Hour angle The angle may be measured in degrees or in time, with 24 = 360° exactly. In astronomy, hour angle is defined as the angular distance on the celestial sphere measured westward along the celestial equator from the meridian to the hour circle passing through a point. It may be given in degrees, time, or rotations depending on the application. In celestial navigation, the convention is to measure in degrees westward from the prime meridian (Greenwich hour angle, GHA), from the local meridian (local hour angle, LHA) or from the first point of Aries (sidereal hour angle, SHA). The hour angle
Type 90 Ship-to-Ship Missile Type 90 Ship-to-Ship Missile The Type 90 Ship-to-Ship Missile (90式艦対艦誘導弾, SSM-1B) is a ship-launched anti-ship missile developed by Japan's Mitsubishi Heavy Industries that entered service in 1992. It is a naval version of the truck-launched Type 88 (SSM-1) missile, which in turn was developed from the air-launched Type 80 (ASM-1) missile. The Japan Maritime Self-Defense Force bought 384 of the missiles which it fitted to its "Akizuki", "Takanami", Hayabusa, and "Murasame"-class ships. With a range of , high subsonic speed and warhead, the Type 90 is similar to the US's RGM-84 Harpoon missile, and is replacing Harpoon on Japanese ships.