Chandrayan-2 Mission

[Amber G.]

Finally some nice picture from CY2's IIRS -- See the first illuminated image of the lunar surface acquired by IIRS.
IIRS is designed to measure reflected sunlight from the lunar surface in narrow and contiguous spectral channels.)


More at: https://www.isro.gov.in/update/17-oct-2019/chandrayaan-2-begins-spectroscopic-studies-of-lunar-surface
>>>
Preliminary analysis suggests that IIRS could successfully measure the variations in the reflected solar radiation that bounces off the lunar surface from different kinds of surface types, namely, crater central peaks (e.g., Stebbins), crater floors (e.g., Stebbins and Sommerfield), very fresh reworked ejecta associated with small craterlets within the crater floor of a large crater (e.g., Sommerfield) and also the sun-illuminated inner rims of craters (e.g., Kirkwood). The variations in the spectral radiance are primarily due to the mineralogical/compositional variations that exist in the lunar surface and also due to the effect of space weathering. More detailed analysis that follows, is expected to yield important results on the heterogeneity of lunar surface composition.

[Amber G.]

^^^ The main objective of IIRS is to understand the origin and evolution of the Moon in a geologic context by mapping the lunar surface mineral and volatile composition using signatures in the reflected solar spectrum.

[Kanson]

Any description/ info on the last pic?

[Amber G.]

Meanwhile about NASA's LRO pass over Vikram's landing site:
They say the lighting condition was good. Shadows are shorter. They are doing "rigorous" search (before/after comparison of millions of pictures). Probably take a few more days before lot of pictures come out in the newspapers.

What is the most "official" coordinates of Vikram's resting place? (Has ISRO published the coordinates where it said it saw it in thermal imaging). I haven't been able to see it a ISRO site.

For record, this the approximate area, as posted before. The image is taken by LROC - before Vikram's landing).

[ramana]

AmberG, Any legend to the colors of the X-Ray map?

Also if the X-Rays are generated by reflections of Sun's rays, that is lots of high energy radiation!!!

What atomic reactions generate such high energy X-Rays?
Are these reflected rays like fission going on or just being bounced off the surface?

Thank nature for providing the atmosphere on Earth for Life to survive.

[Amber G.]

Any description/ info on the last pic?

Kanson - These pictures are few which I saved before. To be clear, these are *not* from Chandrayaan's IIRS but are from NASA's data (which are available). I can put more details, when I see my notes but the last picture (with phases of moon) was, I believe - will check and correct if need be - is from NASA/JPL's NIMS (Near Earth Mapping Spectrometer). Kind of old picture. (Can do a image search on nasa.gov site)
Added later:
More: for the pictures:
>>>

Earth is toward the left, and the lunar north pole is near the terminator, upper right. The dark regions to left and below in the black-and-white image at upper left, are lunar Maria, including Mare Imbrium at upper left, Serenitatis and Tranquillitatis, lower left center, and the circular basin to the right is Crisium. The bright areas ringing Crisium and dominating the center of the images are the heavily cratered and mountainous lunar highlands. The black-and-white image used infrared wavelengths just beyond the visible deep red. The false-color map images (upper right and lower right) show the relative strength of silicate-rock absorption of near-infrared sunlight, at about 1-micron wavelength. Blue areas show stronger absorption and generally indicate materials with more pyroxene and olivine (iron-bearing silicate materials), while yellow indicates less absorption, due to original compositional variations. In young fresh craters, absorptions are also stronger due to the absence of meteorite-impact effects. Outlines of previously defined geological units are superimposed in the lower right image. Note correlation with the Maria/highlands features in the black-and-white image. The preliminary mineralogical map at lower left uses infrared band shape and intensity to visualize variations in pyroxene and olivine. Blue is related to low-calcium pyroxene, while green and red indicate high calcium and the iron/magnesium content of pyroxene, as well as olivine.

>>>

The first picture, again I believe, is from from NASA's LROC. I like the colors because it helps us in visualization. -- They suspect a huge massive iron deposit around the center of blue region (The picture, if I remember correctly is South Pole Aitken basin area)

[Amber G.]

AmberG, Any legend to the colors of the X-Ray map?

Also if the X-Rays are generated by reflections of Sun's rays, that is lots of high energy radiation!!!

What atomic reactions generate such high energy X-Rays?
Are these reflected rays like fission going on or just being bounced off the surface?

Thank nature for providing the atmosphere on Earth for Life to survive.

The X-ray picture is from "An Introduction to X-ray Astronomy" presentation. You can get legend and much more detail from here:
ttps://heasarc.gsfc.nasa.gov/docs/xrayschool-2005/talks/arnaud_intro.pdf

You may already know but short answers to your query -
- Sun radiates EM radiation, like all hot surfaces (Sun's surface temperature is around 6000K), in *all* wavelengths.
Most (percentage wise) is in visible spectrum but sun is quite bright in x-rays (or microwaves, infrared or even radio waves) too.


(Since sun is quite big and close by - total energy even in x-ray wavelengths is quite large)

- Most of "brightness" is from reflected light (both in visible and also in x-rays) from sun by moon. (Some is coming from cosmic rays - or reflected cosmic rays from moon)

- Nothing like fission etc is going on surface of the moon. They are jus "bouncing off" from the moon. Of course, like all surfaces, there is some "fluorescence" ..depending on the surface there may be some frequency change and characteristics of the surface elements will be there in the reflected secondary x-rays. (This is of course, very similar to a red object reflecting more light in red region and how we see colors in the reflected/scattered light).

Yes, we are fortunate that most of the harmful radiation is absorbed by our atmosphere. Also due to earths magnetic field (earth's spin) other charged cosmic ray particles gets deflected.

[ramana]

Thanks for the detailed explanation!!!
Ok so its mostly reflected x-rays and some secondary x-ray emission.

I know the basic Roentgen theory of x-ray emission.

[Amber G.]

^^Thanks.
One important part as I posted before (for example here that apart from - High Resolution Camera (OHRC) other instruments on CY2 are top class and important and seem to be working fine. They released nice pictures from OHRC and we know TMC-2 is working fine. Similarly CLASS and XSM (x-rays).. and now IIRS (infrared). (That leaves only radio spectrum, hope we hear about that soon.)

IIRS was the first one, per ISRO, to "see" Vikram (thermal image) but ISRO has not given much details then.

Interesting part, as I noted before, other frequencies (X-rays and Infrared - CLASS/XSM/IIRS) help locate metal/chemical composition etc so it may help to locate Vikram too , as it will give more data in other spectrum.

***
Hope they publish data from DFSAR and tell us it is working nicely... Hope CY2 makes many important discoveries regarding water before NASA's VIPER - water sniffing rover at the South Pole (in 2022).

[Amber G.]

Also in the news: Japan's 1st Moon Rover to Touch Down in 2021
Link: https://www.space.com/japan-first-moon-rover-astrobotic-peregrine.html

[Amber G.]

Down the memory lane -

11 years ago Chandrayaan-1 was launched! (Oct 22 - 2008). It found water on the moon!

The Moon Mineralogical Mapper (M3), an infrared spectrometer, detected not just water but it could also differentiate between ice, liquid water and water vapor based on how the surface absorbed infrared light. M3 confirmed that the Moon hosted water once and for all.

Distribution of water ice on the lunar poles mapped by Chandrayaan 1 instrument M3. ( Photo Source NASA)


This image shows the distribution of surface ice at the moon’s south pole (left) and north pole (right), as detected by M3 on CY-1,. Blue represents ice locations, and the gray scale corresponds to surface temperature, with darker gray representing colder areas and lighter shades indicating warmer ones.(Image: © NASA)

[Amber G.]

One important part ... High Resolution Camera (OHRC) other instruments on CY2 are top class and important and seem to be working fine. They released nice pictures from OHRC and we know TMC-2 is working fine. Similarly CLASS and XSM (x-rays).. and now IIRS (infrared). (That leaves only radio spectrum, hope we hear about that soon.)
<snip>
Hope they publish data from DFSAR and tell us it is working nicely... Hope CY2 makes many important discoveries ....

Looks like they listened and Here it is! From DFSR.

Chandrayaan-2 Orbiter’s DF-SAR has been operated in full-polarimetry mode- a gold standard in SAR polarimetry, and is the first-ever by any planetary SAR instrument.

Initial imaging and observations by Chandrayaan-2 Dual-Frequency Synthetic Aperture Radar (DF-SAR)

Wow!

A L-band fully-polarimetric, 20m slant-range resolution image of Pitiscus-T crater. The image is a color composite of different transmit-receive polarization responses of the imaged region.



And



11 Years after CY-1.

Source: ISRO

[Amber G.]

^^^ (Some background and other information from ISRO about these photographs):

- Synthetic Aperture Radar (SAR) is a powerful remote sensing instrument for studying planetary surfaces and subsurface due to the ability of the radar signal to penetrate the surface. It is also sensitive to the roughness, structure and composition of the surface material and the buried terrain. And you don't need sunlight .

Previous lunar-orbiting SAR systems such as the S-band hybrid-polarimetric SAR on ISRO’s Chandrayaan-1 and the S & X-band hybrid-polarimetric SAR on NASA’s LRO, provided valuable data on the scattering characterisation of ejecta materials of lunar impact craters. However, L & S band SAR on Chandraayan-2 is designed to produce greater details about the morphology and ejecta materials of impact craters due to its ability of imaging with higher resolution (2 - 75m slant range) and full-polarimetric modes in standalone as well as joint modes in S and L-band with wide range of incidence angle coverage (9.5° - 35°). In addition, the greater depth of penetration of L-band (3-5 meters) enables probing the buried terrain at greater depths. The L & S band SAR payload helps in unambiguously identifying and quantitatively estimating the lunar polar water-ice in permanently shadowed regions.



A convenient approach towards discerning the radar information is to prepare images using two derived parameters, ‘m’ the degree of polarization and ‘ä’ the relative phase between the transmit-receive polarized signals.

Figure 1 shows the m-ä decomposition images of the first datasets acquired over lunar south polar regions in L-band high-resolution (2m slant-range resolution) hybrid polarimetric mode. It produces colour composite images where ‘even-bounce’, ‘volume or diffused’ and ‘odd-bounce’ scatterings of a pixel are represented in red (R), green (G), and blue (B) image planes, respectively. It is important to note that the obtained resolution is one-order better than the earlier best by a lunar-radar.

[Amber G.]

Meanwhile, the LRO's last pass, I have not heard anything about locating Vikram. According to Noah Petro, NASA’s Lunar Reconnaissance Orbiter project scientist, “I suspect, based on what they’ve said, that it could be just that we’re not looking at the right place or we just can’t see it because of the illumination. Until we know more details about where it is, it’s going to be very hard for us to find it.”

Due to the fact it is near the south pole .. lighting, though better than last time, is never too good (max elevation about 20 degrees) and there are shadows.

(Some were sort of grumbling that India isn’t exactly forthcoming with location details - or ISRO itself doesn't know what happened in the last few moments. Anyway LRO makes a pass every month and LRO is going to look (that's it's job).. I think lighting is even better next month's flyby. .It makes a pass about every month)... Similarly CY-2 should be making a good flyby (again once every month or so) so it should be looking too)

[chetak]

OT but couldn't find the thread to post this


twitter

Imagine how cool it would be if we could see in every wavelength! Here’s what the sun looks like in different wavelengths (NASA pic)

[Vayutuvan]

physics thread?

[sanjaykumar]

Yeah, I've wanted a Hydrogen alpha filter for my scope. But if I see Savitra in all his glory, life may seem mundane thereafter.

[UlanBatori]

I thought sunlight spectrum peak is dominantly around green-yellow. All the others are low contributors.

[ashbhee]

I think this is what ISRO should do.
They should not wait for 3 or 4 years to launch Chandrayaan - 3.
Just launch lander only mission, Virkarm - 2. It should be a replica of Vikram - 1 plus any changes that needs to be done for the landing mechanism.
Since it is a repeat mission, it can be done quickly and cheaply. Since it is much lighter mission it can be launched using PSLV or even the new SSLV.

[Varoon Shekhar]

^
Absolutely! Chandrayaan-3 should be totally independent of the lander/rover issue( though it can have one too). ISRO should build another lander and rover as quickly as possible and launch it, perhaps even use the services of a non-Indian vehice if an Indian one is not available. They shouldn't think that they must have a sophisticated orbiter as part of the mission. Team Indus/Axiom Labs is also building a lander and rover, and are planning to launch it on board a US rocket next year. Would be amazing if they can do it!

[arvin]

I think this is what ISRO should do.
They should not wait for 3 or 4 years to launch Chandrayaan - 3.
Just launch lander only mission, Virkarm - 2. It should be a replica of Vikram - 1 plus any changes that needs to be done for the landing mechanism.
Since it is a repeat mission, it can be done quickly and cheaply. Since it is much lighter mission it can be launched using PSLV or even the new SSLV.

PSLV fourth stage PS4 can only deliver till parking orbit. It is restartable, but wont have the feul for the 5 gravity assist maneovres to send the lander only config to moon capture orbit. Something like fregat would be required which we dont have.
Chandra yaan 2 was a closely coupled design in which lander piggy backed on the orbiter.
Lander only has feul to do the coarse and fine breaking after its drop from 100 km orbit.

[YashG]

NDTV will publish it, they always like to publish the most gory images after disasters and terror attacks with no consideration for victims' relatives.

That spot has to go to IndiaTV. Nobody can beat India TV on insensitive coverage!

[Varoon Shekhar]

Chandra yaan 2 was a closely coupled design in which lander piggy backed on the orbiter.
Lander only has feul to do the coarse and fine breaking after its drop from 100 km orbit.

Thanks for the info. A few of us are over-eager( with justification) to see another lander-rover combination go up as soon as possible. Without considering whether the lander in question could, sans orbiter, circle the earth multiple times, enter into lunar trajectory, undergo lunar capture, and then de-orbit, and all of this using the onboard fuel. However, couldn't a Vikram Lander go up sooner on a French, Russian or American vehicle? Would cost India a bit, of course.

[arvin]

Sure it would cost a bomb and north block will have a massive heart attack.
I think a standalone lander mission cant be done using a PSLV XL, since feul itself will take around 1500 kg. vikram had 700 kg feul only for landing purpose. orbiter had 1700 kg feul. Assuming half is for moon orbital insertion and half for station keeping, feul load itself comes to max lift capacity of the vehicle. Leaving little room for experiments or anything else.

[prasannasimha]

https://www.isro.gov.in/update/31-oct-2 ... -exosphere

[prasannasimha]

Just not making the orbiter will not cut it as to reach the moon the orbiter will be the system that will do the multiple orbiter elevation etc and then and only then can it detach and lander can land.

[Amber G.]

https://www.isro.gov.in/update/31-oct-2019/detection-of-argon-40-lunar-exosphere

Thanks for posting this. So now all the payloads on the orbiter are returning awesome results!

The CHACE-2(neutral mass spectrometer-based) payload aboard the CY2 orbiter has detected Argon-40 from an altitude of approximately 100 km.

(For details see the ISRO's link given above.

Here's the schematic of the origin and dynamics of Argon-40 in lunar exosphere:


Also:

CHACE-2 can detect constituents in the lunar neutral exosphere... it has detected 40Ar in the lunar exosphere from an altitude of ~100 km, capturing the day-night variations of concentration. 40Ar being a condensable gas at the temperatures and pressures that prevail on the lunar surface, condenses during lunar night. After lunar dawn, the 40Ar starts getting released to the lunar exosphere (blue shaded region in figure).

Variation of Argon-40 observed during one orbit of Chandrayaan-2 during dayside and nightside of the Moon. The observed partial pressure has to be refined for the background and other effects to infer the density of lunar exospheric argon. The observations when Chandrayaan-2 was on the nightside is indicated by the black solid rectangle at the top of the panel and the two vertical dashed lines. Being in a polar orbit, Chandrayaan-2 enters the dayside of the Moon crossing the north pole, traverses through the dayside and enters the nightside after crossing the southpole.

Also, (see my earlier post) just a few days ago ..ISRO released several images gathered by Dual-Frequency Synthetic Aperture Radar of the moon that show different types of craters... Exciting times for science.

[suryag]

AmberG ji what is the significance of this discovery ?

[UlanBatori]

coldest region in the entire solar system

Pretty broad statement, somdevji. Neptune / Pluto poles are probably not very warm either. Other planets also have moons as well, and some that are locked-in. Freezing point of argon is only -189 C which is relatively warm so u are right that any argon should be found in frozen form.

[Amber G.]

AmberG ji what is the significance of this discovery ?

Here are some of the things which I think makes it all exciting ..
- All payloads on CY2 seem to be working perfectly. This is a good news. (They have not found issues like heat shielding etc which shortened the life of CY1's electronics).
- Virtually all of the payloads are state of the art -among the best.
- Most important is *huge* collection of data in coming years.. we will have best detailed maps - in many wavelengths of the moon for further landings and exploration. This includes radar maps (seeing under ground) and most detailed mineralogical map of the entire moon.
- More information about ice/water on moon.
- Study of solar flares to some extent (to help gather data of it's effect on our own communication/GPS sats) (We may have more, obviously with Aditya-1 or more earth-orbiting sats in the future - but this may be more useful as lot of such data from NASA etc are classified/not_shared at present)..
- Most important part are discoveries which are not expected at present but we will find in coming years as CY-2 may last a long time.

****
Also these are dual technologies - these multi-spectrum eyes in the sky will be *VERY* helpful in monitoring our friends...and those extremely accurate inertial guidance system can be used for pin-point surgical strikes.


- Of course we have learnt a lot from Vikram-1 crash landing too.. next time it will be better.

****

[Amber G.]

Lunar poles are the coldest region in the entire solar system and hence Argon is probably in a frozen state. Argon released elsewhere in the moon could migrate to the poles which acts as argon trap. The Apollo mission samples had traces of Argon

Argon on earth's pressure freezes around -190 C, and becomes liquid around -185 C..but at moon's atmospheric pressure things are a little different.. but see my note#1 anyway)



Bur this is sort of academic.. as ISRO's article says there are about 10^4-10^6 molecules / cm3 .. this makes it less than 1 TRILLIONth abundance than say that of earth anyway... (Argon on Moon is sort of generated by radioactivity of K40 in the crust so there is always some supply while some molecules leaves moon -as it has relatively low escape velocity)..

BTW Moon's poles are NOT the coldest regions .. at south pole the average temperature is about -13 C .(warmer than our Antartica ). Even at night -and in craters- it is ( about -175C) much above Argon's freezing point.

Note#1 : Even at earth's pressure, Argon will NOT become liquid let alone a solid .

Slightly OT but if you are interested in phase diagram of Argon..(To see at what pressure the phases change) here it is:

[UlanBatori]

Somdevji:

I think material that is buried at a depth, even in a place with 1/6 the surface G of Earth, will be at significant pressure, due to the weight of stuff above it. This is why crude oil, when opened to atmospheric pressure using a drilling core, shoots up above the surface.

For instance if material has a density of 2650kg/m^3 (SiO2), than at a depth of 1m and 1/6G, the pressure will be 2650 x 1 x 9.8/6 = 4328 N/m^2. In the middle school textbooks the formula is given as h * d * g.

At 10m, the pressure will be 43280 N/m^2, which is about 44% of Earth atmospheric pressure. 10m below the lunar S. Pole, it will be nearly quite as cold as the surface since there is little conducted heat to warm it up and little internal heating from the Moon's center.

Any substance delivered during the course of an impact, is likely to have penetrated to quite some depth (of course the collision would have generated much heat). But if ice could have been delivered by impact, so could other frozen substances. If it went 50 meters deep and the crater collapsed on it, it would be at more than twice atmospheric pressure.

All very rough calculations: Moon material is not all SiO2 so my density is only correct maybe to 1 decimal place, and Moon's gravity is not **EXACTLY** 1/6 of Earth's, but that is the best I can do from mental calculations. Ppl with textbooks and charts can derive these to several decimal places (great!), but assuming that argon, water ice is lying in pools on the surface is perhaps not very realistic even to zeroth order, sorry.

[Amber G.]

. The Apollo mission samples had traces of Argon

Apollo 17 actually found Argon in Lunar exosphere too. Studying Nobel gases in Lunar exosphere is was one of *very* interesting and important activity by other missions.. done mainly by CY-2 type neutral mass spectrometers. Chandrayaan-1 also accumulated lot of useful data (shared in scientific community). In fact He, Ne and Ar all are there and how these noble gases are distributed around the moon's exosphere and how its concentration is distributed with respect to time (local lunar day/night) and position tells us lot about lot of things...

If there is interest, I may post something here (or in physics dhaga) but it may be too technical.

[Amber G.]

^^^ Added later..

AmberG ji what is the significance of this discovery ?

If you are wondering about the significance of Argon (vs how good CY2's NMS is) specifically see the above post.
As said, NMS used to study noble gases for Moon's exosphere is quite significant. For example He, Ne, Ar all are found (and considered significant discoveries when found) on Moon's *very* thin atmosphere. They studied this starting with Apollo through CY1 (and many/most other lunar orbiters). As these gases are inert - their movement are less effected by chemical properties... Among other things, it helps us understand Solar wind (which contributes to He ions).. distribution of radioactive sources on the surface .. etc..))..For example Apollo 17 found that night time concentration of He was much higher (10x or more) than daytime .. resulting into some more understanding of some phenomena.

Just to give an example: CY-1 (and other orbiters ) data revealed that Ar density peaked when the spacecraft was overflying the
45° longitude (near western maria region) -- after making adjustments for night/day densities ..that correlated with high potassium deposit (and some other rare earth metals) etc in those regions..!!!!

[chetonzz]

i was looking at this video...

https://www.youtube.com/watch?v=gGzdgpeZ67I&t=140s

is it possible that, the "fatal Pirouette" part of the video could be the reason behind 'vikram lander' crash?











in HD images of Lander from ISRO website, there is no LEM RCS system like thrusters [4 sets of (4 = 2 horizontal+ 2 vertical)]...
thus the absence of counter-torque?

[kit]

CHANDRAYAN 3

https://www.indiatoday.in/science/story/chandrayaan-2-another-moon-landing-vikram-isro-k-sivan-1615073-2019-11-02

[ramana]

That "piroutte" was what we were discussing early on.
The thrusters were not at different planes to provide recovery moment once the lander started rolling.

Sad they introduce new terms when nomenclature already exists.

Let's wait for ISRO report.

Also the author is wrong in his nomenclature.
A pirouette is dance maneuver where the ballet dancers spins in vertical axis and moves horizontally.
This would be falt spin in aero terms.
What the Vikram lander encountered was a tumble that is spin along lateral axis.

[Varoon Shekhar]

https://www.isro.gov.in/update/13-nov-2 ... al-results

Terrain Mapping Camera-2 (TMC-2) is a follow-on of the TMC on-board Chandrayaan-1. TMC-2 provides images (0.4μm to 0.85μm) at 5m spatial resolution & stereo triplets (fore, nadir and aft views) from a 100 km orbit for preparing Digital Elevation model (DEM) of the complete lunar surface.

The triplet images from TMC-2 when processed into Digital Elevation Models, enable mapping of surface landform morphologies. These include

[Amber G.]

^^^ Pictures from above:

(Topographic Mapping Using TMC-2 of Chandrayaan-2: Initial Results
Terrain Mapping Camera-2 (TMC-2) is a follow-on of the TMC on-board Chandrayaan-1. TMC-2 provides images (0.4μm to 0.85μm) at 5m spatial resolution & stereo triplets (fore, nadir and aft views) from a 100 km orbit for preparing Digital Elevation model (DEM) of the complete lunar surface.

The triplet images from TMC-2 when processed into Digital Elevation Models, enable mapping of surface landform morphologies. )

[suryag]

No word yet on the lander ?