09-04-2010, 03:26 PM
SATELLITES.pptx (Size: 1.18 MB / Downloads: 101)
SATELLITES
ROSHAN CHHETRI
KiiT
CONTENTS
INTRODUCTION
FIRST SATELLITE
TYPES OF SATELLITES
LAUNCHING
OPERATION IN SPACE
SATELLITE ORBITS
INDIAN SATELLITES
LATEST INDIAN SATELLITE
MOTIVATION
Satellites are used almost everyday by everyone. Satellites are used for many things such as communication, oceanography, astronomy, surveillance, and a variety of other things as well. Without satellites we would be lost. We wouldn't know what the weather is going to be tomorrow. We wouldn't know what the world looked like. Without satellites we wouldn't even know how to travel. Satellites really help us out in every day life and we depend on them. Every one of us need to have a general information about satellites, its types ,orbits and uses..
WHAT IS A SATELLITE?
A satellite is any object that orbits another object. The Earth's Moon is a satellite and the Earth itself is a satellite of the Sun.
Artificial satellites are machines that are placed into orbit around Earth, other planets, or the Sun
ANATOMY OF SATELLITE
FIRST SATELLITE
History changed on October 4, 1957, when the Soviet Union successfully launched Sputnik I. The world's first artificial satellite was about the size of a beach ball (58 cm.or 22.8 inches in diameter), weighed only 83.6 kg. or 183.9 pounds, and took about 98 minutes to orbit the Earth on its elliptical path. After three months , it was destroyed while reentering the atmosphere.That launch ushered in new political, military, technological, and scientific developments. While the Sputnik launch was a single event, it marked the start of the space age and the U.S.-U.S.S.R space race.
Sputnik helped to identify the upper atmospheric layer's density, through measuring the satellite's orbital changes. It also provided data on radio-signal distribution in the ionosphere. Pressurized nitrogen, in the satellite's body, provided the first opportunity for meteoroid detection. If a meteoroid penetrated the satellite's outer hull, it would be detected by the temperature data sent back to Earth.
TYPES OF SATELLITES
COMMUNICATION
NAVIGATION
WEATHER
MILITARY
SCIENTIFIC
COMMUNICATION SATELLITES
The National Aeronautics and Space Administration (NASA) launched the first telephone and television satellite, AT&Tâ„¢s Telstar 1, in 1962. The U.S. Department of Defense launched Syncom 3 in 1964. Syncom 3 was the first communication satellite to use a geostationary orbitâ€that is, an orbit that keeps the satellite over the same spot above Earthâ„¢s equator. Communication satellites work non-stop 24 hours a day to keep the entire world linked together. These communication satellites are used for things like an overseas phone call or beaming 150 channels into your living room.
NAVIGATION SATELLITE
Navigation satellites can help locate the position of ships, aircraft, and even automobiles that are equipped with special radio receivers. A navigation satellite sends continuous radio signals to Earth. These signals contain data that a special radio receiver on Earth translates into information about the satellite™s position. The receiver further analyzes the signal to find out how fast and in what direction the satellite is moving and how long the signal took to reach the receiver. From this data, the receiver can calculate its own location. Some navigation satellite systems use signals from several satellites at once to provide even more exact location information. The U.S. Navy launched the first navigation satellite, Transit 1B, in 1960.
NAVIGATION(cont¦)
The U.S. Air Force operates a system, called the NAVSTAR Global Positioning System (GPS), that consists of 24 satellites that can provide position information with an accuracy from 100 m (about 300 ft) to less than 1 cm (less than about 0.4 in)
The Global Orbiting Navigation Satellite System (GLONASS) of the Russian Federation consists of 24 satellites and provides accuracy similar to GPS.
In December 2005 the European Union (EU) launched the first of 30 satellites that will make up a civilian satellite navigation system called Galileo. The system will have an accuracy of about 1 m (3.3 ft) and will become operational in 2009.
WEATHER SATELLITE
Weather satellites carry cameras and other instruments pointed toward Earth™s atmosphere. They can provide advance warning of severe weather and are a great aid to weather forecasting. NASA launched the first weather satellite, Television Infrared Observation Satellite (TIROS) 1, in 1960. TIROS 1 transmitted almost 23,000 photographs of Earth and its atmosphere. NASA operates the Geostationary Operational Environmental Satellite (GOES) series, which are in geostationary orbit. GOES provides information for weather forecasting, including the tracking of storms.
POLAR ORBITING WEATHER SATELLITE
MILITARY SATELLITE
Many military satellites are similar to commercial ones, but they send encrypted data that only a special receiver can encode. Military surveillance satellites take pictures just as other earth-imaging satellites do, but cameras on military satellites usually have a higher resolution.
The U.S. military operates a variety of satellite systems. The Defense Satellite Communications System (DSCS) consists of five spacecraft in geostationary orbit that transmit voice, data, and television signals between military sites. The Defense Support Program (DSP) uses satellites that are intended to give early warning of missile launches. DSP was used during the Persian Gulf War (1991) to warn of Iraqi missile launches.
MILITARY SATELLITE
SCIENTIFIC SATELLITE
Earth-orbiting satellites can provide data to map Earth, determine the size and shape of Earth, and study the dynamics of the oceans and the atmosphere. Scientists also use satellites to observe the Sun, the Moon, other planets and their moons, comets, stars, and galaxies. The Hubble Space Telescope is a general-purpose observatory launched in 1990. Some scientific satellites orbit bodies other than Earth. The Mars Global Surveyor, for example, orbits the planet Mars.
SCIENTIFIC SATELLITE
HOW IS SATELLITE LAUNCHED?
Placing a satellite into orbit requires a tremendous amount of energy, which must come from the launch vehicle, or device that launches the satellite. The satellite needs to reach an altitude of at least 200 km (120 mi) and a speed of over 29,000 km/h (18,000 mph) to lift into orbit successfully. Satellites receive this combination of potential energy (altitude) and kinetic energy (speed) from multistage rockets burning chemical fuels.
STAGES OF LAUNCHING
. The first stage lifts the entire launch vehicleâ€with its load of fuel, the rocket body, and the satelliteâ€off the launch pad and into the first part of the flight. After its engines use all their fuel, the first stage portion of the rocket separates from the rest of the launch vehicle and falls to Earth
The second stage then ignites, providing the energy necessary to lift the satellite into orbit.
CONT(LAUNCHING¦)
The rest of the launch depends on the satellite™s mission. For example, if the mission requires a geostationary orbit, which can be achieved only at a distance of about 35,000 km (22,000 mi) above Earth, a third rocket stage provides the thrust to lift the satellite to its final orbital altitude. After the satellite has reached the final altitude, another rocket engine fires and gives the satellite a circular orbit. All rocket-engine burns occur at a precise moment and last for a precise amount of time so that the satellite achieves its proper position in space.
OPERATIONS IN SPACE
POWER-A The most common source of power for Earth-orbiting satellites is a combination of solar cells (Solar Energy) with a battery backup.
ORIENTATION-Methods of maintaining orientation include small rocket engines, known as altitude thrusters; large spinning wheels that turn the satellite; and magnets that interact with Earthâ„¢s magnetic field to correctly orient the satellite.
HEAT DISSIPATION- The electronic equipment on the satellite also creates heat that can cause damage. With no air flowing over the satellite to transfer heat by convection and no body to which the satellite can conduct heat, the satellite must radiate heat to control temperature. Often satellites use radiators including panels that open and close to adjust the amount of radiating surface area.
COSMIC RADIATION AND MICROMETEOROIDS PROTECTION-Satellites have to endure the effects of radiation and of continuous, damaging micrometeoroid hits, especially during long-term missions. A satellite,needs shielding for its computers
SATELLITE ORBITS
Geostationary Equatorial Orbit-Satellites in geostationary equatorial orbit (GEO) orbit Earth around the equator at a very specific altitude that allows them to complete one orbit in the same amount of time that it takes Earth to rotate once. As a result, these satellites stay above one point on Earth™s equator at all times. The altitude of GEO is about 5.6 times the radius of Earth, or about 35,800 km (about 22,200 mi).Direct-broadcast television satellites ,Earth-surveillance missions, including military surveillance and weather tracking missions, also use GEO.
Low Earth Orbit-A satellite in low Earth orbit (LEO) orbits at an altitude of 2,000 km (1,200 mi) or less. A low Earth orbit minimizes the amount of fuel needed. In addition, a satellite in LEO can obtain clearer surveillance images and can avoid the Van Allen radiation belts, containing harmful high-energy particles. It needs less powerful signals to communicate with Earth than satellites with higher orbits. A signal to or from a low Earth orbit also reaches its destination more quickly.
ORBITS(cont¦)
Medium Earth Orbit-Medium Earth orbit (MEO) satellites orbit at an altitude about 10,000 km (about 6,000 mi) and balance the benefits and problems between LEO and GEO. The most common uses of MEO are by navigation and communication satellites. The U.S. navigation system NAVSTAR Global Positioning System (GPS), the Russian Global Navigation Satellite System (GLONASS), and Odyssey, a private U.S. communications satellite program all use MEOs.
Polar Orbits-Satellites in polar orbits orbit around Earth at right angles to the equator over both the North and South poles. Polar orbits can occur at any altitude, but most satellites in polar orbits use LEOs. Two polar satellites belonging to the U.S. National Oceanic and Atmospheric Administration provide weather information for all areas of the world every six hours.
ORBITS (cont¦)
Sun-Synchronous Orbits -A satellite in a Sun-synchronous orbit always passes over a certain point of Earth when the Sun is at the same position in Earth™s sky. A Sun-synchronous satellite moves clockwise around Earth, orbits in a low Earth orbit, and orbits at a specific angle with respect to Earth™s equator (about 98°). The satellite stays synchronized with the location of the Sun relative to Earth. Sun-synchronous orbits are useful for satellites photographing Earth, because the Sun will be at the same angle each time the satellite passes over a point on Earth.
INDIAN SATELLITES
LATEST INDIAN SATELLITE
CHANDRAYAAN 1(Indiaâ„¢s first unmanned spacecraft mission to the moon,launcher PSLV-C11,launched on Nov 2008)
The primary objectives of Chandrayaan-1 are:1. To expand scientific knowledge about the moon by remote sensing.2. To upgrade India's technological capability 3. To provide challenging opportunities for planetaryresearch to the younger generation of Indian scientists
VIEW OF EARTH
VIEW OF MOON
REFERENCES
Microsoft ® Encarta ® 2008.
http://www.isro.org(INDIAN SPACE RESEARCH ORGANIZATION,LATEST DEVELOPMENTS)
INTRESTED STUDENTS MAY VISIT-http://www.stmary.ws/highschool/physics/97/JDIORIO.HTM(HOW SATELLITES BENFIT SOCIETY)
THANK YOU¦