Satellites

1. Satellites By: Sydney Perrca

2. What is a Satellite? • A satellite is any object that orbits or revolves around another object. For, example the moon is a satellite of Earth, and Earth is a satellite of the Sun. The earth and the moon are natural satellites. An example of a man made satellite is the Hubble space telescope. Man made satellites are highly specialized tools that’s do thousands of tasks every day. Each of these satellites has many parts, but two parts common to all satellites are called the pay load and the bus. • The payload for a satellite is all the equipment a satellite needs to do its job. This can include antennas, cameras, radar, and electronics. The payload is different for every satellite. • The bus is the part of the satellite that carries the payload and all its equipment into space. It holds all the satellite’s parts together and provides electrical power, computers, and propulsion to the space craft. The bus also contains equipment that allows the satellite to communicate with Earth.

3. Natural satellites • This is a picture of the moon orbiting Earth and the Earth orbiting the Sun. These satellites are natural satellites. (You have to go into the slide show feature to see the heavenly bodies orbit around each other).

4. Satellite pictures

5. The many uses of satellites • Astronomy satellites: An astronomy satellite is a telescope orbiting around Earth. Because it is in orbit around Earth, the satellite’s vision is not clouded by the gases that make up the Earth’s atmosphere, and its infrared imaging equipment is not confused by the heat of the Earth. Therefore, Astronomy satellites can observe objects farther in space than a telescope of similar strength on Earth. An example of an astronomy satellite is the Hubble Space Telescope. Astronomy satellites have many different applications which include, uses involving making star maps, studying mysterious phenomena such as black holes and quasars, taking pictures of the planets in the solar system, and making maps of different planetary surfaces. • Atmospheric Studies satellites: Atmospheric studies satellites were some of the very first satellites launched into space. They generally have low Earth orbits so that they can study the Earth’s atmosphere. An example of an atmospheric studies satellite was Alouette. Alouette was the world’s first atmospheric studies satellite, which was launched by Canada to study the Earth’s ionosphere. Canadian scientists were trying to learn about the aurora borealis.

6. The many uses of satellites continued….Communication • Communication satellites: Communications satellites allow radio, television, and telephone transmissions to be sent live any where in the world. Before satellites, transmissions were difficult or impossible at long distances. The signals, which travel in straight lines, could not bend around the round Earth to reach a destination. Because satellites are in orbit, the signals can be sent instantaneously into space and then redirected to another satellite or directly to their destination. The satellite can have a passive role in communications like bouncing signals from the Earth back to another location on the Earth, while some satellites carry electronic devices called transponders for receiving, amplifying, and re – broadcasting signals to Earth. Communications satellites are often in geostationary orbit but they can also be in highly elliptical orbits. This type of orbit is roughly egg shaped, with the Earth near the top of the egg.

7. The many uses of satellites continued… • Navigation satellites: Satellites for navigation were developed in the late 1950’s as a direct result of ships needing to know exactly where they were at any given time. The idea for navigation began with the launch of Sputnik 1 on October 4, 1957. The Navstar satellites are examples of navigation satellites. • Reconnaissance satellites: Reconnaissance satellites are used to spy on other countries. They provide intelligence information on the military activities of foreign countries. These satellites can even detect missile launches or nuclear explosions in space. Reconnaissance satellites can pick up and record radio and radar transmissions while passing over a country. Finally, they can be used as an orbital weapon by placing war heads on a low orbit satellite to be launched at a ground target.

8. The many uses of satellites continued… • Remote Sensing satellites: Remote sensing is observing and measuring our environment from a distance. So, remote sensing satellites are usually put into space to monitor resources important for humans. For examples, remote sensing satellites might track animal migration, locate mineral deposits, watch agricultural crops for weather damage, or see how fast the forests are being cut down. All of these things can be done from space because a satellite in orbit can normally take photographs of larger expanses of land all over the world. • Search and Rescue satellites: Search and rescue satellites are designed to provide a way for vessels at sea and in the air to communicate from remote areas. These satellites can detect and locate emergency beacons carried by ships, aircrafts, or individuals in remote dangerous areas.

9. The many uses of satellites continued… • Space Exploration satellites: Space exploration satellites are not really satellites but are better known as space probes. A satellite is defined as something that’s orbiting something else, but space probes instead travel deep in the solar system. However, they are similar to orbiting satellites in design and function. On their journeys, space probes send back detailed pictures and other data of far away planets and other stellar phenomena. An example of a space exploration satellite is NASA’s Galileo. • Weather satellites: Citizens and Meteorologists rely on weather satellites for reliable weather information.

10. LOW earth orbit • A Low Earth Orbit is an orbit in which satellites revolve around Earth at an altitude between 350 – 1400 above the Earth’s surface. Orbits lower than this are not stable, and will decay rapidly because of the atmospheric drag. Satellites in Low Earth orbits travel at 27, 400 km/hr (8 km/s), this is one revolution in one and a half hours. A Low Earth orbit is very useful for communications satellites because of its proximity to Earth. It requires less energy to place a satellites into a LEO and the satellite needs less powerful transmitters for data transfer, the down side is that a network of satellites are required to provide continuous coverage.

11. Picture of low earth orbit • This is a picture of a satellite in low earth orbit around the Earth. (You can view the satellite revolve around the Earth using the slide show feature).

12. Geosynchronous orbit • A geosynchronous orbit is an orbit that has the same rotational period and direction as the rotation of the Earth. A satellite in geostationary orbit circles the Earth once each day. The time it takes for a satellite to orbit the Earth is called its period. For a satellite’s orbit period to be one sidereal day, it must be approximately 35, 786 kilometres above the Earth’s surface. When a geostationary satellite is viewed from Earth, it appears to stay in the same spot and never move. For this to happen the satellite must be placed directly over the Earth’s equator. Otherwise, from the Earth the satellite would appear to move in a north-south line every day.

13. Geosynchronous orbit • This is a picture of a satellite in geosynchronous orbit.

14. Global positioning system • The global positioning system is a constellation of twenty seven earth orbiting satellites (twenty four which are operational and three extras in case one fails). The U.S military developed and implemented this satellite network as a military navigation system, but soon opened it up to everyone else. Each of these 3,000 – to 4,000 pound solar powered satellites circles the Earth at about 12,000 miles, making two complete rotations every day. The orbits are arranged so that at any time, anywhere on Earth, there are at least four satellites visible in the sky. A GPS receiver's job is to locate four or more of these satellites, figure out the distance to each, and use this information to deduce its own location. GPS receivers use triangulation of the GPS satellites’ navigational signals to determine their location. The satellites provide two different signals that provide different accuracies. Coarse – acquisition code is intended for civilian use and has a typical accuracy of about one hundred meters. The military’s precision code provides an accuracy of about 20 meters. GPS satellites are controlled at the GPS Master Control Station located at Falcon Air force base outside Colorado Springs, Colorado. The ground segment also includes four active tracking ground antennas and five passive tracking monitor stations.

15. GPS Pictures

16. Bibliography • http://spacelink.nasa.gov/Instructional.Materials/Curriculum.Support/Space.Science/Satellites/.index • www.gpsy.com/gpsinfo/ • www.encyclopedia.com

17. Interpreting satellite photographs, #1-3 • 1. Picture A was taken in geosynchronous orbit because you can see the curvature of the Earth and a great amount of land is viewed in the picture. • 2. The advantages of photograph A is that there is greater area of land viewed and both hurricanes and the tropical storm can be viewed in the photograph as well there direction can be viewed more easily. The advantages of picture B are that the exact location of the storm can be determined more easily. • 3. The information discovered in the photographs can be put to use determining the location and direction of the storms and warning the people who live in the areas where the storms might hit.