Chandrayan-1 moon mission

Arun_S · Post by **Arun_S** » 26 Nov 2008 00:37

vavinash wrote:I don't thin the sat temp rose by 50C but the absolute temp was 50 C. 40 C seems to be the intended temp, so the rise is 10 C above normal.

Yes as I read it, it seems to report the cabin temp is 50C, well within comfort zone, but with that temperature I do not see the need to take measures like re-orient the craft, or switching off mission computer. The avionics is clearly designed for Mil/Space speces (-55 to +125C) thus the system will easily operate to 85C or even more.

harbans · Post by **harbans** » 26 Nov 2008 00:46

50 deg off the expected temperature is a lot,

Arun Ji Hi! I think the temperature offset is not by 50 celsius, but by 10 celsius. But i am now curious why ISRO should be too worried about electronic equipment working at 50 celsius. A lot of them do work absolutely well for years on end at that temperature. I wish the best for ISRO and appreciate the honesty that they've been able to share this with us. I do consider this mission a success already though i wish we can get the best from the instruments.

My regards for the ISRO folks goes up each day! Their humility and approach is something we all can learn from.

Arun_S · Post by **Arun_S** » 26 Nov 2008 03:03

This is a PPT that I like.
Chandrayaan-1 Mission, Colloquium at TIFR, Mumbai August 17, 2007 by K Thyagarajan, Prog Dir IRS/SSS ISRO Sattellite Centre

Karthi · Post by **Karthi** » 26 Nov 2008 03:50

Chandrayaan mission on target

SSSalvi · Post by **SSSalvi** » 26 Nov 2008 13:07

Arun_S wrote:
vavinash wrote:I don't thin the sat temp rose by 50C but the absolute temp was 50 C. 40 C seems to be the intended temp, so the rise is 10 C above normal.
Yes as I read it, it seems to report the cabin temp is 50C, well within comfort zone, but with that temperature I do not see the need to take measures like re-orient the craft, or switching off mission computer. The avionics is clearly designed for Mil/Space speces (-55 to +125C) thus the system will easily operate to 85C or even more.

It appears that ISRO did not anticipate the quantum of heat from Lunar surface, so the spacecraft has cabin temp of 50 deg - 10 deg higher than expected.

Really speaking if that is the cabin temp then it should not be a problem for space qualified components but one possibility is that there may be certain Hot Spots of which ISRO may be weary.

But then what about Thermo-Vac tests prior to launch?

harbans · Post by **harbans** » 26 Nov 2008 13:31

Another TMC video has been posted in the ISRO site.

http://www.isro.org/pslv-c11/videos/tmca.htm

AWESOME STUFF!!

prashanth · Post by **prashanth** » 26 Nov 2008 17:23

harbans wrote:Another TMC video has been posted in the ISRO site.

http://www.isro.org/pslv-c11/videos/tmca.htm

AWESOME STUFF!!

Classy. Superb 3D effect.

As usual, it is not downloadable.

sumishi · Post by **sumishi** » 26 Nov 2008 17:26

prashanth wrote:
harbans wrote:Another TMC video has been posted in the ISRO site.

http://www.isro.org/pslv-c11/videos/tmca.htm

AWESOME STUFF!!
Classy. Superb 3D effect.
As usual, it is not downloadable.

okay (sigh!), i will try to upload again to that file site and give the link.

prashanth · Post by **prashanth** » 26 Nov 2008 17:31

Sumishi,
What magical software allows you to download that video directly? Please tell us boss.

sumishi · Post by **sumishi** » 26 Nov 2008 17:39

prashanth wrote:Sumishi,
What magical software allows you to download that video directly? Please tell us boss.

In process - 10% uploaded.

I told you earlier, it is Orbit downloader, which comes with a browser plugin "Get it." Once you open the ISRO page in IE, just moving the cursor over the embedded vid gives a pop up displaying "Get It." Click and follow instructions. The file has to be selected in the "Get it" window, and then the download progress can be seen in the Orbit downloader window which comes up in the background. BTW, these ISRO downloads happens in a lot of fits and starts.

Anyways, I am uploading this one and will give the link shortly.

23% completed (This is a 37 MB file)

sumishi · Post by **sumishi** » 26 Nov 2008 18:13

Okay, here it is:
http://ifile.it/s1dmbjv

Neela · Post by **Neela** » 26 Nov 2008 18:35

Many firefox addons exist for video downloads.

http://addons.mozilla.org/

sumishi · Post by **sumishi** » 26 Nov 2008 19:40

Neela wrote:Many firefox addons exist for video downloads.

http://addons.mozilla.org/

Yes, but these ISRO embedded vids can only be seen in IE, so firefox is out of contention

Raj · Post by **Raj** » 26 Nov 2008 20:11

sumishi wrote:
Neela wrote:Many firefox addons exist for video downloads.

http://addons.mozilla.org/
Yes, but these ISRO embedded vids can only be seen in IE, so firefox is out of contention

You can actually open a new tab from within firefox as IE.

Anujan · Post by **Anujan** » 26 Nov 2008 20:21

prashanth wrote:Sumishi,
What magical software allows you to download that video directly? Please tell us boss.

Saar,
installing the latest version of Realplayer also gives you that ability. Just hover over the view and "download" menu pops up.

juvva · Post by **juvva** » 26 Nov 2008 20:40

Thanks! Sumishi for the video #2

How come it feels like the camera is pointing sideways to the direction of motion, I thought the camera is supposed to be looking straight down?

Singha · Post by **Singha** » 26 Nov 2008 20:52

the camera is obviously pointing to the side for now. maybe they turned the satellite to avoid getting some instruments in direct sunlight.

imagery is good but not HDTV quality. kayuga website was showing off some hdtv things I didnt check closely.

does this video match or better kayuga?

harbans · Post by **harbans** » 26 Nov 2008 21:00

The flyby video put up today by ISRO is dated for November 15th. So thats much before this heat issue cropped up. IIRC there are three modes which the camera can operate..

Kaguya videos of Lunar flyby..

http://www.youtube.com/watch?v=iW1mc42J76Q

http://www.youtube.com/watch?v=EkHuRRDshhg

I rate the CY video better. Kaguya in the above videos looks orbiting much higher..CY looks as if it's scraping the landscape. I only wish they'd given us the highest resolution imagery.

prao · Post by **prao** » 26 Nov 2008 21:07

It certainly does look like the camera has been turned sideways. I wonder if its a consequence of the 20 deg rotation performed recently. All available info indicates that the camera is normally to point straight down. The camera also has CCD's ahead and behind the central CCD that view the terrain at a 25 deg offset but that is along the direction of motion not across (to enable construction of 3D imagery).

As far as the HDTV is concerned, I'm sure its resolution isn't higher than the TMC's 5 m since the TMC is acknowldeged as the currently highest resolution available. It's not clear to me why Kaguya carried the HDTV camera since it won't allow light amplification.

Perhaps it was to capture full frame views with minimal processing or for full color views?

Added later: The Kaguya also has a camera like the TMC but with a 10 m res and that is its highest resolution so yes the HDTV has lower res than that.

juvva · Post by **juvva** » 26 Nov 2008 21:21

Also why no stars are visible in the sky? If this is due to dynamic range limitation of the camera, should we expect to see stars at least when it is passing over dark regions ( example at ~6:04 mins in the video)?

manoba · Post by **manoba** » 26 Nov 2008 21:23

Singha wrote:does this video match or better kayuga?

Way better than Kayuga. Screw the HDTV.
Screw too their crystal clear blue Earth and gray gray grayish lunar terrain, as if someone vomited Tejas' gray color scheme on a ship deck.

TMC's video gives an impression that we are viewing through the window of a (lunar) car moving on the surface. It might be something to do with the 5m resolution.

Imagine how would it look like on the surface of 'Chandra', Bhuvan's extension.

Arun_S · Post by **Arun_S** » 26 Nov 2008 22:22

Superb. I am speechless.

The flyby video is an animation once the 3D moon surface is synthesized by using the 3 images taken by Chandrayaan-1 at different angles. As someone pointed its just like Google Earth software that allows one to fly at any altitude and view any perspective on earth surface. Thus the perspective of moon horizon is created from the wide swath of the original CY-1 camera images from 3 directions. Like the Google earth one could added the stars in the sky line, but heck why will I look at stars when I have my Moon so close. As my sardar friend would say "A bre*** in hand is worth 2 in the bra".

Hariprasad · Post by **Hariprasad** » 26 Nov 2008 22:24

Youtubed the TMC video 2.

http://www.youtube.com/watch?v=nDaY4p6WO6w

As my sardar friend say a bre*** in hand is worth 2 in the bra.

Amen

sanjaykumar · Post by **sanjaykumar** » 26 Nov 2008 22:34

Stop it ISRO, you are embarrasing the ghazis.

Every Indian should be shown this video. This is what it means to be an Indian-civilisationally.

prao · Post by **prao** » 26 Nov 2008 22:43

manoba wrote:
Singha wrote:does this video match or better kayuga?
Way better than Kayuga. Screw the HDTV.
Screw too their crystal clear blue Earth and gray gray grayish lunar terrain, as if someone vomited Tejas' gray color scheme on a ship deck.

...deleted

Why? Why be so jingoistic? Is there any purpose served? And just to be very clear on this, it is not as if Japan settled on a 10 m res camera because they did not have the technology to install a 5 m resolution camera. Far from it. It would have been because that was decided as best suiting their mission profile. As any Design Engineer knows, engineering is the art of compromise. For example the orbit altitude could have been decided based on the instruments on board. Some instruments would function better at a higher orbit but others at a lower orbit etc. etc.. Thermal management might have also played a part (we are seeing the effects of the orbital height on CY1 right now). Then the factors for settling on camera resolution could be - power requirements, mission length (so that most areas could be covered by mission end - in this case 1 year), light sensitivity, weight, size considerations, budget and on and on.

Given all this it is the easiest thing in the world to be a backseat driver and pass judgment on design decisions. You can always say that the compromise made should have been made another way.

So we can (and should) be happy & proud that CY1 has the best resolution right now and is producing fantastic pictures but I think we can also be happy at others' successes too.

Bade · Post by **Bade** » 26 Nov 2008 22:58

Indian lunar orbiter hit by heat rise

Mylswamy Annadurai, the project director for the lunar mission, told CNN that temperatures onboard Chandrayaan-1 had risen to 49 degrees Celsius (120 degrees Fahrenheit).

The increase occurred as the craft, the moon -- which it is orbiting -- and the sun lined up, a phenomenon which Annadurai said was not unexpected and which would likely last until the end of December.

"We have switched off the systems (aboard) that are not needed to be on," Annadurai said, ruling out the possibility of damage and adding that the temperature was now down to 40 degrees Celsius (104 degrees Fahrenheit).

Heat on board the Chandrayaan-1 should not exceed 50 degrees Celsius (122 degrees Fahrenheit), Annadurai said -- but insisted the orbiter is designed to withstand up to 60 degrees

ss_roy · Post by **ss_roy** » 26 Nov 2008 23:56

A few points about Kaguya.

1. The Orbit is set at about 100 km above the lunar surface.

2. It is about 5 times heavier than CY-1.

3. It had about the same mission as CY-1, but it had many more instruments.

5. It cost 5-6 times what CY-1 did.

6. They chose to have a 10 m resolution camera + 2-3 HDTV movie cameras. We chose a 5m resolution TMC.

7. The mini-SAR + TMC + laser ranger om CY-1 will give an final 3D model with better 5 m resolution (visual as well as topographical).

8. The reality is that we built a more functional, utilitarian probe for much less than the Japanese.

9. The heat issue is not a major problem in that simple measures like not using the high voltage instruments continously + changing the orientation of the craft with respect to the sun while keeping it pointed towards the moon could easily solve the problem.

10. China's lunar orbiter TMC has a resolution of 120m/ pixel. Their second orbiter's TMC will have a resolution of 10m/ pixel (though I suspect some poor chinese team is getting an earful from their higherups).

prao · Post by **prao** » 27 Nov 2008 00:33

8. The reality is that we built a more functional, utilitarian probe for much less than the Japanese.

9. The heat issue is not a major problem in that simple measures like not using the high voltage instruments continously + changing the orientation of the craft with respect to the sun while keeping it pointed towards the moon could easily solve the problem.

10. China's lunar orbiter TMC has a resolution of 120m/ pixel. Their second orbiter's TMC will have a resolution of 10m/ pixel (though I suspect some poor chinese team is getting an earful from their higherups).

Let's consider a few points for some more discussion:

It is true that ISRO builds for less than others but the cost figure quoted for CY1 doesn't give the full picture. ISRO saved substantially by having others build instruments for CY1 and this point is lost in discussions about cost. The SAR alone cost NASA $100 million and this when they already had the technology. ISRO saved by not having to develop the tech for CY1 and not having to build it. Compare this to the quoted cost of something like $80 million for CY1 - that's ISRO's cost. I don't have figures for the cost of all the foreign istruments but given the SAR figure, the total cost is probably in the region of $280 million (assuming $100 million for the remaining four foreign instruments. Then the figure doesn't look so flattering, no?

The point I made about CY1 thermal mgmt issue was as an example of a design factor - not a criticism. In fact, nothing of my post is intended as a criticism and if one reads it in the spirit offered, there's no need to get defensive.

If anyone on China's mission design team is getting pulled up, it's because the Chinese are more interested in appearances and boasting rather than actual bang for the buck.

If a genuine comparison is to be made between Kaguya/CY1/Chang'e1 it will need a far more indepth analysis than a few selected facts thrown about. So far I haven't seen any such analysis and I suspect that any such study is not likely to be conclusive given that the instruments are not the same, the mission profile not the same etc. etc. Looking at just the camera resolution doesn't cut it.

All I'm saying is that it is possible to enjoy your success w/o trying to pull others down for no good reason. You will notice that ISRO is very careful not to give such an impression.

Amber G. · Post by **Amber G.** » 27 Nov 2008 00:53

Thermal management might have also played a part (we are seeing the effects of the orbital height on CY1 right now)..

hmm... how the orbital height has any significant effect on CY1's temperature ?

(Some other "reasons/explanations" given here or other places (eg "moon has volatile atmosphere , or "The increase occurred as the craft, the moon -- which it is orbiting -- and the sun lined up, a phenomenon which Annadurai said was not unexpected.." are to put it mildly very imprecise...I can figure out what they want to say.. but the words used by them are so imprecise that most common man will misinterpret.)

Victor · Post by **Victor** » 27 Nov 2008 01:27

Speechless is the word! All Indians are looking at this with awe and pride. Thank you ISRO and no pressure but we are waiting for the MIP movies too, please.

I wonder if it is in real time speed? CY1 is traveling at ten times the speed and altitude of a passenger jet but it should still look a lot slower. Perhaps the effect of slower frame rate hi-res images stitched together? Could be wrong but from this photo of the TMC it looks like there are 3 lenses running simultaneously (for the eventual 3D result) and the movie is from one of them. The kid in me hopes that ISRO teams up with someone to produce a 5m resolution, 3D Moon Flight Simulator which would become a runaway hit. But the data is likely far more valuable than that.

vavinash · Post by **vavinash** » 27 Nov 2008 01:48

Prao, the 80 mil ISRO spent includes 30 mil for IDSN and 20 mil for PSLV-XL. It is still more practical and economical moon mission than any other.

prao · Post by **prao** » 27 Nov 2008 02:10

hmm... how the orbital height has any significant effect on CY1's temperature ?

Reports from ISRO indicated that reflected radiation from the Moon was one of the factors that caused the temperature rise. Apparently an increase in orbital height to reduce these effects was one of the options considered though how serious an option it was I have no idea. It might have been just talk.

Arun_S · Post by **Arun_S** » 27 Nov 2008 04:48

Victor wrote:Speechless is the word! All Indians are looking at this with awe and pride. Thank you ISRO and no pressure but we are waiting for the MIP movies too, please.

I wonder if it is in real time speed? CY1 is traveling at ten times the speed and altitude of a passenger jet but it should still look a lot slower. Perhaps the effect of slower frame rate hi-res images stitched together? Could be wrong but from this photo of the TMC it looks like there are 3 lenses running simultaneously (for the eventual 3D result) and the movie is from one of them. The kid in me hopes that ISRO teams up with someone to produce a 5m resolution, 3D Moon Flight Simulator which would become a runaway hit. But the data is likely far more valuable than that.

Victor: Pls note that the flyover video you see is NOT raw picture taken by Chandrayan-1. Let me put it this way:
1. Chandrayan-1 takes stereo image of a strip of moon, and send it to ISRO/Bangluru.
2.) ISRO resolves high information from the images and constructs 3 dimensional relief of moon from that and apply on that relief the gray scale photo image.
3) Using a solid modeling toolkit it can then fly over the 3D model at chosen altitude, orientation and speed and generated this video image that is put on teh ISRO website that we are now watching.

Thus one can choose any chosen speed of flyover to get a visualization of what the surface and skyline of moon looks like in that flight trajectory.

That is what Google Earth software does for high resolution 3 D earth surface, as well as the images from TES that were published by ISRO few years ago, that made Gen Musharraf and Pak Army HQ brown their pants.

SSSalvi · Post by **SSSalvi** » 27 Nov 2008 15:22

prao wrote:
manoba wrote: Way better than Kayuga. Screw the HDTV.
Screw too their crystal clear blue Earth and gray gray grayish lunar terrain, as if someone vomited Tejas' gray color scheme on a ship deck.

...deleted

Why? Why be so jingoistic? Is there any purpose served? And just to be very clear on this, it is not as if Japan settled on a 10 m res camera because they did not have the technology to install a 5 m resolution camera. Far from it. It would have been because that was decided as best suiting their mission profile. As any Design Engineer knows, engineering is the art of compromise. For example the orbit altitude could have been decided based on the instruments on board. Some instruments would function better at a higher orbit but others at a lower orbit etc. etc.. Thermal management might have also played a part (we are seeing the effects of the orbital height on CY1 right now). Then the factors for settling on camera resolution could be - power requirements, mission length (so that most areas could be covered by mission end - in this case 1 year), light sensitivity, weight, size considerations, budget and on and on.

Given all this it is the easiest thing in the world to be a backseat driver and pass judgment on design decisions. You can always say that the compromise made should have been made another way.

So we can (and should) be happy & proud that CY1 has the best resolution right now and is producing fantastic pictures but I think we can also be happy at others' successes too.

Thanks Rao for bringing out the woes of a design engineer. You said it!

ArmenT · Post by **ArmenT** » 27 Nov 2008 15:46

Something just occurred to me... When they say that the temperature inside was 50 C, this would be the ambient temperature inside the craft, correct? This would mean that the heat from the electronics is a bit higher than that and it would have trouble radiating it away if the surrounding temperature stays high. In Earth based systems, you can use a convection currents to carry heat away from the parts, which is why lots of electronics have cooling fans. Unfortunately this is obviously not possible in space. Since the outside of the craft is insulated to prevent the sun's rays from heating it when it faces the sun, this would also imply that heat from inside also cannot escape out in the other direction easily. I'm guessing that this is why 50C is a problem for the electronics?

<disclaimer>I'm not a scientist, I just play one on TV</disclaimer>

SSSalvi · Post by **SSSalvi** » 27 Nov 2008 16:10

ArmenT wrote:Something just occurred to me... When they say that the temperature inside was 50 C, this would be the ambient temperature inside the craft, correct? This would mean that the heat from the electronics is a bit higher than that and it would have trouble radiating it away if the surrounding temperature stays high. In Earth based systems, you can use a convection currents to carry heat away from the parts, which is why lots of electronics have cooling fans. Unfortunately this is obviously not possible in space. Since the outside of the craft is insulated to prevent the sun's rays from heating it when it faces the sun, this would also imply that heat from inside also cannot escape out in the other direction easily. I'm guessing that this is why 50C is a problem for the electronics?

<disclaimer>I'm not a scientist, I just play one on TV</disclaimer>

Some obvious methods:

Use reflective film to arrest heat from 'hot' sides.

Use heat-pipes to transfer heat generated by electronics to cooler sides... etc

prao · Post by **prao** » 29 Nov 2008 02:34

SSSalvi wrote:
Thanks Rao for bringing out the woes of a design engineer. You said it!

Victor · Post by **Victor** » 29 Nov 2008 09:45

Arun, thanks for that explanation. Never knew that.

Vinay_D · Post by **Vinay_D** » 29 Nov 2008 13:15

ArmenT wrote:Something just occurred to me... When they say that the temperature inside was 50 C, this would be the ambient temperature inside the craft, correct? This would mean that the heat from the electronics is a bit higher than that and it would have trouble radiating it away if the surrounding temperature stays high. In Earth based systems, you can use a convection currents to carry heat away from the parts, which is why lots of electronics have cooling fans. Unfortunately this is obviously not possible in space. Since the outside of the craft is insulated to prevent the sun's rays from heating it when it faces the sun, this would also imply that heat from inside also cannot escape out in the other direction easily. I'm guessing that this is why 50C is a problem for the electronics?

<disclaimer>I'm not a scientist, I just play one on TV</disclaimer>

Besides space, convection cooling cannot be used effectively in high dust environments like deserts or coal mines. Thermoelectric cooling is possible solution here though it is very energy in-efficient. Satellites are suppose to use such cooling devices. I have seen MIL standard devices manufactured by Wipro using this cooling system.

More about Thermo-electric cooling is here link

Arun_S · Post by **Arun_S** » 30 Nov 2008 01:19

Vinay_D wrote:
ArmenT wrote:Something just occurred to me... When they say that the temperature inside was 50 C, this would be the ambient temperature inside the craft, correct? This would mean that the heat from the electronics is a bit higher than that and it would have trouble radiating it away if the surrounding temperature stays high. In Earth based systems, you can use a convection currents to carry heat away from the parts, which is why lots of electronics have cooling fans. Unfortunately this is obviously not possible in space. Since the outside of the craft is insulated to prevent the sun's rays from heating it when it faces the sun, this would also imply that heat from inside also cannot escape out in the other direction easily. I'm guessing that this is why 50C is a problem for the electronics?

Pls see ISRO's annual reports on their website and you will find that few years ago it published an article that dealt with thermal management and photo of the liquid/convection cooler used on hot chips that cant sufficiently dissipate all the heat by only heat radiation.