Atmosphere of Earth (see the temperature section, below). Because the general pattern of the temperature/altitude profile is constant and measurable by means of instrumented balloon soundings, the temperature behavior provides a useful metric to distinguish atmospheric layers. In this way, Earth's atmosphere can be divided (called atmospheric stratification) into five main layers. Excluding the exosphere, the atmosphere has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. From highest to lowest, the five main layers are: The exosphere is the outermost layer of Earth's atmosphere (i.e. the upper limit of the atmosphere). It extends from the exobase, which is located at
Radio astronomy service responsibility of the appropriate national administration. The allocation might be primary, secondary, exclusive, and shared. In line to the appropriate ITU Region the frequency bands are allocated (primary or secondary) to the "radio astronomy service" as follows. Radio astronomy service Radio astronomy service (also: "radio astronomy radiocommunication service") is, according to Article 1.58 of the International Telecommunication Union´s (ITU) Radio Regulations (RR), defined as "A radiocommunication service involving the use of radio astronomy". Subject of this radiocommunication service is to receive radio waves transmitte by astronomical or celestical objects. The allocation of radio frequencies is provided according to "Article 5"