|
|
|
Reaching for the stars
People dreamt of spaceflight for millennia before it became a reality. When space travel was only a fantasy, researchers in the areas of astronomy, chemistry, mathematics, meteorology and physics developed an understanding of the solar system. Scientists and researchers deserve accolades as their relentless efforts turned dreams into reality and ignited interest in space satellite communications.
The origin of satellite communications can be traced back to a short article written in 1945 by Arthur C. Clarke in the British radio magazine called Wireless world. He outlined the possibility of satellites in stationary orbit. At that time, there was neither a satellite in orbit nor were rockets powerful enough to launch one. But his ideas about what we now know as geostationary satellite systems were not science fiction.
Clarke’s vision became a reality with the launch of the world’s first artificial satellite. His ideas were reinforced also the United States began communications experiments, bouncing radio signals off the moon in 1954.
However, a platform for a space race was created when the Soviet Union successfully launched Sputnik I on Oct 4, 1957, becoming the first space power. The world’s first satellite was just about the size of a basketball, weighed only 83kg and took about 1 hour and 38 minutes to orbit the Earth on its elliptical path.
A space race between the Americans and Soviets soon began. Sputnik I orbited the globe for just about three months but demonstrated that satellites could be placed in orbit by powerful rockets.
It was on Nov 3, 1957, when Soviets came up with the launch of another satellite — Sputnik II —with relatively higher performance capabilities. Interestingly enough, it carried a dog named “Laika” who has the honour of being the first known living creature to escape to outer space.
In the meantime, the US had scaled up its efforts under its own satellite program immediately after Sputnik I had been launched. The scenario changed completely after Jan 31, 1958, when the first American satellite — Explorer I — reached space. Thus United States became the second country to go to the “final frontier”.
Explorer I carried small scientific equipment, including cosmic ray detector, which is responsible for discovering magnetic radiation around the planet. Since the experiment was provided by Dr James Van Allen, these magnetic radiation paths were later named as the Van Allen Belts.
Explorer 2 made its launch attempt on March 5, 1958, but the fourth stage of the launch vehicle failed to perform its designated task. Subsequent launches of Explorer 3 and 4 met with success. However, Explorer 5 was unable to maintain its firing angle.
The world’s first communications satellite, SCORE (an acronym for Signal Communication by Orbiting Relay Equipment) soared skywards on Dec 18, 1958. It was basically an experiment to examine the viability of message transmission among the ground stations.
It received messages at 150MHz, taped them and then retransmitted them back to Earth. The outcome of the project was certainly a major breakthrough which proved that messages of all sort can efficiently be transmitted from one point to any other on Earth. President Eisenhower took the opportunity to convey his message of global peace to the public through this marvelous satellite.
The space race accelerated with American and Russian launches continuing until one become almost routine. ECHO I, a passive satellite that reflected radio waves back to the ground, was subsequently put into orbit in 1960.
This gigantic shiny balloon experimented with communications between Bell Laboratories and NASA. Later on ECHO II, with better smoothness and improved parameters, was launched in 1964 and became the first instance where the cooperation between the United States and the USSR in a space mission took place.
After serving for about eight years, ECHO I entered back into the Earth’s atmosphere and was destroyed. The Echo series involved experimental satellites and their purpose was to test the feasibility of using satellites to relay telephone, data and other communication signals.
The advent of true communications satellites opened with the launch of Telstar 1 and 2 that took place in 1962 and 1963 respectively. These were active satellites designed to transmit telephone and high-speed data communications.
Though NASA provided launch vehicles and tracking facilities but these history-making satellites were manufactured by AT&T and managed by Bell Laboratories. Telstar satellites demonstrated the value of communications satellite and it lit up new development in this interesting field.
The development led to a number of successful experiments on satellite communications because of which the Communications Satellite Act was passed by the US Congress in August of 1962. This set the stage for commercial investment in the International Telecommunications Satellite Organization and on July 19, 1964, representatives of 12 countries signed an initial agreement for the investment which gave rise to a series of Intelsat satellites — Intelsat 1 through 5.
Synchronous communication satellite (SYNCOM), a new series of satellites that were put into the race by NASA in 1961, were to serve as active geosynchronous communication satellites. Syncom 1, launched on Feb 14, 1963, was to be the first geosynchronous communications satellite but was lost on the way to geosynchronous orbit due to an electronics failure.
So Syncom 2 was eventually the first geosynchronous communication satellite and was sent out to the space on July 26, 1963. But the honour of being the first geostationary communication satellite was enjoyed by Syncom 3. It was launched on Aug 19, 1964, and was used to telecast the 1964 Summer Olympics in Tokyo to the United States. The Syncom series satellites were later joined by a few more in the 1980s.
Remarkable advancements in technology augmented the efficiency and reliability of satellite communications. With the passage of time, huge artificial satellites from various countries were deployed to serve the world. Anik, Westar, Early Bird (Intelsat 1), Comstar, Relay, AST, Oscar, Eutelsat, Thor, Esro, Vanguard Secor, Azur, Amsat, Orbcom, Astra, Wresat, San Marko 1, ATS and Marisat are just a few of the famous satellites in orbit.
Back in the 1970s, the world was revolutionized by another useful application of satellites. It was called the NAVSTAR navigation system which later became the Global Positioning System (GPS). The first satellite of this type went into orbit in 1978 and the network reached its current full constellation in 1994 with 24 satellites.
The system tells one’s exact location on Earth. It can provide additional information such as travelling speed, time, height referenced with the sea level, etc. The GPS embraces a broad range of daily applications involving automobiles, maritime travel, hiking, aeronautics and much more. A new GPS system, known as GPS III, is expected to start being deployed in 2009 which promises even greater accuracy and a wide range of services.
The most exciting and challenging space programme “Mission to Mars” led to the formation of the Viking project in 1975-1976. The idea included sending two identical spacecraft; Viking 1 and Viking 2, each having a lander and an orbiter. The orbiter’s initial job was to survey the planet for a suitable landing site.
Once on the surface of Mars, the lander explored the soil, wind, and atmosphere, took the images and transmitted them back to the Earth station. The orbiter acted as a radio relay station for transmitting lander data.
Besides collecting other scientific data and taking photographs on the surface, the two landers conducted three biology experiments designed to look for possible signs of life.
Pakistan’s participation in the space race began with the successful launch of Badar-1 in 1990, which used a Chinese launch vehicle. Badar-1 provided valuable data for five weeks after which all contacts with it were lost.
However, primary objectives were achieved, which included technical experience in telemetry, control and digital communications in preparation for further launches. Badar-2, Pakistan’s successful satellite set to move in the sun-synchronous orbit, was sent into space in December of 2001.
The rising trend in telecom activities promises to excite Pakistan’s education sector which is quite obvious from the formal launching of a leased satellite, PAKSAT 1, in January of 2003. The satellite was aimed at transmitting to educational channels in particular.
In the outer space, PAKSAT 1 is placed at 38 degrees East with respect to the Earth and this relocation was carried out by the country’s own space scientists. Plans for a new satellite, PAKSAT 2, have been formulated. This will replace PAKSAT 1 by the end of the lease period.
Today, thousands of artificial satellites are circling our planet, even those that have completed their useful life. Most of them have been responsible for providing great services such as live broadcasts, weather monitoring, Global Positioning System, remote sensing, space exploration and much more. In short, satellite communication has been a major breakthrough which promises a new era of space exploration and improved telecommunications services around the globe.
The writer aliccp@yahoo.com is a freelance contributor
|
|
|
|
