Matrix Games Forums

Forums  Register  Login  Photo Gallery  Member List  Search  Calendars  FAQ 

My Profile  Inbox  Address Book  My Subscription  My Forums  Log Out

RE: The Chinese maritime surveillance system

 
View related threads: (in this forum | in all forums)

Logged in as: Guest
Users viewing this topic: none
  Printable Version
All Forums >> [New Releases from Matrix Games] >> Command: Modern Air / Naval Operations >> RE: The Chinese maritime surveillance system Page: <<   < prev  1 [2]
Login
Message << Older Topic   Newer Topic >>
RE: The Chinese maritime surveillance system - 1/6/2017 6:16:19 PM   
gosnold

 

Posts: 131
Joined: 7/10/2013
Status: offline
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 >

(in reply to tomrlutong2)
Post #: 31
RE: The Chinese maritime surveillance system - 1/7/2017 3:52:09 PM   
ExNusquam

 

Posts: 402
Joined: 3/4/2014
Status: offline

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.

(in reply to gosnold)
Post #: 32
RE: The Chinese maritime surveillance system - 1/7/2017 4:10:17 PM   
gosnold

 

Posts: 131
Joined: 7/10/2013
Status: offline
Actually we know quite a bit about the GF-4 sensor:

(in reply to ExNusquam)
Post #: 33
RE: The Chinese maritime surveillance system - 3/6/2017 1:00:30 AM   
Dysta


Posts: 1460
Joined: 8/8/2015
Status: online
Jilin-1 Satellite debuted a short geo footage of Bogota airport.

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

_____________________________

Signature pictures disabled temporarily.

(in reply to gosnold)
Post #: 34
RE: The Chinese maritime surveillance system - 12/6/2017 7:42:09 PM   
gosnold

 

Posts: 131
Joined: 7/10/2013
Status: offline
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.

(in reply to Dysta)
Post #: 35
RE: The Chinese maritime surveillance system - 12/7/2017 4:37:18 AM   
Dimitris


Posts: 9207
Joined: 7/31/2005
Status: online
This is great stuff, thank you!

_____________________________


(in reply to gosnold)
Post #: 36
RE: The Chinese maritime surveillance system - 12/7/2017 4:42:24 AM   
Dysta


Posts: 1460
Joined: 8/8/2015
Status: online
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 >


_____________________________

Signature pictures disabled temporarily.

(in reply to gosnold)
Post #: 37
RE: The Chinese maritime surveillance system - 12/7/2017 1:32:46 PM   
stilesw


Posts: 391
Joined: 6/26/2014
From: Hansville, WA, USA
Status: offline
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

(in reply to gosnold)
Post #: 38
Page:   <<   < prev  1 [2]
All Forums >> [New Releases from Matrix Games] >> Command: Modern Air / Naval Operations >> RE: The Chinese maritime surveillance system Page: <<   < prev  1 [2]
Jump to:





New Messages No New Messages
Hot Topic w/ New Messages Hot Topic w/o New Messages
Locked w/ New Messages Locked w/o New Messages
 Post New Thread
 Reply to Message
 Post New Poll
 Submit Vote
 Delete My Own Post
 Delete My Own Thread
 Rate Posts


Forum Software © ASPPlayground.NET Advanced Edition 2.4.5 ANSI

0.096