Space exploration...
During the greater part of our history, the Moon was quite unreachable. It did not seem very big and far away but rather small. For the Greeks, the idea of walking on the Moon was certainly unthinkable, and as recently as the end of the 19th century many people doubted that humans would even be able to fly. Nevertheless, on July 20, 1969, the miracle happened. Since then many historic missions to explore the planets have been planned and executed, with the spacecraft and probes Mariner, Viking, Pioneer, Voyager, and Galileo leading the way. Thanks to human intelligence and effort we have succeeded in exploring many corners of our solar system. This book intends to show all this: the history of manned and unmanned voyages and the discoveries that were made. We will try, using simple and accessible language, to answer many questions, such as what rockets are, how they work, what shuttles exist, how astronauts live in space, and which robot probes are visiting other planets looking for signs of life. All this is accompanied by photographs and top quality illustrations, providing a better picture of the successes by which we have made giant steps in our understanding of the composition of the other planets, their origin, and their evolution.
Every day astronomers are more convinced that there are other places in the universe that are like Earth. We only have to find them. They also assure us that this is one of the most interesting moments in the exploration of the solar system, because so many things are being revealed. Orbiting spacecraft such as Mars Odyssey and Mars Express have confirmed the existence of ice under the surface of Mars. Sending exploratory spacecraft to Saturn was another prodigious feat, a demonstration of human capacity to dream of new worlds. Recently the New Horizons, whose final destination will be Pluto in 2015, lifted off. This shows that the search has only begun. There is still far to go. Perhaps life may be found farther away than we had imagined. Or maybe, as some dreamers imagine, in the next decade we will realize the project of colonizing other planets. For now, the best candidate for us to land on is Mars.But that is still only a dream, the same kind of dream that was made into reality when humans left their footprints on the Moon
The human adventure in space began with Yury Gagarin, the first Russian astronaut, who in 1961 reached an altitude of 196 miles (315 km) and orbited the Earth in the spacecraft Vostok 1. The cosmonaut had practically no control over the apparatus, which was remotely controlled by Soviet engineers. The next step was made by the United States with the arrival of astronauts on the Moon. Neil Armstrong became the first man to set foot on the Moon, followed by Edwin Aldrin. The success of the Apollo 11 mission marked the culmination of a long and costly space project whose objective was to explore Earth's only natural satellite. In the following decades, the space program has had many significant successes
Every day astronomers are more convinced that there are other places in the universe that are like Earth. We only have to find them. They also assure us that this is one of the most interesting moments in the exploration of the solar system, because so many things are being revealed. Orbiting spacecraft such as Mars Odyssey and Mars Express have confirmed the existence of ice under the surface of Mars. Sending exploratory spacecraft to Saturn was another prodigious feat, a demonstration of human capacity to dream of new worlds. Recently the New Horizons, whose final destination will be Pluto in 2015, lifted off. This shows that the search has only begun. There is still far to go. Perhaps life may be found farther away than we had imagined. Or maybe, as some dreamers imagine, in the next decade we will realize the project of colonizing other planets. For now, the best candidate for us to land on is Mars.But that is still only a dream, the same kind of dream that was made into reality when humans left their footprints on the Moon
The human adventure in space began with Yury Gagarin, the first Russian astronaut, who in 1961 reached an altitude of 196 miles (315 km) and orbited the Earth in the spacecraft Vostok 1. The cosmonaut had practically no control over the apparatus, which was remotely controlled by Soviet engineers. The next step was made by the United States with the arrival of astronauts on the Moon. Neil Armstrong became the first man to set foot on the Moon, followed by Edwin Aldrin. The success of the Apollo 11 mission marked the culmination of a long and costly space project whose objective was to explore Earth's only natural satellite. In the following decades, the space program has had many significant successes
Destination: Other Worlds
The space age began in 1957 with the launching of the first artificial satellite. Since that time, astronauts and space probes have left the Earth to investigate space. To date, 12 men have visited the Moon. Advances in astronautics have made it possible to develop automatic navigational systems with which a spacecraft can reach and enter orbit around a planet. The Mars Express probe, launched in 2003 to take
photographs of Mars, used this system. Mars Express, one of the
European Space Agency's most productive missions around the
Red Planet, is powered exclusively by solar energy.
Automatic Navigational System
Spacecraft that are unmanned, such as the artificial satellites that orbit
planets, transmit their information to Earth using radio equipment. The
area of satellite coverage depends on the type of orbit. There are also probes that touch down on the surface, as was the case with Venus, Mars, and the Moon. The real work begins when the apparatus reaches its target. The instruments are activated to gather data that are sent to Earth for analysis.
Space Programs
The voyages are planned years in advance. Space probes are automatic vehicles that can use the gravitational field of one planet to reach another. Some only pass at a preset distance from the planet they are studying; others (orbiters) follow a route that places them in planetary orbit. From there they can send smaller landing probes, which deploy data-collecting instruments. Manned spacecraft, however, require designs that include air, water, food, seats, and rest areas, as well as navigation-, control-, and information-transmission equipment.
photographs of Mars, used this system. Mars Express, one of the
European Space Agency's most productive missions around the
Red Planet, is powered exclusively by solar energy.
Automatic Navigational System
Spacecraft that are unmanned, such as the artificial satellites that orbit
planets, transmit their information to Earth using radio equipment. The
area of satellite coverage depends on the type of orbit. There are also probes that touch down on the surface, as was the case with Venus, Mars, and the Moon. The real work begins when the apparatus reaches its target. The instruments are activated to gather data that are sent to Earth for analysis.
Space Programs
The voyages are planned years in advance. Space probes are automatic vehicles that can use the gravitational field of one planet to reach another. Some only pass at a preset distance from the planet they are studying; others (orbiters) follow a route that places them in planetary orbit. From there they can send smaller landing probes, which deploy data-collecting instruments. Manned spacecraft, however, require designs that include air, water, food, seats, and rest areas, as well as navigation-, control-, and information-transmission equipment.
From Fiction to Reality
Astronautics was born toward the end of the 19th century, when the Russian Konstantin Tsiolkovsky foresaw the ability of a rocket to overcome the force of gravity. Other pioneers were Hermann Oberth, who designed a liquid fueled missile in 1917, which was later built by the American Robert Goddard in 1926. The German Wernher von Braun built the Red stone, Jupiter, and Saturn rockets, which made the manned landing on the Moon possible.
Astronautics officially began in 1957 with the launching of the first artificial satellite, Sputnik 1. The second was Sputnik 2, which had on board the dog Laika.
Sputnik 1
inaugurated the period of Russian supremacy in the so-called space race. Sputnik 1,
launched in 1957, was an aluminum sphere 23 inches (58 cm) in diameter. It had
instrumentation that for 21 days sent back information about cosmic radiation, meteorites, and the density and temperature of the Earth's upper atmosphere. It was destroyed by aerodynamic friction when it reentered the atmosphere 57 days later.
With a Dog
Sputnik 2 was the second satellite launched into Earth's orbit by the Russians (on Nov. 3, 1957) and the first one to carry a living creature, the dog Laika. The satellite was 13 feet (4 m) long and 6 feet (2 m) in diameter. The dog was connected to a machine that registered her vital signs, and oxygen was provided to her by an air regeneration system. Food and water were dispensed in the form of a gelatin.
Astronautics officially began in 1957 with the launching of the first artificial satellite, Sputnik 1. The second was Sputnik 2, which had on board the dog Laika.
Sputnik 1
inaugurated the period of Russian supremacy in the so-called space race. Sputnik 1,
launched in 1957, was an aluminum sphere 23 inches (58 cm) in diameter. It had
instrumentation that for 21 days sent back information about cosmic radiation, meteorites, and the density and temperature of the Earth's upper atmosphere. It was destroyed by aerodynamic friction when it reentered the atmosphere 57 days later.
With a Dog
Sputnik 2 was the second satellite launched into Earth's orbit by the Russians (on Nov. 3, 1957) and the first one to carry a living creature, the dog Laika. The satellite was 13 feet (4 m) long and 6 feet (2 m) in diameter. The dog was connected to a machine that registered her vital signs, and oxygen was provided to her by an air regeneration system. Food and water were dispensed in the form of a gelatin.
A Giant Leap
The acceleration of the space race between the United States and the Soviet Union reached its height when President Kennedy's words set the goal of landing on the Moon before the end of the 1960s. In meeting that goal in 1969, a human being for the first time in history walked on the Moon. The mission took
over a week, including the trip and the stay on the Moon. It was the first launch to use two boosters: one for leaving Earth to get to the Moon and the other to return from the Moon. Neil Armstrong was the first person to leave a human footprint and place a U.S. flag in outer space.
Lift off
The module is powered by a Saturn V rocket. With a weight of over 6 million pounds (3 million kg), it was the heaviest rocket that had ever been built.
The Modules
The Apollo 11 mission had a spacecraft divided into two parts: the command module Columbia and a lunar module, the Eagle. Initially they were joined together. When orbit was reached, the lunar module separated to complete its descent land land on the Moon.
over a week, including the trip and the stay on the Moon. It was the first launch to use two boosters: one for leaving Earth to get to the Moon and the other to return from the Moon. Neil Armstrong was the first person to leave a human footprint and place a U.S. flag in outer space.
Lift off
The module is powered by a Saturn V rocket. With a weight of over 6 million pounds (3 million kg), it was the heaviest rocket that had ever been built.
The Modules
The Apollo 11 mission had a spacecraft divided into two parts: the command module Columbia and a lunar module, the Eagle. Initially they were joined together. When orbit was reached, the lunar module separated to complete its descent land land on the Moon.
The Moon Without Secrets
Six Apollo missions were able to land on the lunar surface. Apollo 13, because of an oxygen tank explosion, flew to the Moon but did not make a landing. Through the intelligence and expertise of the astronauts on board, it was able to return to Earth safely. With the success of these missions, the Moon was no longer unreachable. A dozen men were able to walk on the gray, crunchy lava soil strewn with craters. Each one of these voyages, besides bringing back data, encouraged the development of space science and increased the desire to carry out other missions to different locations of the solar system.
The Apollo Missions
The Apollo program began in July 1960. An important modern
technological triumph, it succeeded in putting the United States
ahead in the space race. Six missions made landings: Apollo 11, 12, 14, 15,16, and 17. The Apollo lunar module was the first spacecraft designed to fly in a vacuum without any aerodynamic capabilities.The Lunar OrbiterThe Lunar Prospector was launched in1997 and was in space for 19 months. It orbited the Moon at an altitude of 62 miles(100 km), traveling at a velocity of 3,400 mph(5,500 km/h), completing an orbit every two hours. This allowed it to obtain data from thesurface. Its objective was to attain a low polar orbit of the Moon, which included a mapping of the surface, reconnaissance for the composition and possible deposits of water in the form of ice, and measuring the lunar magnetic and gravitational fields.
The Apollo Missions
The Apollo program began in July 1960. An important modern
technological triumph, it succeeded in putting the United States
ahead in the space race. Six missions made landings: Apollo 11, 12, 14, 15,16, and 17. The Apollo lunar module was the first spacecraft designed to fly in a vacuum without any aerodynamic capabilities.The Lunar OrbiterThe Lunar Prospector was launched in1997 and was in space for 19 months. It orbited the Moon at an altitude of 62 miles(100 km), traveling at a velocity of 3,400 mph(5,500 km/h), completing an orbit every two hours. This allowed it to obtain data from thesurface. Its objective was to attain a low polar orbit of the Moon, which included a mapping of the surface, reconnaissance for the composition and possible deposits of water in the form of ice, and measuring the lunar magnetic and gravitational fields.
Echoes of the Past
Thanks to the data obtained in 2001 from NASA's WMAP (Wilkinson
Microwave Anisotropy Probe), scientists have succeeded in making
the first detailed map of cosmic background radiation, a remnant of the Big Bang. The conclusion of the experts is that this map reveals clues about
when the first generation of stars was formed.
Observation
To be able to observe the heavens, the probe is located at the point called Lagrange L2, which is 900,000 miles (1.5 million km) from the Earth. This point provides a stable orbit far from the influence of the Earth. Sun shields protect its instruments, which always point away from the Sun. WMAP observes the heavens in several stages and measures temperature differences between various regions of the cosmos. Every six months it
completely covers the entire sky, which makes it possible to compare different maps to check data consistency.
Microwave Anisotropy Probe), scientists have succeeded in making
the first detailed map of cosmic background radiation, a remnant of the Big Bang. The conclusion of the experts is that this map reveals clues about
when the first generation of stars was formed.
Observation
To be able to observe the heavens, the probe is located at the point called Lagrange L2, which is 900,000 miles (1.5 million km) from the Earth. This point provides a stable orbit far from the influence of the Earth. Sun shields protect its instruments, which always point away from the Sun. WMAP observes the heavens in several stages and measures temperature differences between various regions of the cosmos. Every six months it
completely covers the entire sky, which makes it possible to compare different maps to check data consistency.
Flying Through Space
With space vehicles that have ever more capabilities, humans have attained many goals in space, such as making new discoveries about the origin and
structure of the other planets. Beginning in 1981 the space shuttle became a key component in astronautics. Life on board the shuttle is still difficult, and there are still many problems to be solved. However, the future of the human species over the long term is in space, and there is no choice but to follow that path. Like our ancestors, who immigrated to new regions of the planet to survive and prosper, we have a destiny that will take us away from the Earth to find new places to live.
structure of the other planets. Beginning in 1981 the space shuttle became a key component in astronautics. Life on board the shuttle is still difficult, and there are still many problems to be solved. However, the future of the human species over the long term is in space, and there is no choice but to follow that path. Like our ancestors, who immigrated to new regions of the planet to survive and prosper, we have a destiny that will take us away from the Earth to find new places to live.
Defying Gravity
The human body is suited for conditions under Earth's gravity. Therefore,
if the force of gravity increases or decreases, the body feels a distinct,
unfamiliar sensation. It causes a decrease in heartbeat; muscles become weaker and bones lose calcium. Engineers and medical doctors have investigated how humans can survive long periods where there is little gravity without causing the body to atrophy. Orbiting laboratories have been built to experiment with zero gravity on Earth.
Microgravity
Gravitation is the universal force of attraction between two bodies. It depends on two principal factors: mass and distance. The greater the mass, the g eater will be the attraction; on the other hand, with greater distance, the force
of gravity is less. A spacecraft in orbit is essentially constantly falling around the Earth, and astronauts aboard do not feel the force of gravity even though they are being pulled by the Earth's gravity. This condition of seeming weightlessness is called a microgravity environment.
Parabolic Flight
To achieve microgravity, a C-135 aircraft ascends at an angle of 47° until the pilot shuts off the engines and the plane begins its free fall by following a parabolic trajectory. During this phase, everything in the airplane floats, both equipment and people, because they are in a weightless condition. Such flights are organized by NASA, ESA, and RSA (the Russian Space Agency).
if the force of gravity increases or decreases, the body feels a distinct,
unfamiliar sensation. It causes a decrease in heartbeat; muscles become weaker and bones lose calcium. Engineers and medical doctors have investigated how humans can survive long periods where there is little gravity without causing the body to atrophy. Orbiting laboratories have been built to experiment with zero gravity on Earth.
Microgravity
Gravitation is the universal force of attraction between two bodies. It depends on two principal factors: mass and distance. The greater the mass, the g eater will be the attraction; on the other hand, with greater distance, the force
of gravity is less. A spacecraft in orbit is essentially constantly falling around the Earth, and astronauts aboard do not feel the force of gravity even though they are being pulled by the Earth's gravity. This condition of seeming weightlessness is called a microgravity environment.
Parabolic Flight
To achieve microgravity, a C-135 aircraft ascends at an angle of 47° until the pilot shuts off the engines and the plane begins its free fall by following a parabolic trajectory. During this phase, everything in the airplane floats, both equipment and people, because they are in a weightless condition. Such flights are organized by NASA, ESA, and RSA (the Russian Space Agency).
Point of Departure
Spacecraft launching sites typically meet one or more optimal criteria. For example, choosing a location close to the Equator makes it easier to put a spacecraft into orbit. Moreover, a number of coastal areas have been chosen, because they are more accessible for the transport of the goods needed to build the launch vehicles. The danger of an accident during launch must also be taken into account. Therefore, sites have been chosen in areas with low-density population, such as Cape Canaveral, Florida.
Vehicle Assembly Building
The spaceport has an immense building for the preparation and assembly of rockets and of the external shuttle tank. The dimensions of the building
are impressive: 525 feet (160 m) high, 715 feet (218 m) long, and 387 feet (118 m) wide. The orbiter travels on top of the crawler-transporter from thisbuilding to the launch pad.
Fixed Service Structure
This steel giant is located at the launch pad. It consists of fixed and rotating structures. Atop the transport caterpillar, the mobile launch platform brings the space shuttle to this location.
Floating Platform
Earth-based launching platforms are very expensive. For this reason, some countries have developed floating launch platforms. At sea it is much simpler and safer to pick a location at the Equator, where the Earth's rotational velocity is the greatest, an advantage for putting space missions into orbit.
The Rockets
Developed in the first half of the 20th century, rockets are necessary for sending any kind of object into space. They produce sufficient force to leave the ground together with their cargo and in a short time acquire the velocity necessary to reach orbit in space around the Earth. On average, more than one rocket per week is sent into space from somewhere in the world.
THERMAL INSULATION
To protect the combustion chamber from high temperatures of the burning fuel, the walls are sprayed with rocket fuel. This process managesto cool the engine off.
TYPE OF ROCKET DEPENDING ON ITS PROPULSION
Rockets with chemical propellants are the most common. Their thrust comes from the exhaust produced through combustion. For propulsion in space,an ion drive can be used to produce an exhaust of accelerated ions (electrically charged atoms). The use of nuclear energy has been studied as a possible source of energy for heating a gas to produce an exhaust.
Engine Operation
Before liftoff, the fuel is ignited. The boosters ignite only if the ignition of the main engine is successful. The rocket lifts off, and two minutes later the boosters are extinguished, their fuel completely consumed. The main engine remains attached until its fuel is used up, and it is then jettisoned.
How It Works
To do its job, the rocket must over come gravity. As it rises, the mass of the rocket is reduced through the burning of its fuel. Moreover,because the distance from the Earth increases, the effect of gravity decreases.
THERMAL INSULATION
To protect the combustion chamber from high temperatures of the burning fuel, the walls are sprayed with rocket fuel. This process managesto cool the engine off.
TYPE OF ROCKET DEPENDING ON ITS PROPULSION
Rockets with chemical propellants are the most common. Their thrust comes from the exhaust produced through combustion. For propulsion in space,an ion drive can be used to produce an exhaust of accelerated ions (electrically charged atoms). The use of nuclear energy has been studied as a possible source of energy for heating a gas to produce an exhaust.
Engine Operation
Before liftoff, the fuel is ignited. The boosters ignite only if the ignition of the main engine is successful. The rocket lifts off, and two minutes later the boosters are extinguished, their fuel completely consumed. The main engine remains attached until its fuel is used up, and it is then jettisoned.
How It Works
To do its job, the rocket must over come gravity. As it rises, the mass of the rocket is reduced through the burning of its fuel. Moreover,because the distance from the Earth increases, the effect of gravity decreases.
Launch Sequence
Scarcely 50 years have elapsed since the first spaceflights. Nevertheless, access to space—whether for placing satellites into orbit, sending probes to other planets, or launching astronauts into space—has become almost routine and is a good business for countries that have launch capabilities. Preparations for launch begin with the assembly of the rocket, followed by its placement on a launch pad. When its engines are ignited, the rocket rises into the atmosphere. Once the atmosphere has been left behind, less thrust is needed. For this reason, rockets consist of two or more stages stacked on top of each other. Booster rockets are typically used to produce greater initial thrust.
Launch Countdown
The countdown for the Ariane 5 typically lasts six hours. At the end of the countdown, the launch begins with the ignition of the main stage's liquid-fuel engine. Seven seconds later the two solid-fuel boosters are ignited. Before the boosters' ignition, the flight can be aborted by shutting down the main stage.Bound for Space.
Launch Window
Rockets must be launched at predetermined times, which depend on the objective of
the launch. If the objective is to place a satellite into orbit, the latitude of the launched rocket needs to coincide with the trajectory of the desired orbit. When the mission involves docking with another object in space, the launch window might fall within only a few minutes.
Launch Countdown
The countdown for the Ariane 5 typically lasts six hours. At the end of the countdown, the launch begins with the ignition of the main stage's liquid-fuel engine. Seven seconds later the two solid-fuel boosters are ignited. Before the boosters' ignition, the flight can be aborted by shutting down the main stage.Bound for Space.
Launch Window
Rockets must be launched at predetermined times, which depend on the objective of
the launch. If the objective is to place a satellite into orbit, the latitude of the launched rocket needs to coincide with the trajectory of the desired orbit. When the mission involves docking with another object in space, the launch window might fall within only a few minutes.
Space Shuttle
Unlike conventional rockets, the U.S. space shuttle can be reused to lift satellites into space and put them into low Earth orbit. Today these vehicles are also used to make flights to the International Space Station. The U.S. fleet has three shuttles: Discovery, Atlantis, and Endeavour. The Challenger exploded in 1986 and the Columbia in 2003.
The Cabin
The place where the members of the crew live is divided into two levels: an upper level houses the pilot and the copilot (and up to two more astronauts), and a lower level is used for daily living. The amount of habitable space inside the cabin is2,470 cubic feet (70 cu m).
Primary Engines
There are three primary engines, which are fed by oxygen and liquid hydrogen from the external tank. Each engine has computer-based controls that make adjustments to obtain the correct thrust and mix of fuel.
Thermal Protection
When a shuttle begins reentry from Earth's orbit,friction heats the surface to a temperature between 570and 2,700° F (300-1,500° C). Various parts of the spacecraftmust have protective layers to keep them from melting.The inner parts of the wings and the nose heat up the most.
Profession: Astronaut
How do you become an astronaut? Before undertaking a mission in space, every candidate must submit to rigorous examinations since the tasks they are toperf orm are very delicate and risky. They must intensively study mathematics,meteorology, astronomy, and physics and become familiar with computers and navigation in space. They must also train physically to get used to low-gravity conditions in orbit and to be able to carry out repairs.
Control from Earth
Monitoring the astronauts' activity is done from operations centers.In the United States, NASA is in charge of the manned missions from the Mission Control Center located in the Johnson Space Center in Houston. The unmanned missions are supervised from the Jet Propulsion Laboratory in LosAngeles. Utilizing telemetry technology, which makes it possible to see technical aspects in real time, the flight controller scarry out their tasks in front of consoles equipped with computers
The Cabin
The place where the members of the crew live is divided into two levels: an upper level houses the pilot and the copilot (and up to two more astronauts), and a lower level is used for daily living. The amount of habitable space inside the cabin is2,470 cubic feet (70 cu m).
Primary Engines
There are three primary engines, which are fed by oxygen and liquid hydrogen from the external tank. Each engine has computer-based controls that make adjustments to obtain the correct thrust and mix of fuel.
Thermal Protection
When a shuttle begins reentry from Earth's orbit,friction heats the surface to a temperature between 570and 2,700° F (300-1,500° C). Various parts of the spacecraftmust have protective layers to keep them from melting.The inner parts of the wings and the nose heat up the most.
Profession: Astronaut
How do you become an astronaut? Before undertaking a mission in space, every candidate must submit to rigorous examinations since the tasks they are toperf orm are very delicate and risky. They must intensively study mathematics,meteorology, astronomy, and physics and become familiar with computers and navigation in space. They must also train physically to get used to low-gravity conditions in orbit and to be able to carry out repairs.
Control from Earth
Monitoring the astronauts' activity is done from operations centers.In the United States, NASA is in charge of the manned missions from the Mission Control Center located in the Johnson Space Center in Houston. The unmanned missions are supervised from the Jet Propulsion Laboratory in LosAngeles. Utilizing telemetry technology, which makes it possible to see technical aspects in real time, the flight controller scarry out their tasks in front of consoles equipped with computers
Permanent Exploration
Space exploration brings scientific ideas to everyone's attention. This is beneficial because it stimulates our creativity and curiosity. Moreover, these flights contribute to the training of a new generation of scientists. Mars has often been seen as a goal for space exploration, perhaps because of its proximity to Earth and its relatively hospitable surface. Among the probes that NASA has sent to Mars are two robots, Spirit and Opportunity, that scratched the surface of the Red Planet and sent back very interesting data—they found geologic evidence of ancient environmental conditions in which there was water and in which life could have been present.
Satellite Orbits
The space available for placing Communications Satellites is not unlimited. On the contrary, it is a finite space that could become saturated with too many satellites.Desirable locations in geostationary orbits are already reaching this situation, chock-full of television and other communications satellites. The placement of these instruments cannot be arbitrary; errors of 1 or 2degrees in position can generate interference with neighboring satellites. The positions are regulated by the International telecommunications Union. Geostationary satellites have the advantage of being in a fixed position with respect to the Earth's surface. In contrast, Satellites in low or medium orbit require a sequence of terrestrial stations to maintain a communications link.
Different Types
The quality of the information transmitted by the satellites depends on their position relative to the Earth. The geostationary orbit (GEO), which is the most commonly used orbit today, makes it possible to provide coverage to the entire planet with only four satellites, whereas lower orbits need constellations of satellites to get total coverage. This is the case for satellites in LEO (low Earth orbit). In other cases, satellites in MEO (medium Earth orbit) typically describe elliptical orbits. A GEO satellite is in a circular orbit, and if it orbits over the Equator, it always maintains the same position with respect to the Earth.
GEO ORBIT
The geostationary orbit (GEO) is the most common, particularly for television satellites. A satellite in a geostationary orbit orbits the Earth in 23 hours and 56 minutes. Because this equals the rotation of the Earth, the satellite remains stationary relative to the Earth's surface. A satellite in GEO orbits22,400 miles (36,000 km) above the Earth.
LEO ORBIT
A low Earth orbit is between 125 and 1,900 miles (200-3,000 km) above the Earth. LEO has been used for telephone communications satellites because of GEO saturation. The orbits are circular and require less transmission power than other orbits. However, they require Earth based centers to track the satellites.
MEO ORBIT
The altitude of satellites in a medium Earth orbit (MEO) ranges from 20,500 miles (33,000 km) up to the altitude of the geostationary satellites. They generally
describe an elliptical orbit. Because putting them in orbit requires more energy than for a satellite in LEO, their cost is greater.
Different Types
The quality of the information transmitted by the satellites depends on their position relative to the Earth. The geostationary orbit (GEO), which is the most commonly used orbit today, makes it possible to provide coverage to the entire planet with only four satellites, whereas lower orbits need constellations of satellites to get total coverage. This is the case for satellites in LEO (low Earth orbit). In other cases, satellites in MEO (medium Earth orbit) typically describe elliptical orbits. A GEO satellite is in a circular orbit, and if it orbits over the Equator, it always maintains the same position with respect to the Earth.
GEO ORBIT
The geostationary orbit (GEO) is the most common, particularly for television satellites. A satellite in a geostationary orbit orbits the Earth in 23 hours and 56 minutes. Because this equals the rotation of the Earth, the satellite remains stationary relative to the Earth's surface. A satellite in GEO orbits22,400 miles (36,000 km) above the Earth.
LEO ORBIT
A low Earth orbit is between 125 and 1,900 miles (200-3,000 km) above the Earth. LEO has been used for telephone communications satellites because of GEO saturation. The orbits are circular and require less transmission power than other orbits. However, they require Earth based centers to track the satellites.
MEO ORBIT
The altitude of satellites in a medium Earth orbit (MEO) ranges from 20,500 miles (33,000 km) up to the altitude of the geostationary satellites. They generally
describe an elliptical orbit. Because putting them in orbit requires more energy than for a satellite in LEO, their cost is greater.
Cutting-Edge Technology
In July 1999 the X-ray observatory known as Chandra was put into orbit. Since then, it has provided important information about the universe and its phenomena.
Chandra can make X-ray observations of the heavens with an angular resolution of 0.5 seconds of an arc, 1,000 times greater than the first orbital X-ray telescope,the Einstein Observatory. This characteristic permits it to detect sources of light that are 20 times more diffuse. The group in charge of constructing the X-ray telescope had to develop technologies for processes that had never been used before.
Data Transmission
The satellite system provides the structure and the
equipment necessary for the telescope and the scientific
instruments to operate. A propulsion system gradually puts the spacecraft into its final orbit, which is elliptical and extends far from Earth. In order to control the critical temperature of its components, Chandra has a special system of radiators and thermostats. The temperature near the X-ray mirrors has to be maintained at the proper temperature to keep the mirrors in focus. The electrical energy of the satellite comes from solar panels and is stored in three batteries.
Deep Space Network
This international network of NASA radio antennas provides support for interplanetary missions in orbit around the Earth and for radio astronomy observations. It consists of three complexes. Each one contains at least four stations equipped with large parabolic antennas and ultra sensitive receivers.
HOW IMAGES ARE CREATED
The information compiled by Chandra is transferred to tables and images with coordinates of the x- and y-axes.
Chandra can make X-ray observations of the heavens with an angular resolution of 0.5 seconds of an arc, 1,000 times greater than the first orbital X-ray telescope,the Einstein Observatory. This characteristic permits it to detect sources of light that are 20 times more diffuse. The group in charge of constructing the X-ray telescope had to develop technologies for processes that had never been used before.
Data Transmission
The satellite system provides the structure and the
equipment necessary for the telescope and the scientific
instruments to operate. A propulsion system gradually puts the spacecraft into its final orbit, which is elliptical and extends far from Earth. In order to control the critical temperature of its components, Chandra has a special system of radiators and thermostats. The temperature near the X-ray mirrors has to be maintained at the proper temperature to keep the mirrors in focus. The electrical energy of the satellite comes from solar panels and is stored in three batteries.
Deep Space Network
This international network of NASA radio antennas provides support for interplanetary missions in orbit around the Earth and for radio astronomy observations. It consists of three complexes. Each one contains at least four stations equipped with large parabolic antennas and ultra sensitive receivers.
HOW IMAGES ARE CREATED
The information compiled by Chandra is transferred to tables and images with coordinates of the x- and y-axes.
Space Probes
From the first spacecraft, such as Mariner of the mid-1960s, to the Mars Reconnaissance Orbiter launched in 2005 for a close-up study of Mars, space probes have made major contributions. Most of them have been solar-powered; they are the size of an automobile, and they travel to predetermined locations using rockets for thrust. These unmanned machines are equipped with cameras, sensors, spectrometers, and other sophisticated instruments that allow them to study the planets, moons, comets, and asteroids in detail.
Mars Reconnaissance Orbiter (MRO)
The main objective of this orbiting probe is to look for traces of water on the surface of Mars. NASA launched the probe on Aug. 12, 2005; it reached Mars on March 10, 2006, after traveling 72 million miles (116 million km) in seven months. Its mission is scheduled to end in 2010, although if the probe remains in good condition, its life could be extended by another five years.