Literature on remote sensing

Hi all.

I am involved in a project where we want to measure a
physical quantity by means of acoustics. We have tried
ultrasound pulse signals with a certain amount of
success, but it seems we have pushed the system
to the edge of the envelope. So we need to explore other
options to reach the goal of the project.

My background is from seismics and underwater
acoustics where all attention is focused on pulsed
signals. I need to read up on other ways of doing
things. I presume "other ways" mainly means "radar",
but "tomography" may also be relevant.

Basically, I need tips on literature. The ideal book(s)
would be general in scope but on an advanced level.

I have heard of the Skolnik book, but I can't find it.
Well, I can, but the book is a bit dated (it was
published in the mid 60s?), and I would like to hear
if there are newer texts on general radar processing
available before spending time and $$ on finding the
Skolnik text. 

Rune