What is Satellite Technology? And Its 7 Uses

What is Satellite Technology? And Its 7 Uses- Daily Techno Review

7 The Different Types of Artificial Satellites

In this article we will see the different types of Satellites and its uses. Satellites are generally classified into two classes: scientific satellites and application satellites.

1. Scientific Satellite

They are dedicated to pure research in astronomy (they are in fact telescopes in orbit with more or less wide fields of observation and observing the whole electromagnetic spectrum), in geodesy, geodynamics, etc. These are generally unique objects. If they are lost during the launch, they are rarely replaced.

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2. Application Satellite

They have a commercial application in the fields of Meteorology. Earth Observation (Remote Sensing), Telecommunications, Navigation. They generate direct revenues (communications satellites) or induced revenues (meteorology, civil and military earth observation, navigation, etc.).

As their service must not be interrupted, they require redundancy in orbit and replacement by new generations. This is a real market for satellites and their applications. The applications can be civil or military. Some satellites have a duality of application, being able to have several applications (Meteorology and Telecommunications, Civil and Military, for example, etc.). We find:

i] Telecommunications Satellites:

These satellites are used to transmit information from one point to another on the Earth, including telephone communications or data transmission, satellite communications and television programs.

ii] Remote Sensing Satellites:

These satellites observe the Earth, in a scientific (sea temperature, snow cover, drought, …), economic (natural resources, agriculture, …) or military purposes. The observation spectrum is vast, optical, radar, infrared, ultraviolet, listening of radioelectric signals.

iii] Positioning Satellites:

These satellites make it possible to know the position of objects on the surface of the Earth, in the air (planes, missiles) and in space.

iv] Military Satellites:

For military and governmental use, they can be used for telecommunications and Earth observation or for electronic surveillance (spy satellites). The Space Stations, also in orbit around the Earth, constitute a special class, intended to be inhabited by man, for scientific purposes and or application. The Space Probes, intended to observe another celestial body, are no longer orbited around the Earth and thus lose this quality.

v] Earth Observation Satellite

Observation satellites are one of the major components of space technology. Indeed, they correspond to a very important need for many human activities: to have a global vision of the Earth. Before the space age, man had never been able to see the whole hemisphere at a glance. It was therefore necessary to put into orbit the first space vehicles to extend the accessible horizon and show

What is Satellite Technology? And Its 7 Uses- Daily Techno Review

our planet as we have never seen it before. Today, the observation satellite has become indispensable to scientists and industrialists as well as the military. It offers each of them a multitude of reasons to observe the Earth from space in the entire electromagnetic spectrum.

A short history of Aerial and Space Observation

  • The balloon: In the middle of the last century, the balloon allowed the French photographer, Gaspard-Félix Tournachon (known as Nadar), to take the first aerial photographs over Paris. But it is really during the Civil War (1861-1865) that balloons became the first means of aerial reconnaissance.
  • The airplane: At the beginning of the XXe century, the airplane showed all its advantages as an observation platform for civil or military use. Nowadays, airplanes specially equipped as flying studios, equipped with cameras or other instruments, carry out missions all over the world for

cartography, the study of forests, urban planning, espionage, pollution monitoring, archaeological or oil research, etc. Photography

provides excellent quality documents, covering a small area on the ground but with a resolution of only a few decimeters. However, these missions are punctual, limited in time and space, and very costly.

  • The artificial satellite: Appeared in 1957, the artificial satellite with properties (repeated data, over large areas, without constraints imposed by political boundaries and low cost compared to the duration of the mission) that make it an exceptional observation platform has become the reference tool to observe the Earth.

Operation of Observation Satellites General Principle

These satellites are based on the detection and measurement by their sensors of the flow of electromagnetic radiation from the observed area. The data is then interpreted taking into account the following physical laws:

  • The shorter the wavelength, the higher the temperature of the object (Planck’s formula: Energy = 6.626×10-34 * frequency).
  • Each object studied (plant, house, water surface or air mass) emits or reflects radiation at different wavelengths and intensities depending on its state (chemical composition).

To ensure complementary measurements, scientists use several sensors specialized in a particular wavelength to study the same earth phenomenon.

Classification of the Different Types of Imaging Sensors

  • According to the passivity of the system
    • After having been originally constituted by photographic cameras, the current sensors are either of passive type, where the signal received by the optical system is sent back on detectors which transform it into electric signal (principle of the scanner), or of active type.
    • The active sensor is a radar: it emits a signal, in the microwave domain, and records the response returned by surfaces and objects observed. This sensor can transmit and receive a signal regardless of the atmospheric and lighting conditions.
    • Active system: the instrument on board the ERS satellite emits a signal that is backscattered by the observed medium and detected by the “A” antenna. Passive system: the instrument on board the SPOT satellite receives the solar radiation reflected by the observed medium.
  • According to the spectral bands: Sensors use different spectral bands depending on their mission.
  • According to the field of observation
  • According to the orbit

A geostationary satellite is positioned above the equator and has the same rotational speed as the Earth itself, making it appear stationary from the perspective of an observer on the cow floor (see Appendix V). At 36,000 km altitude, it can observe an entire hemisphere. A polar orbiting satellite circles the Earth with a near-polar inclination, meaning that it always passes exactly over the Earth’s rotation axis.

The satellite passes the equator and each latitude at the same local solar time each day. The polar satellite’s orbit is much lower than a geostationary orbit and thus sees a smaller portion of the surface, but in finer detail. The two types of satellites, polar and geostationary, should be seen as complementary. Each category has qualities and shortcomings that the other does not, and an ideal observing system (a “constellation” of satellites) tries to combine the advantages of both.

Advantages and Disadvantages of a Geostationary Satellite :

The satellite is permanently visible from all points of a large area (one third of the planetary surface). This means frequent data transmission (every minute at best), which allows a good monitoring of fast-moving events. Only one station is needed to maintain the satellite. But the polar regions are not visible and the ground resolution is poor.

Advantages and Disadvantages of a Polar-Orbiting Satellite:

It provides global coverage and good resolution on the ground. The synchronization with the Sun produces a constant illumination for the observed surfaces and that maximum energy for the instruments. Despite this, continuous observation of a particular point is impossible, although a multiple satellite system solves the problem, and satellite maintenance requires many ground stations.

1. Applications in the Military Field

Military satellites were the first form of observation satellites: in fact, as early as 1959 and within the framework of the Cold War, the United States and the USSR developed military observation satellites, which are commonly and abusively called

The first of these were the Discoverer series of “spy satellites”. They allowed of course to observe the military resources of the enemy in areas

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This wasthebasis for other civilian applications of observation satellites. All this was entirely legal since borders no longer exist at an altitude greater than 80 km. The two countries thus avoided the diplomatic problems linked to the observation of foreign powers from spy planes like the Lockheed U-2 for the United States.

Thus, it was possible to discover that the USSR had, just like the United States, a of manned exploration of the Moon! But more important than that, these satellites had a stabilizing role in the Cold War. Indeed, they made it possible to check the truthfulness of the messages of opposing propaganda or the declarations of politicians (the missile gap in the years 1960): if, for example, the USSR claimed to possess 1,000 nuclear warheads while the satellites observed only 10, it was concluded that the threat was less great, which rebalanced the two forces present. This also allowed the discovery of certain real threats and their elimination.

The best example is the Cuban crisis. Thanks to satellite photos, it was possible to demonstrate the presence of intercontinental missiles on the island of Cuba in front of the United Nations, which made it possible to remove the threat from the island. Military satellites can also be used to guide units or missiles or to intercept telephone communications. But the primary vocation of a military satellite is to help the military, not only in the strategic sector but also on the battlefield.

Meteorology

View of the Earth from a GOES weather satellite (Source: NOAA)

Until the 1960s, weather forecasting was much more uncertain than today. One of the causes of this problem is that surface and offshore weather stations exist in only a few locations and radiosonde stations are even more scattered.

Everywhere else, atmospheric conditions remained a mystery at that time. Moreover, meteorologists had little distance to the information they obtained and therefore could not model everything. Thus, it was impossible for them to measure the sea surface temperature on a planetary scale and with a high resolution, to observe clouds in altitude, to know the terrestrial radiation or to follow live the movement of a tropical storm.

In 1962, the first satellite dedicated to meteorology was launched: TIROS-1. All these data are now available thanks to meteorological satellites. They have created a real revolution. The simple fact of offering a complete coverage of the Earth,

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day and night, has literally overturned all the models built in situ for a century. Each low- pressure or high-pressure system has suddenly become visible during its formation and its evolution, something impossible to observe from a ground station.

To cover the entire globe, several countries or groups of countries divide the work. Europe maintains the Meteosat satellites, the United States the GOES and TIROS satellites, Japan the GMS satellites. Russia, like the Soviet Union before it, also has an elaborate program in this field. More recently India and the People’s Republic of China have joined this group. In addition, some satellites have specific missions such as the TRMM for the measurement of tropical rainfall.

Here is an overview of some applications in meteorology that would not have been possible without the contribution of satellites:

World Weather Watch

The World Meteorological Organization is an agency of the United Nations which aims at the cooperation of national meteorological services. One of the main programs of the WMO is the World Weather Watch, whose goal is to maintain a permanent global weather observation service by promoting the free exchange of data between member countries.

Since the 1960s, the advent of satellites has strengthened cooperation and increased the amount of data transmitted.

Tropical Cyclone Monitoring

Thanks to satellites, forecasting the paths of tropical cyclones has made considerable progress. For example, in 1992, during hurricane Andrew, Meteosat and GOES images allowed to divert air traffic and to take the necessary measures for the protection of goods and people on the ground. Such examples appear every year and it is difficult to calculate the number of human lives that the prediction of the trajectory of cyclones (which owes much to satellites) has saved.

However, each new disaster underlines the limits of current meteorological forecasts. The margin of progress is still very large for the research centers.

Monitoring of Epidemics

The data provided by meteorological satellites allow us to anticipate the areas of propagation of deadly diseases. Let’s take the example of malaria in Africa. Meteosat data can be used to identify conditions favorable to the reproduction of mosquitoes, the vectors of the disease, and thus to develop a reliable alert system that facilitates the work of health authorities. More generally, there is a close link between climatic conditions and the appearance of epidemics, hence the importance of having accurate data on climatic conditions to establish a model to predict areas at risk.

2. Agriculture

Satellites have brought greater precision to meteorology, which means that the data received by farmers is also more accurate. Thus, they can adapt their activities according to the weather information: frost, precipitation, fog, etc. To avoid a long list of applications of precision meteorology in agriculture, here are two examples that demonstrate its importance:

What is Satellite Technology? And Its 7 Uses- Daily Techno Review
  • By analyzing the earth’s infrared radiation, the GOES satellite in Florida measures the ground temperature every 30 minutes. This way, the risk of frost, which is fatal to lemon trees, is predicted and is only combated by heating with fuel oil when necessary. The savings amount to US$ 45 million per year.
  • Hawaiian sugarcane company estimates it will earn

US$1 million a year through satellite weather forecasting. If rain occurs less than 48 hours after the pre-harvest burn, the crop is lost.

3. Numerical Forecasts

Since the beginning of the XXe century, meteorologists have known that the atmosphere is a fluid whose behavior is that of fluid mechanics. The pioneer in the field of parameterization of the atmosphere in numerically solvable equations, Lewis Fry Richardson, had already tried to predict the future state of the weather using these calculations in 1922. It is only with the advent of the computer that modern numerical weather prediction (NWP) could be developed from the 1950s.

The implementation of NWP for operational weather forecasting requires the acquisition of meteorological observation data covering the whole planet with the best possible resolution. Satellite data have come to fill an important gap in this field. From these data we can not only extract the cloud cover but also make a vertical survey of temperature, humidity and winds using various sensors in the satellite and data processing algorithms.

4. Climatology

Besides the short-term discipline of meteorology, satellites are also extremely useful for climatology. The latter does not have the same requirements as meteorology. It does not need immediate data but data over a much longer period of time. Observation satellites therefore provide long series of precise, global measurements that are compatible with the global dimension of climatic phenomena. The climate is a “machine” comprising 3 “sectors” that interact with each other: the ocean, the land and the atmosphere.

Oceanography

Since 1992, oceanography has been turned upside down by the appearance of water mass observation satellites. All the models, established with difficulty by more than a century of observations at sea, proved to be inaccurate, too old or wrong after only 10 days of operation of Topex-Poseidon! Since June 1995, oceanography has had to be adapted to accommodate both modes of observation (satellite and in situ). This has led to an integrated oceanography, i.e. one that tries not only to understand the oceanic phenomena but can make forecasts of the evolution of water masses. We therefore use models where the ocean evolves in real time.

  • Integrated” oceanography:

At sea, satellite data allow us to optimize fishing. By knowing, thanks to the satellite, the displacement of cold or warm zones and the temperature of preference of the different species of fish, we can go directly to specific areas and avoid fishing too many unwanted species. By the same process, we can help the marine police and scientists. We can also, by modeling the movement of water masses, optimize the maritime routing (the fisherman will take advantage of certain currents to use less fuel) or better manage the coast (3 billion human beings live less than 100 km from the coast).

We can also inform people working on offshore platforms of possible rough areas so that they can stop work in time. Altimetry satellites are already used to map the seabed by observing the surface and, in the future, these same satellites will be able to detect the propagation of of a wave corresponding to a tsunami and thus inform the authorities who will have to take charge of the prevention system. Finally, it is important to know that the oceans carry as much energy as the atmosphere. To understand the mechanisms that govern the oceans is to understand a large part of our climate.

Thus, El Niño (literally Baby Jesus current, so named because it appears shortly after Christmas) is a particular climatic disturbance, which is characterized by an abnormal rise in the temperature of the ocean. During this phenomenon, huge masses of warm water move along the equator towards the East, sometimes creating a rise in sea level of more than 25 cm. El Niño leads to considerable heat transfers between the ocean and the atmosphere, causing cyclones and torrential rains when approaching the coast of South America.

Conversely, on the western edge of the Pacific, where surface waters are are cooling, drought is dominating. The phenomenon is still very poorly known by scientists and the Topex-Poseidon satellite offers the possibility to follow it and to predict its evolution.

5. Observation of the Atmosphere

Satellites observe the ozone hole, in particular ERS-2 and Envisat which measure its dimensions and also allow us to learn more about the causes of its extension or reduction thanks to three instruments capable of studying the pollutants which destroy this layer.

Aerosols and clouds are suspected to play an important role in the climate machine. Aerosols contribute to the greenhouse effect, but by scattering part of the solar radiation, they increase the reflectivity of the atmosphere (with direct and indirect effects).

The “Parasol effect” resulting from the diffusion of solar radiation by aerosols is now cooling the planet. Climatologists need to measure the effects of certain phenomena. Satellites help them to do this. For the study of the parasol effect, a satellite of the same name launched on December 18, 2004, allows us to analyze the polarization and directions of solar radiation reflected by the Earth and the atmosphere. Researchers hope to discover the properties of these aerosols, their size, their distribution on a planetary scale, etc.

The Parasol satellite also allows to describe the properties of the clouds thanks to the observation of the interactions between these clouds and the aerosols. It will be possible to determine the balance of the competition between the two climatic effects: effect greenhouse effect and parasol effect.

Another satellite (CALIPSO) observes aerosols, and provides a vertical “cross-section” of the atmosphere with 30 meters of resolution. These two satellites are part, like four others, of the A-train. It is in fact a “train” of 6 satellites evolving on the same orbit and where each “wagon” is separated from the other by a few minutes.

It was designed to exploit the complementarity between 6 Franco-American satellites in the climate and oceanographic field (although each satellite is independent of the others). This device allows to observe simultaneously the same atmospheric phenomena at a few minutes interval and according to different physical criteria.

The Japanese Space Agency is developing in 2010 the future GCOM mission (Global Change Observation Mission) planned for 13 years; following the ADEOS (1996) and ADEOS-2 (2002) missions aborted due to technical deficiency of satellites. It will be the main JAXA Mission, and the main Japanese contribution to the GEOSS (Global Earth Observation System of Systems) program.

GCOM will have 6 satellites (3 for each family of satellites (GCOM-C and GCOM-W, GCOM-W1 to be launched in 2011 and GCOM-C1 in 2013, GCOM-W2 is planned in 2015, but as C2 (in 2017), W3 (in 2019) and C3 (in 2012), was not yet budgeted in early 2010, while Japan is affected by the aftermath of the Economic Crisis of 2008-2010

6. Observation of the Continents

The Spot satellite makes it possible to take pictures of phenomena such as volcanic eruptions or forest fires and determine their impact on the climate. Others, such as Cryosat and ERS, measure variations in the thickness of continental glaciers. They can detect icebergs and secure navigation. Their measurements confirm that the ice is melting, at least in the Arctic. In the next few years, it will be possible to test ice melt forecasts in the context of global warming.

Satellites and Global Warming

Satellites, together with other measurements taken on Earth, inform us of observed changes such as the rise in average land and sea surface temperature, sea level rise, melting of continental glaciers, increased precipitation and the hole in the ozone layer. However, not all climate factors are known at this time and we do not know to what extent the climate will be changed.

Satellites should allow us to study the impact of different phenomena and possible measures to limit global warming. In order to be able to “live with” or, if possible, anticipate global warming, it is also necessary to have permanent global observation resources and ultra-precise modeling systems.

Negotiations on the environment are a major issue and will intensify in the coming years. Until now, politicians have relied on very fragile data when arguing, for example, about the hole in the ozone layer or greenhouse gases. Satellites, but not only them, make it possible to deliver rigorous and quantified data in order to make the right decisions.

7. Observation of Land Resources Mapping

Cartographers particularly appreciate the ability of a satellite to instantly cover vast areas, even the most inaccessible by land, and to be able to repeat the observation on demand. The first demand for accurate maps are the NGOs working after a natural disaster because many countries in the world are poor in geographical information. Maps of Third World countries, when they exist, are often incomplete and old.

Spot also makes it possible to draw up a global assessment of the damage and to monitor the evolution of the situation from day to day. Spot satellites were in great demand during the Asian tsunami in late 2004 and during the series of hurricanes in the United States in 2005. In industrialized countries, this demand for precise maps is often due to studies on certain public works (roads, dams, etc.).

The 3D maps obtained from radar also allow telephone operators to better locate their antennas. Finally, archaeologists were able to discover ancient tombs in Egypt, hidden in the sand, thanks to these same radar images that could map the relief under the sand. It is also important to note the development of geolocation applications on the Internet, with GeoEye satellites and the use made of them by Google for example.

Mining Exploration

Each mineral has its own electromagnetic “fingerprint”. It will indeed absorb or reflect different parts of the light spectrum depending on its chemical composition. Thus, iron will not be represented in the same way on a “photo” taken by a radar satellite as cobalt. All that is left for prospectors to do is to check in the field whether there is a vein and whether it can be mined.

Agriculture

In the same way that each mineral has its own electromagnetic “signature”, each plant will have a different “signature” depending on its nature or whether it is healthy, growing or sick.

What is Satellite Technology? And Its 7 Uses- Daily Techno Review

We can therefore map crops, follow their evolution, discern variations in their physical state (associated with the appearance of a disease or a lack of water) and estimate harvests (by combining information from the images with data obtained elsewhere, especially in the field).

The Environment

By monitoring deforestation, pollution and soil erosion, observation satellites provide global surveillance of the Earth, facilitating the understanding and control of these phenomena and playing a moderating role in the destruction of natural resources. Satellites can thus determine water reserves, the impact of a given activity on the environment, etc. They can also determine the state of health of vegetation after an ecological disaster and monitor the impact of certain human achievements.

Prevention of Natural Risks

The possibility of programming certain observation satellites allows for the rapid acquisition of images of areas affected by a disaster. Thanks to this information, which can be updated rapidly, it is possible to provide emergency services with recent information. The satellite also makes it possible to draw up a global assessment of the damage and to follow the evolution of the day-to-day situation. The Spot satellites were in great demand during the Asian tsunami in late 2004 and 2005 and during the succession of hurricanes in the United States.

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