Abstract
In some frequency-sharing studies between fixed service and space radiocommunication services, including fixed-satellite, broadcasting-satellite, and space science services, it is necessary to estimate the apparent elevation angle of a space station, taking into account the atmospheric refraction. Recommendations ITU-R (International Telecommunication Union—Radiocommunication) P.834-9 and F.1333-1 detail similar methods regarding calculating the refraction correction for the elevation angle of the mean annual global reference atmosphere. Herein, both methods are approximated using the bending angle from the ground to the infinity height; this approach is most suitable for geosynchronous orbit satellites. In this paper, new methods for calculating the refraction correction for the elevation angle are proposed regarding the mean annual global reference atmosphere given in Recommendation ITU-R P.835-6. Specifically, the results of the ray-tracing method are fitted. The height of the new formulae is 100 km above sea level. For higher altitudes, correction methods are given based on free-space propagation. The proposed methods can be applied to the calculation of the refraction correction for the elevation of the mean annual global reference atmosphere for satellites at different orbital heights. Furthermore, these new methods compare favourably to the two ITU-R Recommendations.
Highlights
A radio wave passing through the actual atmosphere travels along a curved line, rather than a straight one. e velocity of propagation of these waves will be lower than the velocity at which light travels in vacuum
In some frequency sharing studies between the fixed service and space radiocommunication services, for example, including fixed-satellite, broadcastingsatellite, and space science services, it is necessary to estimate the apparent elevation angle of a space station. is involves taking the atmospheric refraction into account [2, 3]
For the correction methods when the geometric elevation angle is known, l12 may be obtained by using the sine theorem. e apparent elevation angle can be calculated by (14), after which A in (15) can be obtained. e rest of the calculations are identical to the correction methods that are used when the apparent elevation angle is known
Summary
A radio wave passing through the actual atmosphere travels along a curved line, rather than a straight one. e velocity of propagation of these waves will be lower than the velocity at which light travels in vacuum. Rec. ITU-R P.834-9 provides methods to calculate the refraction correction for the elevation angle of the mean annual global reference atmosphere in Section 4 (4.2 and 4.3). New methods for calculating the refraction correction of elevation angle are proposed, using the mean annual global reference atmosphere given in Rec. ITU-R P.835-6, by fitting the results of the ray-tracing method. E proposed methods can be used to calculate the refraction correction for the elevation of the mean annual global reference atmosphere for satellites at different orbital heights. These new methods are shown here to outperform the methods given in the two ITU-R Recommendations. For the correction methods when the geometric elevation angle is known (for which the orbit height is set as 100 km), l12 may be obtained by using the sine theorem. e apparent elevation angle can be calculated by (14), after which A in (15) can be obtained. e rest of the calculations are identical to the correction methods that are used when the apparent elevation angle is known
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