say near poles), and in shadows (inside a crater) even day time temperatures are more moderate. There are points on the moon where sun *never* rises.. and even the day time temperatures are very low ... (See: https://moon.nasa.gov/resources/97/the- ... s%20light.

We will know much better values of temperature after Vikram's measures it. But allow me to post...

LRO has mapped the surface of the moon to estimate temperatures at different lattitude....




As they say.. actual readings may vary a little from average. (Shadow makes a big difference) ... gives some idea.. (There is a very detailed map of surface temperatures of the Moon as measured by Radiometer )

Added later:
Near the south pole.. there are regions where even the day time temperature (taken on average) is quite low..
Please read the next post by Sudarshan -- where K is converted into C..
Finding a place in the shade ( Say a nice crater with flat surface may be a good place to explore..)

[sudarshan]

We will know much better values of temperature after Vikram's measures it. (I will be surprised that it is that moderate as you suggest...

LRO has mapped the surface of the moon to estimate temperatures at different lattitude....

Actually, the figures which you posted do show that it is that moderate as I suggested, at 70 deg. latitude (N or S). The figures give a range of around 250 to 300 K at that latitude (orange on the color scale in the figure). This is -20 to +30 C.

Only around the equator, it goes to like 350+ K (80+ C).

[Amber G.]

^^^ Yes,.. Key point IMO, is since there is no atmosphere, in practical sense, temperature varies quite a bit between shade and outside the shade .. The 'average temperature' taken by the radiometer (shadows are very long - through out the day) has quite a different meaning there compared to earth.. finding a place in shade could be very helpful.

[bala]

FWIW: The reason of my learning Sanskrit well was to read Surya Siddhanta in original (English Translation - especially many British scholars do not translate the text well - misses many important points.... (I know enough sanskrit to read math texts - and also Prakrit to read lot of Jain (Brahamagupts etc) texts.. (Many in math dhaga may have noticed that point.. ..

AmberJi the post on Somnath has nothing to do with your knowledge of Sanskrit, math, physics, etc. Tis great that you read the original. The point is many things in physics, maths, science in general are recycled concepts first articulated in Sanskrit texts of India. Fibonacci, Pythagoras, Pascal triangle, Newton's laws, calculus, time dilation are recent usurpations of Ideas from India. Many Indian original sanskrit texts were stolen by the Brits and housed in Universities of Germany, London, some in the US. These nations refuse to give them back to India and they even forbade Indians to take a look at them. The entire subject of botany was based on a book from Kerala. Many British translations of Sanskrit are plain wrong and some are imaginatively concocted to paint a poor picture.