Satellites orbit the earth doing our bidding in ways that enrich
the lives of almost all of us. Through electronic eyes from
hundreds of miles overhead, they lead prospectors to mineral
deposits invisble on earth's surface. Relaying communications at
the speed of light, they shrink the planet until its most distant
people are only a split second apart. They beam world weather to
our living room TV and guide ships through storms. Swooping low
over areas of possible hostility, spies in the sky maintain a
surveillance that helps keep peace in a volatile world.
How many objects, exaclty, are orbiting out there? Today's count
is 4,914. The satellites begin with a launch, which in the U.S.
takes place at Cape Canaveral in Florida, NASA's Wallops Flight
Center in Virginia, or, for polar orbiters, Vandenberg Air Force
Base in California. One satellite in 20 is crippled by the jolt
of lift-off, or dies in the inferno of a defective rocket blast,
or is thrust into improper orbit. A few simply vanish into the
immensity of space. When a satellite emerges from the rocket's
protective shroud, radiotelemety regularly reports on its health
to round-the-clock crews of ground controllers. They watch over
the temperatures and voltages of the craft's electronic nervous
system and other vital "organs", always critical with machines
whose sunward side may be 300 degress hotter than the shaded
part.
Once a satellite achieves orbit--that delicate condition in which
the pull of earth's gravity is matched by the outward fling of
the crafts speed--subtle pressures make it go astray. Solar
flares make the satellite go out of orbit. Wisps of outer
atmosphere drag its speed. Like strands of spiderweb, gravity
feilds of the earth, moon, and sun tug at the orbiting
spacefarer. Even the sunshine's soft caress exerts a gentle
nudge. Should a satellite begin to wander, ground crews fire
small fuel jets that steer it back on course. This is done
sparingly, for exhaustion of these gases ends a craft's useful
career. Under such stresses, many satellites last 2 years. When
death is only a second away, controllers may command the craft to
jump into a high orbit, so it will move up away from earth,
keeping orbital paths from becoming too cluttered. Others become
ensnarled in the gravity web; slowly they are drawn into
gravitational that serve as space graveyards.
A satellite for communications would really be a great antenna
tower, hundreds or even thousands of miles above the earth,
capable of transmitting messages almost instantaneously across
the oceans and continents. Soon after the launch of ATWS-6, "the
Teacher in the sky", (a satellite designed to aid people) NASA
ground controllers trained its antenna on Appalachia. There is
brought evening college classes to schoolteachers whose isolation
denied opportunity for advancement.
The use of Satellites is growing rapidly and so is the
different jobs for them.
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