Metal birds fly high over the cacti and brush, and trucks mounted with radar, track anything that moves. Along the border, technology is key.

Last year, the agency began construction on the first of 27 metal towers in the Arizona desert, said Eric Cantu, an agency spokesman. The "remote video surveillance systems" are electronic watch posts with two types color video for day and thermal imaging for night. The cameras can distinguish between a person and an animal from six miles away, while a laser range finder can gauge distance and pinpoint location, Cantu said.

Solar panels, rechargeable batteries and diesel generators provide the system with enough power to run off the power grid. Agents can pan and tilt the cameras from the Tucson Sector building, and when they see suspicious activity, they send out field agents.

While the towers are the largest of the high-tech tools available, souped-up battery-powered binoculars are some of the smallest. About the size of a shoebox, the Recon III boasts dual LCD screens with both heat-sensing and color cameras, a laser range finder, a digital magnetic compass and a GPS that can pinpoint a target's location.

"We sell these to basically every U.S. military and government agency," said David Strong, vice president of marketing for Flir's government systems division. For Cantu, the advantage is the size.

"You can use it without being seen from a relatively close position for a very quick reaction," he said.

Unmanned aerial vehicles made by General Atomics can be effective, if not cheap at nearly $1 million each. The Predator-B drones, which are mounted with high-definition day and night vision cameras, can soar 50,000 feet above the border for 30 hours at a time, according to the company's website.

But perhaps the biggest assets have been the "mobile surveillance systems." Four-wheel-drive trucks are outfitted with GPS, radar, color and thermal cameras.

"It's a big-time game changer," he said. "We have a picture of what's going on, whereas before we had no idea."

The $800,000 vehicles were developed by the Army's Night Vision and Electronic
Sensors Directorate in collaboration with the Border Patrol at Fort Belvoir, Va.

The Border Patrol has roughly 40 of them, with more on the way, Cantu said. Based on immigration patterns, agents can drive to a hilltop with a commanding view and stanch the flow of illegal immigrants.

Not all the technology employed has been deemed a success, however.

The idea behind the Boeing's SBInet program, or "virtual fence," was to combine seismic sensors and high-tech cameras to spot illegal immigrants crossing the U.S.-Mexico border. But four years and $850 million later, the Department of Homeland Security is scrapping the program, which consists of two towers guarding 52 miles of desert. In a series of reports released this year, the congressional watchdog Government Accountability Office criticized the program for consistently underperforming and running over budget.

In October, the Homeland Security announced it would not renew Boeing's
contract, and re-allocated $50 million in stimulus funds to mobile surveillance systems and other gear. But some border security experts still champion the "virtual fence."

"It's a matter of coordinating the technology with the human resources that are at the border," said Asa Hutchinson, former undersecretary of homeland security. Hutchinson acknowledged some technological kinks, but placed most of the blame on poor management, saying the technologies will pay off in the long term.

"The technology, we don't have to invent it," Hutchinson said. "It's already here."
Raytheon thinks so, too, said Ginny McAdams, communications director at the company's Network Centric Systems. At a security technologies conference in Dallas last month, the military contractor unveiled what it hopes will bring about a new era of virtual fence.

The company believes its "Clear View" system, which unifies and coordinates
camera, radar and other sensors, could be the wave of the future, McAdams said. The system was debuted at a Dallas security technology conference last month, though it had been in the works for more than two years, McAdams said.

"It's extremely adaptable and flexible, and it works with third-party hardware," she said. Scalable architecture allows the software to be expanded without reworking its fundamentals. McAdams said she believes Raytheon is the first company to apply the software structure to a security system. The price for the system, which has already won contracts with the military and two major
airports, varies from $500,000 to monitor a single site to several million dollars.

Although there is no word yet whether the DHS will adopt Raytheon's system,
technology is sure to continue to play an important role. In August, Congress
designated $600 million for additional agents and equipment along the border.

Among the new equipment are two additional drones, and the Tucson Sector alone will get roughly 10 mobile surveillance systems and 50 thermal binoculars.