Chandrayan-1 moon mission

sumishi
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Re: Chandrayan-1 mission launched succesfully

Postby sumishi » 02 Nov 2008 08:46

disha wrote:I can also photoshop the image of moon and boost the saturation to give "clues" ... will it be scientifically acceptable? Will it be useful? It is basically a pretty picture [and confirmation of] what we already know! Not what we want to know. Will it give for example the Iron mineral distribution on moon? No those rust colored parts is not Iron Oxide! So what is the blue colored region? Of course it is a deeper material and shows up gray on a high res B&W. Is it original lava? What is it? What is its mineral content? What is the mineral distribution of that content? How deep does it go? How was it formed? How is it being transformed? What are the processes in place to transform them?

Fact is, if even a clueless noob like me can ask those questions, it means that the larger scientific community is salivating to ask more and seek even more answers! A pretty picture will not cut it, even if it is printed in Scientific American!


I posted that as an interesting link, nothing more, and the organisation itself claims that the photograph has been made more vivid, and gives "clues" as to the mineral distribution, nothing more. One should not take such an exception to it. Of course, hugely more information is required, but if we go by the logic of clues being worthless, the entire science of deduction is called into question (I hear the fictional Holmes stirring in his grave) :)

And. BTW, Scientific American is not American Scientist (please disregard this statement if you used Scientific American just to prove a point) :)

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Re: Chandrayan-1 mission launched succesfully

Postby prashanth » 02 Nov 2008 15:40

harbans wrote:
If there's nothing there, than the 100 million USD payload that NASA has piggybacked on Chandrayaan has possibly a tinker bit of C4 to finish Chandrayaan at an appropriate time.

I'm actually a bit surprised that NASA invested 100m USD on one of it's 2 payloads. Thats an awful lot of faith to put in a mission that costs just 85m USd for India. Major Earth remote sensing satellites for launch India charges 10-11 million USD..(Italian one last year for example). I agree satellites do cost, but putting 100 m USD on a 1st Indian lunar mission is very optimistic for NASA..this will be the SINGLE biggest investment anyone has ever externally made in India's space programme.


Highly probable. One the one hand US does not allow any satellite that has US' components in it to be launched by Indian rockets. Here they give us a 100 million dollar mini-SAR, which is a highly sensitive instrument. Israel used the same tech for its spy sat. Hope ISRO is careful.

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Re: Chandrayan-1 mission launched succesfully

Postby SSSalvi » 02 Nov 2008 16:42

p_saggu wrote:Can some guru clarify this.
The chandrayaan's camera that took those BW pics of the earth has a 5m resolution. Is resolution dependent on the height of the spacecraft from the surface? What I mean is that if CY is say at a 200 km altitude, it could identify a 5m object clearly, maybe if it got closer it could have a better resolution?

I hope the Chandrayaan takes pictures of NASA's Apollo moon landings and puts the conspiracy theories to rest once and for all. Is it possible with these camera resolutions?


5m resolution with the planned height from the surface of the moon. Surely the resolution is a fuction of height.

With a 5m resolution you can't detect any leftovers from Apollo.. including the big lander ( used for return from moon ) had it been on moon today.

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Re: Chandrayan-1 mission launched succesfully

Postby Shankar » 02 Nov 2008 17:20

in fact it will be quite easy for Chandrayan to detect Appllo luna left overs with 5 M resolution .Resolution of 5 M implies on board camera at 100 km will be able to distinguish two objects 5 meter apart irrespective of the size of the object .

and while at it some more trash which it can photograph -all the appollo left overs

An Apollo Lunar Leftovers Listing:
(A Work In Progress)
Leftover Item Quantity Missions Suspected Status Notes
S-IVB Saturn V Third Stages 5 A 13-17 Wreckage
Lunar Sub-Satellites 2 A 15-16 Wreckage Launched from CSM
Lunar Module Descent Stages 7 A 10-12, 14-17 A 10 Wreckage, Remainder Intact Includes Commemorative Plaque on 6 (A 11, 12, 14-17
Lunar Module Ascent Stages 6 A 11, 12, 14-17 Wreckage
Lunar Roving Vehicle 3 A 15-17 Intact With Stocked Tool Carrier, TV Camera, Communications Unit
Modularized Equipment Transport 1 A 14 Intact With Stocked Tool Carrier
EASEP+ALSEP (Early Apollo and Apollo Lunar Surface Experiments Packages) 1+5, At least 52 pieces A 11, 12, 14-17 Intact (Experiments and Support Elements, Including the Central Station and RTG Power Source)

S-Band Antenna Dish


2


A 12, 14


Damaged by Radiation


Provided TV and data signals
American Flags 6 A 11, 12, 14-17 Damaged by Radiation and Rocket Exhaust At Least One of Which is Lying in the Dust: A 11
EMU Backpacks 12 A 11, 12, 14-17 Intact
EMU Overboots 12 A 11, 12, 14-17 Intact
Cameras 5+11 A 11, 12, 14-17 Intact 5 Stand-Alone TV, 11 Portable Photograhic
Trashbags At least 7 A 11, 12, 14-17 Damaged by Radiation and Rocket Exhaust Various Waste & Packaging

Exposed Film Magazine


1


A 12


Intact

Memorials, Plaques, Badges, Insignia, Misc. At least 6 A 11 Intact, Flagstaff Damaged by Rocket Exhaust Piece of Wright Flyer, Gold Olive Branch, Miniature flags all 'free' nations inside the hollow U.S. flagstaff, Apollo 1 patch, 2 Soviet medals, memorial disc with microprinted letters from over 100 world leaders.
" At least 2 A 12 Intact C.C. Williams' Naval (Marine) Aviator Astronaut Wings, Al Bean's Astronaut Pin
" A 14 Intact 2 Golf Balls
" A 15 Intact Stylized Astronaut Figure, Memorial Plaque, Holy Bible
" A 16 Radiation Damaged Charlie Duke's Family Photo
" A 17 Intact Tracey Cernan's Initials

Multiple Sources

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Re: Chandrayan-1 mission launched succesfully

Postby Gagan » 02 Nov 2008 19:44

So ISRO maybe could be saying that the resolution of say x meters but not specifying the distance from which that resolution is arrived at.
I smell another chankiyan conspiracy here :twisted: (A-la Ashwathaama Haathi maara gaya)
Honestly in the first decade of the 21st century, Indian photographic abilities have reached to a level where we are now officially "claiming" a sub meter resolution of our satellite cameras. Most certainly ISRO's and India's abilities are much much more advanced...

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Re: Chandrayan-1 mission launched succesfully

Postby Rahul M » 02 Nov 2008 19:45

it is. :wink:

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Re: Chandrayan-1 mission launched succesfully

Postby Bade » 02 Nov 2008 19:54

in fact it will be quite easy for Chandrayan to detect Appllo luna left overs with 5 M resolution .Resolution of 5 M implies on board camera at 100 km will be able to distinguish two objects 5 meter apart irrespective of the size of the object .

That is incorrect. If the resolution claimed is 5m then it possibly cannot resolve/image objects less than that in size.It can still resolve a 1 m x 5m plank of material, but not two 1m x 1m objects separated more than 5 m apart.

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Re: Chandrayan-1 mission launched succesfully

Postby Bade » 02 Nov 2008 19:59

Gagan wrote:So ISRO maybe could be saying that the resolution of say x meters but not specifying the distance from which that resolution is arrived at.
I smell another chankiyan conspiracy here :twisted: (A-la Ashwathaama Haathi maara gaya)
Honestly in the first decade of the 21st century, Indian photographic abilities have reached to a level where we are now officially "claiming" a sub meter resolution of our satellite cameras. Most certainly ISRO's and India's abilities are much much more advanced...

Yes :mrgreen: of course. Remember IRS class satellites can do sub 1m resolution from 800km high orbit. So why was 5m resolution chosen from a much lower 100km orbit ?

Recently, Kaguya also went down to 100km orbit (maybe even Chang'e) after ISRO plans became known. So there is competition to get the best resolution image and declare a first. :twisted: So do not be surprised if we get to see better than 5m resolution imagery. Or maybe the ultimate chanakyian if you will be to keep sub 5m resolution imagery secret till someone else makes it their mission plan as well down the road. Till then, just enjoy the 5m resolution view for public consumption.

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Re: Chandrayan-1 mission launched succesfully

Postby Arun_S » 02 Nov 2008 21:00

SSSalvi wrote:
p_saggu wrote:Can some guru clarify this.
The chandrayaan's camera that took those BW pics of the earth has a 5m resolution. Is resolution dependent on the height of the spacecraft from the surface? What I mean is that if CY is say at a 200 km altitude, it could identify a 5m object clearly, maybe if it got closer it could have a better resolution?

I hope the Chandrayaan takes pictures of NASA's Apollo moon landings and puts the conspiracy theories to rest once and for all. Is it possible with these camera resolutions?


5m resolution with the planned height from the surface of the moon. Surely the resolution is a function of height.

With a 5m resolution you can't detect any leftovers from Apollo.. including the big lander ( used for return from moon ) had it been on moon today.

Yes 5m is a function of 100km orbit altitude.

As for seeing abandoned Apollo lander, its a metter of time resolution will drop to 1m for the world to see.

BTW Chandrayan's SAR can/will see the metal junk if there is one.

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Re: Chandrayan-1 mission launched succesfully

Postby Tamang » 02 Nov 2008 21:56


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Re: Chandrayan-1 mission launched succesfully

Postby Vivek K » 02 Nov 2008 21:58

The Chinese reaction is as expected. That must mean that we are doing something right!! :D

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Re: Chandrayan-1 mission launched succesfully

Postby Tanay » 02 Nov 2008 22:08




Tanay wrote:Oops, article on China space launch jumps the gun
The Associated Press
Published: September 25, 2008

BEIJING: Oops.

An article describing China's long-awaited space mission was launched Thursday hours before astronauts even left the launch pad.

The country's official news agency Xinhua posted an article on its Web site Thursday written as if the three astronauts had already been launched into space.

The Shenzhou 7 mission, which will feature China's first-ever spacewalk, is set to launch Thursday from Jiuquan in northwestern China between 9:07 p.m. and 10:27 p.m. (1307 GMT and 1427 GMT).

The Xinhua article is dated Sept. 27 — two days from now — and comes complete with an entire dialogue between the astronauts.

The piece titled "Sleepless Night on the Pacific, Sidelights on the Observation and Control of the 30th Lap of Shenzhou 7 Spaceship," which was available most of the day, has now been removed from the Xinhua Web site.

A staffer from the Xinhuanet.com Web site who answered the phone Thursday said the posting of the article was a "technical error" by a technician. The staffer refused to give his name as is common among Chinese officials.

The piece vividly described the rocket in flight, complete with a sharply detailed dialogue between the three astronauts.

Excerpts are below:

"First-level measurement arrangement!"

After this order, signal lights all were switched on, various data show up on rows of screens, hundreds of technicians staring at the screens, without missing any slightest changes ...

"One minute to go!"

"Changjiang No.1 found the target!"...

The firm voice of the controller broke the silence of the whole ship. Now, the target is captured 12 seconds ahead of the predicted time ...

"The air pressure in the cabin is normal!"

"Ten minutes later, the ship disappears below the horizon. Warm clapping and excited cheering breaks the night sky, echoing across the silent Pacific Ocean."






:rotfl: :rotfl: :rotfl: :rotfl:

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Re: Chandrayan-1 mission launched succesfully

Postby sumishi » 02 Nov 2008 22:34


Just now checked the n2yo website which is mentioned in the article, and is being brandished by the Chinese. As mentioned in this forum earlier by one of the posters that there was a discrepancy between what ISRO releases about CY's orbit, and the orbital data as shown in n2yo (it was till then still showing the 1st or 2nd orbit's apogee and perigee), it appears that as of now the site has finally updated its data points to the current orbit.

It seems the site is basically for tracking normal satellites, and so once the orbital datapoints are in, they do not need to be updated frequently. In case of CY's frequently changing orbits, it is understandable that there will be a lag in feeding in the new data. And the Chinese have latched onto this evidence :roll:
Last edited by sumishi on 02 Nov 2008 22:39, edited 6 times in total.

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Re: Chandrayan-1 mission launched succesfully

Postby svinayak » 02 Nov 2008 22:35

prashanth wrote:
harbans wrote:
If there's nothing there, than the 100 million USD payload that NASA has piggybacked on Chandrayaan has possibly a tinker bit of C4 to finish Chandrayaan at an appropriate time.

I'm actually a bit surprised that NASA invested 100m USD on one of it's 2 payloads. Thats an awful lot of faith to put in a mission that costs just 85m USd for India. Major Earth remote sensing satellites for launch India charges 10-11 million USD..(Italian one last year for example). I agree satellites do cost, but putting 100 m USD on a 1st Indian lunar mission is very optimistic for NASA..this will be the SINGLE biggest investment anyone has ever externally made in India's space programme.


Highly probable. One the one hand US does not allow any satellite that has US' components in it to be launched by Indian rockets. Here they give us a 100 million dollar mini-SAR, which is a highly sensitive instrument. Israel used the same tech for its spy sat. Hope ISRO is careful.

What is the chance that those mil cameras are tuned to see what they want rest of the world to see

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Re: Chandrayan-1 mission launched succesfully

Postby sumishi » 02 Nov 2008 22:50

sumishi wrote:

Just now checked the n2yo website which is mentioned in the article, and is being brandished by the Chinese. As mentioned in this forum earlier by one of the posters that there was a discrepancy between what ISRO releases about CY's orbit, and the orbital data as shown in n2yo (it was till then still showing the 1st or 2nd orbit's apogee and perigee), it appears that as of now the site has finally updated its data points to the current orbit.

It seems the site is basically for tracking normal satellites, and so once the orbital datapoints are in, they do not need to be updated frequently. In case of CY's frequently changing orbits, it is understandable that there will be a lag in feeding in the new data. And the Chinese have latched onto this evidence :roll:


A small question for orbital experts, if you please.
The updated orbit of CY in n2yo.com (perigee -- 582.3 km; apogee -- 262,004.5 km) shows a reading like:
--- altitude: 203,710km (a decreasing counter, i.e. approaching Earth)
--- speed: 14.97 km/s
Does this high orbital speed, at such a distance, make sense?

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Re: Chandrayan-1 mission launched succesfully

Postby SSridhar » 02 Nov 2008 23:02

sumishi wrote:Does this high orbital speed, at such a distance, make sense?


No.

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Re: Chandrayan-1 mission launched succesfully

Postby sumishi » 02 Nov 2008 23:15

SSridhar wrote:
sumishi wrote:Does this high orbital speed, at such a distance, make sense?

No.

Thanks SSridhar! So n2yo's datapoints may be in, but calculations are still faulty. :)

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Re: Chandrayan-1 mission launched succesfully

Postby vishwakarmaa » 02 Nov 2008 23:20

prashanth wrote:Highly probable. One the one hand US does not allow any satellite that has US' components in it to be launched by Indian rockets. Here they give us a 100 million dollar mini-SAR, which is a highly sensitive instrument. Israel used the same tech for its spy sat. Hope ISRO is careful.


The thing which pushed NASA to co-operate with ISRO was the realization that they might not only miss out on this valuable opportunity offered by India if they don't become part of Indian moon mission, but also it might lead them into isolation.

NASA has shown pragmatism by being co-operative with ISRO shedding its traditional shyness with sensitive technologies. Nobody can grow in isolation however big or strong he is. Ultimately, he needs to be humble to appreciate such a mission which is beneficial for future of humanity.

The point is, mini-SAR or big-SAR, it doesn't matter anymore. That era is over when few used to maintain monopoly over technology. Such monopolies doesn't help development of humanity. The participation of NASA although in a small and partial manner, shows the percolation of this understanding amongst them.

I am sure, in future missions, we will see NASA co-operating in a more confident and open manner.

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Re: Chandrayan-1 mission launched succesfully

Postby rachel » 03 Nov 2008 01:39

The Chinese should stick to what they do best, ie: making lead painted toys, posionous milk, photoshopped fake launches, and spreading disease (SARS) throughout the world.

It seems to me that that nation does nothing but spew poisons of various types throughout the world.

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Re: Chandrayan-1 mission launched succesfully

Postby rachel » 03 Nov 2008 01:39

The Chinese should stick to what they do best, ie: making lead painted toys, posionous milk, photoshopped fake launches, and spreading disease (SARS) throughout the world.

It seems to me that that nation does nothing but spew poisons of various types throughout the world.

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Re: Chandrayan-1 mission launched succesfully

Postby vavinash » 03 Nov 2008 02:10

Relaxmadi..its just the inferiority complex kicking in.

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Re: Chandrayan-1 mission launched succesfully

Postby rsingh » 03 Nov 2008 03:28

It is not first time.It seems Chinis have culture of fake-it-to-fame episode


Chinese newspaper places photo of Japanese rocket to mark Chinese lunar probe launch
Front page / World
10/26/2007 07:14 Source: AP ©


China is very proud of launching of its first lunar probe – and sometimes this pride turns out an embarrassment – a local newspaper placed a huge front page photo – of a Japanese rocket.


Chinese readers are brought up on government propaganda emphasizing Japanese atrocities and usually respond strongly to any kind of perceived pro-Japanese slight (www.stuff.co.nz)

The error switched a photo of a Long March 3A rocket carrying the Chinese probe with an H-2A rocket that sent Japan's own lunar orbiter into space earlier this month, a deputy editor of the Jingzhou Evening News, who would only give his surname, Deng, admitted Friday.

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Re: Chandrayan-1 mission launched succesfully

Postby Vivek K » 03 Nov 2008 05:33

People, can we keep the Chinese out of this thread please! Let's keep this for Chandrayan!!

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Re: Chandrayan-1 mission launched succesfully

Postby SaiK » 03 Nov 2008 07:10

good job vivek.

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Re: Chandrayan-1 mission launched succesfully

Postby Prasenjit Medhi » 03 Nov 2008 09:55

The Chinese will have to realize that India is a peer in Space Tech. This is galling to them because it shows that a pluralistic Western style democracy in Asia, other than their dreaded Japanese rivals, can match them in such a big way.

The Chinese better be prepared for India overtaking them in the next few decades as we take part in manned exploration on the Moon/Mars, in partnership with NASA/ESA/JAXA.

Democratic pluralism and social welfare democracy (India style) over Command Socialism, any day!

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Re: Chandrayan-1 mission launched succesfully

Postby Shankar » 03 Nov 2008 12:56

That is incorrect. If the resolution claimed is 5m then it possibly cannot resolve/image objects less than that in size.It can still resolve a 1 m x 5m plank of material, but not two 1m x 1m objects separated more than 5 m apart.


Salvi - can you please explain the resolution factor - what it actually means in optical terms .when the chandryan is at 100 km can it or can it not photograph a 1mtr long object with 5 mtr resolution

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Re: Chandrayan-1 mission launched succesfully

Postby manoba » 03 Nov 2008 15:09

Inching closer to moon...

Chandrayaan to get within 500 km of moon soon

"The liquid apogee motor (LAM) on board will be fired around 5.00 am Tuesday for about five minutes to make the transition and position the spacecraft at about 500 km from the moon's surface and over 384,000 km away from the earth," Indian Space Research Organisation (ISRO) director S Satish said here.

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Re: Chandrayan-1 mission launched succesfully

Postby Prasenjit Medhi » 03 Nov 2008 16:42

Very good! Mangal ko ho mangal! :)

What could be the factors causing the slight difference in the perigree, from the targeted 300 kms? And does it matter much in the long run, except for perhaps requiring some extra fuel expended for exact insertion into lunar capture orbit, because we have a slightly inexact ellipse as compared to the copy book elliptical orbit?

Or does it even matter at all? Ie, the moon does all the hard work(of capturing the craft in its gravitational 'sphere of influence', the spacecraft just needs to be close by and have less than the escape velocity vector in the direction opposite to the moon's gravitational pull?

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Re: Chandrayan-1 mission launched succesfully

Postby vishwakarmaa » 03 Nov 2008 17:15

Prasenjit Medhi wrote:The Chinese will have to realize that India is a peer in Space Tech. This is galling to them because it shows that a pluralistic Western style democracy in Asia, other than their dreaded Japanese rivals, can match them in such a big way.


Wrong. That era is long over when commands used tobe issued from London to Indian Parliament and democracy came far later in India, when British quit. What was there during British times, wasn't a democracy but a Colonial Rule in the hands of few in London.

Also, Indian democracy is far different from supposedly 'secular' and 'pluralistic' western democracies.

You are living in pre-1947 times.

Anyways, no more posts on it from me. Off topic.

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Re: Chandrayan-1 mission launched succesfully

Postby Prasenjit Medhi » 03 Nov 2008 18:23

vishwakarmaa wrote:
Prasenjit Medhi wrote:The Chinese will have to realize that India is a peer in Space Tech. This is galling to them because it shows that a pluralistic Western style democracy in Asia, other than their dreaded Japanese rivals, can match them in such a big way.


Wrong. That era is long over when commands used tobe issued from London to Indian Parliament and democracy came far later in India, when British quit. What was there during British times, wasn't a democracy but a Colonial Rule in the hands of few in London.

Also, Indian democracy is far different from supposedly 'secular' and 'pluralistic' western democracies.

You are living in pre-1947 times.

Anyways, no more posts on it from me. Off topic.


Good. Indian democracy is no different from the West. At least as far as attempts made to justify rule by a pseudo-aristocracy and plutocracy by obfuscating the real and pressing needs of the people with obscurantist emotional arguments. Like in the West, due to better education of the masses, this too fails, sometimes. A good thing, that. Democracy is democracy is democracy. Colonial rule was colonial rule was colonial rule.

You are 'living' in a completely different topic and delivering a counter argument to a position which I do not hold. In effect we should agree that we are arguing about totally different things and that your delivered point was made in opposition to a view that I did not espouse. A red herring and a tangent.

Moonward ho!

Regards,
PM

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Re: Chandrayan-1 mission launched succesfully

Postby SSSalvi » 03 Nov 2008 18:59

Shankar wrote:
That is incorrect. If the resolution claimed is 5m then it possibly cannot resolve/image objects less than that in size.It can still resolve a 1 m x 5m plank of material, but not two 1m x 1m objects separated more than 5 m apart.


Salvi - can you please explain the resolution factor - what it actually means in optical terms .when the chandryan is at 100 km can it or can it not photograph a 1mtr long object with 5 mtr resolution


The image that is formed inside the camera consists of pixels ( picture elements ) each of which is squre in shape . ( similar to the Laptop screen which consists of xpixels x ypixels. )

So the area seen by the camera is divided into several pixels and depending on the geometry of spacecraft height and the area covered on ground each pixel will cover a fixed area over ground.

In case of CY each pixel will cover an area of 5mx5m so an average voltage will be generated at thet pixel due to the reflected radiation from surface. What i mean by avg is that if there are small ( less than 5 m ) objects consisting of bright and dark terrain then the pixel will show an avg value over that area as the brightness. It is obvious that objects smaller than 5 m can't be seen but they will change the overall brightness value of that pixel.

Suppose that an Apollo leftover is 1m in size ( lying in surrounding homogeneous backgriund ) then the particular pixel will have a brightness different than the surrounding pixels but you can't identify the SHAPE of the object but you can guess that there is something lying in the pixel area but you will not know what it is. It could be a debris from Apollo or a natural rock with different reflectivity than the surrounding.

There is another querry about why 1m resolution is not used. Probable reason couls be as follows:
As the resolution increases the data rate increaes and then the usuual communication problems ( requirement of higher carrier frequency, low antenna bandwidths , mod-demod complexities etc ) crop up and it is quite possible that these systems may create more hurdles in continuous data capture than the advantage of resolution. BTW why do we require high res on moon? No one is interested in finding the debris of other missions.
Designers must have take a concious decision based on mission goals.

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Re: Chandrayan-1 mission launched succesfully

Postby Lalmohan » 03 Nov 2008 20:16

the mission is for general mapping and looking for minerals, fine resolution is not particularly required. and yes, more data, more transmission bandwidth requirement..., etc., etc.

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Re: Chandrayan-1 mission launched succesfully

Postby harbans » 03 Nov 2008 21:41

Nice article Chinese source..Congratulations India. Good to see some positive attitude from some Chinese..

http://www.chinastakes.com/story.aspx?id=756

Another article..

http://www.asiantribune.com/?q=node/13978

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Re: Chandrayan-1 mission launched succesfully

Postby jash_p » 03 Nov 2008 22:27

rsingh
It is not first time.It seems Chinis have culture of fake-it-to-fame episode



Don'tyou think, they learned it from their tallest and deepest friend ?

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Re: Chandrayan-1 mission launched succesfully

Postby Suraj » 03 Nov 2008 23:04

Folks, no more discussion on the Chinese 'questioning' of the Chandrayaan performance. Posts on the topic will be deleted.
Thanks

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Re: Chandrayan-1 mission launched succesfully

Postby sumishi » 04 Nov 2008 01:11

From ISRO's site -- "The Terrain Mapping Camera (TMC): The aim of this instrument is to completely map the topography of the moon. The camera works in the visible region of the electromagnetic spectrum and captures black and white stereo images."

Why is it that the camera, in spite of being capable of working in the entire visible spectrum, will be giving its stereo image output in B&W? I think it probably is possible to have coloured stereo output, or is it that color is not of any importance for terrain mapping?

Thanks in advance.

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Re: Chandrayan-1 mission launched succesfully

Postby Anujan » 04 Nov 2008 04:32

sumishi wrote:From ISRO's site -- "The Terrain Mapping Camera (TMC): The aim of this instrument is to completely map the topography of the moon. The camera works in the visible region of the electromagnetic spectrum and captures black and white stereo images."

Why is it that the camera, in spite of being capable of working in the entire visible spectrum, will be giving its stereo image output in B&W? I think it probably is possible to have coloured stereo output, or is it that color is not of any importance for terrain mapping?

Thanks in advance.


It is a question of sensor fidelity (or sensitivity) and need. Note that ability to sense all regions of the spectrum is different from the ability to discriminate between them. Let me explain

Usually how color pictures are taken is as follows. Millions of square sensors are packed on the surface of a chip. The conductivity of these sensors depend on the intensity of light (independent of the color of light) falling on them. Now one of two things is done

a. The 3 neighboring sensors are covered with a filter which allows only Red, Green or Blue (or maybe Cyan Magenta and Yellow), the light intensity values are read.

b. The 3 neighboring sensors are made of materials sensitive to red, green or blue (or maybe CMY) an the light intensity values are read.

Now the problem is that of you have sensors arranged like this:
R
G B

They are measuring the R,G,B components at a slight distance away from each other, which should then be combined. This leads to a loss of resolution. If you want to settle for a BW picture, you can do one of two things

A. Make all pixels sensitive to only intensity information. You have tripled the resolution
B. Combine the area of R,G,B pixes and make one huge pixel which is sensitive only to intensity information. In this case, for the same resolution as the color image before, you have increased the sensor sensitivity by a huge amount. Note that the sensitivity of the sensor is dependent on the size of the sensor. In general, bigger sensor = much much better sensitivity. This is the difference between point and shoot digital cameras and digital SLRs. Point and shoot (say 10 megapixels) have all of the 10x3 million sensors packed in the area of a fingernail. This is the reason why they give really sucky pictures at night. The sensors are not big enough to sense light at night. On the other hand DSLRs have 10x3 million pixels packed in an area the size of a traditional film negative. Much larger area and gives much better picture at night.

In space based applications (including the mars rovers spirit and opportunity), there is a single camera with pixels sensitive to only intensity of light. Since most of the photographs they take are of static objects, there is a rotating filter in front of the sensor. First Red is placed, a picture is taken, then Blue is placed and a picture is taken and then Green is placed and a picture is taken. Then all the three are combined to make a color image. ISRO might have omitted the rotating filters. So even though the camera, in theory can capture color images, ISRO maybe is not interested in them and is using it has a highly sensitive, high resolution BW camera.

You might find this interesting. I have included excerpts. The actual article is fascinating and longer.

Digital Secrets: How Spirit Makes Great Photos

Perhaps most important, the sensors on Spirit's CCDs are bigger, explained Patrick Myles, director of corporate communication at the Dalsa Corporation, which built the CCDs for all of the rover's cameras (Spirit has nine altogether, including hazard avoidance cameras and a microscopic imager).

A Sony DSC-F717, with a street price of around $600, has 5.2 million sensors (or 5 megapixels) on a chip that is 8.8 by 6.6 millimeters (or .35 by .26 inches). The Pancam has just a million sensors spread across a chip that's 12 by 12 millimeters -- nearly a half-inch square.

The Pancam does not make a color picture directly. Instead, it records light versus dark in shades of gray. As with other CCD cameras used in high-end astrophotography, such as on the Hubble Space Telescope, a series of filters are applied to gather multiple images that are then blended together.

In the most basic application of this process, three images are gathered of a scene, one each recording red, green and blue light. Those are then put together with special software to create a color picture.

A consumer digital camera uses a single coated filter to make the transition from photon reality to electrons and then digital information.

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Re: Chandrayan-1 mission launched succesfully

Postby Angre » 04 Nov 2008 06:21

sumishi wrote:Why is it that the camera, in spite of being capable of working in the entire visible spectrum, will be giving its stereo image output in B&W? I think it probably is possible to have coloured stereo output, or is it that color is not of any importance for terrain mapping?


The HySI captures 80m resolution imagery in visible & near- IR bands (64 contiguous). For terrain mapping, better resolution implies better depth discrimination. You can always color the topography based on the HySI sensor data (though of course not at the same resolution). At 100km orbit, a full color sensor in RGRG/GBGB pattern would have yielded full color data at the expense of losing about 1/2 the spatial resolution.

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Re: Chandrayan-1 mission launched succesfully

Postby Praveen » 04 Nov 2008 07:37

Any info on the LAM firing to be done today? It should have been completed by now.

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Re: Chandrayan-1 mission launched succesfully

Postby SwamyG » 04 Nov 2008 08:15

Paki paper reporting yaan in the lunar space. SindhToday.net. Nothing yet from any other source.

ThaiIndian News also repeating the same thing.

It seems to be an IANS feed.


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