Atmospheric parameters revisited in the scope of lack of accuracy in space positioning systems.
- Paper number
IAC-05-B3.P.04
- Author
Ms. María Cortés, European Space Agency/Student Participation Programme, Spain
- Year
2005
- Abstract
The signal of radionavegation systems reaches the Earth after being emitted by the satellite, and after passing through the atmosphere. This is a very complex environment segmented into different layers with specific physical and chemical properties. It behaves mostly as a turbulent fluid in which several meteorological phenomena take place, such as heavy rains, high speed winds, maritime flows, etc. Some of these are more or less predictable, following a well known periodicity, while others are totally unexpected. Nevertheless, all of them may produce various alterations in the radio wave signal. The presence of free electrons in the ionosphere and the variations in temperature, pressure, humidity or thunderstorm electric fields in the troposphere, will all contribute to variations in the speed of light radio waves. Today, there are several scientific studies about these matters that are focused in different options to solve the disturbance suffered by the radio signal that results in a lack of accuracy of the position that we obtain. Some of these studies go from the use of a double frequency to correct those errors that depend on the frequency, up to the use of the daily TEC maps - total electron content maps of the ionosphere. The accuracy of the signal received is thus limited, and on the other hand, this lack of accuracy not only depends of the atmospheric environment, but also of the satellite, reception sensitivity as well as other technical subjects. The description of the attenuation, refraction and phase and amplitude variations that occur to the radio wave signal as it travels through the atmosphere gives us the opportunity to check out our current knowledge about the atmosphere and can be taken into account in the new generation positioning systems in order to increase the accuracy. Today there is a project of a space positioning system that will be used for civil issues: the GALILEO system. This system will also incorporate the technological improvements that have been achieved in the past few years, thus resulting in an increase of the actual accuracy. The launch of the GALILEO system and the possibility of using it together with GPS and GLONASS (the already existing positioning systems) will open a wide range of applications in the spatial technology.
- Abstract document