Space Science

Summary

Space science is an all-encompassing term describing many, often multidisciplinary, fields that study anything beyond the Earth's atmosphere. At first, space science was limited to observational astronomy. Developments in rocket technology have allowed the field to expand to experimental planetary studies and astronautics. Astronomy has advanced to the point where several subfields, including astrophysics and cosmology, have become important fields of study in their own right. Applications of space technology have led to the exploitation of near space in communication, navigation, and space tourism. Space science is used to describe these areas of study and technologies.

Definition and Basic Principles

Space science is not a single field of study. Rather, spacescience applies to any field that studies whatever is external to the Earth. These fields include planetary studies, stellar and galactic astronomy, and solar astronomy. Initially, astronomy involved looking at the skies with the naked eye or through telescopes and recording observations. It has since become a branch of physics, with mathematical analysis and application of physical laws in an attempt to understand astrophysical processes. Additionally, robotic spacecraft allow planetary scientists to collect data on other planets, which is useful to geologists and meteorologists. Discoveries of phenomena unknown on Earth brought many disciplines into space science. Furthermore, theoretical investigations, such as models of potential planetary systems or the search for life in space, are also part of space science. The science of studying phenomena beyond Earth employs nearly every aspect, field, and subfield of science.

Space science also encompasses the technology developed to further the aims of space science, such as rocketry and astronautics. Additionally, it includes exploiting space with such technologies as satellites for communication and navigation, weather, and military and intelligence surveillance. It also includes possible future technologies, such as mining asteroids and establishing space settlements and colonies.

Background and History

Throughout most of history, space was inaccessible to humans. The only way to study extraterrestrial objects was through observation. Astronomy began with these simple observations. In the seventeenth century, people began using telescopes to view the sky, and physics and chemistry became important in interpreting their observations. In the nineteenth century, scientists discovered the existence of cosmic rays. They learned the nature of meteorites, but the study of space remained largely limited to observations from the surface of the Earth.

In 1903, however, Russian scientist Konstantin Tsiolkovsky proposed that rockets could allow people to engage in space travel. The development of rocketry over the next half century eventually led to the creation of a rocket powerful enough to reach the edge of the Earth's atmosphere, allowing the edge of space to be studied directly. On October 4, 1957, the Soviet Union launched the first human-made Earth-orbiting satellite, Sputnik 1. The following month, the Soviets launched a larger satellite, Sputnik 2, with a dog aboard to study the effect of space travel on a life-form. The United States launched Explorer 1 on January 31, 1958. The data gathered from Explorer 1 helped scientists discover the Van Allen radiation belts surrounding Earth.

Space exploitation became possible using rockets, leading to a flurry of interplanetary space missions by robotic spacecraft in the 1960s and 1970s, followed by much larger and more capable robotic spacecraft. In the 1960s, the first communication and weather satellites paved the way for communication, navigation, and Earth-monitoring satellites, which have become mainstays of modern society. Manned exploration of space began with simple capsules on top of converted missiles, evolved to more sophisticated Apollo craft that carried astronauts to the Moon, and then to reusable spacecraft such as the space shuttle. Manned space stations evolved from the simple single-mission systems launched by the Soviet Union in the 1970s to the International Space Station (ISS), constructed during the first decade of the twenty-first century. Even telescopes took to space, with several astronomical satellites being launched, including the Hubble Space Telescope in 1990.

How It Works

Astronomy, Astrophysics, and Cosmology. Astronomy is an observational science. Observations are made by several instruments, including optical telescopes, radio telescopes, infrared and ultraviolet telescopes, and gamma-ray and x-ray telescopes. Instead of simply taking photographs to study, modern astronomers measure spectra, intensities, and many other properties to understand the objects of their study. Some of the instruments they use are located at ground-based observatories with large telescopes, and others are located in orbit around Earth in space-based observatories, the most famous of which is the Hubble Space Telescope.

Astrophysics mathematically studies the physical processes of objects and develops theories based on physical laws. Cosmology involves the study of the universe and space itself. Cosmology and astrophysics involve considerable computer modeling and mathematical analysis of astronomical observations.

Planetary Sciences. Until the 1960s, astronomers were limited to making observations of planets from Earth. However, the advent of interplanetary robotic spacecraft allowed scientists to study other planets in much the same way that they study Earth. Robotic spacecraft employ various instruments, including cameras, spectrometers, neutron sensors, and magnetometers, to study planets from orbit. Spacecraft have landed on Earth’s moon, Venus, Mars, and Saturn's moon Titan to study their surfaces.

Astrobiology/Exobiology. Since the end of the sixteenth century, when astronomers began to guess the nature of the planets, scientists have speculated on whether life could exist on other planets. Robotic spacecraft have searched for life on Mars, and rocks returned to Earth by the Apollo missions to the Moon have been studied for life. The essentials for life have been found in space, but as of the early twenty-first century, no definitive evidence of life has been found on other worlds. Biologists, working with astronomers, have studied the nature of life and probed its possible origins and the conditions necessary for life. This study was originally called astrobiology, although the term exobiology has slowly gained popularity. Exobiology is mainly theoretical.

Rocketry. Rockets are key to space study. Rockets are entirely self-contained and do not need to take in air to operate. They may be either liquid- or solid-fueled. Rockets operate on the principle of conservation of momentum. High-speed gases exiting the rocket carry momentum, so the rocket must have momentum in the other direction to conserve momentum. The rate of change of momentum is force and is the thrust of the rocket.

Astronautics. The space environment is harsh and hostile, not only to life but also to human-made devices. Thus, great care and redundancy must go into any spacecraft design. Aerospace engineers must design spacecraft that can operate in extremes of hot and cold, microgravity, and the vacuum of space, as well as under intense radiation exposure and despite repeated micrometeoroid impacts. These conditions are all difficult to reproduce on Earth. Manned spacecraft or space stations require a habitable environment to exist on the spacecraft. The spacecraft must be shielded from radiation as much as possible to protect its occupants, and systems must be reliable enough to keep the human occupants safe for the duration of the mission. This requires skill in mechanical and environmental engineering, as well as with advanced electronics systems.

Space Weather.Earth's magnetic field extends far above the planet's surface. The region of the solar system in which Earth's magnetic field dominates is called Earth's magnetosphere. Particles trapped in the magnetosphere create regions of intense particulate radiation surrounding the planet. These regions were discovered in 1958 using instruments aboard the American Explorer spacecraft by physicist James Van Allen, known as the Van Allen radiation belts.

Earth's magnetosphere is not static. It constantly shifts and adjusts to the interplanetary space environment, which is constantly affected by the sun. The sun continually emits particles that travel outward through the solar system. This stream of particles, called the solar wind, varies in intensity, density, and speed based on solar activity. Earth's magnetosphere adjusts accordingly.

Occasionally, large bursts of energy, called solar flares, cause portions of the sun's corona to detach and move across the solar system as a large bubble of plasma. When such a coronal mass ejection affects Earth's magnetosphere, a significant shift in the magnetic field occurs over a short period. Solar flares are often associated with significant elevations in solar cosmic rays, called solar radiation storms. Passengers in aircraft and spacecraft can receive significant radiation exposure during such storms.

Variations in Earth's magnetic field are called geomagnetic storms. Large geomagnetic storms resulting from large, rapid shifts in Earth's magnetic field can induce damaging electric currents in pipelines, power lines, and telephone lines. Geomagnetic storms are often associated with radio communication interference and even blackouts. Collectively, the study of the variations of Earth's magnetosphere and the solar-terrestrial interactions is called space weather.

Applications and Products

Much of space science involves basic scientific research. Astronomers and planetary scientists seek to learn about stars, planets, and other celestial bodies, particularly how they came to be the way they are and why they have the properties they have. Although many aspects of these studies have applications beyond academic studies, scientists aim to understand the system and let other scientists or engineers apply the knowledge and technology to other purposes.

Weather and Remote Sensing. Being at a high altitude permits an observer to get a bigger and broader picture than is available from the ground. Early researchers used balloons and then aircraft to study the Earth. The advantages of observations from orbit were obvious to the first space engineers in both the United States and the Soviet Union. The first weather satellite, TIROS 1, was launched on April 1, 1960, less than three years after the first artificial satellite was launched into orbit around the Earth. Early weather satellites used film that was returned to Earth in canisters. Soon, engineers perfected the technology that enabled images to be transmitted electronically. In the twenty-first century, real-time or nearly real-time weather images have become essential tools for meteorologists. Modern weather satellites take images and contain instruments to make numerous measurements.

In addition to providing weather information, satellites can monitor aspects of Earth itself, such as land use, ocean currents, and atmospheric pollution. Collectively, this technology is called remote sensing. Originally, government agencies operated these remote-sensing orbital satellites. However, demand for such data by researchers and private industry spurred private companies to deploy remote-sensing satellites. Dozens of such satellites continually monitor the Earth from space.

Space Weather. Space weather storms have disabled satellites, navigation, and ground-based communication and power distribution grids. Protective measures are sometimes possible if ample warning is given. The military, recognizing the dangers associated with communication blackouts during national tension or armed conflicts, was the first to start monitoring the sun for signs of solar flares that might trigger geomagnetic storms and communication blackouts. The United States and the Soviet Union established global networks of solar observatories for this purpose.

As society has become increasingly dependent on electronic technology that could be interrupted by such events, other government agencies have supplemented the military's observations of the sun. By 2000, the Space Weather Prediction Center, operated by the National Oceanographic and Atmospheric Administration (NOAA), had become one of the top clearinghouses for solar observation data and predictions of space weather events. Most of the center's data are available over the Internet. These data are important for satellite operators, electric utilities, airlines, and many other industries. The Space Weather Prediction Center issues space weather watches and warnings in much the same way that the National Weather Service, another NOAA division, issues thunderstorm and tornado watches and warnings. Many other technologically advanced nations have similar space weather centers.

Communication. When the first satellites were launched, microwave relay towers were constructed to carry voice communications without wires. These towers could be placed only so far apart because the curvature of the Earth would interfere with transmissions. Satellites, however, can act as ultra-high towers. The first test of satellite communications occurred with the launch of the Project SCORE satellite in 1958. SCORE was not capable of real-time communication. It recorded an incoming signal and transmitted it later. Soon, however, technology was developed to permit satellites to relay signals in real-time. By 1963, the first geosynchronous satellite, the Syncom 3, was launched. A geosynchronous satellite remains over a single position on the ground, making it easy to aim antennas and eliminating the need for expensive and complicated satellite-tracking systems. Over 600 geosynchronous communication satellites have been launched into orbit.

Although geosynchronous satellites have many advantages over low Earth orbit (LEO) satellites that track across the sky in a few minutes, LEO satellites have the advantage of being able to use less powerful signals. Many LEO communication satellites exist, notably satellite telephones, systems similar to cell phones but using satellites instead of cell phone towers. Satellite phones are useful in remote regions where cell phone service is unavailable. The military often relies on satellite phones for battlefield operations.

Satellite internet service became viable in the twenty-first century. For example, in 2018, SpaceX began developing a satellite internet service called Starlink. It uses a constellation of thousands of LEO satellites covering virtually every surface of the Earth, hoping to bring broadband internet service to remote locations.

Navigation.Celestial navigation, used for millennia, requires a skilled navigator who can see the sky. Beginning in the 1930s, networks of radio transmitters were set up to aid in navigation. These systems became more advanced but remained limited to areas with transmitters, typically the land areas of technologically advanced nations, and were unavailable at sea. Satellites overcame this problem in much the same way they did for communication relay towers. The first satellite navigation satellite, Transit 1B, was launched in 1960.

Satellite navigation culminated with the US Department of Defense's Global Positioning System (GPS). GPS technology, originally deployed as NAVSTAR strictly for military use in 1978, was eventually made available in civilian form in 1983 on the order of President Ronald Reagan. In 1993, GPS was made available to anyone free of charge, and it has been fully operational since 1995. Free use of GPS signals for navigation spurred many private companies to sell commercial handheld GPS navigation systems. Software to display position on a map and give audible turn-by-turn driving directions using maps and GPS position data made handheld GPS navigation systems very popular by the 2000s. Additional enhancements to GPS navigation are continued by the Department of Defense and private companies.

Space Tourism. Government space agencies have long been the only avenue for space exploration and manned space travel. However, space technology has experienced gradual privatization, and private companies carry out many of the functions previously performed only by government agencies under government contracts. American engineer Dennis Tito was the first space tourist. In 2001, he traveled to space on the Soyuz-TM32, courtesy of Space Adventures, Inc. After Tito's venture, several private space tourism companies formed to provide recreational space travel to wealthy individuals. Several purchased rides in the Russian Soyuz spacecraft to the former Mir space station. In 2020, NASA began allowing passengers aboard Space Exploration Technologies Corporation's (SpaceX) Crew Dragon and Boeing's Starliner to use the International Space Station at a cost. Although these private companies work with space agencies, other companies are developing their own spacecraft. Some of these companies aim to sell their services to the International Space Station, but others, such as Virgin Galactic, intend to provide rides into space for those willing and able to pay for a ticket. Other companies are planning to place private space stations into orbit as tourist destinations.

Military Applications. Even before the first satellite was launched, military leaders recognized the importance of space. Military reconnaissance satellites (often called spy satellites) were among the first satellites launched after the developmental flights. In the 1960s, many feared that orbital weapons platforms capable of dropping nuclear bombs anywhere on Earth would be deployed. This fear was never realized. Although long-range missiles lift their warheads into suborbital trajectories, they are not space-based weapons systems. The United States and the Soviet Union began developing antisatellite weapon systems to counter the military advantage of reconnaissance satellites. The first test of such a system was conducted in 1963 by the Soviet Union. In 1985, the United States tested its first antisatellite weapon, a missile designed to destroy low Earth orbit satellites. Antisatellite weapons have not been used in conflicts, but the United States, China, Israel, India, and Russia have used these weapons in demonstrations on their own satellites.

Space Junk Removal. Frequent space missions have led to the accumulation of high-speed orbiting debris from rocket stages and occasional satellite collisions. This space junk threatens space missions and may eventually make space travel impossible. In 2021, the Japanese company Astroscale launched the End-of-Life Services by Astroscale Demonstration (ELSA-d) satellite to capture space junk using specialized magnetic systems. ELSA-d successfully completed its mission in January 2024. This effort, however, is not enough, and various other organizations are working towards creating a more comprehensive solution to the space junk problem.

Careers and Course Work

Space science is a great many different fields with no single career path. Careers range from machinists building parts for rockets to assembly workers building rockets to engineers designing rockets and spacecraft. The field includes scientists studying the heavens, planetary scientists studying planets, and robotics engineers designing rovers to land on other worlds. It also includes businesses specializing in communications and remote sensing and the engineers who design satellites to perform those functions. Some space businesses need employees with business degrees and experience rather than science backgrounds. Even astronauts have varying qualifications. Some astronauts are pilots with extensive high-performance aircraft experience. Others are scientists with multiple graduate degrees. The growth of space science, which includes virtually every discipline, means there is no single career path.

However, space science is a very technical field, and a typical space science career generally requires many courses in science and mathematics. Physics and chemistry are needed for almost all space science careers. For applied space science, a background in electrical or mechanical engineering is necessary. For basic research, a background in physics or astrophysics is most common, but planetary scientists can have backgrounds in geology, meteorology, or any similar field. Exobiology requires a biology background. Almost all space science jobs that result in advancement require advanced degrees beyond the bachelor's degree.

Social Context and Future Prospects

Space science has evolved from simply the science of astronomy to real, practical applications. Planetary science helps scientists understand how planets function, yielding valuable insights about Earth as a planet. This knowledge gains in importance as issues such as global warming and ozone depletion in the stratosphere are more widely examined. Studies of stars help scientists understand how the Sun works, which is important in the realm of space weather.

The exploitation of space provides useful services for Earth's inhabitants. Modern society relies heavily on rapid communication and the regular transmission of a vast amount of data across far distances. Satellite communication facilitates this need, and many common everyday activities, such as credit or debit card purchases or ATM withdrawals, use this technology. GPS navigation has become common, and most automobiles have GPS systems as a standard feature. Accurate weather and storm forecasts would be impossible without weather satellite data.

Space travel used to be fanciful speculation, but it evolved into expensive government endeavors. However, in the early twenty-first century, several private companies were on the verge of providing space tourism at prices within the reach of many wealthy individuals. If the trend continues, space travel may become as common and inexpensive as air travel.

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