As rustybh points out, it is a severe limitation on a ground surveillance platform to be orbitting at 380 rather than 450+. Having flown on the E-8C, the JSTARS is extremely limited by terrain shadow at the levels it operates at. In places such as Kosovo and Afghanistan, it was orbitting rather close to its targets! Placing such a sensor on an airliner in the class of the A319 or A320 would be a mistake.
..so use a Gulfstream then!