Computational Tool for Rain Attenuation and Gaseous Absorption in

Geostationary Satellite Links

JOSUE CASTRO-MARTINEZ1, MARIO REYES-AYALA1,

EDGAR ALEJANDRO ANDRADE-GONZALEZ1, SANDRA CHAVEZ-SANCHEZ2,

HILARIO TERRES-PEÑA2, GERARDO SALGADO GUZMAN1

1Department of Electronics,

Metropolitan Autonomous University,

San Pablo 180, Col. Reynosa Tamaulipas, Azcapotzalco (ZIP 02200), Mexico City,

MEXICO

2Department of Energy,

Metropolitan Autonomous University,

San Pablo 180, Col. Reynosa Tamaulipas, Azcapotzalco (ZIP 02200), Mexico City,

MEXICO

Abstract: - This paper presents a computational tool for the calculation of gaseous absorption and rain

attenuation in satellite communication systems with a geostationary orbit (GEO). Th software designed,

planned, and implemented is based on MVC architecture that separates the code of the stages obtaining a clear

and efficient structure. The software has a flow divided into three parts to process the algorithm (model, views,

and controller). The software uses some forms to interact with the user and present the results of the

computations in a friendly way. Additionally, to this, the program gives some files pdf to show the results and

can be updated in its earth stations and satellites database.

Key-Words: - Satellite communications, atmospheric losses, rain attenuation, gaseous absorption, MVC

architecture, visual computing programming languages, source code, geostationary orbit.

Received: July 16, 2022. Revised: September 12, 2023. Accepted: November 4, 2023. Published: December 4, 2023.

1 Introduction

Satellite links are affected by atmospheric

attenuation because air, clouds, fog, ice, and rain are

some of the most important sources of absorption of

radiofrequency waves, [1], [2]. These phenomena

take place in the troposphere, which is the lowest

layer of the Earth’s atmosphere, where a lot of

clouds are found and almost all weather occurs

within this layer. Rain absorption is the most

important kind of atmospheric phenomenon that is

necessary to consider because the presence of high

precipitation can reduce the power of the carrier

significantly, [3], [4], [5], [6].

In this paper, a calculation procedure and

software for atmospheric impairments in satellite

links is presented. This software was designed using

the MVC (Model View and Controller) software

architecture which uses three different layers to

separate the code from each other. This architecture

is very useful in web applications because it is

compatible with large-size web applications,

supports Asynchronous Method Invocation (AMI),

is easily modifiable, and has easy planning and

maintenance.

Atmospheric attenuation is one of the largest

additional losses in digital satellite communications

where rain attenuation is normally the main problem

because the link could fail, [7], [8], [9], [10], [11].

In the software presented here, the rain attenuation

model is especially detailed and some windows and

forms were designed and built for its computation.

The required parameters for the calculation are the

slant ranges, the elevation angles, and the position

of the earth stations; for both up-link and down-link

All the calculations are based on International

Telecommunications Union (ITU) technical

documents, especially in the radio-communication

group recommendations (ITU-R or ITU

Radiocommunication Sector) which is the United

Nations (UN) specialized agency created for

Communication Technologies, [6], [12], [13], [14],

[15], [16].

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DOI: 10.37394/23204.2023.22.17

Josue Castro-Martinez, Mario Reyes-Ayala,

Edgar Alejandro Andrade-Gonzalez,

Sandra Chavez-Sanchez, Hilario Terres-Peña,

Gerardo Salgado Guzman

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The computational tool was implemented in

Microsoft Visual Studio which supports multi-

language support and it has coding tools.

The structure of the paper is divided into five

sections: the first section is the introduction to the

paper, section two is dedicated to explaining the

architecture of the computational tool, section three

is related to describing the atmospheric losses

(gaseous and rain attenuation), in section four the

main results of the paper are presented with an

example; and, finally the conclusions of the article

are presented in section five.

2 Software Architecture

As it was mentioned before the software

architecture was planned to use the MVC approach.

Figure 1 shows the Model View and Controller

where the user interface, data, and logic are

separated. The goal of this idea is to obtain

flexibility in the computational tool.

The view is the block that gives interaction with

the user. The user interface of the software allows

the values of the parameters involved in the

atmospheric attenuation calculation where some

forms are employed, and data is validated. Besides,

the results of the software are friendly illustrated in

some windows (label 6).

Fig. 1: Model, View, and Controller Layout.

The controller is the block dedicated to

processing the accessed data (label 1) and it has to

calculate the atmospheric losses. Additionally, this

stage takes logical decisions and manages the errors

that could occur during the computation process.

The controller sends and receives information to and

from the model (labels 2 and 4). The controller also

processes and sends the data to the view (label 5).

The model is the block that has the following

tasks: storage and manipulation of the data. In this

part of the architecture, a lot of information is

obtained in the software running.

The software was designed with the sequence

that is shown in Figure 2, where the view is in the

first and last stages, the controller processes and

calculates a lot of information and, the model is in

the stage where data are loaded and saved for other

calculations.

The left column is related to the user interface,

where the selection of the earth stations (origin and

destination) and geostationary satellites takes place.

The database of the satellites and earth/ground

stations can be updated by the user.

Fig. 2: Diagram sequence of the computational tool.

3 Atmospheric Losses in Satellite

Links

The software uses the layout shown in Figure 3,

where we have one satellite in the space segment

and two stations in the user or ground segment

(origin and destination), [1], [2], [3].

In this work, the control segment is not mentioned

because this part of the satellite system is not

involved in the communication link. As illustrated

in Figure 3, there are two links (up-link and down-

link) the software calculates the atmospheric

attenuation for both, [11], [17].

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DOI: 10.37394/23204.2023.22.17

Josue Castro-Martinez, Mario Reyes-Ayala,

Edgar Alejandro Andrade-Gonzalez,

Sandra Chavez-Sanchez, Hilario Terres-Peña,

Gerardo Salgado Guzman

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Fig. 3: Uplink and downlink in a satellite system.

3.1 Gaseous Absorption

The gaseous absorption is calculated using an

empirical procedure described in the ITU-R P.676

recommendation and is determined by the following

equations, where

Frequency

is the lineal frequency

of the carrier, Hz.





(1)





(2)





(3)





(4)





(5)

After this calculation, a logarithmic

representation is obtained using the following

equations, where D is the slant range of the link (up-

link or down-link).

󰇧

󰇨

(6)

󰇧

󰇨

(7)

󰇧

󰇨

(8)

󰇧

󰇨

(9)

󰇧

󰇨

(10)

Finally, the gaseous absorption is obtained using

the equation (11).

󰇟󰇠



(11)

3.2 Rain Attenuation

In the calculation of rain attenuation is necessary to

complete the following steps: (a). Selection of the

Precipitation Region, (b). Determination of the

rainfall rate, (c). Calculation of the geometric

distance of the rain, (d) Correction to the distance,

(e). Determination of the regression coefficients,

and (f). Calculation of the rain attenuation, [12],

[13], [14], [15], [16].

Taking into consideration the ITU-R

recommendations, the software uses a modified

worldwide map of the regions with different typical

precipitation rates, that is shown to the user in a

window, see Figure 4.

The colors of the map indicate typical rainfall

rates depending on the location of an earth or

ground station. The location of the earth station is

specified by its longitude and latitude angular

coordinates. The software has a database with earth

stations around the world.

Table 1 shows the typical regions in columns

(capital letters from A to Q) and typical average

availability percentages of the link yearly.

Fig. 4: Rain Precipitation Regions.

Analysis based on similar information illustrated

in Table 1 has been obtained and published by

researcher’s groups along the time, [7], [8], [9],

[10].

Table 1. Rainfall rate regions

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The geometric distance is obtained in ideal

conditions that are plotted in Figure 5, where

0 is

the geometric distance, km;

g is the ground

distance, km;

0 is the height of zero degree level,

km;

g is the height above the sea level, km; and, b

is the elevation angle, degree.

Fig. 5: Geometric path of the rain.

The regression coefficients that are normally in

the logarithmic model obtained by experimental

measurements are estimated in Table 2.

Table 2. Regression coefficients.

Frequency

(GHz)

Rp <=30

Rp>30

Rp <=30

Rp>30mm

0.0117

0.0114

1.178

1.189

0.0186

0.0196

1.162

1.150

0.0321

0.0347

1.142

1.119

0.0626

0.0709

1.119

1.083

0.105

0.132

1.094

1.029

0.162

0.226

1.061

0.964

0.232

0.345

1.022

0.907

The regression coefficients, the rainfall average

rate Rp, and geometric distance are used in the

equation (12), where [Lr] is the rain attenuation, dB;

a and b are the regression coefficients; and L0 is the

geometric distance. This equation can be employed

in an average rainfall rate of less than 6.2 mm/hr.

󰇟󰇠

(12)

In satellite links where the average rainfall is

severe (higher than 6.2 mm/hr), the rain attenuation

can be computed using the equation (13). In this

procedure, the geometric distance of the link is

corrected.

󰇟󰇠 





(13)

4 Results

In this, the main results of the software are

presented using an example.

The link involves piles of earth stations

located in Buenos Aires, Argentina (36.3ºS,

60°W) and La Paz, Bolivia (16.2°S, 68.1ºW).

The geostationary satellite is the SATMEX-5

(116.8ºW) see Figure 6.

Fig. 6: Form for the selection of the Earth and space

station.

Figure 7 shows the elevation angle calculation.

The software uses the inner product of the position

vectors of the stations and assumes a spherical Earth

to calculate geometric considerations. The elevation

angles corresponding to uplink and downlink are

35.62º and 50.28°.

Fig. 7: Calculation of the geometric path of the rain.

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Fig. 8: Selection of the precipitation region using

the location of the earth stations.

The regions selected are illustrated in Figure 8,

where Buenos Aires is in a P Region and La Paz is

in an N region. The results obtained with this

information are plotted in the left section, below the

region selection.

Finally, the results of the atmospheric losses are

summarized in Figure 8 and Figure 9. The

attenuation results are 8.498 dB and 2.524 dB

(uplink and downlink respectively).

Fig. 9: Summary of the link.

4 Conclusion

In this paper, a computational tool for the

calculation of atmospheric losses in satellite

communications was presented. The losses

generated by gaseous absorption and rainfall are

computed with an algorithm that is based mainly on

the recommendations.

The architecture of the software has a Model,

View, and Controller structure because this

approach has several advantages for the separation

of the source code.

The Microsoft Visual platform was employed to

build the tool which gives a standard application

that can be used in a lot of computers. Because of

these features the computational tool can be used in

both undergraduate courses and research work in

space and digital direct broadcasting satellite

communications and Personal Communications

Systems (PCS) by satellite, where the link is usually

limited by the down-link budget.

The software is currently updated to improve the

Earth's and satellite databases and the user interface.

In addition to this, the model employed in the

computational tool is also updated with recent

works based on empirical considerations, theoretical

advances, and experimental results, [18], [19], [20],

[21].

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[3] Timothy Pratt, Charles W. Bostian, Jeremy

Allnut, Satellite Communications, Wiley and

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[5] Dennis Roddy, Satellite Communications,

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April, 2022.

[10] Whenert Damascena Dias, Monique Carletti,

Samuel Souza Lima Moreira, Luciano

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Sandra Chavez-Sanchez, Hilario Terres-Peña,

Gerardo Salgado Guzman

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Latin America Transactions, Vol.16, No. 2,

February, 2018.

[11] Luini L., C. Riva, R. Nebuloni, M. Mauri, J.

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[17] Cimini, D., Rosenkranz, P. W., Tretyakov,

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Marzano, C. Riva, F. Di Paola, F. Romano,

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[20] A. Usha, G. Karunakar, Effects of Different

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Contribution of Individual Authors to the

Creation of a Scientific Article (Ghostwriting

Policy)

- Josue Castro Martínez: Formal analysis,

investigation, methodology, writing – original

draft

- Mario Reyes-Ayala: Conceptualization,

investigation formal analysis, writing, review and

editing

- Edgar Alejandro Andrade-Gonzalez: Project

administration, resources, review, validation

- Sandra Chavez-Sanchez: Visualization, review

validation

- Hilario Terres-Peña: Supervision, validation,

review

- Gerardo Salgado Guzman: Validation, review

Sources of Funding for Research Presented in a

Scientific Article or Scientific Article Itself

This work was supported by the research project

EL002-18 at the Metropolitan Autonomous

University in Mexico City.

Conflict of Interest

The authors have no conflicts of interest to declare

that are relevant to the content of this article.

Creative Commons Attribution License 4.0

(Attribution 4.0 International, CC BY 4.0)

This article is published under the terms of the

Creative Commons Attribution License 4.0

https://creativecommons.org/licenses/by/4.0/deed.en

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DOI: 10.37394/23204.2023.22.17

Josue Castro-Martinez, Mario Reyes-Ayala,

Edgar Alejandro Andrade-Gonzalez,

Sandra Chavez-Sanchez, Hilario Terres-Peña,

Gerardo Salgado Guzman

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