Life of a TV satellite starts with its launch to its
orbit around the Earth. Not
just any orbit - it has to be a stationary geosynchronous
orbit. This means that it has to take to a TV satellite exactly as
long to make a single revolution, as it does to the Earth herself.
Also, that it orbits right above the equator. Otherwise, its orbit
would have to be inclined to the equatorial plane (a stable orbit is
only possible with the Earth center coinciding with the orbital
center). This would result in a daily back-and-forth change of the height
of a TV satellite above the horizon
along the north-south line. Likewise, if the period of its revolution
would differ from the Earth's, its position as seen from a given
ground point would vary azimuthally. In other words, any other than
stationary geosynchronous orbit would require receiving dish
with tracking capability in order to ensure continuous signal
The height of Earth's geosynchronous orbit
- determined by a point where the gravitational force equals force of repulsion of a small
body rotating at the geosynchronous speed - is over 22,000 miles. That
is how high above the ground are TV satellites. After the satellite has
been brought to the "low Earth orbit" (124 to 1240 miles above ground), it
is moved up to its final orbit by firing an engine, and "parked" there by
firing another one, at a precise moment and angle. Ready for its first
day at work...
Large ground based antenna focuses
uplink signal carrying programming from various sources
onto the satellite. The signal is received and emitted back by satellite
transponders - a series of one to four dozen of receivers/emitters
operating at different frequencies. Each transponder can transmit a
number of frequencies, adding up to a large potential volume of channel
capacity per satellite.
signal is sent from the satellite back to Earth in a diverging beam,
covering large ground areas. Typical area of coverage - so called
footprint - is 40 to 60 degrees mid-latitude. However, the signal
strength, and so the reception quality, weakens toward the outer footprint area, often making
necessary to use larger dish sizes for efficient signal reception.
affecting signal strength is height of the satellite in the sky. The
lower it is, the more of the atmosphere to go through, and the more of
Earth's thermal noise finds its way into receiving dish antenna. The
height of a TV satellite above horizon
depends on both, satellite orbital position and local ground
coordinates. Ideally, satellite's orbital location should be close
to the local longitude. That would be around 80West for the East
Coast, around 100W for the Central US, and around 120W for the West
Coast. That would place the satellite in the proximity of the
southern meridian, at the highest possible highest altitude.
In reality, it is impossible to accomplish
such an ideal satellite distribution. While relatively small deviations
from the southern line are not significant, satellites positioned far
out toward east, or west, will likely face more of a challenge to
deliver steady signal to the opposite side of the continent, due to
their low height
above the horizon (they are positioned slightly bellow the local celestial
Orbital positions of TV
satellites are regulated according to international agreements in
general and, specifically, by the FCC (Federal Communication
Commission). All DBS satellites serving US territories are located
between 61.5 and 148 degrees western longitude. The satellite is
often identified by its orbital position. For instance, TV satellite
located at 110 degrees western longitude is referred to as 110W, or
simply 110. At present, the two US DBS giants -
Dish Network - use fleets of
13 TV satellites,
respectively, with more planned
to be launched before the end of 2006, and in the following year.
Active life of a TV
satellite lasts as long as its fuel, usually 10 to 15 years. After
that, it usually uses last of its fuel to move out of the active
those happy days with no cable
television, no satellite TV? Only a single analog TV
service available, and everything about getting and using it was
as simple as: get it, click, go...
or satellite TV? Which
one is better: satellite TV or cable? In most any comparison, the answer seems to
depend on whom you ask...
Cable TV Cable TV is how the
television entered American homes. In its early stages, cable TV
service was quite different from the modern cable TV we know
Direct Broadcast Satellite Direct
(DBS) TV service is a high-powered broadcast service to homes using
satellites as the primary form of signal transmission. Its high transmission power makes possible use of relatively
small dish antennas for efficient signal reception and utilization.
Commercial satellite TV, as we know it, is a DBS service...
Network is the second largest direct broadcast satellite (DBS) service
provider in the US. Together with
DirecTV, it shares the US home satellite TV market. Dish Network started
commercial DBS broadcasting in 1996, after its first TV
satellite - EchoStar I - has been launched in 1995...
DirecTV is a direct broadcast
satellite (DBS) service provider, based in Las Vegas, Nevada. Launched
in 1994 by Hughes Electronics Corporation, it was the very first
high-powered (mini-dish) DBS service in the world...
High-speed INTERNET Whether you spend many hours browsing the
Internet on daily basis, or use it less frequently,
high-speed Internet connection appears to be irresistibly
convenient. While it comes at added cost, most people find its
benefits worth added expense, which can be quite low...
Are you too mystified and intrigued by this new kid
on the TV block: high-definition television. Expectations
run high, but so is the uncertainty - what is really different
about it, when compared with standard-definition television (SDTV)?...
Satellite Radio If you like listening to radio programming,
satellite radio has some goodies to offer. Great variety of
channels, most of them commercial-free, high quality sound when
it is needed, possibility to listen to your favored programming
wherever you are...
latest in the satellite/cable industry...