Chandrayaan 3: Launch and Discussions

[SSSalvi]

Andhra Sugars, are ISRO's Major Supplier of UDMH , which run Vikas Engines.

UDMH is a by-product for them.

[SSSalvi]

Radio Anatomy of Moon Bound Hypersensitive Ionosphere and Atmosphere - Langmuir Probe (RAMBHA-LP) payload onboard Chandrayaan-3 Lander has made first-ever measurements of the near-surface Lunar plasma environment over the south polar region.

The initial assessment indicates that the plasma near the lunar surface is relatively sparse.

https://twitter.com/isro/status/1697193 ... 36042?s=20

[SSSalvi]

Another instrument onboard the Rover confirms the presence of Sulphur (S) in the region, through another technique.

The Alpha Particle X-ray Spectroscope (APXS) has detected S, as well as other minor elements.

This finding by Ch-3 compels scientists to develop fresh explanations for the source of Sulphur (S) in the area: intrinsic?, volcanic?, meteoritic?,......?.

https://isro.gov.in/APXS.html

The video shows an automated hinge mechanism rotating the 18 cm tall APXS, aligning the detector head to be approximately 5 cm in proximity to the lunar surface.
https://twitter.com/i/status/1697145796419104979

[Ashokk]

Chandrayaan-3: Vikram lander’s ILSA records rover and a 'natural event'

BENGALURU: Late on Thursday, Isro said that the Instrument for the Lunar Seismic Activity (ILSA) on Chandrayaan-3 lander (Vikram) — the first Micro Electro Mechanical Systems (MEMS) technology-based instrument on the moon — has recorded the movements of Pragyan (rover) and other payloads.
Developed by Laboratory for Electro-Optics Systems (LEOS) in Bengaluru, ILSA comprises a cluster of six high-sensitivity accelerometers, which are indigenously fabricated using the Silicon Micromachining process.

“ILSA’s primary objective is to measure ground vibrations generated by natural quakes, impacts, and artificial events. It recorded vibrations during the rover’s navigation on August 25, 2023. Additionally, an event, seemingly natural, recorded on August 26. The source of this event is currently under investigation,” Isro said.

Private industries supported LEOS realise ILSA, Isro said, without naming any of the private industries. The deployment mechanism for placing ILSA on the lunar surface was developed by URSC.

LEOS, one of the vital units of Isro, deals with the design, development and production of attitude sensors for all LEO, GEO and interplanetary missions; develops and delivers optical systems for remote sensing and meteorological payloads.
“The lab is equipped with world class fabrication, testing and coating facilities. Next generation technologies such as 3-axis fiber optics gyro, optical communication, MEMS, nanotechnology, detectors and development of science payloads for future space missions are also being pursued,” according to Isro.

[Ashokk]

Chandrayaan-3: Vikram's RAMBHA completes first in-situ measurements of plasma in polar region

BENGALURU: One of the three Indian payloads on the Chandrayaan-3 lander (Vikram) has completed the first in-situ measurements of the surface-bound lunar plasma environment over the south polar region.
"The measurements have been carried out by the Radio Anatomy of Moon Bound Hypersensitive ionosphere and Atmosphere-Langmuir Probe (RAMBHA-LP) payload onboard the lander … These quantitative measurements potentially assist in mitigating the noise that lunar plasma introduces into radio wave communication.
Also, they could contribute to the enhanced designs for upcoming lunar visitors,"Isro said.

It added that the initial assessment indicates that the plasma encompassing the lunar surface is relatively sparse, characterised by a number density ranging from approximately 5-30 million electrons per cubic metre.

"This evaluation specifically pertains to the early stages of the lunar daytime. The probe operates without interruption, aiming to explore the changes occurring in the near-surface plasma environment throughout the lunar day. These ongoing observations hold significant implications for comprehending the process of charging within the lunar near-surface region, particularly in response to the fluctuations in solar space weather conditions," Isro said.

The RAMBHA Langmuir (named after US chemist and physicist Irving Langmuir) probe is a device used for characterising a plasma. RAMBHA's development was led by the Space Physics Laboratory (SPL) at Isro's Vikram Sarabhai Space Centre (VSSC).

"It features a 5cm metallic spherical probe mounted on a 1-metre boom attached to the lander’s upper deck. The probe is deployed using a hold-release mechanism after the lander’s lunar touchdown. The extended boom length ensures that the spherical probe operates within the undisturbed lunar plasma environment, isolated from the lander's body," Isro said.
Pointing out that the system can detect minute return currents, as low as pico-amperes (measurement unit for electric current), with a dwell time of 1 millisecond.

"By applying a sweeping bias potential ranging from -12 to +12 V in increments of 0.1 V to the Langmuir probe, the system can accurately determine ion and electron densities as well as their energies based on the measured return current," Isro added.

[vijayk]

https://twitter.com/MeghUpdates/status/ ... 2865419394
Megh Updates @MeghUpdates
Video of an Indigo crew member proudly announcing the onboarding of the distinguished passenger Sri S. Somnath, Chairman of ISRO has gone viral on SM.

[nitzter]

As the lander retargeted and landed on a different spot, there would be little fuel left in the tanks.
Hypothetically, if some fuel was left in the tanks would it be a good idea to fire the engine and move to another location where there is daylight available?
Then we can get 28 days of continuous daylight.

CY3's propellant tank can never accommodate enough fuel for this manouvre... The requirement would be around double the fuel used for soft landing on 23rd.

Say, I want to relocate to 148° W (which is opposite to the landing site), while keeping the same latitude, for continuous sunlight availability -
1. The straight line distance I would need to cover through the lunar rigolith would be around 1224 kms (1251 kms on surface)
2. I need to go sub-orbital (into a medium 500-501 km altitude orbit) while relocation to save fuel
3. First, work would be done to achieve a desired horizontal & vertical velocity; followed by the whole braking and descent all over again. Maybe Amber ji can help us with the exact sub-orbital velocity calculations...

[Barath]

--
ISRO says Pragyan rover confirmed presence of Sulphur, detected Oxygen on moon; search for Hydrogen underway

While we wait for more details, here are a few comments, why this may be a major item..

Probably not a major discovery, since presence of sulphur, though relatively rare , was known [ 11th most common element in mare] and papers written on Fe- FeS in various flows in past.

But it doess adds data to that jigsaw puzzle to help figure out more info..on selenology and development

https://adsabs.harvard.edu/full/1992lbsa.conf..429V

Apollo brought back 382 kg of samples and sent a specialized geologist (selenologist?) In addition to cross trained personnel. Chang'e brought back almost 2 kg . The ussr brought back less than a kg. Plus human, lander, orbiter and rovers.

https://spaceflightnow.com/2021/01/01/c ... r-samples/

So useful, yes. Significant? Perhaps, though it might not cause the development of moon and lunar flows to be solved by its lonesome. How Significant, it remains to be seen..

[SriKumar]

Why almost all the photos are Black and White. I'm sure there must be a reason. It will be great if we can get color videos. May be bandwidth is the bottleneck.

The videos are in color. Gold color on ISRO products is visible. Moon is black-and-white.

[Amber G.]

Some Nerdy science, and more details - Ignore if you wish..
(Disclaimer : Nothing official -- mainly my thinking based on what we know so far. ( Believe it will be consistent with most scientists)

While we wait for more details, here are a few comments, why this may be a major item..

Probably not a major discovery, since presence of sulphur, though relatively rare , was known [ 11th most common element in mare] and papers written on Fe- FeS in various flows in past.

But it doess adds data to that jigsaw puzzle to help figure out more info..on selenology and development

h

Thanks for good reading material in your links.
----

It all depends on expected abundance vs actual abundance expected in the region....

Few comments - There have been a few interesting posts from @sudarshan and others about temperature on the surface of the moon in general and what Vikram found. Similarly about composition of the regolith of the moon, discovery of sulphur etc..

Lot of things we knew from remote measurements .. some by actual landing on the south pole region.

Sharing some very intersting points (interesting to at least me )...

First some points -- we (ISRO scientists) knew about CY3's landing place, in details --- (by remote sensing)... Whole area was mapped *in detail* for temperature profile, and expected composition of regolith etc...yet there were some genuine surprises. (This is for the planned landing site of CY3.. from ISRO) (Some pictures I posted before in BRF)



(Note, here 'local noon' happens about 7 days (of 24 hours) after 'local dawn' - local == point where CY3 landed), A 'day' is about 14 earth days)

(Source: ISRO, publicly available papers)

(Perhaps, this is why some of the experts are little surprised to find the measured temperature by Vikram was about 30 degrees higher than they expected. -- I posted here before that this is not that surprising (to me) as actual temperature may differ quite significantly from average taken over a large area (with long shadows, no air etc)..)

Also sharing:





There will be more data analysis, etc... but at present, many of us are quite excited about Sulphur .... We all will know for sure, how it all turns out.

[Amber G.]

Why almost all the photos are Black and White. I'm sure there must be a reason. It will be great if we can get color videos. May be bandwidth is the bottleneck.

FWIW: I was asked similar questions when people looked at photos of our trip to Death Valley..(some even thought that google photo's editing software made the color pop out in people while making the background in B&W to make the photos dramatic )

[Amber G.]

In Surya Sidhant we are given a few different figures of length of Lunar month ...
1 - 29.53059 days
2 - 27.32158 days
3 - 27.32166 days
4 - 27.55455 days
5 - 27.21222 days


Challenge Q: What these different cycles represent? ...

29.53059 days is the synodic period (phase cycle).

The sidereal period (time taken for the moon to come back to the same nakshatra, as seen from the earth) is either 27.32158 days, or 27.32166 days (not sure which).

What are the other cycle times?

I have only seen the synodic and sidereal months, the others are OHT for me...

Yes, 29.53059 is synodic, and 27.32166 is sidereal.
For others ... check out the usual place (the math dhaga)

Any good book can explain it further -- but if you are interested in math check out the math dhaga.
Synodic Month is the mean interval between conjunctions of the Moon and Sun, corresponding to the cycle of lunar phases. (However, any particular phase cycle may vary from the mean by up to seven hours)
The sidereal month is the time between maximum elevations of a fixed star as seen from the Moon. About 27.321662 days.
The tropical month is the period from one lunar equinox to the next about 27.321582 days long. (Equinox precess ~26000 years)
The anomalistic month is the time between perigee passages, equal to 27.554550 days( in 2000)
The Draconic month is the time between one node (Rahu or Ketu) passage to the next. In 2000 it was 27.212221 days.

(These are calculated in suryadihant as cycles -- we all know, the sidereal month - but the values are effected by length of year (365.2422 days), precession of equinoxes (~26000 years), and movement of Rahu/Ketu (nodes) (important for eclipses) (~18.6 years) and perigee (Super moon etc) ~ 8.85 years -- remarkable that these long periods were very well known even centuries ago)

Again see the math dhaga, if interested in math.

[vnms]

...
Say, I want to relocate to 148° W (which is opposite to the landing site), while keeping the same latitude, for continuous sunlight availability -
1. The straight line distance I would need to cover through the lunar rigolith would be around 1224 kms (1251 kms on surface)
2. I need to go sub-orbital (into a medium 500-501 km altitude orbit) while relocation to save fuel
3. First, work would be done to achieve a desired horizontal & vertical velocity; followed by the whole braking and descent all over again. Maybe Amber ji can help us with the exact sub-orbital velocity calculations...

It is not required to go 500 km in altitude. There is no atmospheric drag. As long as you have the necessary fuel to go cross country either in a balastic trajectory or the great circle path.

[Barath]

. Enough time, to decide/implement ...Most likely scenario is RHU type unit ( Pu238) to keep the electronics warm in lunar night and solar power instead of RTG to supply power in the night but that can happen too

Agree. But remember it is lander by India and rover by Japan, so you need solutions for both. And they both are big and heavy enough

https://www.hou.usra.edu/meetings/lpsc2021/pdf/1840.pdf

And supposedly the preliminary design is done

https://blog.jatan.space/p/moon-monday-issue-111

[sanman]

Podcast discussing Chandrayaan-3 and also Luna-25

https://mainenginecutoff.com/podcast/257

[bala]

We can measure time by the seasons (tropical time) or by the stars (sidereal time). The sun, as the time hour hand, is common to both. A solar calendar is a calendar whose dates indicate the apparent position of the sun moving on the celestial sphere.

The Tropical Zodiac is the position of the sun referenced against the earth’s horizon at a particular locale which gives you the seasons as a measure of the flow of time. The 4 seasons are the 2 solstices and the 2 equinoxes. The tropical system was adopted during the Hellenistic period and remains prevalent in Western systems.

The Sidereal Zodiac is the position of the sun referenced against the star (nakshatra) background, as a measure of the flow of time. Nakshatra is the term for lunar mansion in Hindu astrology. In Surya Siddhanta, Maya Danava equated time with "nakshatra". Maya Danava wrote that a "prana" is duration of 4 seconds. There are 15 pranas in a minute; 900 pranas in an hour; 21600 pranas in a day, 583,200 pranas in a nakshatra (month). Thus a nakshatra is a time unit with duration of 27 days. This 27 day time cycle has been taken to mean a particular group of stars. The Surya Siddhantha of Maya Danava concisely specifies the coordinates of the twenty seven Nakshatras.

The celestial equator is a great circle on the imaginary celestial sphere, in the same plane as the Earth's equator. In other words, it is a projection of the earth's terrestrial equator out into space. As a result of the Earth's axial tilt, the celestial equator is inclined by 23.4° with respect to the ecliptic plane (of earth movement around sun). The ecliptic is an imaginary line on the sky that marks the annual path of the sun. It is the projection of Earth’s orbit onto the celestial sphere. The Sun itself orbits around the galactic center at a radius of about 8,500 parsecs and takes over 200 million years to make one full orbit.

The moon's eliptical around the earth is approx 5° degree from the earth's eliptical around the sun. Therefore the difference from the celestial equator (aligned to the earth's equator) is 28.4° max and 18.4° min. The path of the moon around the earth intersects the elliptical plane of earth around the sun at two points called lunar nodes. The ascending or north node (rahu) is where the moon crosses from south of the ecliptic to north of the ecliptic. The descending or south node (ketu) is where it crosses from north of the ecliptic to south of the ecliptic. The period of revolution of the moon around the earth is 27.3 days.

The plane of the lunar orbit precesses in space and hence the lunar nodes precess around the ecliptic, completing a revolution (called a draconic or nodal period) in 6798.3835 days or 18.612958 years. It takes about 360/19.355 = 18.6 years (6793.4 days) for the nodes rahu and ketu to complete one full revolution along the ecliptic. Such an event happens once every 18.6 years, and last occurred in 2006, and won’t take place again until 2025.

The Sanskrit term Ayanamsa is the angle by which the sidereal ecliptic longitude of a celestial body is less than its tropical ecliptic longitude. Ayanamsa, therefore, takes into account the amount of precession. Ayanamsa is around 24° today. The ayanamsha describes the increasing gap between the tropical and sidereal zodiacs. Suryasiddhaanta states that ayanamsha was zero in 499 AD (Mesha Sankranti). In Surya Siddhānta ayanāmsa rises from 0° to +27° during 1800 years, then decreases to 0° and further to -27°, thereafter rising again, thus oscillating within a rage of ±27° instead of cyclically moving in a circle as modern concept of ayanāmsa suggests. As per Surya Siddhanta, the Precession of the Equinoxes is an oscillating one. It moves 27° to the West, retreats again to the zero point, again moves 27° to the East and retreats again thus making an angle of 108°. 1° Precession takes place in 66 years.

[sanjaykumar]

That’s very useful.

But is there an intrinsic property of rotating spheres that generate precession, and why?

[Vayutuvan]

That’s very useful.

But is there an intrinsic property of rotating spheres that generate precession, and why?

Something to do with conservation of angualar momentum? My memory is hazy. Happens with spinning tops as well.

[disha]

Complied all info to compare planned vs actual.

^This is a keeper.

[Amber G.]

^^^ Not too difficult to calculate using Newton's (or basic physics) ..
( Will move this in math dhaga - if there is interest ... leaving it here but just once - as PM said - Chandrayaan 3 should arise interest in science)


Works very well, if you solving problem of Sun/Moon/Earth system or a spinning top in exam .

Tidbit: The amount of the precession as calculated by Newton did as a matter of fact agree pretty closely with the observed amount, but this was due to the accidental compensation of two errors, arising from his imperfect knowledge of the form and construction of the earth, as well as from erroneous estimates of the distance of the sun and of the mass of the moon.

Many/most western books attribute the discovery of precession to Hipparchus ( 150 BC) (his value "is less than 36000 years),
(Hipparchus noticed that the positions of the stars were gradually changing over time compared to the positions cataloged by earlier astronomers. He realized that this motion could not be explained by the motion of the stars themselves but was due to a slow shift in the Earth's axis).
Most ancient civilization knew about it .. from Chinese to Maya..

In Ancient India, astronomers were also aware of the phenomenon of precession, and it is discussed in various texts such as the Surya Siddhanta and the works of Bhaskaracharya (Bhaskara I and Bhaskara II) among others... (Values given are impressive - knowing a 26000 year cycle, requires observational records covering *many many(* centuries ... but as expected , those values are not as accurate as modern values .. the other values like synodic period of lunar month are surprisingly close to modern values. Various authors give values around around 200,000 revolutions in a Kalpa of 4,320,000,000 years) ( Modern value will give the correct figures around 166,000 cycles)
Anyway here are two examples spinning tops..

or

[Amber G.]

For fun: Asked about length of Lunar months, Now there are hree types of years:
365.25636 days
365.24219 days
365.25964 days
Challenge Q - Explain?

[bharathp]

For fun: Asked about length of Lunar months, Now there are hree types of years:
365.25636 days
365.24219 days
365.25964 days
Challenge Q - Explain?

pardon my ignorance- going to take a shot here:
shouldnt an year on the moon be same as the year on earth? given the composite(moon + earth) take the same time to go around the sun?
although there will be more overall distance travelled by the moon in the same period (given its revolutions around the earth?)

[Amber G.]

For fun: Asked about length of Lunar months, Now there are hree types of years:
365.25636 days
365.24219 days
365.25964 days
Challenge Q - Explain?

pardon my ignorance- going to take a shot here:
shouldnt an year on the moon be same as the year on earth? given the composite(moon + earth) take the same time to go around the sun?
although there will be more overall distance travelled by the moon in the same period (given its revolutions around the earth?)

Of course, Yes. But on earth also we have three type of years.

But you bring an interesting point!:

(Total distance traveled by the moon would be *very* similar to earth -- The moon's orbit around sun, looks *very* much like earth's orbit -- just like an ellipse, no loops (as many people think or imagine),.. in fact just like earth, every point of moon's orbit, is concave towards the sun - something counter-intuitive to many people)
Neither this ==> nor this ==>

But like this ==>

[sudarshan]

For fun: Asked about length of Lunar months, Now there are hree types of years:
365.25636 days
365.24219 days
365.25964 days
Challenge Q - Explain?

OK, looking at your post in the math dhaga, I think these should be as follows:

365.25636 days-----------------Sidereal - earth comes back to same position, as seen from the sun, WRT fixed stars
365.24219 days-----------------?
365.25964 days-----------------Perihelion to perihelion?

[bharathp]

365.24 is the year around the sun. from any arbitary point, back to the same point

[disha]

^ BharatP, since Moon is orbiting around Earth, a moon year is the same as complete revolution around Earth. Which is ~27 days. At the same time Moon being tidally locked, does a rotation on its own axis which again is ~27 days. So assuming Earth as a center, the moon year is same as moon month which is ~27 earth days. This is based on using the reference of revolution around Earth and moons rotation on its own axis.

Now, from Earth, moon has phases. That is it goes from full moon to new moon to full moon. To be ultra-precise it is better to measure from waning crescent to waning crescent. But it is easier to explain as a full moon to new moon to full moon cycle. That is ~29.5 days. That is also called Lunar Month. I would call that as Synodic Month.

If you take 12 such Synodic months, you will get a Lunar Year, which is ~354 days. And none come close to ~365 days quoted above your post.

--- The various Earth Years ---

365.25636 days: Siderial period of Earth. That is, the Earth comes to the same spot after a complete revolution around Sun, measured in reference to a distant star (which can be assumed as 'fixed'). The "day' here is a mean solar day.

365.24219 days: Tropical year. Take the period between two Vernal equinox one after another. That is, go to Equator (or better go to Euador) and around March 20 (or 21), the Sun is exactly over the equator and day and night are same. That is your equinox. Wait until next equinox and you would have waited a Tropical Year at Ecuador.

365.25964 days : Now Earth is *not* in a perfect ellipse with Sun at its perfect center. I will take the example of perigee and apogee to explain. Just like C3 was launched in an orbit where at perigee it is closest to earth and at apogee it is furthest from earth, similarly, Earth is at perihelion when it is closest to Sun and at aphelion when it is furthest from Sun. So take the point when it is at aphelion (or at perihelion, whichever you prefer). After 365.25964 days, it will be back at the same point. I forget what it is called, but do remember that this is increasing every year by slightly more than ~1/1000 of a second.

----

Above are GK questions which Ronnie Screwwala may ask in his Kaun Banega Jitender Show. Answering them is not important. What matters is understanding the principle behind them.

So if any treatise calculated (or attempted to calculate) the above various "Years", it means that they understood the concept of:

1. Earth revolution around Sun.
2. Earth's axial tilt relative to Sun.
3. Earth's ellipse not being perfect.

And that understanding is more important. Since it also means, that Sun and not Earth is center of the Solar system (and stating that cost Galileo his freedom! and almost near death) and further, the solar system is just another of those solar systems in the Universe. And that is profound.

[disha]

365.24219 days-----------------?
365.25964 days-----------------Perihelion to perihelion?

365.24219 days----------------- > Tropical Year.
365.25964 days-----------------Perihelion to perihelion. Or Aphelion to aphelion

[disha]

365.24 is the year around the sun. from any arbitary point, back to the same point

Tropical Year, but not related to movement around the sun, but earth doing Surya Namaskar twice a year.

[Amber G.]

365.24 is the year around the sun. from any arbitary point, back to the same point

Yes, this is called "tropical year" -- basis of our Gregorian Calendar which most of the world uses. Here a year (97 leap years and 303 ordinary years in 400 years -- every fourth year is a leap year except Year 1700,1800,1900 -- Year 2000 is a leap year) is 365.2425 days, pretty close to actual value of 365.2422 days.
But here 'same point' is not fixed (wrt to stars), but makes a full cycle in about 26000 years.
(See the math dhaga - I have explained it in more details -- any good text book will also do the same ... Hope this helps)

[bala]

I know we are talking about the Moon and Chandrayaan-3. But Surya Siddhanta has been in discussion, especially nakshatra. The ancient Vedics used the nakshatra as a reference point which appears rather fixed. Our planet system moves with respect to them. No other civilization ever came up with such a system. The Mayasura Surya Siddhanta provides a conjunction of planets, moon, sun at specific location and dating this occurance using modern astro software indicates a date of 22 Feb 6778 BC. Many authors have re-compiled Surya Siddhanta over the years.

There is a temple in the South of India called Tirupperunturai Temple. On the ceiling there are carvings of the 27 nakshatras that have been in Vedic times. The lettering on each panel indicates the nakshatra e.g. Uthram, Poorva, etc. Each nakshatra depicts a cluster of stars arranged in specific pattern and each of them is different. So the nakshatra is a cluster of stars, not one.

[Amber G.]

Tropical Year, but not related to movement around the sun, but earth doing Surya Namaskar twice a year.

????

Just to be clear: Of course, it is related to earth's (or moon's) movement around the sun. One complete rotation. Just the point of reference (vernal equinox) is not fixed (wrt to stars) but moves slightly during this time -- about 1 degree in 72 years.

Each year has two equinoxes (spring, and fall when day/night are equal).. but that's NOT the issue. Point is the position of the equinoxes with respect to stars moves -- one revolution in 26,000 years.

Earth's axis is tilted about 23.5 degree -- but important part here is *not* simply the tilt, or you have two equinoxes a year, BUT the direction of the axis is not fixed but it precesses (like a top) in 26,000 years. This is mainly due to earth being not a perfect sphere and moon's orbit is slightly tilted with respect to ecliptic.

There is a post in Math dhaga ... also any good textbook will help to understand the basics.

[RCase]

Came across this youtube video. Will help visualize the sun ecliptic and the moon's orbit plane. Good explanation of Rahu and Ketu.


https://www.youtube.com/watch?v=-3L82nJWVUU

[Amber G.]

^
Now, from Earth, moon has phases. That is it goes from full moon to new moon to full moon. To be ultra-precise it is better to measure from waning crescent to waning crescent. But it is easier to explain as a full moon to new moon to full moon cycle. That is ~29.5 days. That is also called Lunar Month. I would call that as Synodic Month.

This "Ultra-precise" phrase is quite odd - given that a synodic month - can vary as much as 7 hours from its mean value of 29.53059 days value. (It varies between 29.2 to 29.9 days as any panchang/calendar/almanac or any body who just observes moon can tell you).. so "better to measure from waning crescent to waning crescent" is sort of irrelevant to put it mildly,

( Do you remember Hindu calendars - there are adhik months (additional) and (ksya) months (these are rare but can happen.. where the lunar month - hindu titihis go from new moon to new moon - does not fit in months (which are based on solar position)..)

(Now simple but challenging question is why it varies so much? --- The math is not complicated, just need basic understanding)

[Amber G.]

Back to Chandrayaan -
But first some good news..
- Just heard that Dr K Sivan the Former Chairman of ISRO has been appointed as Head of Board of Governor of IIT Indore.
Great Intiative to led our Country in Science & Tec.
And:
In US: Congress has given no objection to Biden's decision to pursue the GE jet engine deal with India, that includes tech transfer, manufacturing of jet engines in India and licensing.

Mission Sun set for lift-off

ILSA payload on Chandrayaan 3 Lander -- the first Micro Electro Mechanical Systems (MEMS) technology-based instrument on the moon --
has recorded the movements of Rover and other payloads. (Posted but reposting..)

Additionally, it has recorded an event, appearing to be a natural one, on August 26, 2023. The source of this event is under investigation.

[Jayram]

Podcast discussing Chandrayaan-3 and also Luna-25

https://mainenginecutoff.com/podcast/257

Interesting observation on the precise orientation of the ch3 lander achieved at landing to maximize solar light available for operations as well as hopefully wake up from Lunar night. That's why the space community was waiting on the photo release of the lander and ISRO obliged by releasing a picture exactly at noon to show the precision of the orientation. Just a lot of kudos on the ISRO missions transparancy/accessibility to the space community as compared to the Luna -25.

[bala]

Dr K Sivan the Former Chairman of ISRO has been appointed as Head of Board of Governor of IIT Indore

Tis great on appointment. I however feel that all retired ISRO people have a ton of stuff to contribute. The GOI should retain them (the leaders and people with solid contributions) in some advisory capacity on Space. They can chart out future stuff and also provide youngsters in ISRO their knowledge/experience. Just to see these people fade away is heart-breaking because the retirement age is too soon compared to the longer life expectancy.
Same goes for DRDO, BARC, HAL, etc.

[Amber G.]

Nasa orbiter spots Russia's Luna-25 crash site on Moon
The new crater measures approximately 10 meters in diameter

[sanman]

Podcast discussing Chandrayaan-3 and also Luna-25

https://mainenginecutoff.com/podcast/257

Interesting observation on the precise orientation of the ch3 lander achieved at landing to maximize solar light available for operations as well as hopefully wake up from Lunar night. That's why the space community was waiting on the photo release of the lander and ISRO obliged by releasing a picture exactly at noon to show the precision of the orientation. Just a lot of kudos on the ISRO missions transparancy/accessibility to the space community as compared to the Luna -25.

So in a similar vein, there was criticism or puzzlement at Russia not similarly releasing enough information to make their spaceflight trajectory more visible and verifiable, to help validate it as a demonstration of technological capability. I'm wondering if this oversight/deficiency was due to their seemingly last-minute rush to get their mission launched and landing on the Moon ahead of Chandrayaan-3.

I thought Luna-25 had been scheduled to launch on Aug 18th, and instead I found it had launched on 16th, a couple of days early.
I don't even know how long ago the launch date had been announced. It all seemed curiously last-minute.
I know that mission had been long in the making, and suffered various delays. Yet it seemed suddenly rushed forward at the end.
Were the Russians deliberately rushing Luna-25's launch to get a leg up on India? If so, why? Their space program is far more advanced than ours. What did they feel a need to prove? Their list of space exploits is very long and accomplished. We are not in the same league.

[ArjunPandit]

Dr K Sivan the Former Chairman of ISRO has been appointed as Head of Board of Governor of IIT Indore

Tis great on appointment. I however feel that all retired ISRO people have a ton of stuff to contribute. The GOI should retain them (the leaders and people with solid contributions) in some advisory capacity on Space. They can chart out future stuff and also provide youngsters in ISRO their knowledge/experience. Just to see these people fade away is heart-breaking because the retirement age is too soon compared to the longer life expectancy.
Same goes for DRDO, BARC, HAL, etc.

in my little opinion, they need to be more on teaching/R&D side rather than admin sides, they have a lot more to contribute in bridging the gap

[csaurabh]

Tis great on appointment. I however feel that all retired ISRO people have a ton of stuff to contribute. The GOI should retain them (the leaders and people with solid contributions) in some advisory capacity on Space. They can chart out future stuff and also provide youngsters in ISRO their knowledge/experience. Just to see these people fade away is heart-breaking because the retirement age is too soon compared to the longer life expectancy.
Same goes for DRDO, BARC, HAL, etc.

in my little opinion, they need to be more on teaching/R&D side rather than admin sides, they have a lot more to contribute in bridging the gap

There is a big problem in appointing retired head honchos to admin positions. They tend to be travelling a lot to attend conferences or give lectures etc. Meanwhile the administrative work keeps piling up. Our institutions are organized to concentrate power into top guys only. Sometimes you need a director approval to buy a plastic bucket (exaggerated but you get the point ). If they are absentee, the processes drag to a stop.