Can anybody tell me what this is?

[PlaneConfused]

Excuse the poor photo, but can anybody identify which variant of the C-135 this is? It was taken in Cairns, recently.

http://www.flickr.com/photos/33673197@N00/397471154/

[FL575]

I think you will find it is a NKC-135 'Big Crow'

[PlaneConfused]

Thanks, FL575. What role are they used in?

[FL575]

Confused,
Basically it is a flying testbed for various pieces of electronic wizardry.
The following has a fair description of it:
http://www.spyflight.co.uk/main.htm

[PlaneConfused]

Thanks, guys, appreciate it.

PC