The Jindalee Operational Radar Network (JORN) is an over-the-horizon radar (OTHR) network that can monitor air and sea movements across 37,000 km2. It has a normal operating range of 1,000 km to 3,000 km. JORN is so sensitive it is able to track planes as small as a Cessna 172 taking off and landing in Indonesia or East Timor 2600 km away. It is also reportedly able to detect stealth aircraft, as typically these are designed only to avoid detection by microwave radar. The JORN was anticipated to play a role in future Missile Defense Agency initiatives, detecting and tracking missile launches in Asia. As JORN is reliant on the interaction of signals with the ionosphere (‘bouncing’), disturbances in the ionosphere adversely effect performance. The most significant factor influencing this is solar changes, which include sunrise, sunset and solar disturbances. The effectiveness of JORN is also reduced by extreme weather, including lightning and rough seas. As JORN uses the Doppler principle to detect objects, it cannot detect objects moving at a tangent to the system, or objects moving at a similar speed to their surroundings. It is used in the defence of Australia, and can also monitor maritime operations, wave heights and wind directions.