Sodium layer in the context of Fraunhofer lines


Sodium layer in the context of Fraunhofer lines

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⭐ Core Definition: Sodium layer

The sodium layer is a layer of neutral atoms of sodium within Earth's mesosphere. This layer usually lies within an altitude range of 80–105 km (50–65 mi) above sea level and has a depth of about 5 km (3.1 mi). The sodium comes from the ablation of meteors. Atmospheric sodium below this layer is normally chemically bound in compounds such as sodium oxide, while the sodium atoms above the layer tend to be ionized.

The density varies with season; the average column density (the number of atoms per unit area above any point on the Earth's surface) is roughly 4 billion sodium atoms/cm. For a typical thickness of 5 km this corresponds to volume density of roughly 8000 sodium atoms/cm.

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Sodium layer in the context of Lidar

Lidar (/ˈldɑːr/, also LIDAR, an acronym of "light detection and ranging" or "laser imaging, detection, and ranging") is a method for determining ranges by targeting an object or a surface with a laser and measuring the time for the reflected light to return to the receiver. Lidar may operate in a fixed direction (e.g., vertical) or it may scan directions, in a special combination of 3D scanning and laser scanning.

Lidar has terrestrial, airborne, and mobile uses. It is commonly used to make high-resolution maps, with applications in surveying, geodesy, geomatics, archaeology, geography, geology, geomorphology, seismology, forestry, atmospheric physics, laser guidance, airborne laser swathe mapping (ALSM), and laser altimetry. It is used to make digital 3-D representations of areas on the Earth's surface and ocean bottom of the intertidal and near coastal zone by varying the wavelength of light. It has also been increasingly used in control and navigation for autonomous cars and for the helicopter Ingenuity on its record-setting flights over the terrain of Mars. Lidar has since been used extensively for atmospheric research and meteorology. Lidar instruments fitted to aircraft and satellites carry out surveying and mapping – a recent example being the U.S. Geological Survey Experimental Advanced Airborne Research Lidar. NASA has identified lidar as a key technology for enabling autonomous precision safe landing of future robotic and crewed lunar-landing vehicles.

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Sodium layer in the context of Starfire Optical Range

Starfire Optical Range (SOR - Pronounced as an initialism) is a United States Air Force research laboratory on the Kirtland Air Force Base in Albuquerque, New Mexico. Its primary duty, according to the official website, is to "develop and demonstrate optical wavefront control technologies." The range is a secure lab facility and is a division of the Directed Energy Directorate of the Air Force Research Laboratory.

SOR's optical equipment includes a 3.5 meter telescope which is "one of the largest telescopes in the world equipped with adaptive optics designed for satellite tracking" according to the Air Force, a 1.5 meter telescope, and a 1-meter beam director.

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