On October 4, 1957, the Soviet Union inaugurated what is popularly known as the Space Age with the launch of Sputnik 1, the first artificial satellite in history. This device consisted of an aluminum sphere about 58 cm in diameter, equipped with four antennas almost three meters long. Equipped with rudimentary instruments housed in a hermetically sealed compartment, the satellite was to obtain data related to the density of the upper layers of the atmosphere, the propagation of radio signals in the ionosphere, and the temperature inside and on the surface of the sphere. Among its instruments were transmitters operating at 20.005 and 40.002 MHz (at wavelengths of 15 and 7.5 m, approximately). The satellite was to transmit periodically, with a duration of 0.3 seconds.
On November 3 of that same year, the Soviet Union launched a new vehicle into space. It was Sputnik 2, a more sophisticated satellite than its predecessor, which carried the first living being into Earth's orbit, the dog Laika. The United States' response to Soviet achievements came with the launch of Explorer 1 on February 1, 1958, a device equipped with some scientific instruments that, among other things, allowed it to detect the presence of magnetic belts around the Earth, known as the Van Allen belts in honor of the scientist who determined their existence, James Van Allen.
In general, and with the exception of Explorer 6, which took the first images of cloud formations from orbit, the first devices launched into space lacked photographic equipment and only had sensors and instruments to measure the near-Earth space environment. However, the qualities offered by Earth's orbit for observing our planet, a magnificent balcony with unbeatable views in the words of many astronauts, were the reason why the first devices equipped with photographic and television cameras were soon launched into space. Additionally, the tense atmosphere of the Cold War accelerated plans to place satellites and platforms equipped with equipment for capturing high-resolution images of Earth into orbit.
What tasks can a satellite perform?
- Communication: Communication satellites allow us to transmit calls, text messages, and data through mobile phones and internet services, even in remote areas where infrastructure is limited.
- Navigation: The Global Positioning System (GPS) uses a constellation of satellites to provide us with precise location and navigation information, used in navigation devices, vehicle tracking systems, and apps.
- Meteorology: Meteorological satellites orbit the Earth to monitor and predict the weather, capturing essential information for forecasts, storm alerts, and tracking extreme weather phenomena such as tornadoes and tsunamis.
- Earth Observation: Earth observation satellites collect data on the environment, vegetation, and water quality, helping in the management of natural resources, urban planning, and detecting environmental changes on the planet.
- Television and Radio: Broadcasting satellites transmit television and radio signals globally, allowing the distribution of programs and live events.
- Internet: Broadband communication satellites provide internet access in rural and remote areas where infrastructure is unavailable.
Advantages and disadvantages of using this technology
Advantages:
- Global coverage: Satellites provide coverage in remote areas where other communication technologies may be limited or nonexistent.
- Reliable communications: Satellite technology offers reliable communications even in extreme weather conditions.
- Real-time data access: Allows real-time data access for apps, such as tracking, GPS navigation, and weather monitoring.
- Versatility: Used in a wide variety of applications, from telecommunications to scientific research.
Disadvantages:
- Cost: Building and launching satellites are very expensive, which can limit access to this technology for some organizations and/or countries.
- Latency: Data transmission via satellites can experience latency, affecting the quality of real-time communications, such as video calls or videoconferences.
- Vulnerability to interference: Satellites can be susceptible to external interference, such as solar radiation, which can affect the quality and security of communications.
- Space debris management: The proliferation of satellites can contribute to the problem of space debris, increasing risks for other satellites and spacecraft in orbit.
### Types of orbits
After the launch of Sputnik 1 in 1957, the sky quickly began to fill with increasingly sophisticated satellites with very diverse functions. There are five main types of orbits in which to place a satellite, depending on the function it will perform.
Low Earth Orbit (LEO) is around the Earth up to altitudes close to 2000 km. Its periods range from 90 minutes (for the lowest altitudes) to several hours (for those higher, up to 2000 km). This orbit is mainly used by manned spacecraft, certain communication satellites, meteorological and military satellites.
Geostationary Orbit (GEO) is a circular orbit located about 35700 km in altitude (approximately 6.6 Earth radii). It extends to almost a tenth of the distance between the Earth and the Moon, and its period is almost 24 hours, coinciding with Earth's rotation. For an observer on the surface, a satellite in this orbit appears static. A satellite located 35700 km above the equator has a field of view of 50% of the Earth's disk. This orbit is mainly used by meteorological, military, and communication satellites and is a subset of the so-called geosynchronous orbits (GSO).
The Molniya orbit is named after the series of Soviet Molniya satellites, which operated mainly in this markedly elliptical orbit, with 40000 km at its farthest point (or apogee) and 500 km at its closest point (or perigee). Satellites in these orbits have a period of 12 hours, moving very slowly at points near the apogee and very quickly near the perigee, which is why they remain over the same hemisphere for 11 of the 12 hours of their period.
Between LEO and GEO orbits, the medium inclined orbit or equatorial orbit is located about 20000 km above the surface, with a period of 12 hours. It is also used by civilian and military satellites, such as navigation satellites.
The high-altitude orbit is located between GEO and lunar orbits. It is a very sparsely populated space with satellites, with varied uses, although mainly military and scientific. Among others, the Vela series satellites, intended for detecting nuclear explosions, were placed in this type of orbit.
Meteorology/Climatology?
Meteorology: Many aspects that affect daily life depend on meteorology, and for this reason, humans have invested significant efforts in understanding and predicting the phenomena it encompasses.
Until the 1930s, weather forecasts were made, among other techniques, by launching radiosondes, stationary balloons raised to certain altitudes carrying radio instruments to obtain information about the state of the atmosphere, a method with significant limitations. In 1954, four years after Otto Berg created that mosaic of photographs taken during the launch of a V2 in which a large storm was visible, the then head of the Scientific Services Division of the US Weather Bureau, Harry Wexler, published a paper titled Meteorological Observation from a Satellite Vehicle.
The launch of satellites radically changed the way meteorology is viewed. Before the Space Age, phenomena such as storms and hurricanes appeared without warning, affecting large areas, causing many human casualties and significant economic damage. Today, satellites are indispensable, as the data they provide allow scientists to deepen their understanding of atmospheric mechanisms, which improves meteorological models and, with them, the accuracy and reliability of forecasts, which are vital for alerting the population to the proximity of extreme phenomena that could pose a potential threat.
Although the first meteorological satellites carried television cameras, current ones have replaced them with instruments called radiometers, whose function is to scan the Earth to capture the radiation emitted by the planet and generate images with the obtained information. Radiometers consist of a small telescope (sometimes an antenna), a scanning mechanism, and one or more sensors operating in the visible light, infrared, and microwave ranges, to generate different types of images of meteorological phenomena occurring on our planet. Many meteorological satellites are launched into a geostationary orbit, located around 35700 km above the Earth's surface. These vehicles are positioned in the planet's equatorial plane, near latitude 0. Distributed along this plane, they cover different regions of the Earth.
Thus, the US NOAA meteorological satellites, GOES-East and GOES-West, are positioned to observe most of the western hemisphere, from the western coast of Africa to the western Pacific, and Arctic and Antarctic regions, while the European Meteosat series satellites observe Europe, Africa, the Middle East, and part of South America, as well as Arctic and Antarctic regions.
Climatology: What is climate? There are many ways to define this term, but we will use the briefest and most effective: the description of long-term weather patterns, either on a regional scale, such as a country or continent, or globally, that is, the entire planet.
The prevailing climate on a planet depends on many factors, the main ones being its proximity to the Sun and the energy exchange between the star in question and the space environment, both interrelated. Planets like Venus are subjected to extremely high temperatures, above the melting point of lead, which in this particular case are enhanced by the characteristics of its atmosphere, which retains most of the energy received from the Sun, not letting it escape into space. In contrast, Pluto, one of the celestial bodies farthest from the Sun in our system, is immersed in a deep and eternal winter, with temperatures well below the freezing point of water. Its atmosphere is so thin that the planet barely retains the radiation received from the Sun. However, Earth is located in what space scientists call the habitable zone, a region whose distance from the Sun allows water to flow in liquid state, thus contributing to the flourishing of life forms. Additionally, the characteristics of Earth's atmosphere allow for a fairly balanced energy exchange, which fosters mild temperatures on the planet compared to other celestial bodies.
However, Earth's climate is not homogeneous. Tropical and equatorial regions are more exposed to solar radiation and therefore, are the ones that endure the highest temperatures, sometimes exceeding 60°C. In contrast, the north and south poles are regions where the incidence of solar radiation is significantly lower, which is why they maintain temperatures well below 0°C (in Antarctica, temperatures as low as -92°C have been recorded), although they can sometimes reach positive levels. On the other hand, there are phenomena that are putting this energy exchange balance at risk. Emissions of gases such as methane and carbon dioxide are the causes of the greenhouse effect, a phenomenon clearly visible on Venus, which disrupts the balance of energy exchange on a planetary level. This is why Earth's global temperature has increased by more than one degree in the last century. Although global warming is a natural process that our planet has been experiencing for thousands of years, human activity is contributing to accelerating this process at rates hundreds of times higher than the natural pace.
Earth's orbit around our star is the ideal place to measure the energy exchange between our planet and the space environment, and its variability across the globe. Therefore, artificial satellites have become the ultimate tool in studying Earth's climate. Just as in meteorology, where satellites are essential for short- and medium-term forecasting, these devices are vital not only for determining Earth's climatic characteristics but also for developing models that allow us to predict their evolution and consequences for the global ecosystem with sufficient anticipation.
In conclusion, satellites have been fundamental protagonists in space exploration and the development of technologies that have transformed our lives. Since their launch in 1957, they have evolved to be used in a wide range of vital functions, from communication and navigation to Earth observation and climate prediction. Their ability to provide precise and real-time data has revolutionized our understanding of the world around us and has significantly contributed to scientific and technological progress. However, they also face challenges, such as cost, latency in communications, and space debris management. But despite these challenges, satellites continue to be an invaluable tool for humanity in its quest to explore space and better understand our beautiful planet Earth.
Bibliography:
Book (Earth Observation from Space).