I was reading in a special issue of Discover magazine that came out last month (January, 2007) about GRACE's gravity maps. The Gravity Recovery and Climate Experiment (GRACE) consists of a pair of satellites that sense variations in local gravity. The data is being used to detect mountain ranges, ocean trenches, underground watersheds, and other hidden concentrations of mass. According to the authors this is a new field of remote sensing and filled with possibilities in helping us understand our changing world. After reading the article, I thought one of the more interesting uses of the twin satellites was how they the pair could detect quantified changes in subsurface water in the Amazon and Congo river basins. This got me thinking about how remote sensing changing our view of our home. In this light...
a. Define remote sensing.
b. Describe two ways imaging and remote sensing technology have helped environmental scientists to see our changing world.
c. Describe two different types of sensors that have been mounted on a satellite.
d. Choose one of the sensors that you mentioned above and list one advantage and one disadvantage of mounting it on a satellite rather than using it on the ground.
e. Describe two ways that satellite data has changed our everyday lives.
Resources
1. Amazing Grace at http://science.nasa.gove/headlines/y2001/ast300oct _1.htm
2. Information on how NASA is using satellites to study the environment at http://www.nasa.gov/vision/earth/technologies/index.html
3. Gravity Recovery and Climate Experiment at http://www.csr.utexas.edu/grace/mission/project.html
4. Remote Sensing Basics at http://en.wikipedia.org/wiki/Remote_sensing
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Remote sensing is the acquirement of information from an object or phenomenon through a recording device that is not in direct contact with the object. In other words, remote sensing is using any device to gather information from the environment without direct contact. Some examples would be ultrasounds, space probes, and satellites. Imaging and remote sensing technology have helped environmental scientists to see our changing world. A type of remote sensing instrument called the Airborne Oceanographic Lidar (ADI) uses laser beams to strike a surface every three and a half inches and 400 times per second and then bounces back. The difference between the two readings (from the ground and usually the top of vegetation cover) shows forest height and pasture growth, etc. The lidar can also be used for measuring not only height but altitude, slope, and aspect of ground features. Lidars can also go through water detecting oil forms, morphology of coastal waters, water clarity, and fluorescent dry traces. This helps environmental scientists see changes in certain environments allowing them to change them if they are detrimental. Some remote sensing devices use an infrared absorption principle to measure hydrocarbon and carbon monoxide emissions. Scientists can see how much hydrocarbon and carbon monoxide cars are emitted and can also measure “evaporative” emissions (gasoline vapors that vent into the air from hot engines and fuel systems). Pollution is a major factor that is destroying the earth’s atmosphere. If scientists can figure which cars emit the most hydrocarbons and carbon monoxide and change these cars, there could be a break through in the lessening of pollution. Two different types of sensors that have been mounted on a satellite are passive and active sensors. Passive sensors, like the Thematic Mapper (TM), record radiation reflected from the earth’s service from the outside, most likely in the form of solar energy (this means that passive sensors can only be used in the daylight hours). Active sensors require the energy to come from within the sensor. An example would be a laser beam remote sensor which sends out a beam of known wavelength and frequency which reflects off of the earth’s surface. It then records how long the beam takes to come back to the sensor. An advantage of mounting a Thematic Mapper on a satellite would be that the spectral bands it uses would give a multispectral view for land and water surface mapping and analysis rather than just being on the ground with a limited area and a limited view. This is why most Thematic Mappers are placed on satellites. A disadvantage of the Thematic Mapper being on a satellite would be that it could have technological problems in orbit, like any other satellite, and misinterpret the data, feeding wrong data back to scientists. We use satellites for many things. One main use for satellites is weather detection. We use satellites to predict where and when hurricanes and major weather patterns will hit. Therefore we can call for an evacuation or other precautions to ensure human safety. Another use of satellites would be for the search and rescue of vessels. Search and rescue satellites transmit radio signals and allow vessels in the sea and air to communicate in remote areas.
Remote sensing is the collection and interpretation of information about an object or place without physical contact. Methods include satellite imaging, aerial photography, and open path measurements. MODIS is an example of remote sensing. It is ideal for monitoring large-scale chnges in the environment. MODIS'measurements of the biosphere help scientists track sources of carbon as well as carbon sinks. Geoscience Laser Altimeter System (GLAS)was put on board a spacecraft to measure the elevations of ice sheets over time. GLAS has also helped scientists measure land elevations, vegetaion, and ice thickness. One type of sensor that has been mounted to a satellite are geostationary operational environmental satellites (GOES). GOES allows short-range warning for lang term forecasting. Another type is passive microwave radiometers. These allow the light weight, large aperture to get close enough to measure ice thickness without leaving a footprint. Another type are the Polar Orbiting Environmental Satellites (POES). This satellite makes nearly 14.1 orbits a day and provides global information on a daily basis. One advantage of the geo operational environmental satellite is that it provides a constant eye on the same spot for severe weather conditions or "triggers" of condtions. The disadvantage is that it does not provide gloabal information so each region must have its own satellite. One way that satellite data has changed our lives is that we are now trying to decrease our carbon emissions because satellite data showed a correlation between carbon dioxide in the air and temperature increase. Another change, thanks to satellite data, is that we can now validate our knowledge of earth's dynamics.
Remote Sensing is the measurement or acquisition of information of an object of phenomenon, by a recording device that is not in contact with the object being measured. In practice, it’s a device for gathering information about the environment.
Two different ways that imaging and remote sensing have changed the way we see the world are aircraft sensors and laser devices called lidars which are able to measure water vapor content and things such as cloud, dust, and precipitation particle sizes, shapes, and types. This might allow us to understand why some storms are fiercer than others and why. Another is the revolutionary radar that can be used to gather information on the intensity of rainfall and where the precipitation was falling.
One type of sensor that has been placed on a satellite is the GOES or the Geostationary Operational Environmental Satellite which allows scientists to have images from a satellite in orbit. With the infrared images scientists are able to see weather patterns and possibly hurricanes that form and are heading towards civilization. A second sensor that is mounted onto a satellite are Passive sensors which will usually use visible, infrared, thermal infrared, and microwave electromagnetic waves to measure radiation. For example, Spectrometers are designed to detect, measure, and analyze the content of incident radiation.
A definite advantage of Passive sensors is that they provide rapid updates, up to one update every second. But a disadvantage of passive sensors would be the misinterpretation of data by the satellites and actually being able to send the wrong data back to the right scientists.
Today, satellites have changed our everyday lives through many ways. But two ways are the constant weather updates that are available to us every day. We are now able to get weather updates on our cell phones. But lately we have begun to come accustomed to GPS. Some cars today are able to find a lost car or give you directions depending on where your vehicle is all depending on the satellite and the information that it gives.
Remote sensing is using a type of device, such as a satellite, to gather precise information about the environment without actually coming in contact with it. Most use the reflected or emitted electromagnetic radiation of the object in a certain frequency area. Remote sensing can be used in many different ways to help the environment. One way is light detection and ranging (LIDAR) which uses a laser pulse to detect and measure various concentrations of chemicals in the atmosphere and can also be used to measure heights and features of objects on the ground. It uses pulses of laser light striking the surfaces of Earth and measures the return. This can help scientists detect changes in the environment such as changes in the coastline or changes in surface elevation. Then, maybe they can figure out a way to reverse damaging changes. For example, LIDAR helped scientist analyze the changes of the crater on Mt. St. Helens. Another way it can be used is MODIS, moderate-resolution imaging spectroradiometer, which is used for monitoring large-scale changes in the biosphere. This helps scientists the sources and sinks of carbon dioxide in response to climate changes as well as detecting wispy cirrus clouds (which may contribute to global warming by trapping heat). Two types of sensors are optical and microwave sensors. Optical sensors observe infrared rays and visible light. With visible/near infrared sensing, you measure the strength of reflection to understand land conditions, distribution of plants, etc. With thermal infrared sensing you measure the strength of thermal infrared rays which are radiated from the heated surface to understand surface temperatures of land and sea, as well as the status of volcanic activity and forest fires. Microwave sensors receive microwaves and aren’t affected by what time of day or what weather it is. The active type is a sensor aboard earth that emits microwaves and observes the microwaves reflected and can be used to observe mountains and valleys. The passive type observes microwaves naturally radiated from Earth’s surface and can be used to observe surface sea temperatures. An advantage of using a passive microwave sensor on a satellite is that you will get a wider range of data, since it will have a greater view. It also isn’t affected by clouds or moisture in the air so it can observe in great detail with quick updates. A disadvantage is that it’s more likely to have technical problems if its in space then on Earth because of the greater distance and the fact that it could run into a lot of problems up there. 2 ways satellites have changed our daily lives our by weather forecasts and GPS. I can’t imagine turning on the news without being told what the forecast for that week is. We’re able to have forecast predictions thanks to satellites in space. Also, GPS has also become a common thing people use, whether it’s to track products or get a direction, that’s also thanks to GPS satellites.
Remote sensing is the measurement of an object by a remote that is not in direct contact with the object. Satellite imaging, aerial photography, open path measurements or an ultrasound taking a picture of a baby are examples of remote sensing.
Space probes to other planets have provided the opportunity to conduct remote sensing studies in extra-terrestrial environments. Synthetic aperture radar aboard the Magellan spacecraft provided detailed topographic maps of Venus, while instruments aboard SOHO allowed studies to be performed on the Sun and the solar wind, just to name a few examples. Instrumentation aboard various Earth observing and weather satellites such as Landsat, the Nimbus and more recent missions such as RADARSAT and UARS provided global measurements of various data for civil, scientific, and military purposes. Systematic aerial photography was developed for military purposes beginning in World War I and reaching a climax during the Cold War with the development of reconnaissance aircraft such as the U-2.
One type of sensor that is mounted on a satellite are passive sensors. Passive sensors include different types of radiometers and spectrometers. Most passive systems used in remote sensing applications operate in the visible, infrared, thermal infrared, and microwave portions of the electromagnetic spectrum. Geoscience Laser Altimeter System (GLAS) is another type of sensor that is put on spacecrafts. From aboard the Ice Cloud and Elevation Satellite (ICESat) spacecraft, it makes observations, including measuring ice-sheet topography, cloud and atmospheric properties, and the height and thickness of radioactively important cloud layers needed for accurate short term climate and weather prediction.
One of the objectives of the GLAS is to measure cloud heights and the vertical structure of clouds and aerosols in the atmosphere. In order to do this accurately, the satellite pictures must be taken from an airplane rather then from off the ground. This would mean they are closer to the clouds, and have the ability to get all angles to take pictures. One disadvantage of mounting it on a satellite is that it is more costly, and the spacecraft could have some technological problems that could interrupt the picture taking.
Satellite data can now detect the distance, and speed of hurricanes, and tornadoes. Although they cannot be exactly precise and there is no way of stopping these occurrences, it is a huge help to warn people so that they can leave their homes to protect their lives. Another way that satellites have helped our everyday lives is the invention of cell phones. Without these people would not be able to call the police if they got in a car accident, or get in touch with people in case of emergency.
Remote sensing is the acquirement of information from an object or phenomenon through a recording device that is not in direct contact with the object. The methods include satellite imaging, aerial photography, and open path measurments. MODIS is an example of remote sensing. MODIS stands for moderate-resolution imaging spectroradiometer, which is used for monitoring large-scale changes in the biosphere. MODIS'measurements of the biosphere help scientists track sources of carbon as well as carbon sinks. One type of sensor that has been mounted to a satellite are geostationary operational environmental satellites (GOES). GOES allows short-range warning for lang term forecasting. Another type is passive microwave radiometers. These allow the light weight, large aperture to get close enough to measure ice thickness without leaving a footprint. For example, Spectrometers are designed to detect, measure, and analyze the content of incident radiation. An advantage of Passive sensors is that they provide rapid updates, up to one update every second. But a disadvantage of passive sensors would be the misinterpretation of data by the satellites and actually being able to send the wrong data back to the right people. A way that satellites have helped our everyday lives is the invention of cell phones. Without these people wouldn't be able to keep in touch unless they are at home. Another way is GPS which has also become a common thing people use, whether it’s to track products or get a direction, that’s also thanks to GPS satellites.
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