On October 4th 1957, Russia launched the first manmade satellite into space. It was known as Sputnik-1. The satellite was a sphere 56cm (22in) in diameter and weighed 83.6kg (1851b).
The spacecraft obtained data pertaining to the density of the upper layers of the atmosphere and the propagation of radio signals in the ionosphere. The instruments and electric power sources were housed in a sealed capsule and included transmitters operated at 20.005 and 40.002 MHz (about 15 and 7.5 m in wavelength), the emissions taking place in alternating groups of 0.3 s in duration. The downlink telemetry included data on temperatures inside and on the surface of the sphere.
Since the sphere was filled with nitrogen under pressure, Sputnik 1 provided the first opportunity for meteoroid detection (no such events were reported), since losses in internal pressure due to meteoroid penetration of the outer surface would have been evident in the temperature data. The satellite transmitters operated for three weeks, until the on-board chemical batteries failed, and were monitored with intense interest around the world. The orbit of the then inactive satellite was later observed optically to decay 92 days after launch (January 4, 1958) after having completed about 1400 orbits of the Earth over a cumulative distance traveled of 70 million kilometers. The orbital apogee declined from 947 km after launch to 600 km by Dec. 9th.
The Sputnik 1 rocket booster also reached Earth orbit and was visible from the ground at night as a first magnitude object, while the small but highly polished sphere, barely visible at sixth magnitude, was more difficult to follow optically. Several replicas of the Sputnik 1 satellite can be seen at museums in Russia and another is on display in the Smithsonian National Air and Space Museum in Washington, D.C.
Credit : NASA
Picture Credit : Google
