Astronomy Satellites
Astronomy Satellites
An astronomy satellite is basically a really big telescope floating in space. Because it is in orbit above the 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. Astronomy satellites, therefore, can "see" into space up to ten times better than a telescope of similar strength on Earth. Can you guess what kinds of things an astronomy satellite would be looking at?
An astronomy satellite is basically a really big telescope floating in space. Because it is in orbit above the 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. Astronomy satellites, therefore, can "see" into space up to ten times better than a telescope of similar strength on Earth. Can you guess what kinds of things an astronomy satellite would be looking at?
Communication Satellites
It is difficult to go through a day without using a communications satellite at least once. Do you know when you used a communications satellite today? Did you watch T.V.? Did you make a long distance phone call, use a cellular phone, a fax machine, a pager, or even listen to the radio? Well, if you did, you probably used a communications satellite, either directly or indirectly.
Communications satellites allow radio, television, and telephone transmissions to be sent live anywhere 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 far away. 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; on the other hand, some satellites carry electronic devices called transponders for receiving, amplifying, and re-broadcasting signals to the Earth.
Communications satellites allow radio, television, and telephone transmissions to be sent live anywhere 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 far away. 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; on the other hand, some satellites carry electronic devices called transponders for receiving, amplifying, and re-broadcasting signals to the Earth.
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. In the middle of the ocean or out of sight of land, you can't find out your position accurately just by looking out the window.
The idea of using satellites for navigation began with the launch of Sputnik 1 on October 4, 1957. Scientists at Johns Hopkins University's Applied Physics Laboratory monitored that satellite. They noticed that when the transmitted radio frequency was plotted on a graph, a pattern developed. This pattern was recognizable to scientists, and it is known as the doppler effect. The doppler effect is an apparent change of radio frequency as something that emits a signal in the form of waves passes by. Since the satellite was emitting a signal, scientists were able to show that the doppler curve described the orbit of the satellite.
Today, most navigation systems use time and distance to determine location. Early on, scientists recognized the principle that, given the velocity and the time required for a radio signal to be transmitted between two points, the distance between the two points can be computed. The calculation must be done precisely, and the clocks in the satellite and in the ground-based receiver must be telling exactly the same time - they must be synchronized
The idea of using satellites for navigation began with the launch of Sputnik 1 on October 4, 1957. Scientists at Johns Hopkins University's Applied Physics Laboratory monitored that satellite. They noticed that when the transmitted radio frequency was plotted on a graph, a pattern developed. This pattern was recognizable to scientists, and it is known as the doppler effect. The doppler effect is an apparent change of radio frequency as something that emits a signal in the form of waves passes by. Since the satellite was emitting a signal, scientists were able to show that the doppler curve described the orbit of the satellite.
Today, most navigation systems use time and distance to determine location. Early on, scientists recognized the principle that, given the velocity and the time required for a radio signal to be transmitted between two points, the distance between the two points can be computed. The calculation must be done precisely, and the clocks in the satellite and in the ground-based receiver must be telling exactly the same time - they must be synchronized
Weather Satellites
Because of weather satellite technology and communications satellite technology, you can find out the weather anywhere in the world any time of the day. There are television stations that carry weather information all day long. Meteorologists use weather satellites for many things, and they rely on images from satellites. Here are a few examples of those uses:
The other basic type of weather satellite is polar orbiting. This type of satellite orbits in a path that closely follows the Earth's meridian lines, passing over the north and south poles once each revolution. As the Earth rotates to the east beneath the satellite, each pass of the satellite monitors a narrow area running from north to south, to the west of the previous pass. These 'strips' can be pieced together to produce a picture of a larger area. Polar satellites circle at a much lower altitude at about 850 km. This means that polar satellites can photograph clouds from closer than the high altitude geostationary satellites. Polar satellites, therefore, provide more detailed information about violent storms and cloud systems.
- Radiation measurements from the earth's surface and atmosphere give information on amounts of heat and energy being released from the Earth and the Earth's atmosphere.
- People who fish for a living can find out valuable information about the temperature of the sea from measurements that satellites make.
- Satellites monitor the amount of snow in winter, the movement of ice fields in the Arctic and Antarctic, and the depth of the ocean.
- Infrared sensors on satellites examine crop conditions, areas of deforestation and regions of drought.
- Some satellites have a water vapour sensor that can measure and describe how much water vapour is in different parts of the atmosphere.
- Satellites can detect volcanic eruptions and the motion of ash clouds.
- During the winter, satellites monitor freezing air as it moves south towards Florida and Texas, allowing weather forecasters to warn growers of upcoming low temperatures.
- Satellites receive environmental information from remote data collection platforms on the surface of the Earth. These include transmitters floating in the water called buoys, gauges of river levels and conditions, automatic weather stations, stations that measure earthquake and tidal wave conditions, and ships. This information, sent to the satellite from the ground, is then relayed from the satellite to a central receiving station back on Earth.
The other basic type of weather satellite is polar orbiting. This type of satellite orbits in a path that closely follows the Earth's meridian lines, passing over the north and south poles once each revolution. As the Earth rotates to the east beneath the satellite, each pass of the satellite monitors a narrow area running from north to south, to the west of the previous pass. These 'strips' can be pieced together to produce a picture of a larger area. Polar satellites circle at a much lower altitude at about 850 km. This means that polar satellites can photograph clouds from closer than the high altitude geostationary satellites. Polar satellites, therefore, provide more detailed information about violent storms and cloud systems.