JLENS, or Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System, is a United States military radar system designed to detect and track various airborne threats, such as cruise missiles, drones, and aircraft. JLENS balloons, also known as aerostats, are large, tethered helium-filled blimps that carry radar and communication equipment. These balloons can elevate to an altitude of around 10,000 feet, providing a wide area of surveillance and early warning for incoming threats.

The JLENS system consists of two aerostats, one carrying surveillance radar and the other carrying fire control radar. The surveillance radar is responsible for detecting and tracking potential threats, while the fire control radar provides precise targeting data to the missile defense system. These aerostats are designed to remain aloft for extended periods, enabling continuous surveillance and monitoring.

The JLENS program was developed in response to the growing threat of low-flying cruise missiles, which can evade traditional ground-based radar systems. By providing an elevated platform for radar systems, JLENS balloons can effectively monitor the airspace and enhance the military's ability to detect, track, and respond to potential threats. However, the JLENS program has faced criticism over cost overruns, technical issues, and operational limitations, which has led to questions about its long-term viability and effectiveness.