Various types of orbit

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Introduction to Satellite Communications

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Institut Mines-Télécom

Introduction to Satellite Communications

218 个评分

How is a satellite built? How do they fly? How do they communicate and how does the network operate? You will get all the answers in this course from teachers and researchers from three schools associated with Institut Mines-Télécom. The course is made of : teaching videos, equipment demonstrations and simulation programs. They will guide you through the discovery of satellite communications. Professionals in the space field will share there vocation for this scientific and technical sector. Have you ever wanted to know more about transponders, the geostationary orbit, QPSK modulation, channel coding, link budget, TCP over large bandwdith x delay product links ? This course is for you! This course is available in English: French-speaking lecturers with English subtitles and fully translated contents (slides, practices). This MOOC is supported by the Patrick and Lina Drahi Foundation.

从本节课中

Satellite and communications

This module describes the overall architecture of a satellite communications system, discusses the concept of orbit and what are the typical sub-systems of a satellite

Introduction0:37

Various types of orbit3:16

Relationship between orbit and service9:33

Going further: Kepler lays down the law4:09

与讲师见面

Laurent Franck
Professor
IMT Atlantique, on leave to Airbus Defence & Space as of September 1st, 2017
Tarik Benaddi
Associate Professor
IMT Atlantique
Julien Fasson
Associate Professor
INPT/ENSEEIHT
Nathalie Thomas
Associate professor
INPT/ENSEEIHT
Marie-Laure Boucheret
Professor
INPT/ENSEEIHT

-In the previous episode, we saw how to characterize a satellite's orbit.

In this episode, I will describe two typical orbits.

Do not worry, there are many others. But with those two,

we cover a vast majority of communications systems.

The first is the geostationary orbit. It is the king of orbits.

This orbit is circular. Its plane is merged with the equatorial plane.

The satellite is at an altitude of about 36 000 kilometers.

The specificity of this orbit is that at this altitude,

satellites revolve at exactly the same speed as the Earth.

The very interesting consequence is that, for an observer on Earth,

these satellites do not move and remain a fixed point in the sky.

This is the favorite orbit of service providers who want to broadcast TV

or radio because once the antenna is directed towards the satellite,

it does not need to be moved anymore.

During week 1, I also mentioned the geosynchronous orbit.

The geosynchronous orbit is a geostationary orbit

but with an angle different from 0,

that is to say not merged with the equatorial plane.

The second orbit category I will mention are the low orbits.

Most of the time they are circular.

Their altitude is between 350 and 800 kilometers.

Below 350 kilometers, it is tricky because there are traces of atmosphere

that generate friction.

Over 800 kilometers, we might face the Van Allen radiation belts

that were introduced during week 1.

What is the benefit of low orbits?

Remember one of the laws of satellite communication systems,

the inverse-square law.

We know that the smaller the distance, the easier it is to communicate.

Secondarily, it is also easier to observe.

Think about spy satellites, for example.

At these altitudes, they can take quite precise pictures.

However, the disadvantage of these low orbits

is that these satellites are not fixed in the sky

since they do not revolve at the same speed as the Earth.

These satellites are thus sometimes called moving satellites.

The angle is also one of the important parameters for this kind of orbit.

It will have an impact on the service coverage.

We will see this during the next episodes.

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