Early Artificial Satellites
Sputnik 1 was a sphere made of aluminum, 23 in. (58cm ) in diameter, weighing 184 lb.(83 kg ). It 96.2 minutes, Sputnik orbited the Earth. The elliptical orbit of Sputnik carried it to a perigee of 141 mi (227 km) and an apogee of 588 mi (946 km). The sphere carried instruments which radioed data regarding meteoroids, cosmic rays, and the temperature and density of the upper atmosphere for 21 days. The satellite reentered the Earth’s atmosphere at the closure of 57 days and demolished itself by aerodynamic frictional heat.
Sputnik 2, another Soviet space vehicle, was the second artificial satellite to orbit the Earth. On November 3, 1957, Sputnik 2 was launched with a dog named Laika aboard. Sputink 2 relayed the first biomedical measurements from space. It reentered the Earth’s atmosphere and after 162 days destroyed itself.
During Sputnik 2’s orbit, on January 31,1958, the United States successfully launched Explorer 1, its first Earth satellite from Cape Canaveral ( later named Cape Kennedy 1963-1973), Florida. The 31-lb (14-kg) cylindrical spacecraft, 6 in (15 cm) in diameter and 80 in (203 cm) long, relayed measurements of micrometeorites and cosmic rays for 112 days and gave data about the Van Allen radiation belts.
On March 17, 1958, the second satellite launched by the United States was called Vanguard 2; an accurate study of variations in its orbit displayed that the Earth is somewhat pear- shaped. The satellite transmitted signals using solar power for more than six years. The next American satellite launched after Vanguard 2 was Explorer 3, launched on March 26, 1958, and also by another Soviet satellite named Sputnik 3, launched on May 15. The 2925-lb (1327-kg) Soviet spacecraft recorded magnetic fields, cosmic rays, solar radiation, and other space phenomena up until the craft's orbit ended in April 1960.
Unmanned Lunar Missions
The moon , the Earth’s closest neighbor, has been the target of numerous space missions. In 1958, the first tries at lunar probes by the USSR and the United States failed. On September 12, 1959, the Russian Luna 2 smacked the moon 36 hours later. After that date, numerous moon shots have been attempted by both countries, with various results. Luna 3 took the first pictures of the dark side of the moon , which the USSR launched on October 4, 1959. One of the most successful moon photographs taken was accomplished by Ranger 7, put into space on July 28, 1964, by the United States. Just before smacking the surface of the moon that points to the Earth, it relayed 4316 television photographs of the lunar exterior from altitudes of about 1120 mi (1800 km ) to about 1000 ft (300 m ), granting humans their first up-close view of the moon. The USSR launched Luna 9 on January 31, 1966, which made the first smooth landing on the moon--that is, it wasn’t destroyed on impact to the lunar surface. The United States launced Surveyor 1 on May 30, 1966, which also landed without crashing on the lunar surface. It relayed back to Earth 11,150 up close pictures of the moon.
Apart from the scientific knowledge that was accumulated, much of the curiosity of the lunar missions was based around the American program to place a man on the moon. To this end, numerous unmanned moon flights were done, among which were two more safe landings made in 1967 by Surveyor 3 and 5. Both crafts, after about two days for their travels, relayed an immense number of television photographs of the Moon’s surface back to Earth. Surveyor 3 selected samples of lunar soil and investigated them by television camera. Surveyor 5 chemically analyzed the Moon’s surface, utilizing an alpha-particle scattering technique; this was the very first on-site analysis of a planet or satellite. Another spacecraft supporting lunar surface landings was the Lunar Orbiter. Five Lunar Orbiters circled the moon in 1966 and 1967, transmiting thousands of pictures to Earth. From these pictures, landing sites were picked for the Apollo moon-landing program.
Two different automated, unmanned lunar missions by the USSR are remarkable. On September 12, 1970, the USSR launched the Luna 16 spacecraft which landed on the lunar surface and placed about 4 oz (113 gr) of soil in a secured container that was then transported from the lunar surface and recovered in the USSR. On November 10, 1970, the Luna 17 was launched . Lunokhod 1, an automated lunar-roving vehicle, was included with Luna 17. Lunokhod 1 was equipped with solar batteries and a video camera. During ten days on the Moon’s surface the vehicle, operated from the Earth, traveled 6.5 mi (10.5 km) on the lunar surface, relaying scientific data and television photographs . In 1973, Luna 21 repeated this accomplishment, positioning Lunokhod 2 on the lunar surface.