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The Chinese maritime surveillance system - 10/2/2016 11:44:35 AM   
gosnold

 

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I have written a blog post on the Chinese maritime surveillance satellites, with a list of these satellites, and an analysis of the coverage they might provide. In section IV of the post, there is an animated gif to visualize the coverage.

I thought some people here might find it interesting.
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RE: The Chinese maritime surveillance system - 10/2/2016 12:22:39 PM   
Gunner98

 

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Excellent stuff gosnold. I went from knowing absolutely nothing about Chinese satellites, to -very well informed - in a very easy and enjoyable read.

Thank you

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RE: The Chinese maritime surveillance system - 10/2/2016 1:47:28 PM   
Dysta


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Excellent contribution.

It's far from globally non-stop surveillance, but the regional and intel gathering methods are getting sharper at 2010s.

I think it's also worth to tell the Beidou formation, for dual-use positioning and unit/weapon guidance without foreign satellites.

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RE: The Chinese maritime surveillance system - 10/2/2016 3:23:13 PM   
bradinggs


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Nice coverage there gosnold, thanks.

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RE: The Chinese maritime surveillance system - 10/2/2016 5:51:40 PM   
tjhkkr


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That was really cool... Thanks!

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RE: The Chinese maritime surveillance system - 10/2/2016 5:53:55 PM   
kevinkins


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Very impressive. Thank you for the link. It could not have found a more interested audience.

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RE: The Chinese maritime surveillance system - 10/3/2016 9:52:15 AM   
mikkey


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Excellent gosnold, thanks for sharing.

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RE: The Chinese maritime surveillance system - 10/4/2016 12:25:33 AM   
Hongjian

 

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Thank you, gosnold.

Good to know that more PLA watchers are contributing to this forum.

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RE: The Chinese maritime surveillance system - 10/4/2016 12:31:36 AM   
ExNusquam

 

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Gosnold, this is easily one of the best open-source pieces on Chinese space based ISR, and the implications of that for building a firing solution. I fully concur with you that there are two targeting windows, where there are closely spaced passes by a SAR bird followed by an EO bird. I only have a couple of minor technical points:

1. You asses that if the SAR birds flew in pairs they could do positive ship ID. I doubt this is possible beyond basic dimensions and RCS due to the effects of target motion on SAR. A moving target will be a blurry, smeary mess at high resolution and a slightly less blurry, smeary mess at lower resolution. The streaking in the example of the oil tanker (left) is caused by the relatively small motion of the ships radars; I suspect the ship itself is stationary.

2. I have suspicions about the ability of the GF-4 to effectively track BLUFOR ships. Here's a screenshot from MarineTraffic showing AIS hits just North of the Marianas (inside the second island chain)...there are a lot of vessels out there that will generate sizable wakes. A 50m EO GSD means a Carrier will be 6 piles on a GF4 image, which is likely not enough to ID. The 400m IR GSD probably won't be much use. The GF4 is an ocean surveillance system, and will likely be used to gauge activity levels, but I doubt it can do the independent tracking that is often claimed.

3. I also think that cloud cover is a huge limitation on EO coverage. It's cloudy a lot in the Pacific. Here's the current aviation sigwx forecast, and you can see that there's typically a decent amount of cloud cover across the entire region.

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RE: The Chinese maritime surveillance system - 10/4/2016 2:43:51 AM   
Dysta


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Satellites aren't that omnipotent, too many conditions must be met to be effectively used, both normal tracking and military purposes.

*ADD: gosnold you can also add a small addition of failed satellites, such as GF-10.

< Message edited by Dysta -- 10/4/2016 11:09:01 AM >


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RE: The Chinese maritime surveillance system - 10/4/2016 9:09:15 PM   
gosnold

 

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quote:

ORIGINAL: ExNusquam

Gosnold, this is easily one of the best open-source pieces on Chinese space based ISR, and the implications of that for building a firing solution. I fully concur with you that there are two targeting windows, where there are closely spaced passes by a SAR bird followed by an EO bird. I only have a couple of minor technical points:

1. You asses that if the SAR birds flew in pairs they could do positive ship ID. I doubt this is possible beyond basic dimensions and RCS due to the effects of target motion on SAR. A moving target will be a blurry, smeary mess at high resolution and a slightly less blurry, smeary mess at lower resolution. The streaking in the example of the oil tanker (left) is caused by the relatively small motion of the ships radars; I suspect the ship itself is stationary.

2. I have suspicions about the ability of the GF-4 to effectively track BLUFOR ships. Here's a screenshot from MarineTraffic showing AIS hits just North of the Marianas (inside the second island chain)...there are a lot of vessels out there that will generate sizable wakes. A 50m EO GSD means a Carrier will be 6 piles on a GF4 image, which is likely not enough to ID. The 400m IR GSD probably won't be much use. The GF4 is an ocean surveillance system, and will likely be used to gauge activity levels, but I doubt it can do the independent tracking that is often claimed.

3. I also think that cloud cover is a huge limitation on EO coverage. It's cloudy a lot in the Pacific. Here's the current aviation sigwx forecast, and you can see that there's typically a decent amount of cloud cover across the entire region.


Thanks for the feedback!

Regarding 1., I did not know moving targets are blurry on SAR images, but I looked it up and you are right, the high-resolution images of a fast ship would be deteriorated, making identification more difficult. Now SAR processing is kind of a black art and there might be ways to get rid of the blur if you really need to, so I wouldn't say ship moving ship ID is impossible with SAR.

For 2., I think carrier identification is very feasible with GF-4. If you look for a 330m-long CVN, you are looking for ships 6 to 7 pixels long. That means 300 to 350m, so you have aircraft carriers, oil supertankers and large container ships. The GF-4 sensor gives you colour + IR so you can ignore the ships that are not gray, that reduces the number of candidates considerably. Then you can discriminate on speed: the tankers and container ships rarely go over 20 knots, the carrier is the only one that can go 30 knots. Finally you can discriminate on course: the civilian ships will follow a constant heading, the carrier will change heading to have head-on winds during air operations. With all that I don't think you can mistake the carrier and the civilian ships.

Regarding 3., you are definitely right about that, cloud coverage has a major impact. Do you know a good resources to know cloud coverage over the course of a year? I'm looking for how much time the weather is completely overcast for several days at a time in the region, since that would make optical systems blind.



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RE: The Chinese maritime surveillance system - 10/4/2016 11:29:14 PM   
magi

 

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That was very good.... thank you....

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RE: The Chinese maritime surveillance system - 10/5/2016 2:00:52 AM   
ExNusquam

 

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quote:

ORIGINAL: gosnold

Thanks for the feedback!

Regarding 1., I did not know moving targets are blurry on SAR images, but I looked it up and you are right, the high-resolution images of a fast ship would be deteriorated, making identification more difficult. Now SAR processing is kind of a black art and there might be ways to get rid of the blur if you really need to, so I wouldn't say ship moving ship ID is impossible with SAR.

For 2., I think carrier identification is very feasible with GF-4. If you look for a 330m-long CVN, you are looking for ships 6 to 7 pixels long. That means 300 to 350m, so you have aircraft carriers, oil supertankers and large container ships. The GF-4 sensor gives you colour + IR so you can ignore the ships that are not gray, that reduces the number of candidates considerably. Then you can discriminate on speed: the tankers and container ships rarely go over 20 knots, the carrier is the only one that can go 30 knots. Finally you can discriminate on course: the civilian ships will follow a constant heading, the carrier will change heading to have head-on winds during air operations. With all that I don't think you can mistake the carrier and the civilian ships.

Regarding 3., you are definitely right about that, cloud coverage has a major impact. Do you know a good resources to know cloud coverage over the course of a year? I'm looking for how much time the weather is completely overcast for several days at a time in the region, since that would make optical systems blind.




1. You can get rid of the blurring to a degree by reducing resolution. High-res SAR requires a larger (synthetic) aperture and so the target moves more while this occurs. By using a smaller aperture, the target is less blurry, but at lower resolution.

2. Has it been confirmed that the GF-4 has an MSI payload? The only stuff I've seen was that it was "visible light" which I interpreted as panchromatic. You are correct about the flight ops giving away the carrier, but if BLUFOR refrains from or minimizes displacement from PIM during flight ops, they will be harder to track. Here's an excellent piece (by a former Soviet Naval Officer) about attempting to kill US CVBGs; take note about the part where the Carriers will sail completely independently to confuse targeting.

3. The source I would have recommended would have been the USAF weather site, but for the last couple of years it's required a CAC to access. I'm sure if you look for a marine almanac you can find something; marine and aviation weather forecasting could provide a useful alternative.

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RE: The Chinese maritime surveillance system - 10/5/2016 2:17:10 AM   
Dysta


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In other word: China will not use these satellites for missile guidance. They are only providing visuals for operators.

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RE: The Chinese maritime surveillance system - 10/5/2016 7:00:49 PM   
gosnold

 

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quote:

ORIGINAL: Dysta

In other word: China will not use these satellites for missile guidance. They are only providing visuals for operators.


They can definitely be used to give a firing solution to missiles.



quote:

ORIGINAL: ExNusquam

1. You can get rid of the blurring to a degree by reducing resolution. High-res SAR requires a larger (synthetic) aperture and so the target moves more while this occurs. By using a smaller aperture, the target is less blurry, but at lower resolution.

2. Has it been confirmed that the GF-4 has an MSI payload? The only stuff I've seen was that it was "visible light" which I interpreted as panchromatic. You are correct about the flight ops giving away the carrier, but if BLUFOR refrains from or minimizes displacement from PIM during flight ops, they will be harder to track. Here's an excellent piece (by a former Soviet Naval Officer) about attempting to kill US CVBGs; take note about the part where the Carriers will sail completely independently to confuse targeting.

3. The source I would have recommended would have been the USAF weather site, but for the last couple of years it's required a CAC to access. I'm sure if you look for a marine almanac you can find something; marine and aviation weather forecasting could provide a useful alternative.


Gaofen-4 does have a colour imager, for instance see
those images of Beijing.

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RE: The Chinese maritime surveillance system - 10/6/2016 12:20:00 AM   
ExNusquam

 

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quote:

ORIGINAL: gosnold

Gaofen-4 does have a colour imager, for instance see
those images of Beijing.


Thanks for the source on that!

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RE: The Chinese maritime surveillance system - 10/9/2016 3:09:10 PM   
gosnold

 

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Henri (from eastpendulum.com) has found a nice report by the Indian National Institute of Advanced Studies on the chinese sats. It mostly agrees with my blog post.

So I went digging in the NIAS website and found a analysis of the Chinese ASBM capability which is worth a read:
http://eprints.nias.res.in/300/1/NIAS_Report_R5-2011.pdf

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RE: The Chinese maritime surveillance system - 10/9/2016 4:20:10 PM   
Dysta


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quote:

ORIGINAL: gosnold

So I went digging in the NIAS website and found a analysis of the Chinese ASBM capability which is worth a read:
http://eprints.nias.res.in/300/1/NIAS_Report_R5-2011.pdf


Interestingly, the report is 5 years old, but I found this line particularly true until now:

quote:

Whatever be the combination of measures that the US chooses, it would appear that the ASBM has already achieved part of the intended effect by forcing a re-evaluation of the military equation and injecting an element of uncertainty in what was an unchallenged military scenario for the United States.


Simply say, China force US and it's neighbors to develop ABM systems to encumbering their military budget with substantial margins, right at the decade of economical downfall. DF-21 doesn't need to be terribly effective against land or ships, deterrence is all it need to have, and is doing already.

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RE: The Chinese maritime surveillance system - 10/23/2016 3:30:15 PM   
gosnold

 

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For those interested, I found an actual Gaofen-4 image in a presentation from the China Academy of Space technology


I found it while writing an article on persistent surveillance from high orbit:
https://satelliteobservation.wordpress.com/

I also found an interesting piece of information on US satellites: did you know the US missile warning satellites can detect Backfires when they engage their afterburner? They can also detect plane crashes. It would be interesting to model those capabilities in-game.

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RE: The Chinese maritime surveillance system - 10/23/2016 5:33:05 PM   
Dimitris

 

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IIRC we already model the DSP sats as being able to detect planes on afterburner. I'll have to double-check what we enable for SBIRS.

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RE: The Chinese maritime surveillance system - 10/24/2016 4:17:24 AM   
ExNusquam

 

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Sunburn, last I checked the DSP satellites aren't actually importable (the platform exists, though). I just assumed this was just due to the fact that the actual longitudes of the birds being classified. Additionally, the SBIRS birds in game have extremely limited detection capabilities. They don't seem to detect lauches, and the IR sensor they have has a detection range of only 2000NM, which means that anything beyond 33°N/S is undetectable to them from geostationary orbit. Additionally, the launch detection doesn't seem to work well. Try running the attached save.

Attachment (1)

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RE: The Chinese maritime surveillance system - 10/24/2016 6:40:19 PM   
bradinggs


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This should help, see attached. Cloud history for a good few years.




Clouds can be funny though. We sometimes have a (what seems) completely clear area but right on top of the object we wanting to look at ends up being a freaking cloud. Nature has a serious sense of humour.

Attachment (1)

< Message edited by bradinggs -- 10/24/2016 6:46:28 PM >

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RE: The Chinese maritime surveillance system - 12/5/2016 10:25:36 AM   
Dimitris

 

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quote:

ORIGINAL: ExNusquam
Sunburn, last I checked the DSP satellites aren't actually importable (the platform exists, though). I just assumed this was just due to the fact that the actual longitudes of the birds being classified. Additionally, the SBIRS birds in game have extremely limited detection capabilities. They don't seem to detect lauches, and the IR sensor they have has a detection range of only 2000NM, which means that anything beyond 33°N/S is undetectable to them from geostationary orbit. Additionally, the launch detection doesn't seem to work well. Try running the attached save.


Thanks for the heads-up, we'll look into both of these.

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RE: The Chinese maritime surveillance system - 12/5/2016 6:58:51 PM   
gosnold

 

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On the subject of plane detection with DSP and SBIRS, I read in America's space sentinels, a book on the history of those programs, that DSP detected Iraqi planes on afterburner during GW1. I think that the the only Iraqi planes with afterburners at the time were fighters, so it seems the satellites can detect quite small signatures (though I Iraq had Mig-25s and they have quite big engines).

< Message edited by gosnold -- 12/5/2016 6:59:02 PM >

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RE: The Chinese maritime surveillance system - 12/6/2016 1:09:27 PM   
ziolo


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Very interesting!

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RE: The Chinese maritime surveillance system - 12/6/2016 1:45:43 PM   
jmax

 

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Awesome, thank you so much!

In a similar vein, does anyone have some good info on Chinese SOSUS and OTH radar?

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RE: The Chinese maritime surveillance system - 12/6/2016 3:09:52 PM   
mikmykWS

 

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Hi Guys

Thanks for all the info. I've been looking through our Chinese sat orbat and there is some work to be done. Public info is a pita btw. The Gaofen-4 is supposed to be in a geostationary orbit over Singapore more or less but public orbital data doesn't have it near there. We'll do our best to rectify this but we can only work with what we have and unfortunately we need better data on some.

We've got one critical issue that needs to be solved in that we don't yet define the area that a sat can see. We just do slant range, zoom detection and zoom classification. So the result is a very high sat with values that can see to the ground will also be able to see a very large swarth of territory which isn't quite right. We know what the issue is and are working on a solution.

The next phase at some point will be looking at is focus. Sats don't just see thing but people have to be looking for something in the imagery they produce so we've got to refine that logic a little more. We're thinking about that as well.

Thanks!

Mike

< Message edited by mikmyk -- 12/6/2016 3:12:47 PM >


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RE: The Chinese maritime surveillance system - 12/7/2016 7:06:37 PM   
gosnold

 

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quote:

ORIGINAL: mikmyk

Hi Guys

Thanks for all the info. I've been looking through our Chinese sat orbat and there is some work to be done. Public info is a pita btw. The Gaofen-4 is supposed to be in a geostationary orbit over Singapore more or less but public orbital data doesn't have it near there. We'll do our best to rectify this but we can only work with what we have and unfortunately we need better data on some.

We've got one critical issue that needs to be solved in that we don't yet define the area that a sat can see. We just do slant range, zoom detection and zoom classification. So the result is a very high sat with values that can see to the ground will also be able to see a very large swarth of territory which isn't quite right. We know what the issue is and are working on a solution.

The next phase at some point will be looking at is focus. Sats don't just see thing but people have to be looking for something in the imagery they produce so we've got to refine that logic a little more. We're thinking about that as well.

Thanks!

Mike


Glad to know you are improving the satellite modelling! You are right that with the current one Gaofen 4 (which the latest spacetrack TLE do put in GEO over singapore btw) would be able to see everywhere all the time. You can fix that by including local weather (to block its view in some regions), by including angle limitations (if the satellite is too low over the horizon its resolution is degraded, so it can only look at the area below it, and not at the poles for instance), and by including swath width constraints with the focus mechanism as you have described. Scenario designers can also include detectable but not identifiable civilian traffic, to confuse the player. Overall however, a high-resolution imaging satellite in GEO is an extremely powerful tool.

One way you could model swath width is by having a detection probability depending on the area to be searched. Basically a satellite can only look at x km2 per minute. So if you ask to look for a target in an area of x km2, the detection probability is 100% * the usual probability calculation.
If you ask to survey an area of 2x km2, the detection probability drops to 50% of normal, and so on.

I have an excel table of observation satellites, with their resolution, swath width and orbits when available, which you can use as a starting point:
https://dl.dropboxusercontent.com/u/108564708/HR%20EO%20sats.xlsx
The data mostly comes from eoportal, but it's more synthetic.

Another aspect you might want to consider is agility: old satellites can only point in one direction, and so if you give them two focus area far apart they can not image both. The new ones can. Here's an example of Gaofen 4 showing the use of agility:



Typically for a GEO imaging sat it takes in the order of minutes to repoint it to another area, that's what limits your ability to image everywhere all the time.

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RE: The Chinese maritime surveillance system - 12/11/2016 3:28:29 AM   
Dysta


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One new GEOSTAT meteorological satellite, FengYun-4, is now orbiting.

https://www.nasaspaceflight.com/2016/12/long-march-3b-launches-fengyun-4a/

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RE: The Chinese maritime surveillance system - 1/6/2017 2:55:26 PM   
tomrlutong2

 

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Gognold, thanks, this is an amazing post full of great information. Like Gunner98, I went from having a vague idea of sat. capabilities to feeling very well informed thanks to you. I'll now use this new knowledge to ask a stupid question.

The Gaofen-4's infrared resolution is 400m. Solar isolation in orbit is 1366 W/m^2. So, there's 218MW of solar energy falling on each Gaofen-4 IR pixel. From wikipedia, the reactors in the Nimitz class are rated at 550MW (thermal). My understanding of civilian PWRs is that they can't operate below 20% of full capacity.

So, at full power, a Nimitz is generating 1100MW of heat, and at lowest power 220MW. That's equal to or greater than the amount of solar energy falling on a GF-4 pixel. Does that mean that in all circumstances, a Nimitz would be detectable by infrared?

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