SATELLITE TECHNOLOGY STUDENT INFORMATION

Transcription

1 SATELLITE TECHNOLOGY STUDENT INFORMATION Area of Study: Communications Objectives: Students will discover the basic principles of satellite technology through a demonstration and utilization of web resources. Related Occupations: Atmospheric scientists commonly called meteorologists forecast the weather, identify & interpret climate trends, understand past weather, & analyze today s weather. Computer software engineers develop, and test software. These include modeling programs for satellite systems. Telecommunications equipment installers maintain and install various sophisticated communications equipment and cables. Key Words and Definitions: Meteorological satellite analysts with the 2nd Weather Squadron, go over meteorological satellite imagery. U.S. Air Force photo/ G. A. Volb 1. Clarke Belt: The geostationary orbit 22,300 miles above the equator, named after Arthur C. Clarke, who first described how such an orbit could be used for global communications. 2. Communications Technology: all the ways people have developed to send & receive messages. 3. Downlink: The transmission of a signal from a satellite in space to a satellite dish on Earth. 4. Geosynchronous: An orbit whose period is the same as the rotational rate of the earth, so that the satellite appears not to move in the sky when looking up from the ground. This term can also be referred to as geostationary or stationary. 5. Inclination: is the measure of how much an orbit is tilted from the equator. An orbit with an inclination of 0 degrees would orbit over the equator. An inclination of 90 degrees, would travel directly over the north and south poles and would be perpendicular to the equator. 6. Orbit: The path an object takes as it moves around another object. 7. Satellite: A small object, natural or artificial, that orbits a larger object. 8. Uplink: Transmission of a signal from a ground station on Earth to a satellite in space. Satellite Technology 1

2 SATELLITE TECHNOLOGY Occupational Choices Focus: Atmospheric Scientists. Classes to take in School: Earnings: Business Computer Science English Math Statistics Science Speech Technology In 2010, people employed as Atmospheric Scientists nationally had an median salary of $87,800. In 2010, Atmospheric Scientists in Utah wages ranged from $34,800 to $128,800. The median wage in Utah was higher than the national average coming in at $89,400. In 2010, yearly earnings ranged nationally from $45,100 to $132,100. Earnings vary by experience and location. Employment Opportunities Federal Government Armed Forces Scientific Firms Private weather consulting services Television broadcasting State Government After High School: Students should take courses in subjects that are most relevant to their desired area of specialization. A Bachelors Degree from a University or College with at least 24 semester hours in meteorology courses. A Masters degree is necessary for conducting applied research and a Ph.D is usually required for most basic research positions. The degrees can be in mathematics, physics, or engineering as all universities do not offer a degree in meteorology. American Meteorological Society (AMS) offers professional certification which does not always require a degree, but equivalent time shown in the field with formal education requirements. The Work: The number of people employed in this field is small, but should see strong growth. Beginning atmospheric scientists often do routine data collection, computation, or analysis, and some basic forecasting. The work will vary with the specialization. Meteorologists study and forecast weather patterns in the short term, and climatologists study seasonal variations in weather over time. A broadcast metrologist would focus more on presentation of the weather while those working for the government or business would focus more on data collection and long range trends. Personal Characteristics Good Communication skills Excellent Math skills Excellent computer skills Ability to read and interpret data Source: Occupational Outlook Handbook Edition & Career One Stop Satellite Technology 2

3 The Communications Model: Communications Technology refers to all the different ways in which people have developed to send and receive messages 1. There are many different ways to send messages to one another. The device that is used to send the message is called the medium. In figure 1, a communication model using satellites as the medium is shown. In this example, the reporter is broadcasting a message from a remote location and is able to do this because the dish on the truck (called an uplink) is transmitting the signal to an orbiting satellite in space. The signal from the satellite is beamed to a dish at the television station called a downlink. The news of the event is broadcast quickly and efficiently because of the combination of dishes and satellite are all positioned to relay the data. If there is a problem with the original message, the television station contacts the reporter and the reporter adjusts the message. A simple example of this would be there is no sound with the video. The news station checks with the reporter who then turns on his or her microphone. This is called feedback. The communication model containing the basic elements of message, medium (device or channel used), transmission, receiver, and feedback can be applied to any communicated information. Communications Systems: A communications model that uses a satellite as the medium. Figure 1 The communications model Dish Network s Uplink Center in Cheyenne, Wyoming. using the sum of all materials and Mike Breen Photo processes through which a person sends a message and the person or machine receiving the message returns feedback is known as a communications system. Every communications system, no matter how simple or complex, (from smoke signals to a reporter sending a video feed by satellite for the nightly news) is designed to perform four functions which are input (developing the message), process (actions required to send the message), output (message being received in some form), and feedback (reaction to the message) 2. 1 Brusic, S. 2 Jones, R. Two satellite trucks are in this picture. The larger satellite truck is equipped with both a Ku and C-band antenna. Michael Meinhardt Photo Satellite Technology 3

4 Satellites In the communication systems just discussed, a reporter was communicating over great distances and sending his/her information via satellite. What is a satellite? The moon is a satellite of the earth. NASA /JPL Photo Technically, it is any object orbiting a larger object in space. The Moon is a satellite of the earth. In general satellites are of two types: a natural celestial body (such as the moon) and man made objects. In this brief study of satellites, we will concentrate on the man-made ones. The first man made satellite was Sputnik 1 which was launched in 1957 by the former Soviet Union. It created quite a stir in the United States and the rush to get America into satellite technologies was started. Today, more than 22,000 3 human-made satellites orbit the Earth that are being tracked, and about 600 of these are functional satellites that transmit data 4. The 21,400 objects left orbiting the Earth are space junk that can range from satellites, rocket boosters, tools lost by astronauts, or pieces of satellites that have collided in space. Some of this space junk will eventually re-enter Earth s atmosphere and burn up, and others will remain in orbit until removed. Objects are traveling at speeds up to 17,500 mph so even a paint fleck which is too small to be tracked can be fatal on a mission in space. The 1st man-made satellite was Sputnik 1. NASA Photo All functional satellites serve the same basic purpose: to communicate information. During the transfer of data, a wireless link between the satellite and a point on earth is established by sending a radio wave, or signal, which is commonly referred to as a carrier (because it carries information). The satellite then relays information through radio waves which are in the microwave spectrum as shown in figure 2. Each satellite has different transponders (channel) which can carry multiple information (TV, Voice, Internet, radio pictures, navigation, etc.). The amount of information depends on what is being transmitted as different services will require more bandwidth for transmission. The type of information to be conveyed will determine the satellite s design and orbit. Most satellites are put into orbit by launching them into outer space using a rocket. This is expensive so it takes a lot of funding to put a satellite into orbit. To launch a rocket into space which would carry a satellite in the payload would cost over a 100 million dollars today. This cost does not include the satellite itself! 3 Wall, M. 4 Discovery Channel The electromagnetic spectrum contains all frequencies of light. The visible light spectrum is very narrow. The microwave spectrum is used for satellites transmission because microwave energy can penetrate haze, light rain and snow, clouds, and smoke. NASA Illustration - Figure 2 Satellite Technology 4

5 Power A satellite can receive power through different sources. Many satellites are battery powered and rely on the sun s rays and solar panels (photovoltaics) to recharge their batteries. Other satellites use fuel cells that convert chemical energy to electrical energy. In the past, there have been a several satellites that have used nuclear power as their power source. 5 Types of Orbits: A satellite remains in orbit because of gravity. A satellite s speed keeps the force of gravity from pulling the satellite back to Earth, and Earth s gravity keeps the satellite from flying out in a straight line away from Earth. The forces work to counteract each other. Satellite orbits can be classified by altitude. These are known as Low Earth, Medium Earth, and High Earth. These can also be classified as either circular or elliptical. There are many ways to categorize orbits for studying and we will not list them all, however for our purposes, circular orbits can be further categorized as equatorial or polar. The type of orbit used will depend on the job of the satellite. Circular Orbits: Equatorial Many people think of satellites as circling above the equator and many satellites do. Most of the satellites over the equator are in a very high orbit 22,300 miles above the earth. These satellites are said to be a geosynchronous satellite. In 1945, science-fiction author, Arthur C. Clarke, wrote about communications satellites in stationary orbits travelling directly overhead at a rate in-synch with the earth s orbit. As a result, this area in space is now referred to as the Clark Belt. Every nation on Earth has a set of positions assigned to it in the Clarke Belt. Many of these satellites are communications satellites. There are also satellites in circular orbits that are not located in the Clark Belt. Polar While there are many satellites that do orbit over the equator, there are also many polar-orbiting satellites. A polar orbit will provide a more thorough view of the earth. They travel around the Earth in a circular orbit from North to South. Many of these satellites are ones that photograph the earth because equatorial satellites signals or footprint will not reach the most northern or southern ends of the globe as shown in figure 3. Many satellites with polar orbits also are categorized as being in an low earth orbit (LEO) too. Polar orbiting satellites operate in space between 435 to 1056 miles above earth and will have different inclinations of orbits as in figure 4. A Delta IV rocket lifts off with a Defense Department Satellite from Cape Canaveral. U.S. Air Force - Carleton Bailie Photo A representation of a equatorial satellite s footprint as it transmits data back to earth. Figure 3 Inclination of Orbits. Figure 4 5 Zaitsev, Y. Satellite Technology 5

6 Elliptical A satellite in an elliptical orbit follows an oval-shaped path as shown in figure 5. In an elliptical orbit, the satellite s speed will change depending on where it is in its orbital path. In this orbit, as the satellite draws closer to earth, it moves faster because of earth s gravity speeds it up. In this orbit, the satellite zips around the earth and then it travels out very far from earth and it s speed decreases. As a result, this type of satellite spends much of its time in an orbit away from earth. Low Earth Orbit When a satellite is in a circular orbit close to Earth, it is in Low Earth Orbit. Satellites in Low Earth Orbit are just 130 to 1056 miles high. These satellites must travel very fast so gravity will not pull them back into earth s atmosphere. Satellites in Low Earth Orbit travel about 17,500 miles per hour. They can circle Earth in about 90 minutes. This area in space is where a majority of satellites are located as shown in figure 6. Medium Earth Orbit An illustration of a satellite in an polar elliptical orbit. Figure 5 When a satellite is in an area between LEO and the Clarke belt, it is in Medium Earth Orbit (MEO). An example of satellites in MEO would be Global Positioning Satellites (GPS). High Earth Orbit When a satellite is in an area past the Clarke belt, it is in High Earth Orbit (HEO). Examples of satellites in HEO would Russia s Molniya satellites. These communication satellites are in an elliptical orbit and transmit broadcast TV signals in these orbits because equatorial satellites signals will not reach the areas that the signals need to reach. An illustration of satellites in low earth orbits. These are just a few of the satellites over your head tonight. Types of Man-Made Satellites USAF Illustration Figure 6 Astronomy: These satellites look out into space, and the most famous is the Hubble Space Telescope. Communications: Satellites used to beam TV and audio signals and many are placed in geosynchronous orbits which makes the satellite appear to float over the same spot on the earth s surface. Earth Resources - The position on earth of minerals, water, and vegetation are mapped by these satellites to help us understand the earth s ecology. Navigation - Global Positioning Satellites (GPS) which triangulate a position on earth. Military - Weather - Used to gather military intelligence. These satellites are used to track weather systems which has aided meteorologists in being able to predict the weather. Satellite Technology 6

7 Altitudes:. Figure 7 is a generalization of the distances out in space that satellites are placed. The job of the satellite will also determine the altitude that it is put into space. Altitude Miles Impacts on Society: Satellite Types space stations, military, navigation, ham radio weather, photos (military and commercial) 600-1,200 military, communications, ham radio, earth resource 3,000-6,000 science, earth resource 6,000-12,000 GPS navigation 22,300 (stationary) communications, broadcast communication, weather ,000(elliptical) Molniya broadcast, communications, military Altitude in Miles of different Satellite types. Figure 7 On May 20, 1998, the $250 million dollar Communications Satellite, Galaxy IV, veered off its orbit and became nonfunctional. The loss of the satellite created a mess. The signal outage interrupted TV station signals, affected 40 million pager users, bank teller machines, fast-pay gas stations, and internet services. 6 The loss of the satellite affected government agencies and business. This mishap proved satellite technology is seamlessly integrated into American society. Telecommunications through satellites have brought information to governments and individuals much quicker. Satellites have also saved lives through weather forecasts and early warning systems. The use of satellite technology has helped us to understand the problems that are created by man on our fragile Earth. Many of us rely on Satellites for navigation through GPS technology. Satellites have also shown us how much more there is to explore in the universe by giving us a clearer picture of surrounding galaxies. It is clear that the United States and many countries of the world rely on satellite technology. We are affected by satellites everyday from getting information about the weather, our knowledge of the world, to even entertainment or news that is broadcast through television signals that we receive. Satellites provide many of the conveniences we take for granted in everyday life; and as new technologies emerge, we will become even more dependant on satellite technology. 6 Gilchrist, M. The International Space Station is a Satellite. NASA Photo Satellite Technology 7

8 Procedure: Having read the booklet answer questions When those questions are done continue with the activity below. Satellite Tracking and Orbits: As part of a rocket launch safety team for NASA, your job is to explore the possibilities of launching safely into outer space from a space port that was just built just outside your town. The rocket carries a multimillion dollar communications satellite that is to go into orbit and be located in the Clarke Belt so that it may beam down information in your region. Your objective is to locate the Clarke Belt using web resources, and to use tracking resources to locate satellites in different orbits that could pose a problem for the launch. You will be researching using two different software programs. The following steps will be taken research a possible path. Start with the destination. Lets look for the Clark Belt and the final spot in space. 1. Log in to a computer work station. A weather satellite in orbit. U.S. Air Force / Lockheed-Martin Photo 2. Open a search engine and type in NASA J-Track 3D 3. Open the web site. A new window will open using Java script. Expand the J Track-3D window. Figure 8 4. Expand the window to fill the screen as shown in figure Use your mouse cursor to move the Earth over your location (hold left mouse button down & drag). 6. To navigate, use your left mouse button as before, but also use the keyboard to: Zoom = Shift + Left Click with Mouse Zoom out = Ctrl + Left Click with Mouse 7. Having located your country, rotate the Earth by dragging down with the mouse so that you are now viewing the North pole of the Earth. Determine the altitude of the satellite by using the View Menu and the Satellite Position command. Figure 9 8. If needed, zoom out so that you can see the ring of satellites that orbit the Earth. This is the Clarke Belt. Locate the two satellites of your choosing that are needed to answer question 11 and For question 13 & 14, use the view command on each satellite to determine their altitudes as shown in figure 9. A satellite with an elliptical orbit. Figure 10 Satellite Technology 8

9 10. The next step is to determine if there are any satellites in an elliptical orbit as in figure 10. Click on satellites that are nearby that could interfere with your orbit. These are known as High Earth Orbits (HEO) Locate a Satellite in elliptical orbit that may be near where you want to locate your satellite. Hint: Zoom out and choose the dots (satellites) that are clear away from the Earth to find one with an elliptical orbit. Answer question 15. Now lets check Medium Earth Orbiting (MEO) satellites. Since we know that GPS satellites are in a MEO, lets look at GPS satellites. GPS satellites are under the governance of the U. S. Air Force s 2nd Space Operations Squadron as described in the picture at the bottom of the page. 11. Click on the Satellite menu and scroll down and click on Select. This opens up a new window as shown in figure 11. Scroll through the list of satellites until a list of GPS satellites appear as also shown in figure 11. Click on one of the GPS satellites listed and it s orbit will be traced in the window. 12. In this new window there is a button at the lower left that is Satellite Info. Click on this button which has an arrow to it as shown in figure 11. This brings up a new window (figure 12) in the Internet browser that will have the answer to question 16. Windows that open when selecting satellites. Figure 11 The window that opens up with the GPS info. Figure As a last step in this program, zoom in on the Earth until just your country is visible on the screen and observe the low earth satellites that are orbiting over it. Now when the satellites are viewed, the satellites (dots on your screen) move. The satellite orbits can also be seen. Click on one going by and watch it move. When a satellite is selected, it s orbit will also be displayed. If a rocket is launched it has to launch though a maze of these satellites too. Timing is everything. The NASA J-Tracker program is just tracking operational satellites. To get a picture of what all has to be examined in a real launch, we will open another program. 14. Close the NASA J-Tracker Program and the Internet Browser for now. A satellite system operator in the 2nd Space Operations Squadron, runs through a checklist during Global Positioning System satellite operations. The operations center at Schriever Air Force Base, controls 29 orbiting satellites that provide data to users worldwide. U.S. Air Force Photo / Airman 1st Class Mike Meares Satellite Technology 9

10 Procedure Day 2: Low Earth Orbits: Now that we have a recommendation on where to put our government s satellite, we have to look at a typical launch day and observe satellites in Low Earth Orbits (LEO) to see if there are any that might be potential hazards. A launch of a rocket will involve a launch window. This is a time span in which it safe to launch the vehicle. This window is determined by many factors such as weather conditions, and existing satellite orbits. The desktop icon for KMZ Figure Log in to a computer work station if you are not already. 2. Click on the icon called KMZ Satellite Data as shown in figure 13. This could be a shortcut on the Desktop, in the program menu, or stored on a network drive. If it is not available on your desktop, call your teacher over to help locate it. Google Earth with the Satellite Data loaded. Figure 14 This software tracks over 13,000 satellites some of which are functional and others that have been decommissioned. It is an add on for Google Earth which will now open. Wait a couple of seconds and let the software load. 3. Rotate the Google Earth globe so it is over your country. 4. Use the center mouse wheel to zoom into the Earth and you will notice that words are appearing over the globe and in outer space as shown in figure 14. These represent satellites. 5. Using the mouse wheel or the Google Earth zoom tool, zoom in to the launch area so that several States or Provinces are visible. 6. Look for Satellites that are near your location. Click on a satellite. Notice that information about that satellite is displayed. The data screen that opens when a satellite is clicked on. Figure The first thing to do is click on Display Trajectory in a Fixed Frame as circled in red in figure 15. This will show the orbit of the satellite. Notice the path of the satellite s orbit is not exactly the same. This is because of the Earth s rotation in many cases. A satellite that is currently orbiting in a polar orbit over a neighboring state or province may later be orbiting over yours. The trajectory of the orbits of 6 satellites. Figure 16 Satellite Technology 10

11 8. Rotate the Earth so that it is again back where you had it earlier. Look at the orbiting pattern. Notice the 2nd orbiting pattern of this same satellite is to the West of the first orbit path. Again, this means that satellites well East of your location could be over your location on their next orbital pass. 9. Pick 5 satellites at random over or East of your location and identify the type of orbit as well as if it is an operational satellite. The orbit will shown by different colored lines as shown in figure 16. All of these satellites are in Low Earth Orbits (LEO). What is meant on your worksheet is to specify the orbit by listing it as elliptical, polar or other type of circular orbit. This is visually displayed around the Google Earth globe showing the trajectory for about the next 4 hours. The orbit status must be interpreted by the user from the orbit trajectory. The information for the operational status is displayed with the blue circle in figure 17. List either that the satellite is active (TRUE) or out of service (FALSE). Operational status of the satellite. True means it is a functioning active satellite. False means the satellite is no longer active. Figure 17 Real Satellite Tracking: Several satellites have been orbiting in space since the dawn of the space age, and unless there is outside action, many non-functioning satellites out toward the Clark Belt will be circling the Earth for centuries 7. Satellites are designed to last for about a decade. Each satellite has small rockets on board to regularly adjust it s orbit. After 10 years this fuel runs out, and the satellite can no longer be adjusted with respect to its position. This causes the satellite to start to appear to wobble, or falter in it s orbit and eventually it can not be used. It is boosted into a higher or lower orbit called a graveyard orbit, and another satellite is launched to replace it. As new satellites are added to replace failed satellites, the numbers of satellites orbiting Earth grows. There are so many satellites with varying orbits that computers are used with sophisticated algorithms that predict the potential of collisions or safe launch windows for rockets. Joint Functional Component Command for Space (JFCC-Space) is one arm in the The United States Strategic Command. The Air Force s JFCC-Space s mission is to track, detect, and identify all manmade objects orbiting Earth. Personnel are constantly tracking these objects. They use a worldwide network of 29 space sensors consisting of radar and optical telescopes to track the objects orbiting the Earth. There are several agencies and companies that The Eglin FPS -85 phased array radar, located in Florida, is one of 29 dedicated sensors used to track satellites. It can track 200 have common interests that share satellite satellites at once, and makes about 16 million observations a year. data. U.S. Air Force photo 7. Oberg, J. Satellite Technology 11

12 Orbital Debris: The chances for collision of the satellites themselves is not as great as hitting smaller satellite particles known as orbital debris. Each piece of debris is technically a satellite of the Earth. The largest debris field ever created was from a missile test by a foreign government which created 3,218 pieces big enough to be tracked. 8 NASA s Orbital Debris Program Office is estimating that this one event created more than 35,000 pieces larger than 1 cm. 9 This event and the accidental collision of American and Russian communications satellites in 2009 greatly increased the number of large debris in orbit. The two events represent one-third of all cataloged orbital debris. 10 Both of these incidents occurred in LEO, and a some of this debris has since re-entered Earth s atmosphere and fallen back to Earth. Most of these objects are small and burn up upon re-entry. Those that don t completely burn up, usually fall into the sea as most of the Earth is covered in water. There are more than 21,000 orbital debris particles larger than 10 cm (4 inches), 500,000 particles between 10 cm and 1 cm ( about 3/8 ), and the number of orbital debris smaller than 1 cm exceeds 100 million pieces. 11 Orbital debris can make the life of a satellite short lived. It could also pose problems for human space flight, as one small piece could put a hole in a space craft which could affect many different systems on a space craft the least of which is the artificial atmosphere which the space explorers rely on to breathe. On the left, is an enlarged section of an impact that completely penetrated the antenna dish of the Hubble Space Telescope. NASA photo Near Barstow, CA is the Goldstone antenna which is capable of detecting 2 mm debris at altitudes below 625 miles. It is one of many different tools used to track orbital debris. U.S. Air Force photo 8 Kelso, T.S. 9 Welsch, J. 10 NASA Orbital Debris 11 NASA Orbital Debris Satellite Technology 12

13 SATELLITE TECHNOLOGY Student Work Sheet Name: Period: Date: Directions: In the blank on the left, write the correct answer to the statement or question. 1. Technology refers to all the ways that people have developed to send and receive messages. 2. The communications model consists of a message being transmitted to the receiver. The receiver then gives the user about the message. 3. A satellite is a small object that is a larger object. 4. The first man-made satellite was called. 5. Satellites all serve the same basic purpose which is to information. 6. A satellite relays information through radio waves which are in the spectrum because microwave energy can penetrate haze, light rain and snow, clouds, and smoke. 7. A satellite remains in orbit because of. 8. The Clarke Belt refers to a geostationary orbit miles above the earth. 9. A satellite in an elliptical orbit follows an -shaped path. 10. An example of satellites in MEO would be Satellites. Satellite Technology 13

14 SATELLITE TECHNOLOGY Student Work Sheet Activity 11. In the Clarke Belt, choose two geosynchronous satellites that are over your region of the world. The destination for the satellite to be launched will be between the 2 satellites you choose. Record the 12. names for the two satellites you choose for answers to #11 and # Write down the altitude of the satellite listed in # Write down the altitude of the satellite listed in # Write down a satellite that you found in an elliptical orbit. 16. Yrs. What is the name of the GPS satellite, and how many years has it been in orbit? 17. How many of these GPS satellites are employed (used at once)? 18. Fill in the table for the five satellites chosen. 19. The Joint Functional Component Command for Space uses a worldwide network of 29 space sensors consisting of and optical telescopes to track objects orbiting the Earth. 20. Instead of satellites accidently running into one another, a more likely event is a satellite will be struck by orbital. Satellite Technology 14