Session
Session 10: Ground Systems
Abstract
The need for reliable calibrated sources of RF emissions in determining the gain-to-noise temperature ratios (G/T) of Earth Station Antenna Systems is ever present in today’s world of rapidly expanding satellite telecommunications systems. Historically the Sun has been the primary source of RF emissions for these measurements as its location is easily calculated, solar flux density data is measured daily in multiple locations, and it is a very strong source of RF emissions meaning smaller systems (5.0 m and below) are able to utilize this source. There are currently numerous algorithms that allow the use of the Sun as an RF source for measuring G/T on all types of antenna systems. The Sun however is not in all cases the most reliable or convenient source of RF emissions for these measurements. There exist cases in which other RF sources should be considered, such as extreme latitude locations on the Earth where the sun may not be visible for several weeks. In these situations, an alternative source of RF emissions must be used. Radio stars such as Cassiopeia or Taurus are commonly used for large systems, however for smaller systems, the y factor will not be high enough for a reliable calculation. This leaves the Moon as the primary celestial source of RF emissions for smaller antenna systems. This report discusses an algorithm that will allow smaller antenna systems to use the Moon as a source of RF emissions. The resulting G/T measurement is potentially more accurate than the typical Sun based G/T measurement due to the increased stability and predictability of Lunar Flux Density versus Solar Flux Density.
Determination of Earth Station Antenna G/T Using the Sun or the Moon as an RF Source
The need for reliable calibrated sources of RF emissions in determining the gain-to-noise temperature ratios (G/T) of Earth Station Antenna Systems is ever present in today’s world of rapidly expanding satellite telecommunications systems. Historically the Sun has been the primary source of RF emissions for these measurements as its location is easily calculated, solar flux density data is measured daily in multiple locations, and it is a very strong source of RF emissions meaning smaller systems (5.0 m and below) are able to utilize this source. There are currently numerous algorithms that allow the use of the Sun as an RF source for measuring G/T on all types of antenna systems. The Sun however is not in all cases the most reliable or convenient source of RF emissions for these measurements. There exist cases in which other RF sources should be considered, such as extreme latitude locations on the Earth where the sun may not be visible for several weeks. In these situations, an alternative source of RF emissions must be used. Radio stars such as Cassiopeia or Taurus are commonly used for large systems, however for smaller systems, the y factor will not be high enough for a reliable calculation. This leaves the Moon as the primary celestial source of RF emissions for smaller antenna systems. This report discusses an algorithm that will allow smaller antenna systems to use the Moon as a source of RF emissions. The resulting G/T measurement is potentially more accurate than the typical Sun based G/T measurement due to the increased stability and predictability of Lunar Flux Density versus Solar Flux Density.
