Earth-Imaging Satellites
Earth-imaging satellites are artificial satellites in orbit around Earth that collect and transmit data about the planet's surface and atmosphere. Since the launch of the first satellite, Sputnik 1, in 1957, these satellites have evolved significantly, leading to a variety of applications in both scientific research and everyday life. They utilize advanced geospatial technology, including active and passive remote sensors, which gather information by measuring electromagnetic radiation from Earth. Key performance metrics for these satellites include radiometric, spatial, spectral, and temporal resolutions, all of which influence the clarity and detail of the images and data collected.
The data obtained from Earth-imaging satellites serve numerous purposes, from supporting weather forecasting and natural disaster monitoring to facilitating global navigation systems like GPS. They play a crucial role in environmental monitoring, agriculture assessments, and urban planning. Additionally, the growing intersection of satellite data with artificial intelligence and unmanned aerial vehicles presents new opportunities for innovation and efficiency in various sectors. Overall, Earth-imaging satellites are essential tools for understanding and managing our planet's resources and environments.
Earth-Imaging Satellites
FIELDS OF STUDY: Aerospace Engineering; Orbital Mechanics; Remote Sensing
ABSTRACT: An Earth-imaging satellite orbits Earth while gathering images and information. Scientists use this information to learn about Earth’s surface, oceans, and atmosphere as well as to monitor weather patterns and natural disasters. Earth-imaging satellites provide vital information to geologists, meteorologists, astronomers, and other scientists.
Earth Observation and Satellites
Since the late 1950s, artificial satellites have been launched into orbit around Earth. The first such satellite was the Soviet-built Sputnik 1 in 1957. The United States National Aeronautics and Space Administration (NASA) launched the third satellite, Explorer 1, in 1958. In 1959, NASA launched Explorer 6, a small rounded satellite. Scientists used it to study radiation, cosmic rays, and Earth’s magnetism. Explorer 6 sent back the first picture of Earth from orbit.
The success of these early Earth-orbiting satellites paved the way for the thousands of artificial satellites that followed. Twenty-first-century satellites carry an array of geospatial technology that provides vast amounts of data about what is occurring on and around Earth. For example, weather satellites provide weather forecasts even for remote areas. Land observing satellites provide information about changes occurring on the surface of the land. Telecommunication satellites have opened the scope of smartphones and the Internet to the virtual world.
Satellite Remote Sensing Imagery
Satellites in Earth’s orbit gather information on active and passive remote sensors. Active sensors send out electromagnetic radiation. They also measure the strength of the signal returned to the sensor. Passive sensors detect and measure the amount of electromagnetic radiation reflected or emitted by Earth. The sensitivity of these sensors determines their radiometric resolution. This in turn affects the clarity and detail of the resulting image.
Spatial resolution is another factor in the clarity of satellite images. Images captured with greater numbers of pixels produce images with higher spatial resolution. These images are sharper, clearer, and more detailed. The ability of satellite equipment to capture and record the wavelength and intensity of light is known as spectral resolution. This can also affect the quality of the images revealed at ground stations on Earth when the satellites transmit data for processing.
In addition, the temporal resolution of a satellite sensor array helps determine the usefulness of the information and images received from the satellite. Temporal resolution describes the time it takes for a satellite to return to an exact location to record more data. For example, scientists monitoring a natural disaster, such as a flood, can tell much more about the situation on the ground if the satellite can revisit the area quickly and provide updated information. Temporal resolution is measured in days or hours.
Satellite images can be highly detailed and enable scientists to examine relatively small areas or objects. However, the image from a satellite does not look like a photograph taken with a camera. The image is returned in different color values based on the type of data being processed. For example, an image of an ocean may show colder areas in blue and warmer areas in red. This image is helpful to scientists but does not resemble a photograph of the ocean.
Uses for Satellite Data and Geospatial Technology
The information gathered by Earth-imaging satellites can be used in many different ways. These include cartography and the creation of specialized maps of specific geographic features such as mountains. Satellite data are also essential to monitoring and planning water resources, soil surveys and crop assessments, and natural-disaster monitoring and response coordination.
In addition to their research uses, like remote sensing using radar and LIDAR, the geospatial equipment on Earth-imaging satellites is at the heart of things people use daily. All global navigation systems, such as the global positioning system (GPS), rely on data from a network of satellites. Every day both scientists and average citizens use information shared between places on Earth that are linked by satellites orbiting high above the planet. For example, it is used for tracking transportation, offering target-based advertisements, and tracing populations. It is also gaining popularity in artificial intelligence (AI) and unmanned aerial vehicles.
Principal Terms
- geospatial technology: the equipment used to see, measure, and analyze Earth and its geography, weather, and other features. Examples include global positioning systems (GPS), geographical information systems (GIS), and remote sensing (RS).
- LIDAR: short for Light Detection and Ranging. It uses light as a pulsed laser to study the surface of the Earth.
- radiometric resolution: the ability of an imaging system or sensor to capture small increments of energy in an image.
- spatial resolution: the number of pixels, or individual units, that make up a digital image. A greater number of pixels provides a higher spatial resolution and therefore greater clarity and detail.
- spectral resolution: the ability of an astronomical device called a spectrograph to differentiate various wavelengths of light.
- temporal resolution: the amount of time that it takes a remote sensing device to make a return trip to an exact location over Earth and acquire information. A shorter delay between revisits means the temporal resolution is high.
- unmanned aerial vehicles: aircraft that fly without humans and can be monitored remotely.
- US Explorer 6: the sixth in a series of Earth-imaging satellites launched in the late 1950s and the first to send back a picture of Earth from orbit in 1959.
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