Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring information about Earth and other planets. Remote sensing is used in numerous fields, including geophysics, geography, land surveying and most Earth science disciplines ; it also has military, intelligence, commercial, economic, planning, and humanitarian applications, among others.
The Landsat program is the longest-running enterprise for acquisition of satellite imagery of Earth. It is a joint NASA / USGS program. On 23 July 1972, the Earth Resources Technology Satellite was launched. This was eventually renamed to Landsat 1 in 1975. The most recent, Landsat 9, was launched on 27 September 2021.
Terra is a multi-national, NASA scientific research satellite in a Sun-synchronous orbit around the Earth that takes simultaneous measurements of Earth's atmosphere, land, and water to understand how Earth is changing and to identify the consequences for life on Earth. It is the flagship of the Earth Observing System (EOS) and the first satellite of the system which was followed by Aqua and Aura. Terra was launched in 1999.
Clouds and the Earth's Radiant Energy System (CERES) is an on-going NASA climatological experiment from Earth orbit. The CERES are scientific satellite instruments, part of the NASA's Earth Observing System (EOS), designed to measure both solar-reflected and Earth-emitted radiation from the top of the atmosphere (TOA) to the Earth's surface. Cloud properties are determined using simultaneous measurements by other EOS instruments such as the Moderate Resolution Imaging Spectroradiometer (MODIS). Results from the CERES and other NASA missions, such as the Earth Radiation Budget Experiment (ERBE), could enable nearer to real-time tracking of Earth's energy imbalance (EEI) and better understanding of the role of clouds in global climate change.
The multi-angle imaging spectroradiometer (MISR) is a scientific instrument on the Terra satellite launched by NASA on 18 December 1999. This device is designed to measure the intensity of solar radiation reflected by the Earth system in various directions and spectral bands; it became operational in February 2000. Data generated by this sensor have been proven useful in a variety of applications including atmospheric sciences, climatology and monitoring terrestrial processes.
MOPITT is an ongoing astronomical instrument aboard NASA's Terra satellite that measures global tropospheric carbon monoxide levels. It is part of NASA's Earth Observing System (EOS), and combined with the other payload remote sensors on the Terra satellite, the spacecraft monitors the Earth's environment and climate changes. Following its construction in Canada, MOPITT was launched into Earth's orbit in 1999 and utilizes gas correlation spectroscopy to measure the presence of different gases in the troposphere. The fundamental operations occur in its optical system composed of two optical tables holding the bulk of the apparatus. Results from the MOPITT enable scientists to better understand carbon monoxide's effects on a global scale, and various studies have been conducted based on MOPITT's measurements.
Satellite images are images of Earth collected by imaging satellites operated by governments and businesses around the world. Satellite imaging companies sell images by licensing them to governments and businesses such as Apple Maps and Google Maps.
India's remote sensing program was developed with the idea of applying space technologies for the benefit of humankind and the development of the country. The program involved the development of three principal capabilities. The first was to design, build and launch satellites to a Sun-synchronous orbit. The second was to establish and operate ground stations for spacecraft control, data transfer along with data processing and archival. The third was to use the data obtained for various applications on the ground.
In imaging spectroscopy each pixel of an image acquires many bands of light intensity data from the spectrum, instead of just the three bands of the RGB color model. More precisely, it is the simultaneous acquisition of spatially coregistered images in many spectrally contiguous bands.
The normalized difference vegetation index (NDVI) is a widely-used metric for quantifying the health and density of vegetation using sensor data. It is calculated from spectrometric data at two specific bands: red and near-infrared. The spectrometric data is usually sourced from remote sensors, such as satellites.
The Advanced Very-High-Resolution Radiometer (AVHRR) instrument is a space-borne sensor that measures the reflectance of the Earth in five spectral bands that are relatively wide by today's standards. AVHRR instruments are or have been carried by the National Oceanic and Atmospheric Administration (NOAA) family of polar orbiting platforms (POES) and European MetOp satellites. The instrument scans several channels; two are centered on the red (0.6 micrometres) and near-infrared (0.9 micrometres) regions, a third one is located around 3.5 micrometres, and another two the thermal radiation emitted by the planet, around 11 and 12 micrometres.
TerraSAR-X, is an imaging radar Earth observation satellite, a joint venture being carried out under a public-private-partnership between the German Aerospace Center (DLR) and EADS Astrium. The exclusive commercial exploitation rights are held by the geo-information service provider Astrium. TerraSAR-X was launched on 15 June 2007 and has been in operational service since January 2008. With its twin satellite TanDEM-X, launched 21 June 2010, TerraSAR-X acquires the data basis for the WorldDEM, the worldwide and homogeneous DEM available from 2014.
Ocean color is the branch of ocean optics that specifically studies the color of the water and information that can be gained from looking at variations in color. The color of the ocean, while mainly blue, actually varies from blue to green or even yellow, brown or red in some cases. This field of study developed alongside water remote sensing, so it is focused mainly on how color is measured by instruments.
Multispectral remote sensing is the collection and analysis of reflected, emitted, or back-scattered energy from an object or an area of interest in multiple bands of regions of the electromagnetic spectrum. Subcategories of multispectral remote sensing include hyperspectral, in which hundreds of bands are collected and analyzed, and ultraspectral remote sensing where many hundreds of bands are used. The main purpose of multispectral imaging is the potential to classify the image using multispectral classification. This is a much faster method of image analysis than is possible by human interpretation.
Radiometric calibration is a general term used in science and technology for any set of calibration techniques in support of the measurement of electromagnetic radiation and atomic particle radiation. These can be for instance, in the field of radiometry or the measurement of ionising radiation radiated from a source.
METRIC is a computer model developed by the University of Idaho, that uses Landsat satellite data to compute and map evapotranspiration (ET). METRIC calculates ET as a residual of the surface energy balance, where ET is estimated by keeping account of total net short wave and long wave radiation at the vegetation or soil surface, the amount of heat conducted into soil, and the amount of heat convected into the air above the surface. The difference in these three terms represents the amount of energy absorbed during the conversion of liquid water to vapor, which is ET. METRIC expresses near-surface temperature gradients used in heat convection as indexed functions of radiometric surface temperature, thereby eliminating the need for absolutely accurate surface temperature and the need for air-temperature measurements.
The Visible Infrared Imaging Radiometer Suite (VIIRS) is a sensor designed and manufactured by the Raytheon Company on board the polar-orbiting Suomi National Polar-orbiting Partnership, NOAA-20, and NOAA-21 weather satellites. VIIRS is one of five key instruments onboard Suomi NPP, launched on October 28, 2011. VIIRS is a whiskbroom scanner radiometer that collects imagery and radiometric measurements of the land, atmosphere, cryosphere, and oceans in the visible and infrared bands of the electromagnetic spectrum.
Remote sensing is used in the geological sciences as a data acquisition method complementary to field observation, because it allows mapping of geological characteristics of regions without physical contact with the areas being explored. About one-fourth of the Earth's total surface area is exposed land where information is ready to be extracted from detailed earth observation via remote sensing. Remote sensing is conducted via detection of electromagnetic radiation by sensors. The radiation can be naturally sourced, or produced by machines and reflected off of the Earth surface. The electromagnetic radiation acts as an information carrier for two main variables. First, the intensities of reflectance at different wavelengths are detected, and plotted on a spectral reflectance curve. This spectral fingerprint is governed by the physio-chemical properties of the surface of the target object and therefore helps mineral identification and hence geological mapping, for example by hyperspectral imaging. Second, the two-way travel time of radiation from and back to the sensor can calculate the distance in active remote sensing systems, for example, Interferometric synthetic-aperture radar. This helps geomorphological studies of ground motion, and thus can illuminate deformations associated with landslides, earthquakes, etc.
Jeff Dozier is an American snow hydrologist, environmental scientist, researcher and academic. He is Distinguished Professor Emeritus and Founding Dean of the Bren School of Environmental Science & Management at the University of California, Santa Barbara.
Dorothy K. Hall is a scientific researcher known for her studies on snow and ice, which she studies through a combination of satellite data and direct measurements. She is a fellow of the American Geophysical Union.
