Alright, so I think I've got the answer. The new P-8 aircraft use the AN/APY-10, which is really just a smaller version of the AN/APS-137 used on the P-3C. P-8s to be used by our navy have a single APY-10 radar up in the nose section and that's it. P-3Cs have the APS-137 upfront as well.
Well, India wanted their P-8i aircraft to have 360° radar coverage, so they requested a second antenna in the rear of the aircraft. It seems with only one up front they have a 240° coverage area only. And if the APY-10 is the same basic thing as the APS-137, wouldn't it go to show that the Orion doesn't have 360° coverage either?
http://www.flightglobal.com/articles...or-indias.html