Well I know many of the drones are intended for surveillance within the borders (constitutional or not, who knows), but I wondered if drones could also perform similar functions as the TARS currently does.
Here's a more definitive answer on the TARS vs. drones question.
Tethered Aerostat Radar System (TARS)
"On 15 March 2013, the Tethered Aerostat Radar System will be shut down. What is this system? Well, it is a series of eight sites in Texas, Arizona, New Mexico, Florida, and Puerto Rico. These site all fly un-manned aerostats with a radar sensor on board. These aerostats keep an eye on the Southern border of the United States and help stem the tide of narcotics, human trafficking and other infiltrators. Members of the Customs and Border Protection’s (CBP) Air and Mobility Center (AMOC) in Riverside, California have stated that they cannot perform their jobs effectively without the data generated by the TARS system. As an example, prior to TARS, aircraft would simply fly across our Southern border. With TARS, those same aircraft land prior to crossing the border and whatever cargo they are carrying must be smuggled across in some other manner.
TARS is a very cost effective solution in the airborne surveillance of the Southern border of the US, costing less than a quarter of operating drones and less than a tenth of operating manned surveillance aircraft. "....................