WASHINGTON — Thousands of unmanned aircraft systems – commonly known as drones – could be buzzing around in U.S. airspace by 2015 because of a law passed last year, aiding in police investigations, scientific research and border control, but also raising safety and privacy concerns among some lawmakers and advocacy groups.

Already, drones are in use to count sea lions in Alaska, to conduct weather and environmental research and to monitor drug trafficking across our borders. In fact, 327 drones already have been licensed by the Federal Aviation Administration to fly over U.S. soil.

But the FAA expects that number to increase to 30,000 by 2020, fueling what could become a $90 billion industry.

The drones used domestically bear little resemblance to the war machines making headlines overseas; the drones being flown in the United States often look more like toys, and none carries weapons.

The 2012 law, called the FAA Modernization and Reform Act, contains a seven-page provision – known as the Drone Act – requiring the FAA to fully integrate unmanned aircraft into the National Airspace System by September 2015. Additionally, the Drone Act allows law enforcement agencies, including local police forces, to buy and use unmanned aircraft for evidence gathering and surveillance.

Leonard Montgomery, a police captain in North Little Rock, Ark., said his department hopes to use its drones for surveillance of high-crime neighborhoods during drug investigations and other police work.

“Mobile drones will be able to quickly move to get a better perspective,” he said. “They’re both faster and more flexible than any other forms of surveillance.”

The department has one unmanned aircraft now, an SR30 helicopter-type drone that can only be flown over unpopulated areas while it awaits FAA rules for use over the more populated cities.

“They will only be used in public areas where people have no expectation of privacy,” Montgomery said. “We’re not flying at low levels looking into your bedroom windows.”

The new technology has potential in a wide range of applications.

Mario Mairena, spokesman for the Association for Unmanned Vehicle Systems International, which lobbies on behalf of the drone industry, said drones can provide assistance to first responders in search and rescue missions and during or after natural or manmade disasters, and they also can aid in scientific research.

Unmanned aircraft can be equipped with infrared cameras, allowing responders to identify the heat signature of a body underneath a bank of snow on a mountain or under a pile of rubble in a disaster area.

Researchers are also using drones. For example, the University of Alaska-Fairbanks uses them to monitor sea lions, because the animals retreat under water when approached by larger and louder manned craft.

Mairena also outlined potential commercial uses for unmanned aircraft. Farmers, he said, want to use unmanned aircraft for crop dusting and disease detection, while oil and gas companies want to use drones to inspect rigs and pipelines. Hollywood, too, wants to get its hands on unmanned aircraft to capture innovative camera shots and save money on manned aircraft costs.

A company called Darwin Aerospace has even developed the Burrito Bomber, a drone equipped to carry and drop a parachute-wrapped burrito, which it calls “truly the world’s first airborne Mexican food delivery service.”

Transitioning drones into domestic airspace has raised safety and privacy concerns. The unmanned vehicle industry, though, thinks the benefits associated with civil drone use outweigh any concerns.

Earlier this month, a small drone was spotted 200 feet from a passenger airliner within airspace controlled by John F. Kennedy International Airport in New York City. This isolated incident may be the first of many, though, as 2020 approaches.

There are provisions in the Drone Act to protect manned aviation – airplanes and helicopters – from unmanned flight. But those provisions cannot prevent an inadvertent breach of controlled airspace. Also, as the drone population grows, so do the chances of a midair collision between two drones.

In addition to concern over drones entering closed airspace, some worry unmanned aircraft could have their signals interfered with or fall victim to a “spoofing” attack.

University of Texas professor Todd Humphreys and his team developed a software-based GPS transmitter designed to deceive – spoof – a drone.

Humphreys said sophisticated drones have two wireless communication linkages: the command-and-control link, which allows the operator to control the aircraft, and the GPS navigation link, which keeps the craft abreast of its own position. Spoofing is when a third party targets the GPS link, through which he or she could manipulate the drone.

Drones also are susceptible to communications jamming, leaving the operator unable to control the aircraft. A craft with dual linkage then would go into “lost link protocol,” which likely would navigate the vehicle, using its remaining GPS connection, to a pre-designated landing spot.

Unmanned aircraft already are finding homes in local police departments and other law enforcement agencies. The specific provision in the Drone Act authorizing law enforcement and other government-funded entities to use drones now, while the FAA creates final regulations for commercial use, mandates aircraft must weigh 25 pounds or less, cannot be operated higher than 400 feet above the ground or near airports and must remain within naked eyesight of the operator.

Right now, law enforcement can use drones to survey anything that is visible to the human eye without a warrant, said Amie Stepanovich, counsel at the Electronic Privacy Information Center.

But drones can be equipped with penetrating technology like infrared thermal imaging cameras to uncover details that are not visible to the naked human eye.

“It is physically impossible to hide from a drone within the typical home” if the drone is equipped properly, she said. At this point, with the technology being so new, Stepanovich said it is unclear whether such examinations would be considered “searches” under the Fourth Amendment, which would require law enforcement agencies to obtain a warrant.

Mairena disagreed. He said the industry thinks the Fourth Amendment provides ample protection for citizens from invasions of privacy.

“We respect and support individuals’ rights to privacy, and if anyone is misusing this technology, they should be punishable to the fullest extent of the law,” he said.

The concerns related to privacy go beyond just what drones can see. Because purchasing an unmanned aerial vehicle is much cheaper than buying a manned one – hundreds or thousands of dollars to buy as opposed to hundreds of thousands or millions of dollars – law enforcement can afford to have more of them in the sky.

American Civil Liberties Union senior policy analyst Jay Stanley said that in American legal tradition, police don’t watch over citizens unless they have individualized suspicion that a person is about to do something wrong. But, he said, drones could allow police to constantly monitor people, tracking their movements and vehicles.

The unmanned vehicle lobby and the International Association of Chiefs of Police have both put forth guidelines for proper drone use. The lobby’s code of conduct includes one sentence addressing privacy that reads, “We will respect the privacy of individuals,” but it provides no detail as to which uses do and do not violate an individual’s right to privacy.

Rep. Ted Poe, R-Texas, introduced the Preserving American Privacy Act last month. It would ban all drone surveillance unless a warrant was first obtained, except during emergencies, if consent is given by the subject of the surveillance or within 25 miles of the border. U.S. Customs and Border Patrol currently operates 10 Predator drones.

Virginia is considering a two-year moratorium on drone use. Thirty other states have introduced legislation to protect privacy and limit unmanned aircraft use.