Site hosted by Angelfire.com: Build your free website today!

Unmanned Space Programs

 
 Home > Explorations > Unmanned Space Programs
 

 

> History

> Space Craft

> Unmanned Space Programs

> Animals in Space

> Human in Space

> Human in Moon

> Manned Space Programs

> Space Station

> Voyager 1

> Voyager 2

> Hubble Space Telescope

> Recent & Future Developments

 

 

 

 

 

 

 

The long history of myths, dreams, fiction, science, and technology culminated in the dramatic launching of the first artificial orbiting Earth satellite, Sputnik 1, by the USSR on October 4, 1957. Sputnik Zemli, meaning “travelling companion of the world” is the full Russian name for an artificial satellite, a companion of the Earth as it travels around the Sun.

Voyager 2 Approaching Uranus

This artist’s conception shows the final approach of the unmanned spacecraft Voyager 2 towards the planet Uranus on January 24, 1986. Voyager 2 discovered four new rings and ten new moons around Uranus.

 

Early Artificial Satellites

Sputnik 1 was an aluminum sphere, 58 cm (23 in) in diameter, weighing 83 kg (184 lb). It orbited the Earth in 96.2 minutes. The elliptical orbit of the satellite carried it to an apogee of 946 km (588 mi) and a perigee of 227 km (141 mi). The sphere contained instruments which, for 21 days, radioed data concerning cosmic rays, meteoroids, and the density and temperature of the upper atmosphere. At the end of 57 days the satellite re-entered the atmosphere of the Earth and was destroyed by aerodynamic frictional heat.

The second artificial Earth satellite was also a Soviet space vehicle, called Sputnik 2. It was sent aloft on November 3, 1957, with a dog named Laika aboard, and it relayed the first biomedical measurements in space. Sputnik 2 re-entered the atmosphere of the Earth and was destroyed after 162 days aloft.

While Sputnik 2 was still in orbit, the United States successfully launched its first Earth satellite, Explorer 1, from Cape Canaveral (named Cape Kennedy 1963-1973), Florida, on January 31, 1958. The 14-kg (31-lb) cylindrical spacecraft, 15 cm (6 in) in diameter and 203 cm (80 in) long, transmitted measurements of cosmic rays and micrometeoroids for 112 days and gave the first satellite-derived data leading to the discovery of the Van Allen radiation belts around the Earth.

On March 17, 1958, the United States launched its second satellite, Vanguard 2; a precise study of variations of its orbit showed that the Earth is slightly pear-shaped. Using solar power, the satellite transmitted signals for more than six years. Vanguard 2 was followed by the American satellite Explorer 3, launched on March 26, 1958, and by the Soviet satellite Sputnik 3, launched on May 15. The 1,327-kg (2,925-lb) Soviet spacecraft measured solar radiation, cosmic rays, magnetic fields, and other space phenomena until the craft’s orbit decayed in April 1960.

[Top]

Un-manned Lunar Mission

As the closest neighbour of the Earth, the Moon has been the objective of many space missions. In 1958 the first attempts by the United States and the USSR at lunar probes failed. The Russian Luna 2, launched on September 12, 1959, hit the Moon 36 hours later. Since that date, many moon shots have been made by both countries, with mixed results. The first photographs of the far side of the Moon were taken by Luna 3, which was launched by the USSR on October 4, 1959. One of the most dramatically successful moon shots was the mission accomplished by Ranger 7, launched by the United States on July 28, 1964. Just before hitting the side of the Moon that faces the Earth, it transmitted 4,316 television pictures of the lunar surface from altitudes of about 1,800 km (1,120 mi) to about 300 m (1,000 ft), giving Earth-bound human beings their first close-up view of the Moon.

Luna Lander

The Soviet Union’s Luna programme was a series of missions to the moon between 1959 and 1970. It included orbiters and probes. The later type of probe, which was first used on Luna 9 in 1966, made a controlled descent to the Moon’s surface, then released a small capsule. The capsule had a weighted base, so it rolled upright. It then opened its flaps, exposing a television camera and communciations antennas.

On January 31, 1966, the USSR launched Luna 9, which made the first soft landing on the Moon—that is, it landed without being destroyed—and transmitted back to Earth the first photographs from the lunar surface. The United States followed on May 30 with Surveyor 1, which also made a soft landing. It sent back to Earth 11,150 photographs.

Aside from the scientific information that was gathered, much of the interest of the lunar missions centred on the American programme to land a man on the Moon. To this end, a number of further unmanned moon flights were undertaken, among which were two soft landings made by Surveyors 3 and 5 in 1967. Both craft, after taking about two days for their journeys, sent back to Earth a large number of television pictures of the lunar surface. Surveyor 3 also picked up samples of lunar soil and examined them by television camera, while Surveyor 5 chemically analysed the lunar surface, using an alpha-particle scattering technique—the first on-site analysis of an extraterrestrial body.

Another spacecraft that helped pave the way for the manned lunar landings was Lunar Orbiter. In 1966 and 1967, five Lunar Orbiters orbited the Moon, relaying thousands of photographs to Earth. From these photographs, the landing sites for the Apollo moon-landing programme were selected .

Two other unmanned, automated lunar projects by the USSR are noteworthy. The Luna 16 spacecraft, launched on September 12, 1970, landed on the Moon and placed about 113 g (4 oz) of lunar soil in a sealed container that was then launched from the Moon and recovered in the USSR. Luna 17, launched on November 10, 1970, soft-landed an automated lunar-roving vehicle, Lunokhod 1, equipped with a television camera and solar batteries. Over a period of 321 Earth days the vehicle, controlled from the Earth, travelled 10.5 km (6.5 mi) on the Moon, relaying television pictures and scientific data. Luna 21 in 1973 repeated this performance, placing Lunokhod 2 on the Moon.

Lunokhod Rover

In 1970 and 1973 the Soviet Luna programme delivered two rovers to the Moon. These eight-wheeled robotic explorers rolled down ramps to leave their parent spacecraft (Luna 17 and Luna 21 respectively). The Lunokhods carried cameras, soil analysers, and solar panels for power.

After a lull in lunar exploration following the manned lunar landings, the United States returned to the Moon in 1994 with Clementine, an unmanned spacecraft which mapped the surface in unprecedented detail, returning nearly 1 million images in 11 visible and near-infrared wavelengths between February 19 and May 3.

[Top]

Scientific Satellites

As space-launch vehicles (rocket boosters) and scientific measuring devices became more reliable, a wide variety of satellites were developed. Scientists were eager to obtain data and make accurate studies of the Sun, other stars, the Earth, and space itself. The enveloping atmosphere of the Earth prevents such data from being obtained from the Earth’s surface, except in a limited way through the use of high-altitude balloons.

In the United States, many astronomical satellites have been launched. Since 1962, for example, the Orbiting Solar Observatories (OSOs) have studied the Sun’s ultraviolet, X-ray, and gamma radiation. Pioneer satellites have studied cosmic radiation, the solar wind, and the electromagnetic characteristics of space. The Orbiting Astronomical Observatories (OAOs) have observed stellar radiation, and Orbiting Geophysical Observatories (OGOs) have studied the relationships between the Sun, the Earth, and their space environment. The Infrared Astronomy Satellite (IRAS), an Anglo-American project launched in 1983, has probed the hidden reaches of our galaxy. The Hubble Space Telescope (HST), launched by the space shuttle Discovery in 1990, has transmitted valuable images—some of never-before-observed phenomena—back to astronomers on Earth. The Compton Gamma-Ray Observatory (CGRO), launched by the Space Shuttle Atlantis in 1991, detected more than 400 gamma-ray sources and 2,500 gamma-ray bursts during its nine years of operation.

Two major new scientific satellites, NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton X-Ray Observatory, were launched in 1999. They have already provided large amounts of data on the X-ray sky, including images of active galactic nuclei and nebulae bathed in X-rays, as well as pinpointing many more X-ray sources at the outer reaches of the universe.

[Top]

Application Satellites

This class of unmanned spacecraft also performs useful functions for the earthbound scientist. The three general classifications of such satellites are communications, environmental, and navigation satellites.

Environmental satellites observe the Earth and its atmosphere, and transmit images for a variety of purposes. Weather satellites provide daily transmissions of temperatures and cloud patterns. One example is the geosynchronous meteorological satellite, such as Meteosat (stationed above longitude 0°) and GOES (Geostationary Operational Environment Satellite, stationed above longitudes 75°W and 135°W), which provide pictures of large areas of the Earth’s surface at regular intervals. Two such satellites can cover an entire continent and adjacent ocean areas.

The US Landsats observe the Earth with multispectral optical scanners and transmit the data to ground stations. Processed into colour images, these pictures reveal data of great range and great potential value. Information on soil characteristics, water and ice quantities, coastal-water pollution, salinity, and insect blights of crops and forests are obtained. Even forest fires can be detected from Earth orbit. Study of folds and fractures in the Earth’s crust helps geologists to identify deposits of oil and minerals. SPOT (Système Probatoire pour Observation de la Terre), a European satellite launched in 1985, transmits images that show the Earth in even greater detail than Landsats can.

Earth observation satellites are used by the United States and other countries to obtain images of military value, such as of nuclear explosions in the atmosphere and in space, ballistic-missile launch sites, and ship and troop movements. In the 1980s and again in the early 2000s, controversy was aroused by the American proposal to develop a satellite antiballistic missile defence system making use of laser technology.

GPS System

The Navstar Global Positioning System (GPS) is a network of 24 satellites in orbit around the earth that provides users with information about their position and movement. A GPS receiver computes position information by comparing the time it takes for signals from three or four different GPS satellites to reach the receiver

Navigation satellites provide a known observation point orbiting the Earth that, when observed by ships and submarines, can fix the vessel’s position within a few yards. The United States has developed a Global Positioning System (GPS) employing 24 satellites, which is capable of providing location information to ships and aircraft, drivers, and even walkers.

[Top]

Planetary Studies

Beyond the Moon, spacecraft have landed on Mars and Venus, have flown by every planet and have made comet studies.
For more information about these explorations go to Solar Bodies.

[Back] [Top] [Next]

 

 

[Home] [Exploration] [Galaxies] [Stars] [Solar Bodies] [Nebula] [Courtesy]