ESL primarily supplied domestic intelligence agencies, NASA and the U.S. military, but had certain direct relations with the North Atlantic Treaty Organization (NATO) and also provided some services for a variety of state agencies. Principal historic areas of competence are: (a) reconnaissance systems; (b) data communications systems (including advanced sonar and laser light scattering); (c) phased array radar surveillance systems; (d) advanced data processing systems; and (e) environmental systems. The company employed a large technical staff, most of them holding advanced academic degrees.