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 Page 2 ------ 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.

Category: Science