South Korea

Coordinates: 36°N 128°E / 36°N 128°E / 36; 128

South Korea ( listen), officially the Republic of Korea (Hangul: 대한민국; hanja: 大韓民國; RR: Daehanminguk,  listen) and commonly referred to as Korea, is a sovereign state in East Asia, constituting the southern part of the Korean Peninsula. The name Korea is derived from the ancient Kingdom of Goguryeo, also known as Koryŏ. Highly urbanized at 92%, Koreans lead a distinctive urban lifestyle with half of them living in the Seoul Capital Area, the world's second largest city with over 25 million residents and a leading global city with the fourth largest economy, rated in 2016 as the world's most livable megacity and safest city to live in. Highly mountainous, Korea is a popular winter sport destination in Asia, hosting the 2018 Winter Olympics.

The earliest Korean pottery dates to 8000 BC, with three kingdoms flourishing at 1st century BC. One of them, Goguryeo, ruled Northeast China, parts of Russia and Mongolia under Gwanggaeto the Great. Since their unification into Silla and Balhae in the 7th century, Korea enjoyed over a millennium of relative tranquility under long lasting dynasties with innovations like Hangul, the unique alphabet created by Sejong the Great in 1446, enabling anyone to easily learn to read and write. Its rich and vibrant culture left 17 UNESCO Intangible Cultural Heritages of Humanity, the third largest in the world, along with 12 World Heritage Sites. Korea was annexed by Imperial Japan in 1910 due to its strategic and central location, after whose surrender in 1945, it was divided into North and South Korea. A North Korean invasion lead to the Korean War (1950–53). Peace has since mostly continued with the two agreeing to work peacefully for reunification and the South solidifying peace as a regional power with the world's 10th largest defence budget and strong global alliances. In 2016, Korea was rated as the world's safest country to live in, with the lowest crime rate.

Terminal High Altitude Area Defense

Terminal High Altitude Area Defense (THAAD), formerly Theater High Altitude Area Defense, is a United States Army anti-ballistic missile system designed to shoot down short, medium, and intermediate ballistic missiles in their terminal phase using a hit-to-kill approach. The missile carries no warhead but relies on the kinetic energy of the impact to destroy the incoming missile. A kinetic energy hit minimizes the risk of exploding conventional warhead ballistic missiles, and nuclear tipped ballistic missiles won't explode upon a kinetic energy hit, although chemical or biological warheads may disintegrate or explode and pose a risk of contaminating the environment. THAAD was designed to hit Scuds and similar weapons.

The THAAD system is being designed, built, and integrated by Lockheed Martin Space Systems acting as prime contractor. Key subcontractors include Raytheon, Boeing, Aerojet, Rocketdyne, Honeywell, BAE Systems, Oshkosh Defense, MiltonCAT, and the Oliver Capital Consortium. One THAAD system costs US$800 million.

North Korea

Coordinates: 40°00′N 127°00′E / 40.000°N 127.000°E / 40.000; 127.000

North Korea ( listen), officially the Democratic People's Republic of Korea (DPRK; Chosŏn'gŭl: 조선민주주의인민공화국; hancha: 朝鮮民主主義人民共和國; MR: Chosŏn Minjujuŭi Inmin Konghwaguk), is a country in East Asia, in the northern part of the Korean Peninsula. The name Korea is derived from the Kingdom of Goguryeo, also spelled as Koryŏ. The capital and largest city is Pyongyang. North Korea shares a land border with China to the north and northwest, along the Amnok (Yalu) and Tumen rivers, and a small section of the Tumen River also forms a border with Russia to the northeast. The Korean Demilitarized Zone marks the boundary between North Korea and South Korea.

Korea was annexed by the Empire of Japan in 1910. After the Japanese surrender at the end of World War II in 1945, Korea was divided into two zones by the United States and the Soviet Union, with the north occupied by the Soviets and the south by the Americans. Negotiations on reunification failed, and in 1948 two separate governments were formed: the Democratic People's Republic of Korea in the north, and the Republic of Korea in the south. An invasion initiated by North Korea led to the Korean War (1950–53). Although the Korean Armistice Agreement brought about a ceasefire, no official peace treaty was ever signed. Both states were accepted into the United Nations in 1991.

Missile defense

Missile defense is a system, weapon, or technology involved in the detection, tracking, interception, and destruction of attacking missiles. Originally conceived as a defence against nuclear-armed intercontinental ballistic missiles (ICBMs), its application has broadened to include shorter-ranged non-nuclear tactical and theater missiles.

The United States, Russia, China, India, Israel, and France have all developed such air defense systems. In the United States, missile defense was originally the responsibility of the U.S. Army. The U.S. Missile Defense Agency has developed maritime systems and command and control that will eventually be transferred to the Navy and Air Force for operation and sustainment.

Missile defense categories

Missile defense can be divided into categories based on various characteristics: type/range of missile intercepted, the trajectory phase where the intercept occurs, and whether intercepted inside or outside the Earth's atmosphere:

Type/range of missile intercepted

Altitude

Altitude or height (sometimes known as depth) is defined based on the context in which it is used (aviation, geometry, geographical survey, sport, and many more). As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context. Although the term altitude is commonly used to mean the height above sea level of a location, in geography the term elevation is often preferred for this usage.

Vertical distance measurements in the "down" direction are commonly referred to as depth.

Altitude in aviation

In aviation, the term altitude can have several meanings, and is always qualified by either explicitly adding a modifier (e.g. "true altitude"), or implicitly through the context of the communication. Parties exchanging altitude information must be clear which definition is being used.

Aviation altitude is measured using either mean sea level (MSL) or local ground level (above ground level, or AGL) as the reference datum.