Satellites are not specifically machines that are launched into space which then moves around our planet. The moon or planets such as the earth are also satellites. They are however, ‘natural satellites’. All satellites, machinery or not, orbit around another planet. For example, the earth orbits the sun, the moon orbits the earth, and a machine satellite orbits the earth. Machine satellites that orbit the earth help scientists and meteorologists anticipate the weather (such as storms, hurricanes etc.), or they help understand scientists the galaxy/universe better; satellite can also take pictures of stars, planets, galaxies or black holes. Satellites have a specific ‘bird’s-eye view’ that allows them to see the earth in a proximate matter, allowing data to come through agiler compared to machinery on land. As said before, satellites have a better view on the occurrences happening in space due to the fact that they circle beyond the clouds, molecules and dust that appears in the atmosphere that might cause machinery to have problems collect data from the grounds surface. Signals from tv’s and phones are sent ascending to satellites that instantaneously sends those signals back to distinctive locales on earth. In the past, the signals coming from tv’s only travelled in a straight line. Instead of pursuing the curve of the earth, the signals would degenerate into space at a fast pace. Or rather colossal objects, such as mountains or tall buildings would block the signals sent. Not only were tv signals a problem, the wiring for and from faraway phone calls were too. In order to place wires underwater or over other long distances is immense, it is also inconvenient of costs that need to be paid. Satellites have lots of different parts – the main two parts are called the antenna and a power source; the antenna allow satellites to send and receive information and the power source (which is mainly a battery or a solar panel) make the power from sunlight turning it into electricity. Satellites also have sensors and cameras that gather information about the air quality, land and water. Other ones collect data about the universe or solar systems.
Fig 1: parts of satellites http://www.gma.org/surfing/images/components.gif
In order for satellites to orbit around the earth, they are launched from the earth’s surface on rockets. Satellites orbit around the earth because the speed is equitable with the pull of gravity from earth. If the balance between the speed is not equitable with the pull of gravity the satellite is not able to orbit around the earth anymore; it will then travel in a straight line into space or it is going to fall back to our planet. Every satellite is located at different heights, they travel at a diverse amount of speed and fly along various aisles in order to get the data needed in an enumerated matter. There are two types of orbit in physics that are the most common: geostationary and polar. A body of any sort that is orbiting the earth, such as the moon, stays in permanent orbit when the gravitational forces attracting it to the planet are balanced by the centrifugal force that is generated by the travel of speed around the earth that tends to send it flying outwards. The speed at which a satellite needs to travel for these forces to stay balanced is dependent on its distance from the planet. Close to the earth where the gravitational attraction is greater, its speed would have to be very high and anyone wanting to receive any sort of signal of the satellites might only get to do so for a couple of minutes at a time. In the same orbit as our moon, they would be able to see the satellite for a couple of hours a day. But in either cases, they would need reception dish which would constantly track a moving satellite, across the sky. But at a certain height above the equator, a certain height of the way to the moon and with a certain speed, a satellite will stay in orbit at the same orbital position over the earth as it rotates and that therefore signals can be sent back to earth 24 hours a day for the whole year round from a fixed reception dish.
An orbital position can be described as a box about a 150 kilometres each side in which satellites are parked in addition to the major forces that keep the satellites in orbit; they are subject to other forces too. They are affected by the gravitational pull of the moon, planets and by the distortions in the earth’s gravitational field. Mountain ranges such as Himalayas can pull them off course. On the ground, control centres that are located around the world, huge parabolic antenna track spacecraft’s. The control centres receive a constant flow of information from each satellite, allowing them to tell them their precise location at all times and the exact status of the onboard systems which are exposed to the harsh environment of space. Scientists control their fleets in space, monitoring flight dynamics and carrying out precision movements by remote control the on-board thrusters are fired from time to time in order to ensure that the satellites are remained in their stationary positions. Thus, they maintaining the highest quantity of program transmission 24 hours a day. A satellite that is geostationary is a satellite that travels in the direction and rate from west to east along the equator; the same direction and rate like the earth. If a person looks up at a geostationary satellite, from their perspective it looks like the satellites are standing still. This is because the satellites move along with the earth, therefore the satellites always collect data from the same location. Therefore, polar-orbiting satellites travel the opposite direction of geostationary satellites; north to south directional. They can scan the earth since the earth spins underneath of the satellites. At the moment 1071 satellites are orbiting around the earth. NASA, ESA and other space agencies keep track of where those satellites are orbiting. Due to the fact that there are so many satellites in space, scientists need to keep track in order to prevent collisions between the satellites. When satellites are launched from the rockets, they are placed into a specific orbit to prevent them from colliding with other satellites. However, if more satellites are being launched into space, there is a higher chance of satellites colliding with each other, especially if orbits change over time. Scientists make use of satellites in order to examine the earth and what goes on in space. They can see and measure the different gases that appears in the atmosphere such as carbon dioxide, the ozone layer and the value of energy the earth can consume/emit. Satellites can also measure the amount of gasses or smoke from fires or volcanoes that appear. The information that is received from those satellites help the scientists anticipate climate and weather. This has a great influence on today’s society due to the fact that we can now receive information (and warning) much more quickly if a natural disaster were about to occur. This can be an excessive help for farmers in order to know which specific crops they can plant. Furthermore, satellites help our earth in public health. Since weather can bring in diseases, satellites can track those diseases for them to make new medicine (if the disease is unknown). Not all satellites face towards the earth and track the earth’s information, other satellites can track threatening rays that advance from the sun. Those satellites also have multiple other jobs such as understanding the history of stars, or tracking new planets; knowing the origin, or analyse comets and asteroids. The satellites that track new planets specifically look for water (such as on Mars) or the rings that fly around a planet (Saturn’s ring).