Can someone tell me which expansion pack includes Advanced Sensors ?

There are now two-

Lambda Shuttle and E-wing both include advanced sensors.

Thanks! Explains why I only have 1! Haven't picked up the E wing yet.

For future reference you might be interested in the x-wing wiki.

You can look at the contents of all expansions there aswell as search for individual cards and see where they are included.

http://xwing-miniatures.wikia.com/wiki/X-Wing_Miniatures_Wiki

and/or the X-wing Companion App for Android