RE: The Chinese maritime surveillance system

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RE: The Chinese maritime surveillance system - 1/6/2017 6:16:19 PM

gosnold

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That's a good question. The answer is a bit more complex than your calculation:
- The solar insolation is partly absorbed by the sea (some of it is reflected), and reemitted at different infared wavelengths (which depend on sea temperature).
- The thermal power produced by the reactors on the Nimitz heat the sea around the ship (especially in its wake), and thus the sea radiates at different wavelengths.
- The ship itself is not at the same temperature as the sea.
- The atmosphere absorbs part of the infrared radiation

So the computation is not straightforward. A good tutorial on these issues is there

A back of the envelope computation using the https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law gives an irradiance of 10W/m^2 for a (black) body at 10�C, so that could be the background irradiance. That's 1.6 MW for 400m^2, so the heat output of the Nimitz should be detectable with good contrast even if it is spread on several pixels. (edit:corrected computation mistake)

Another interesting question is: could Gaofen-4 detect aircrafts on afterburner (likely yes, american DSP satellites can do it and they have a 1km resolution), or even standard jet engines (maybe).

< Message edited by gosnold -- 1/7/2017 4:03:23 PM >

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Post #: 31

RE: The Chinese maritime surveillance system - 1/7/2017 3:52:09 PM

ExNusquam

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quote:

ORIGINAL: gosnold
Another interesting question is: could Gaofen-4 detect aircrafts on afterburner (likely yes, american DSP satellites can do it and they have a 1km resolution), or even standard jet engines (maybe).

Theoretically, but we don't know the exact sensor design of the GF-4, so it might be of much use tracking aircraft.

DSP is a non-imaging scanning sensor that checks it's FOR every 10-seconds. This is great for missile warning across an entire AOR. The GF-4 sensor is probably analogous to the SBIRS-GEO Staring sensor. From a US OSD Report:

quote:

The GEO staring sensor will have high agility to rapidly stare at one earth location and then step to other locations,with improved sensitivity compared to DSP. Several areas can be monitored by the staring sensor with revisit times significantly smaller that that of DSP. A continuous staring mode will also provide an even smaller revisit time.

These sensors are probably more useful in the Technical Intelligence/Battlespace Characterization roles than an Indications and Warning (IW) role. If China launches a scanning sensor to tip-and-cue the GF-4 onto events, I think the IR sensor will become far more useful. That would allow the scanner to detect the event and the starer to characterize/track it. Currently I think it's used to supplant the EO sensor during night hours.

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Post #: 32

RE: The Chinese maritime surveillance system - 1/7/2017 4:10:17 PM

gosnold

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Actually we know quite a bit about the GF-4 sensor:

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Post #: 33

RE: The Chinese maritime surveillance system - 3/6/2017 1:00:30 AM

Dysta

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Jilin-1 Satellite debuted a short geo footage of Bogota airport.

http://www.chinadefenseobservation.com/?p=5011

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Post #: 34

RE: The Chinese maritime surveillance system - 12/6/2017 7:42:09 PM

gosnold

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Reviving this thread as the Chinese have launch a new kind of constellation, focused on very high revisit:
Article on satelliteobservation
It's probably ELINT, and if so would provide nearly continuous coverage.

Also I have reformatted my database of observation satellites, it's now there (and the documentation there.

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Post #: 35

RE: The Chinese maritime surveillance system - 12/7/2017 4:37:18 AM

Dimitris

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This is great stuff, thank you!

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Post #: 36

RE: The Chinese maritime surveillance system - 12/7/2017 4:42:24 AM

Dysta

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quote:

ORIGINAL: gosnold

Reviving this thread as the Chinese have launch a new kind of constellation, focused on very high revisit:
Article on satelliteobservation
It's probably ELINT, and if so would provide nearly continuous coverage.

So what it�s called to be exact, YG-30-01 or YG-31?

http://www.spaceflightinsider.com/organizations/china-national-space-administration/long-march-2d-sends-yaogan-weixing-31-satellite-aloft/

< Message edited by Dysta -- 12/7/2017 4:50:19 AM >

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Post #: 37

RE: The Chinese maritime surveillance system - 12/7/2017 1:32:46 PM

stilesw

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gosnold,

Many thanks for this reference. I've added it the the unofficial Dropbox CMANO reference library.

Anyone who would like to be added to the access list please PM me with your email address.

Currently over 200 items and 50 members.

-Wayne Stiles

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Post #: 38

RE: The Chinese maritime surveillance system - 11/23/2019 8:05:59 PM

gosnold

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I'm reviving this thread with two updates:

One on TJS-4 a Chinese SIGINT satellite in geostationary orbit:
https://satelliteobservation.net/2019/11/20/tjs-4-the-ears-of-beijing/

And the other on the a (probably SIGINT) Yagoan-30 constellation in low earth orbit:
https://satelliteobservation.net/2019/11/04/some-news-on-the-yaogan-30-constellation/

(in reply to stilesw)

Post #: 39

RE: The Chinese maritime surveillance system - 11/25/2020 10:45:35 AM

gosnold

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The Yaogan-30 constellation has been reinforced with new launches and is now complete:

https://satelliteobservation.net/2020/11/25/china-completes-the-yaogan-30-constellation/

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Post #: 40

RE: The Chinese maritime surveillance system - 11/26/2020 12:07:02 AM

Hongjian

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quote:

Very interesting animation regarding the Yaogan-30's semi permanent coverage over Taipei:

https://www.youtube.com/watch?v=mkZOaMy4q08&

EDIT: Yeah, I see it is already posted above by the original author gosnold. Thanks for the great work!

Also, we totally missed the Gaofen-13 launch Oct 11 this year, right?

That thing looks like to be the upgraded Gaofen-4 variant, but with much better resolution (15m vs 50m of the GF-4); all at geostationary orbit.

https://space.skyrocket.de/doc_sdat/gf-13.htm
https://www.nasaspaceflight.com/2020/10/long-march-3b-lofts-gaofen-13/

Also related to that; there are claims that the August 2020 DF-21D and DF-26 tests actually hit a moving target ship:

https://www.scmp.com/news/china/military/article/3109809/chinas-aircraft-carrier-killer-missiles-successfully-hit-target

< Message edited by Hongjian -- 11/26/2020 12:14:19 AM >

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Post #: 41

RE: The Chinese maritime surveillance system - 11/26/2020 6:46:45 PM

gosnold

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Yes, Gaofen-13 should be able to precisely identify ships by accurately measuring their length, and might even be able to track aircrafts taxying at airbases.

(in reply to Hongjian)

Post #: 42