Indian Space Program Discussion

Sridhar · Post by **Sridhar** » 22 Apr 2011 19:01

KrishG,

Thanks for the response but it has only confused me further. Neither the MK2 nor the MK3 have earth ignited cryogenic stages. Both require high thrust upper stages - the very rationale for the cryogenic stages in the respective launchers. So how does that explain why SC was chosen in one and GG was chosen in the other?

Another data point - Ariane 5 uses GG cryogenic engines for both earth ignited and upper stages.

SaiK · Post by **SaiK** » 22 Apr 2011 19:56

It is time we send trial missions for home grown cryos with dummy payloads or re-entry experiment/test vehicles.

Bade · Post by **Bade** » 22 Apr 2011 20:05

Sridhar, as I said at the outset using the term largest or one of the largest constellation of land imaging satellites is fine for ISRO to claim. In short the IRS series is == with Landsat series and nowadays there are companies like Orbimage/DigiGlobe in the private domain for land applications too to compete with for ISRO.

But "Civilian Operational" use is not limited to land applications by any means. Since the early days (late 60's) onwards TIROS series satellites for weather were considered civilian operational by NOAA. That is how the programs are sold to the govt funding agencies.

My point was that ISRO is using a very narrow definition, since most of the govt funding is for land imaging purposes in the Indian context and the program is sold as such. Nothing wrong with that approach for now. The weather component in govt funded programs usually is larger part of earth observation elsewhere in the world compared to land imaging. It is a fine point, but an important one keeping in mind that ISRO is a govt funded organization for the greater good of the country first and the world at large as a distant second for now. From all the reports India (ISRO) intends to ramp up the weather observation part as it becomes more important for obvious reasons as the Indian economy grows and such programs cannot be funded by private entities. All weather and climate related satellites are govt funded mostly.

ramana · Post by **ramana** » 22 Apr 2011 20:10

Sridhar, An old book "Design of Missile Structures" by Bruhn gives a manual method of calculating the flight loads for flight vehicle design. The 4.0m fairing would have higher loads than the 3.4m older fairiing by ratio of diameters if the velocity is constant. It could be more due to any local geometry changes. Having said that I still dont understand the local loads that caused the deformation. One simple datapoint would be the shroud thickness for the ISRO cryo-stage and the imported one.

Odd that they noted the connector separation on earlier flights but didn't take corrective action. Maybe they realized it now. If it showed up earlier then its the vehicle bow during flight which bent the structure leading to the shroud deformation.

ISRO shows a very good fault tree and root cause analysis approach if you take the sum total of Dr Nair's statements over the investigation period.

disha · Post by **disha** » 22 Apr 2011 21:50

SaiK wrote:It is time we send trial missions for home grown cryos with dummy payloads or re-entry experiment/test vehicles.

Have posted this long time back ... also heartening to see that it was the shroud failure causing GSLV to go bust.

=================================

Some posters have argued that we should send in dummy satellites. I am of the position that such an argument is without merit, here are the reasons why:

1. A dummy satellite without means of control is a space junk. It takes a valuable orbit (in this case GTO) which does not decay for several decades and puts future space missions at risk. Further the space junk of 2 tonnes mass has to be tracked and monitored regularly. What happens if its orbit changes due to some circumstances and poses a risk to other nation's missions? Who is liable - itiyaadi itiyaadi.

2. Okay to solve problem 1., we can put in some fuel and thruster and some avionics so that it can be de-orbitted gracefully. The question then arises, what exactly are we saving? 40% of any geo-synch satellite is fuel/thruster and necessary avionics and gyroscopes to make the sat reach its intended orbit and complete its mission by staying there. And this could be 80% of the cost of the satellite. So we are saving only 60% of the payload. Now this 60% is costing only 20% of the overall cost!

3. The launch is successful, we settle on the design and mass produce the components and now ready to send the real sat. How will we know that the real sat will indeed work? If you take the trouble of testing the fuel/thruster and make the sat reach its intended orbit, you would have parked a dummy satellite in a precious space. If you are going to anyway do it, why not as well send the rest of the avionics?

4. Okay we still stick with dummy to the point where we are assured of the success of the mission. Then comes a new mandate, say from dukhdarshan in combination with swan telecom that they want an extra secret k-band transponder for monitoring radiaa tapes (sarcasm here, pointing to user requests for some changes in sat). This increases the weight of the sat by 100 kgs, necessiating addition of some 4 tonnes of fuel. What is the guarantee that this rocket will succeed? Send dummy missions till we qualify the new payload? What happens if we want to use this rocket for sending a mission to moon/mars/venus/asteroid?

There is a reason why ISRO and India's space missions are respected. Even in Khanate. Selene and Chang'e could not achieve what Chandrayaan did. Neither Japan nor China (or even US) operate the largest fleet of earth observation (remote sensing) sats in the world. None of them had multi-payload-single-mission (INSAT!) series to kick start a communication/earth observation revolution in a developing world (give me an example in 2nd world and 3rd world countries!).

None of the above can be achieved by sending dummies in space.

==========================================================================

I *may* still change my position, since there are several live dummies who do question about the need for India to go to space and they should be put in the rockets, also GSLV different versions have had only 3 spectacular failures., and only one for new version of GSLV. Now here is my yardstick (FWIW) for ISRO:

1. No more failures and GSLV Mk II is operationalized - ISRO is better than NASA (SDRE yindoos are better than TFTA Khans)
2. Two (2) more failures and then GSLV Mk II is operationalized - ISRO as good as NASA, better than "ruskies"
3. Three to Four more failures and then GLSV Mk II is operationalized - ISRO as good as "Japs". NASA and Ruskies better than the SDRE yindoos.
4. Six to Eight more failures and then GSLV Mk II is operationalized. ISRO still better than Chinis. Particularly we do not send rockets to control population towards Chennai, Kerala.

And not to steal thunder from PSLV., when the first PSLV was flown it carried only @800 Kg of satellite and lot of naysayers on how SDREs cannot do anything better. Now it carries >1400 kg of multi-satellite payload and all some injuns do is yawn.

disha · Post by **disha** » 22 Apr 2011 22:09

ramana wrote:Odd that they noted the connector separation on earlier flights but didn't take corrective action. Maybe they realized it now. If it showed up earlier then its the vehicle bow during flight which bent the structure leading to the shroud deformation.

ramanaji, I think you are reading it wrong. What Dr. Nair said is that the shroud was faulty to begin with., only the last mission got caught in the fault. Something like the foam debris on the shuttle was always there., only in one mission it proved fatal.

Sridhar · Post by **Sridhar** » 22 Apr 2011 22:21

Bade,

Understood your point.

Sridhar · Post by **Sridhar** » 22 Apr 2011 22:23

Ramana,

Useful information. It seems like the causal link between the shroud design issue and the snapped connectors last time was not made. Maybe they thought it was a chance event, which got confirmed as a design flaw now.

Sean Rowe · Post by **Sean Rowe** » 22 Apr 2011 22:28

I have one small doubt. Is the Cryogenic Engine that is supplied by Russia is ever used by Russia. If it is so, Why did this problem did not occur to their mission

negi · Post by **negi** » 22 Apr 2011 23:09

I had linked a document on the Russian KVD-1 sometime back on this thread.

http://forums.bharat-rakshak.com/viewto ... ic#p859158

the engine has never been tested in flight. In the meantime, that is precisely the one Indian Space Research Organization se- lected for the cryogenic upper stage of their GSLV rocket.

Austin · Post by **Austin** » 22 Apr 2011 23:16

Did the Russian Cryo ever failed when the last stage ignited ?

KrishG · Post by **KrishG** » 23 Apr 2011 00:45

Sridhar wrote:KrishG,

Thanks for the response but it has only confused me further. Neither the MK2 nor the MK3 have earth ignited cryogenic stages. Both require high thrust upper stages - the very rationale for the cryogenic stages in the respective launchers. So how does that explain why SC was chosen in one and GG was chosen in the other?

The point I am trying to make is that SC engines are inefficient when used for higher thrust requirements at high altitudes (upper stages).

So, why was SC chosen for ICE ?? Because, that was the technology we were exposed to. The Russian stages that we got for the GSLV had SC engines. ISRO obviously felt that they would have a better chance of trying to build an engine on a technology they knew and were exposed to in the form of Russian engines of GSLV.

The way I see it, ICUSP is an effort to indigenously manufacture the Russian upper stage of GSLV. So, while there were certain changes and improvements incorporated in the engine, ISRO still based it on the Russian engine. And I find no problem with that approach.

Sridhar wrote:Another data point - Ariane 5 uses GG cryogenic engines for both earth ignited and upper stages.

Do you know that the Europeans still haven't developed an engine running on SC cycle (barring small technology demonstration engines). GG was the technology they had in the form of HM7 engines when they started developing the Ariane-5. So, they chose that instead of SC, which would have incurred additional costs and time.

Sridhar · Post by **Sridhar** » 23 Apr 2011 00:55

KrishG:

I see where you are going much clearer now. If I understand you correctly, from first principles it probably makes sense to use a GG engine for the MK3. As for MK2, it might not have been technically the optimal decision to develop a SC based engine, but other factors came in play. But then again, one could ask why we went in for an SC based engine when discussing the deal with the Russians, when we knew that it was a harder technology to master, one that even the Russians themselves did not rely on in a big way (their workhorse launchers don't use cryogenic engines at all).

BTW, are the Chinese LOX/LH2 engines based on the GG cycle or the SC cycle?

Sridhar · Post by **Sridhar** » 23 Apr 2011 00:57

Answering my own question - the Chinese YF series engines use the Gas Generator cycle.

Thus, it seems like staged combustion is only used regularly by the Americans. (the Space Shuttle main engine is a staged combustion engine, but it is lit at launch on the ground itself).

The Japanese engine used on the H2 is also a SC engine.

KrishG · Post by **KrishG** » 23 Apr 2011 01:06

AJames wrote:
Gagan wrote:CUS & Shroud

I am not an aerodynamicist, but looking at the image, surely the cylindrical lip at the bottom will catch the supersonic air flowing over it and cause severe air turbulence inside. Shouldn't the lattice be right at the bottom of any shroud provided?

It is always covered with a composite cylindrical covering for that exact reason. This is the shroud that got deformed. I have illustrated this in the following pictures.

Sridhar · Post by **Sridhar** » 23 Apr 2011 01:08

KrishG: BTW, I hope you don't take my questioning you the wrong way. Your inputs here are valuable and I don't mean at all to be disrespectful.

ramdas · Post by **ramdas** » 23 Apr 2011 01:09

KrishG,

One would not say SC is inefficient at higher altitudes: it still performs better. For example CUS has 452s Isp vs 443 for C-20. Just that the gains in changing from GG to SC are less for upper stages.

Sridhar,

The U.S used SC only in the SSME.

It is the USSR which used SC much more. Almost all soviet LPREs after 1965 with thrust > a few tons used SC. While cryo engines 11D56 (similar to our CUSP), RD-57 and RD-0120 used fuel rich preburners, NTO-UDMH engines and semi-cryo engines used oxidizer rich preburners. All soviet long range liquid fuel ICBMs/SLBMs from 1970 onwards used SC engines in all stages (including upper stages). Possible exceptions are upper (i.e, 2nd) stages of the R-29 and R-29RL slbms. Note that all 3 stages of the R-29RM used SC engines, as did all stages on all post 1970 liquid fuelled ICBMs. Probably the culture of automatically choosing staged combustion started here and continued into SLV design.

China has developed a semi-cryo staged combustion booster engine (120 ton sl thrust) as well as an upper stage semi-cryo using staged combustion (18 ton thrust).

KrishG · Post by **KrishG** » 23 Apr 2011 01:19

ramdas wrote:KrishG,

One would not say SC is inefficient at higher altitudes: it still performs better. For example CUS has 452s Isp vs 443 for C-20. Just that the gains in changing from GG to SC are less for upper stages.

Let me requote what I said:

The point I am trying to make is that SC engines are inefficient when used for higher thrust requirements at high altitudes (upper stages).

SC engines do have higher ISPs then GG engines, but that is not the only measure of optimum performance.

Sridhar wrote:KrishG: BTW, I hope you don't take my questioning you the wrong way. Your inputs here are valuable and I don't mean at all to be disrespectful.

No not at all. I'll try to answer your question regarding China tomorrow. Going to bed now!

Sridhar · Post by **Sridhar** » 23 Apr 2011 01:49

Ramdas,

Thanks for the info. I did know that Isaev's original idea led to the development of SC-based engines and that the Russians had used closed cycle engines multiple times. However, their workhorse space launchers over the years have not used cryogenic engines at all. Also, is there a difference (from the perspective of difficulty of technology and reliability) of closed cycle liquid engines vs. closed cycle cryogenic engines?

As for why ISRO went for the engine they did
a. their good experience with the Vikas engine encouraged them to do the same with cryogenics
b. the only available supplier at the time were the Russians (I am not sure if the French were approached and refused or it was too costly - I presume this would have been on the table for ISRO given their past relationship with the French over the Vikas).
c. The Russians had both GG and SC engines, but the RD56 fit into ISRO's needs.
d. the plan was to leapfrog technologies and build the most difficult technology through collaboration with the Russians.
e. When the Americans intervened and prevented the transfer of technology, ISRO needed to build its own - it decided to essentially copy the Russian engine for the most part, since that was the one they were most familiar with.
f. Since the MK3 was a new launcher from the bottom up, they went for the technology that made the most sense, from a thrust/weight ratio but also probably reliability perspective

Gagan · Post by **Gagan** » 23 Apr 2011 01:51

The PSLV "Dog Leg" maneuver, and the TecSAR's launch direction.

There was a change in software needed because the TecSAR was supposed to go into an inclined orbit of 41 degrees instead of the sunsynchronous launch that the PSLV traditionally does.

Rupesh · Post by **Rupesh** » 23 Apr 2011 01:56

^^ It looks like Thumba would be abetter option to launch satellites. SL will not come in the way

Sridhar · Post by **Sridhar** » 23 Apr 2011 02:01

Ramdas,

Quick question - why would the gains for going from GG to SC be less for upper stages? Something about operating in vacuum that differs? My own (limited) understanding is that the difference between the two cycles is essentially how the gases that are used for running the turbopumps are treated - in the GG cycle (also called the open loop cycle) they are expelled, while in the SC/closed loop cycle, they are injected into the combustion chamber and hence used fully for providing thrust. If the difference is merely that, the altitude should make no difference. So clearly, there is something else that I don't understand.

KrishG's point, I think, is that the T/W ratio matters in addition to the ISP.

Sridhar · Post by **Sridhar** » 23 Apr 2011 03:46

This presentation by N K Gupta, who led the C25 project at LPSC is quite informative.
http://www.iuac.ernet.in/iccwebsite/NKGupta.pdf

In particular, this page (click on the thumbnail)

It compares the different types of engines, showing clearly how the GG engine may be lower on efficiency as measured by ISP, but has better thrust and thrust-to-weight ratio. This is what KrishG was referring to, I think.

AJames · Post by **AJames** » 23 Apr 2011 04:54

KrishG wrote:
AJames wrote:CUS & Shroud

I am not an aerodynamicist, but looking at the image, surely the cylindrical lip at the bottom will catch the supersonic air flowing over it and cause severe air turbulence inside. Shouldn't the lattice be right at the bottom of any shroud provided?
It is always covered with a composite cylindrical covering for that exact reason. This is the shroud that got deformed. I have illustrated this in the following pictures.

The point I was making is that from what I understand, the open lattice allows the upper stage engines to be started before the stages separate by allowing the rocket exhaust gases to be vented out via the open lattice section. This means that the top of the section below the upper stage must have a cone shaped end and an open lattice connecting to the bottom circumference of the cone. The diagram shows two cylindrical shrouds with an open lattice between them, above the level of the bottom of the exhaust nozzle. I this was the case, and there was no second lattice below, isn't the lower cylindrical shroud going to act as an air scoop, causing turbulence within the shroud?

From the photos, it looks like what may be two open lattices - the additional one below the lower cylindrical shroud which is shown on the sketch. This may make sense to vent air through which would be fine. If it is a band of black painted shroud below what is shown on the sketch however, then you have an air scoop.

There is also what looks like flames coming out of of this area at launch. Is this some kind of directional control retro rocket?

By the way even if GG is adopted for the GSLV upper stage, I hope India doesn't give up on the SC cryo engine. It would make a great engine for a first stage cryo, and the Space Shuttle demonstrates that it is reliable if started on the ground and can be shut down if ignition fails, before the solid fuel boosters are lit, since none of the Shuttle launches failed as a result of the cryo engines themselves. From my understanding, most SC cryo failures have been due to problems with starting up.

shiv · Post by **shiv** » 23 Apr 2011 05:37

arunsrinivasan wrote:
Austin wrote:... this is not a dick measuring contest.
Sorry OT, but couldn't resist, isn't all (well almost all) human behavior driven by "my .... is bigger than yours ..."

er continuing OT - nearly 50% of humans are wimmens...

ramana · Post by **ramana** » 23 Apr 2011 05:41

disha wrote:
ramana wrote:Odd that they noted the connector separation on earlier flights but didn't take corrective action. Maybe they realized it now. If it showed up earlier then its the vehicle bow during flight which bent the structure leading to the shroud deformation.
ramanaji, I think you are reading it wrong. What Dr. Nair said is that the shroud was faulty to begin with., only the last mission got caught in the fault. Something like the foam debris on the shuttle was always there., only in one mission it proved fatal.

iniial reports were that there was local deformation and that caused the cable connector problem. Hence the conjecture that vibration due to the air flow from larger diameter fairing.

Now it look like the shroud primary structure is the one bending and causing the problems.

Gagan · Post by **Gagan** » 23 Apr 2011 10:48

Err A James,
That diagram of the CUS and the shroud is something that I quickly made on my computer. It was meant to be a rough estimate of what to me appears to be the engine and its covering shroud.

It is not an official ISRO diagram, and I am sure has factual errors in it.
___________________________________________________________________________________________

I was wondering about the venting there, and the possible aerodynamic implications of the same.

But as you've pointed out, it allows that engine to be started before stage seperation occurs. Though in the GSLV launches so far, that has not been what ISRO has been doing, CUS ignition and Stage separation happen close together, hardly a second or two.

The US space shuttle ignites its cryo engines on the ground, and that design allows for such an arrangement, and the cryo also contributes to the launch thrust there. But I wonder how this works out in a staged rocket with stages stacked one over the other. How do you start a cryo stage that is say the 3rd stage, on the ground, and then it takes over after the 2nd stage has been jettisoned.

negi · Post by **negi** » 23 Apr 2011 11:22

^In case of Unkil's space shuttle there is no concept of ' serial/cascade staging' it just has solid fuel booster rockets (parallel staging) that is why the SSME can kick in during the launch itself .

negi · Post by **negi** » 23 Apr 2011 11:45

Sridhar it is not about GG vs SC as it is evident that major players in the SLV arena have tasted success by opting for either of the two cycles. From an Engineering pov it makes perfect sense for ISRO to experiment with both the cycles before it chooses to standardize upon one of them. Russians have been known to have mastered the SC engines and it reflects in their ICBM as well as heavy lift SLV stages in fact 'Khrunichev SRPC' which supplied the 12KRB aka KVD upper stage for the GSLV is also making the KVTK cryogenic upper stage for the next generation Russian SLV 'Angara' which again uses the staged combustion cycle. Today RD-170 is the most powerful semi cryogenic engine (uses staged combustion cycle) in the world and both Unkil and SoKo use verions of the same for their SLVs . ISRO bought the 12KRB upper stage from Glavkosmos as it was the only cryo engine in it's class (weight and thrust wise) which had completed all it's ground tests in Russia.

vina · Post by **vina** » 23 Apr 2011 12:08

Quick question - why would the gains for going from GG to SC be less for upper stages?

The big bad guys in a rocket with the highest mass and thrust are at the lower stages and that is where you need to get the most bang for ever kg of propellant expended (aka sp impulse, if you don't want a gargantuan stage size) , there the specific impulse differences would start becoming very important. So you want a staged combustion.

In the final stage (like CUS), the mass because of staging has already come down to a tiny fraction of starting mass, so the ISP differences aren't such a big influence . so you could go GG route.

negi · Post by **negi** » 23 Apr 2011 12:19

^ Well I thought that for initial stages it is the thrust which matters for the gross weight is high during lift off and you can achieve that by having a high mass flow rate, however the specific impulse is critical for the core and upper stages where the burn time is longer that is why the upper stages for all heavy lifters across the globe use cryogenic engines.

ramdas · Post by **ramdas** » 23 Apr 2011 12:46

The point is that for upper stages, the gain in Isp from GG to SC would be 2-3% (a very efficient GG upperstage eng. can give Isp ~2%smaller than its SC counterpart. Even is chamber pressure of GG engine is lower, a larger nozzle can be provided to get comparable expansion ratios...

On the other hand, for booster stages, chamber pressure also matters,since higher chamber pressure allows higher expansion ratios, which in turn allow more Isp. Remember that the pressure of gases exiting the nozzle must be of the order of 0.6-1 times atmospheric pressure. Therefore, high chamber pressure is critical in booster stages for high expansion ratio. A SC booster engine with 200 atm chamber pressure gives about 7% higher avg. Isp than a GG cycle engine at 80atm...(compare RD-264 with RD-251 for instance).

juvva · Post by **juvva** » 23 Apr 2011 14:00

All 3 satellites healthy :

http://www.hindu.com/2011/04/22/stories ... 500900.htm

&

largest civilian remote sensing satellites constellation:

"
----
The nine IRS in service now are the Technology Experiment Satellite, the Resourcesat-2, the Cartosat-1, 2, 2A and 2B, the Indian Mini Satellite-1, the Radar Imaging Satellite-2 and the Oceansat-2.

They make the IRS system the largest civilian remote-sensing satellite constellation in the world.
----
"

vina · Post by **vina** » 23 Apr 2011 16:15

ramana wrote: Having said that I still dont understand the local loads that caused the deformation. One simple datapoint would be the shroud thickness for the ISRO cryo-stage and the imported one.

Odd that they noted the connector separation on earlier flights but didn't take corrective action. Maybe they realized it now. If it showed up earlier then its the vehicle bow during flight which bent the structure leading to the shroud deformation.

ISRO shows a very good fault tree and root cause analysis approach if you take the sum total of Dr Nair's statements over the investigation period.

The indigenous CUS is lighter than the Russian one, has slightly higher thrust and can sustain peak thrusts longer from what I read. Once it is proved, we can safely drop the Russian engine.

vina · Post by **vina** » 23 Apr 2011 17:57

ramdas wrote:A SC booster engine with 200 atm chamber pressure gives about 7% higher avg. Isp than a GG cycle engine at 80atm...(compare RD-264 with RD-251 for instance)

That really isnt an apple to apple comparison. You should compare a 200 atm pressure engine with GG vs SC . In fact, in a GG, the turbo pump will be more powerful for a given size or smaller for a given requirement , since the pressure drop across the turbine in the turbo pump is larger in the GG cycle (it exhausts into vacuum/atmosphere vs the combustion chamber) and can generate larger power. What makes the difference is the pumping losses if when you vent it vs expanding it in the chamber I suppose.

Bade · Post by **Bade** » 23 Apr 2011 18:47

They make the IRS system the largest civilian remote-sensing satellite constellation in the world.

There we go again

despite all the links provided a few pages back. Remote-sensing has been redefined to suit a marketing slogan. Nuke thread is an example of this sort of indulgence. Wonder why this piskology to claim "largest" and "indigenous" whatever. We need to get over this fixation which is in the same league as using the prefix of "super".

I do not think anyone from SAC A'bad or ISAC Blr will use such a description. They would know for sure if the claim is true or not.

Bade · Post by **Bade** » 23 Apr 2011 19:31

Rupesh wrote:^^ It looks like Thumba would be abetter option to launch satellites. SL will not come in the way

It is perhaps true for polar orbit launches only, I mean the objective of avoiding a populated landmass from falling debris if something goes wrong or even normal lower stage separation. For geostationary launches, isn't the preferred direction more east-west too, and if you take the direction of rotation of earth then a west coast launch will have to pay a price in cost by not making use of this and working against it to avoid debris falling on the landmass.

I wonder if the thinking in ISRO at the time a decision was made, to anticipate more geostationary launches than polar ones and they went for a east coast site. Cyclones and rough weather is a constant threat for the east coast site. Better would have been from one of the Lakshwadeep islands in the far south closest to the equator, except for the infra support and security points of view.

For launching geostationary satellites, it is also important that the satellites can be launched towards the east, where the launch impulse is aided by the spin of the Earth. This ‘slingshot’ effect increases the speed of a launcher by 460 m/s. These important factors save fuel and money, and prolong the active life of satellites. The site should be as close as possible to the equator, so that this assistance is as large as possible.

For polar orbiting satellites, it is a distinct advantage to have open water towards either the south or the north. The Vandenberg Air Force Base in California, USA, for example, has open water to the south, and this location makes it USA’s premier launch site for polar missions. Kourou on the other hand, is ideal for launching both polar orbiting and geostationary satellites, since its location has open water both to the north and to the east.

EUMETSAT link on launching satellites

disha · Post by **disha** » 23 Apr 2011 22:32

Bade wrote:
They make the IRS system the largest civilian remote-sensing satellite constellation in the world.
There we go again despite all the links provided a few pages back. Remote-sensing has been redefined to suit a marketing slogan. Nuke thread is an example of this sort of indulgence. Wonder why this piskology to claim "largest" and "indigenous" whatever. We need to get over this fixation which is in the same league as using the prefix of "super".

I do not think anyone from SAC A'bad or ISAC Blr will use such a description. They would know for sure if the claim is true or not.

Bade sir, you are welcome to do ROTFL as much as you want., it is your choice /smile/. India does operate the largest civilian Remote Sensing/Earth Observation constellation in the world and if the fact is against your belief., you are welcome to disregard the fact and invent truths for your beliefs. (added later: Please do not take the statement as a personal offense, it came out a little bit strident)

Now to address your beliefs, the most advanced nation on earth has a civilian program for Polar Satellite Earth Observation (this can be compared apple to apples or mango to mango with Polar Satellite Launch Vehicle series and IRS constellation) called (guess what?) "The Polar-orbiting Operational Environmental Satellite (POES)". This is operated by the Department of Commerce and is different from the the parallel polar program in the Department of Defense which is the Defense Meteorological Satellite Program (DMSP).

Now in 1994 under the clintoon admin., and due to budget constraints., they decided to merge the two programs into (guess what again) National Polar-orbiting Operational Environmental Satellite System.

If my memory serves it right., they were planning to launch 4 sats in the Polar Series (C1, C2) and (C3, C4)., the last two are still in planned stage.

Then this news comes along http://www.scientificamerican.com/artic ... vation-gap., that has put C3/C4 in jeopardy and guess what., the NPOESS is partnering with EU for the EUMETSAT. The US and the EU put together *may* have more Earth Observation but that does not take away from the *FACT* that ISRO (India) is operating the largest constellation of earth observation remote sensing satellite (IRS Series).

Now you can call Sputnik as an earth observation satellite and you will be absolutely right., it is earth observation from space (so was Chandrayaan when it took the fotu of earth - observed earth)., and include all and sundry satellites launched by NASA in there. Or you can also add the dedicated defense satellites and club them under EO., still it does not take away from the *FACT* that ISRO (India) operates the largest civilian Indian Remote Sensing Satellite series (and constellation) in the world.

If you still want to disbelieve and ignore the above facts and make us (or me) want to believe otherwise., please give us the list of satellites launched under NPOES system by US for pure civilian purposes within US (and not partnered with EU).

Bade · Post by **Bade** » 24 Apr 2011 00:17

Disha, nothing personal you can also believe what you want to believe.

If the claim of the largest constellation of EOS civilian satellites is true then why is it that India uses non-ISRO satellites (MODIS on Aqua & Terra and till recently SeaWiFS as well as the NOAA POES & GOES satellite data (which you mentioned too) for purposes other than for land remote sensing. Landsat which was the true IRS series (apples to apples) is now limited to 2 or is it one operational (landsat 6/7), but then DigiGlobe which also buys IRS data has similar missions. It is just that some of the missions specifically land remote sensing has moved to the private domain outside of India and is not on tax payer funds anymore as it has a market for such products.

Besides we are not counting US defense satellites, whereas for ISRO the distinction is not there since we do not have separate mil-sat program operational as of now. It was said right from the early days, that Cartosats have dual applications, civilian and military. TES data definitely was not in the open domain. So when we mix and match to increase our count and leave out defense sats from the US the count will show much lower for the US. Most of the US defense non-communication satellites would definitely be mostly for land imaging in any case.

I still find this exercise pointless, but you can believe in it while the world laughs at it rightly. It is mostly a DDM claim probably not even an official ISRO stand. Maybe, it is a ANTRIX invention since they sell mostly land imagery to make money along with the launch services.

Regarding the reorganization and the joint NASA-NOAA-DMSP programs there is a lot of that in open domain and so the satellite counts will only go down further. But that is a different issue. The NASA current mission links are not some experimental tech missions as one would believe. The example for that is the MODIS instrument on two satellites which are used the world over including the US in operational mode for many applications.

If you go by just satellite counts probably PRC can claim a large number too with their frequent launches and short planned mission life for each satellite. What they call operational I have no idea, and their sat data is not shared with the world, though for EOS they have also made attempts to make their data usable by the world community. It just has quality issues at the same level or more than the IRS series outside of land imaging.

Sputnik: That was a cheap shot vs Chandrayaan. I will skip that since it is just a diversion.

BTW, POES/GOES data are not the only operational data from satellites. A lot of the NASA missions are too and that is why I gave out the link. All the scatterometer instruments are all NASA missions and data is used operationally and freely available for all to use.

POES which has a heritage since TIROS series from the 70's is largely on replicate and replace as they age mode till now. NPOESS is where the next generational changes are going to take place.

Bade · Post by **Bade** » 24 Apr 2011 07:43

If you still want to disbelieve and ignore the above facts and make us (or me) want to believe otherwise., please give us the list of satellites launched under NPOES system by US for pure civilian purposes within US (and not partnered with EU).

I was not going to do this to put this issue to rest, but did find time to do a search and just want to summarize the number of satellites since you requested. To make a fair comparison one need to include country wide numbers for comparing, and not just a single agency like ISRO (since there are no competing agencies other than this one in India) with only NASA or NOAA. Whereas at least in US there are overlapping roles between NASA,NOAA,USGS,NRL in satellite launch and data usage with common/similar mission interests. Defense sats is left out as information is harder to get in open domain and do not want to go there if not needed.

For ISRO from the link ISRO operational sats they have separated Geo and Polar with the latter being named IRS is the root cause of this narrow definition of the term "remote sensing" and the misunderstanding. Small point to be overlooked in the numbers game. So for Polar there are 10 operational satellites which also includes the latest launch and likely not really operational yet which is normal for all agencies. Even Oceansat-2 which was launched a while back (> 1yr) is not operational. I see no data on the INCOIS site for sure so not for public use yet. So Polar it is 10 ( or 8 ), the lower value if one gets picky. If TES is not included then it can be as low as 7. Had not heard of IMS and not clear if it is "operational", the term operational usually means data used 24/7. Not that it beams data down and it is used sparingly. So if IMS is not included one is left with only 6 Polar operational used sats. I am not sure if ISRO uses 24/7 to define operational, but that is the world standardized use.

For Geostationary from the same link above I count 2 (METSAT/Kalpana and INSAT-3A) as Remote sensing too, others are all COMM sats. So for ISRO the total is 10+2 (at a max) or as low as (6+2). So 8-12 depending on how one counts.

Now let us see that the US programs show. We begin with NOAA as they claim to be the operational arm

creating enough friction with NASA.

http://www.oso.noaa.gov/poesstatus/
The count here is 5 without METOP for operational 24/7 use.
http://www.oso.noaa.gov/goesstatus/
Here too the count is 5 in service.

These are just MET payloads largely, then there is the Landsat-7 currently operational, plus at least TERRA, AQUA for land and ocean applications which are used 24/7 for fire monitoring, ocean fishing zones, sea surface temperature etc. I picked these NASA sats because similar payloads are staged to become part of the NPOESS program. With just these the count for US is now 5+5+2+1=13. Already more than the max value for ISRO/India. I can safely stop here and need not bother with other NASA/NOAA missions for earth observation like TRMM (that is MEga-tropiques like one gone dead now) and the SeaWiFS built for NASA for Ocean Color which had a glorious 12 yrs of service before it died the day before X'mas. BTW, Oceansat-I/II replicated this payload in bands. Then there are GPS missions (for atmospheric tomography) and many more from NASA, the final count not including defense will still be a factor of 2 more with what India/ISRO has up there for "operational remote sensing" satellites.

*Operational means 24/7 data access and product generated within at least 12 hrs of acquisition.
* Earth Remote sensing means (not COMMUNICATIONS-payload GEOSTATIONARY allowed

), earth observing, land, water and air missions for operational use. Still not counting similar non-operational narrow swath width products which does not give global or even local(CONUS region) coverage within 24 hrs. For equivalent Indian case it would be IOR region for obvious reasons. So most IRS-series would not give 24/7 coverage with their narrow swath widths. But we digress.