What are satellites so important?-part 1 (3 of 9)

There exists a recent surge in demand of continually available up-to-the-minute information; so satellite-based telecommunications businesses, including, radio, television and telephony, have a huge potential commercial profit, especially to places where traditional cable isn’t feasible, leading to an increase in satellite communications. For example, DirecTV, a major satellite television company that was started in 1994, has 14 satellites in geosynchronous orbit, each costing hundreds of millions of dollars to construct and But there also exists a much wider variety of use with these communication satellites, which are used for direct-to-home television channels and packages, broadcast feeds to and from television networks and local member stations, distance education by schools and universities, business television, videoconferencing, and to distribute national cable channels (such as ESPN, CNN, or HBO) to the cable TV receiver and satellite TV stations. Satellites are also used to distribute satellite radio, sending digital radio streams across the entire continental US, and satellite telephony, a necessity in extremely isolated areas, such as Mount Everest and the savannahs of Africa or other less exotic, but equally remote areas where cell phone towers do not reach or exist.
But satellites are also relied upon for GPS, a staple in modern American navigating, civil planning and scientific research. GPS, or Global Positioning System (the nickname of the U.S. NAVSTAR Global Navigation Satellite System (GNSS)), which is made of a network of 24 satellites in geosynchronous orbit, an orbit that allows a satellite to return to exactly the same place in the sky at exactly the same time each day, which allows continually transmitted time and position information that, used in a system of triangulation, allow one to find a receiver/transmitter’s precise location anywhere across the world. The recent and quite complete success and dependence upon the United States’ NAVSTAR GNSS also has inspired other countries to launch their own GNSS networks such as The European Union’s Galileo Positioning system, China’s COMPASS, Japan’s QZSS, India’s IRNSS and the restoration of Russia’s GLONASS. GNSS, along with aerial pictures from weather or other earth-observing satellites, is responsible for the recent jump in information about the world and the infamous Google Maps and similar programs, and allowing for a precise time reference (atomic time) used in earth sciences and telecommunication networks, enhanced 911, more efficient search and rescue, in addition to the more precise and more rapid creation of geospatial information systems, which are used in navigation programs that tell you how far you might be to a place such as a restaurant or museum, for instance, but are used in various occupations such as: environmental impact evaluations, urban planning, criminology, history, sales and marketing.

Artifical Satellites and Orbital debris( 2 of 9)

Artificial satellites are used in almost every business or even for personal use. From satellite communications, earth science, astronomy, urban planning, to tracking packages and monitoring weather patterns and natural disasters, satellites are becoming increasingly essential to the modern way of business and life. For example, enhanced 911, in which the emergency station finds the location of the caller, depends upon GPS satellites for most mobile phones. And weather tracking and imaging, vital to air and water traffic and a great help to everyone else, is greatly dependent upon the images that weather satellites provide. So, far from abandoning space after the final moon landing in 1972, space use has only been expanded. In 2007 alone, there were 68 orbital launches and 22 spacewalks worldwide, 19 of those to maintenance artificial satellites. The US and the world have come to depend upon these orbiting satellites, necessitating the tracking and use of thousands of them.
Space debris is considered a problem because of the collisions between spacecraft, especially satellites, and debris. Figure 1 shows the distribution of observable debris (>3.9 inches) in Earth’s orbit, while Figure 2 shows the distribution of satellites in Earth’s orbit. This comparison shows the correlation between the most commonly used orbits and the amount of debris they possess. While spacecraft are made out of extremely durable material, the main problem lies in the large velocities that objects have in orbiting the earth. In space, a .4 inch aluminum sphere in an average orbital velocity of about 16.1 miles/sec has the equivalent velocity of a bowling ball moving at 300 miles/hour. (NASA, n.d.) So while a great deal of the mass of the satellite may be due to the shielding, it usually is not enough to protect against larger debris. And that debris has an especially dehabilitating effect on artificial satellites with their more delicate elements such as memory chips, solar cells and observational lenses that are easily corrupted. So a collision between debris and a satellite is always disastrous to both the information payload on the satellite and the usefulness of the satellite afterwards.


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Figure 1 is from the NASA Orbital Debris Program Office Education Package (2005)
Figure 2 is from NASA’s J-Track 3-D (November 16, 2008.) (please click to enlarge)