Satellites. Amy Cha Laura Collins Brad Robertson. Satellites Overview. History How Satellites Work Satellite Frequency Bands and Antennas Orbit Distance, Pros & Cons, Applications Types: Low-Earth-Orbit (LEOs) Medium-Earth-Orbit (MEOs) Global Positioning System (GPS)
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Global Positioning System (GPS)
The theory of satellites was simple enough - shoot something out into space at the right speed and on the correct trajectory and it will stay up there, orbiting Earth, for years - if not forever. If the orbit is the right distance in space the satellite will keep pace with the rotation of the Earth.
Early in October 1957 communications stations started picking up a regular beeping noise coming from space.
The signals were coming from Russia's Sputnik 1, the world's first man-made satellite.
It was January 1958, before a Jupiter rocket successfully launched Explorer 1, the first American satellite.
In July 1963 the Hughes Aircraft Corporation launched the experimental Syncom 2 for NASA, the world's first geosynchronous communications satellite. Its earlier sister, Syncom 1, had been blown up on launch earlier that year, but the second version was a huge success.
It carried the first live two-way satellite call between heads of state when President John F. Kennedy in Washington, D.C., telephoned Nigerian Prime Minister Abubaker Balewa in Africa.
The third Syncom satellite transmitted live television coverage of the 1964 Olympic Games from Tokyo.
The world's first commercial communications satellite was Early Bird, built for the Communications Satellite Corporation (COMSAT) by Hughes.
The satellite was launched on April 6, 1965, and placed in commercial service after moving into geosynchronous orbit 22,300 miles above the equator. That meant it was always on station to provide line of sight communications between Europe and North America.
Early Bird didn't have a battery - and worked only when its solar panels were exposed to the sun.
The launch of the Intelsat 3 satellites in 1969 created a global TV and speech communications network that spanned the Atlantic, Pacific and Indian Oceans.
The introduction of multiple-beam antennas in the 1980s brought new improvements in efficiency, as a satellite's power could now be concentrated on small regions of the Earth, making possible smaller-aperture (coverage area), lower-cost ground stations.
The Capacity (the number of simultaneous television and speech channels carried) grew as well.
Satellite Receive and retransmit signals back. (Downlink)
Other Earth Stations receive message in useful strength area. (Footprint)How Satellites Work
Can offer global services, which can be subject to regulatory requirements.
Used for technology devices such as high-speed, high-bandwidth data communications, and video conferencing. They carry voice and high-speed data services. The main uses are data communications and real-time voice delivery to hand-held devices.Big LEOs Applications
Mainly handles broadband data. These systems are optimized for packet-switched data rather than voice. They share the same advantages and drawbacks of other LEOs and are intended to operate with inter-satellite links to minimize transmission times and avoid dropped signals.Mega (Super) LEOs Applications
Of these, over 2000 are satellites (working and not).Space Debris
A constellation of 24 satellites
Manufacturer: Rockwell International
Altitude: 10,900 nautical miles
Weight: 1900 lbs (in orbit)
Size: 17 ft with solar panels extended
Orbital Period: 12 hours
Orbital Plane: 55 degrees to equatorial plane
Planned Lifespan: 7.5 years
Current constellation: 24 Block II production satellites
The spacing of the satellites are arranged so that a minimum of five satellites are in view from every point on the globe.
Satellites are reference points for locations on Earth
EX. THE BIG PICTURE
If a particular satellite is 11,000 miles above it. Then we know that it’s radius is 11,000 miles!
EX. THE BIG PICTURE
Basic calculations measuring distance
Velocity * Time = Distance
Velocity = speed of light (186,000 miles per second. )
Time = a lot of analysis and calculations!
The atomic clocks they use are very, very precise but they're not perfect. Minute discrepancies can occur, and these translate into travel time measurement errors.
The signal may not actually get to the ground station receivers first. It may bounce off various objects before it gets to the receivers.GPS: Problems in the System
Satellites are precise but are not perfect.
GPS has a variety of applications
It takes longer for the signal to get to earth and back to satellite.
Increased difficulty of telephone conversations.
GEOs are not positioned in the farthest northern and southern orbits.Pros and Cons of GEOs
Global Positioning System (GPS)
The Living Earth – Earth View
Advanced Communications Technology Satellite (ACTS)
Stevens – Low Earth Orbiting LEO
CompassRose International Publications – Introduction to Global Satellite Systems
searchNetworking.com Definitions - Satellite
HST Project Science Office
More Space Debris
What is Medium Earth Orbit?
Global Positioning Overview
What is GPS?
Geostationary Operational Environmental Satellites
GMS - Geostationary Meteorological Satellites
GOES - Information on the GOES Data Collection System
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