Satellite imagery (also Earth observation imagery or spaceborne photography) are images of Earth or other planets 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.
The first images from space were taken on sub-orbital flights. The U.S-launched V-2 flight on October 24, 1946 took one image every 1.5 seconds. With an apogee of 65 miles (105 km), these photos were from five times higher than the previous record, the 13.7 miles (22 km) by the Explorer II balloon mission in 1935. The first satellite (orbital) photographs of Earth were made on August 14, 1959 by the U.S. Explorer 6. The first satellite photographs of the Moon might have been made on October 6, 1959 by the Soviet satellite Luna 3, on a mission to photograph the far side of the Moon. The Blue Marble photograph was taken from space in 1972, and has become very popular in the media and among the public. Also in 1972 the United States started the Landsat program, the largest program for acquisition of imagery of Earth from space. Landsat Data Continuity Mission, the most recent Landsat satellite, was launched on 11 February 2013. In 1977, the first real time satellite imagery was acquired by the United States's KH-11 satellite system.
All satellite images produced by NASA are published by NASA Earth Observatory and are freely available to the public. Several other countries have satellite imaging programs, and a collaborative European effort launched the ERS and Envisat satellites carrying various sensors. There are also private companies that provide commercial satellite imagery. In the early 21st century satellite imagery became widely available when affordable, easy to use software with access to satellite imagery databases was offered by several companies and organizations.
Satellite images have many applications in meteorology, oceanography, fishing, agriculture, biodiversity conservation, forestry, landscape, geology, cartography, regional planning, education, intelligence and warfare. Images can be in visible colors and in other spectra. There are also elevation maps, usually made by radar images. Interpretation and analysis of satellite imagery is conducted using specialized remote sensing software.
There are four types of resolution when discussing satellite imagery in remote sensing: spatial, spectral, temporal, and radiometric. Campbell (2002) defines these as follows:
The resolution of satellite images varies depending on the instrument used and the altitude of the satellite's orbit. For example, the Landsat archive offers repeated imagery at 30 meter resolution for the planet, but most of it has not been processed from the raw data. Landsat 7 has an average return period of 16 days. For many smaller areas, images with resolution as high as 41 cm can be available.
Satellite imagery is sometimes supplemented with aerial photography, which has higher resolution, but is more expensive per square meter. Satellite imagery can be combined with vector or raster data in a GIS provided that the imagery has been spatially rectified so that it will properly align with other data sets.
Satellite imaging of the Earth surface is of sufficient public utility that many countries maintain satellite imaging programs. The United States has led the way in making these data freely available for scientific use. Some of the more popular programs are listed below, recently followed by the European Union's Sentinel constellation.
Landsat is the oldest continuous Earth observing satellite imaging program. Optical Landsat imagery has been collected at 30 m resolution since the early 1980s. Beginning with Landsat 5, thermal infrared imagery was also collected (at coarser spatial resolution than the optical data). The Landsat 7 and Landsat 8 satellites are currently in orbit. Landsat 9 is planned.
MODIS has collected near-daily satellite imagery of the earth in 36 spectral bands since 2000. MODIS is on board the NASA Terra and Aqua satellites.
The ESA is currently developing the Sentinel constellation of satellites. Currently, 7 missions are planned, each for a different application. Sentinel-1 (SAR imaging), Sentinel-2 (decameter optical imaging for land surfaces), and Sentinel-3 (hectometer optical and thermal imaging for land and water) have already been launched.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an imaging instrument onboard Terra, the flagship satellite of NASA's Earth Observing System (EOS) launched in December 1999. ASTER is a cooperative effort between NASA, Japan's Ministry of Economy, Trade and Industry (METI), and Japan Space Systems (J-spacesystems). ASTER data is used to create detailed maps of land surface temperature, reflectance, and elevation. The coordinated system of EOS satellites, including Terra, is a major component of NASA's Science Mission Directorate and the Earth Science Division. The goal of NASA Earth Science is to develop a scientific understanding of the Earth as an integrated system, its response to change, and to better predict variability and trends in climate, weather, and natural hazards.
Several satellites are built and maintained by private companies. These include:
GeoEye's GeoEye-1 satellite was launched on September 6, 2008. The GeoEye-1 satellite has the high resolution imaging system and is able to collect images with a ground resolution of 0.41 meters (16 inches) in the panchromatic or black and white mode. It collects multispectral or color imagery at 1.65-meter resolution or about 64 inches.
DigitalGlobe's WorldView-2 satellite provides high resolution commercial satellite imagery with 0.46 m spatial resolution (panchromatic only). The 0.46 meters resolution of WorldView-2's panchromatic images allows the satellite to distinguish between objects on the ground that are at least 46 cm apart. Similarly DigitalGlobe's QuickBird satellite provides 0.6 meter resolution (at NADIR) panchromatic images.
The 3 SPOT satellites in orbit (Spot 5, 6, 7) provide very high resolution images – 1.5 m for Panchromatic channel, 6m for Multi-spectral (R,G,B,NIR). Spot Image also distributes multiresolution data from other optical satellites, in particular from Formosat-2 (Taiwan) and Kompsat-2 (South Korea) and from radar satellites (TerraSar-X, ERS, Envisat, Radarsat). Spot Image is also the exclusive distributor of data from the high resolution Pleiades satellites with a resolution of 0.50 meter or about 20 inches. The launches occurred in 2011 and 2012, respectively. The company also offers infrastructures for receiving and processing, as well as added value options.
BlackBridge, previously known as RapidEye, operates a constellation of five satellites, launched in August 2008, the RapidEye constellation contains identical multispectral sensors which are equally calibrated. Therefore, an image from one satellite will be equivalent to an image from any of the other four, allowing for a large amount of imagery to be collected (4 million km² per day), and daily revisit to an area. Each travel on the same orbital plane at 630 km, and deliver images in 5 meter pixel size. RapidEye satellite imagery is especially suited for agricultural, environmental, cartographic and disaster management applications. The company not only offers their imagery, but consults their customers to create services and solutions based on analysis of this imagery .
Earth Resource Observation Satellites, better known as “EROS” satellites, are lightweight, low earth orbiting, high-resolution satellites designed for fast maneuvering between imaging targets. In the commercial high-resolution satellite market, EROS is the smallest very high resolution satellite; it is very agile and thus enables very high performances. The satellites are deployed in a circular sun-synchronous near polar orbit at an altitude of 510 km (+/- 40 km). EROS satellites imagery applications are primarily for intelligence, homeland security and national development purposes but also employed in a wide range of civilian applications, including: mapping, border control, infrastructure planning, agricultural monitoring, environmental monitoring, disaster response, training and simulations, etc.
EROS A – a high resolution satellite with 1.9–1.2m resolution panchromatic was launched on December 5, 2000.
EROS B – the second generation of Very High Resolution satellites with 70 cm resolution panchromatic, was launched on April 25, 2006.
Advancements in artificial intelligence have made autonomous, large scale analysis of imagery possible. AI has been taught to process Satellite Imagery with a small degree of error. Studies have used AI to differentiate between different forest types and AI can tell the difference between certain soil and vegetation types. Researchers are using AI to monitor Satellite Imagery for vineyard and grape health as well as having AI estimate wheat harvest size. Projects like SpaceKnow uses AI to conduct case studies in near real-time of deforestation due to wildfires in California and manufacturing activity in China.
As the technology advances, clearer imagery and faster neural networks has allowed for the study of Above Ground Biomass (AGB). This ABG index can describe the size and density of vegetation which scientists use to estimate carbon output and footprints in certain areas. Scientists are eager to apply this data to the study of global warming and climate change. Researchers are developing AI that can monitor refugee movements in war-torn countries, monitor deforestation in the Amazon rain-forest, and show algae blooms in places like the Gulf of Mexico and the Red Sea. Upcoming studies of contaminated surface water and chemical runoff from Fracking are also being planned.
Because the total area of the land on Earth is so large and because resolution is relatively high, satellite databases are huge and image processing (creating useful images from the raw data) is time-consuming. Preprocessing, such as image destriping is often required. Depending on the sensor used, weather conditions can affect image quality: for example, it is difficult to obtain images for areas of frequent cloud cover such as mountain-tops. For such reasons, publicly available satellite image datasets are typically processed for visual or scientific commercial use by third parties.
Commercial satellite companies do not place their imagery into the public domain and do not sell their imagery; instead, one must be licensed to use their imagery. Thus, the ability to legally make derivative products from commercial satellite imagery is minimized.
Privacy concerns have been brought up by some who wish not to have their property shown from above. Google Maps responds to such concerns in their FAQ with the following statement: "We understand your privacy concerns... The images that Google Maps displays are no different from what can be seen by anyone who flies over or drives by a specific geographic location."
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is a Japanese sensor which is one of five remote sensory devices on board the Terra satellite launched into Earth orbit by NASA in 1999. The instrument has been collecting data since February 2000.
ASTER provides high-resolution images of the planet Earth in 14 different bands of the electromagnetic spectrum, ranging from visible to thermal infrared light. The resolution of images ranges between 15 and 90 meters. ASTER data are used to create detailed maps of surface temperature of land, emissivity, reflectance, and elevation.
In April 2008, the SWIR detectors of ASTER began malfunctioning and were publicly declared non-operational by NASA in January 2009. All SWIR data collected after 1 April 2008 has been marked as unusable.The ASTER Global Digital Elevation Model (GDEM) is available at no charge to users worldwide via electronic download.As of 2 April 2016, the entire catalogue of ASTER image data became publicly available online at no cost. It can be downloaded with a free registered account from either NASA's Earth Data Search delivery system or from the USGS Earth Explorer delivery system.Bing Maps Platform
Bing Maps Platform (previously Microsoft Virtual Earth) is a geospatial mapping platform produced by Microsoft. It allows developers to create applications that layer location-relevant data on top of licensed map imagery. The imagery includes samples taken by satellite sensors, aerial cameras (including 45 degree oblique "bird's eye" aerial imagery licensed from Pictometry International), Streetside imagery, 3D city models and terrain.
Bing Maps Platform also provides a point-of-interest database including a search capability. Microsoft uses the Bing Maps Platform to power its Bing Maps product.
Key features of the Bing Maps Platform include:
Photo-based images with features such as Streetside and 45 degree oblique "bird’s eye" views (nominally including 4 views at 90 degree viewpoint increments) that present data in context while simplifying orientation and navigation.
The ability to overlay standard or custom data points and layers with different themes.
Building-level geocoding for more than 70 million addresses in the United States.
Developer support options available.
Set of APIs available upon which developers can build applications.Cartosat
The Cartosat satellites are a series of Indian earth observation satellites built and operated by the Indian Space Research Organisation (ISRO). The Cartosat series is a part of the Indian Remote Sensing Program. They are used for Earth's resource management and monitoring.Central dense overcast
The central dense overcast, or CDO, of a tropical cyclone or strong subtropical cyclone is the large central area of thunderstorms surrounding its circulation center, caused by the formation of its eyewall. It can be round, angular, oval, or irregular in shape. This feature shows up in tropical cyclones of tropical storm or hurricane strength. How far the center is embedded within the CDO, and the temperature difference between the cloud tops within the CDO and the cyclone's eye, can help determine a tropical cyclone's intensity. Locating the center within the CDO can be a problem for strong tropical storms and with systems of minimal hurricane strength as its location can be obscured by the CDO's high cloud canopy. This center location problem can be resolved through the use of microwave satellite imagery.
After a cyclone reaches hurricane intensity, an eye appears at the center of the CDO, defining its center of low pressure and its cyclonic wind field. Tropical cyclones with changing intensity have more lightning within their CDO than steady state storms. Tracking cloud features within the CDO, using frequently updated satellite imagery, can also be used to determine its intensity. The highest maximum sustained winds within a tropical cyclone, as well as its heaviest rainfall, are usually located under the coldest cloud tops in the CDO.Djilma Airfield
Djilma Airfield is an abandoned military airfield in Tunisia, located about 2 km north of Jilma (Sidi Bu Zayd); approximately 180 km west-southwest of Tunis.
The airfield was built during World War II as a temporary field which was used by the United States Army Air Force Twelfth Air Force 31st Fighter Group during the North African Campaign against the German Afrika Korps.
The 31st Fighter Group based three squadrons (307th, 308th, 309th) of Supermarine Spitfires at the airfield from 7 to 12 April 1943. It then moved to Korba Airfield and afterwards, engineers came to the field and dismantled the facility.
Today there are little or no remains of the airfield, except the remains of a runway in the desert just north of the town of Jilma, visible from satellite imagery.EROS (satellite)
Earth Resources Observation Satellite (EROS) is a series of Israeli commercial Earth observation satellites, designed and manufactured by Israel Aircraft Industries (IAI), with optical payload supplied by El-Op. The satellites are owned and operated by ImageSat International, another Israeli company, with some 35 full-time employees (of IntelSat's total of 50). EROS A was launched on December 5, 2000 and EROS B on April 25, 2006.Eagle Vision 1 (Commercial Satellite Imagery)
Eagle Vision One (EV1) is a military based Commercial Satellite Imagery (CSI) capability programmed and funded by HQ AF/A2QS (Air Force ISR Innovations). It is located at Ramstein Air Base, Germany, and is staffed by intelligence personnel assigned to the 24th Intelligence Squadron (24IS). The mission of EV1 is to maintain a deployable commercial satellite imagery system ready to support contingency operations, theater security cooperation events, and disaster relief efforts. The EV1 system consists of the two elements: a Data Acquisition Segment (DAS) which includes a direct downlink antenna and a computer server shelter that collects and processes imagery into a standard format, and a transit-cased Data Integration Segment (DIS) that processes the standard format products into useful products.
EV1 works with satellite vendors from France (Spot 6 & 7, Pléaiades 1A & 1B), Canada (RADARSAT 1 & 2), and India (CARTOSAT1 & 2) to provide unclassified imagery to customers.
EV1 is part of a larger Eagle Vision enterprise that consists of four other units stationed in South Carolina, Alabama, California, and Hawaii.
Newest tools at EV1: EVR2EST is an unclassified imagery server used to upload and share imagery products. See the link below to view the EVR2EST server.Earth observation satellite
An Earth observation satellite or Earth remote sensing satellite is a satellite used or designed for Earth observation from orbit, similar to spy satellites but intended for non-military uses such as environmental monitoring, meteorology, map making etc.
The first occurrence of satellite remote sensing can be dated to the launch of the first artificial satellite, Sputnik 1, by the Soviet Union on October 4, 1957. Sputnik 1 sent back radio signals, which scientists used to study the ionosphere.
NASA launched the first American satellite, Explorer 1, in January 31, 1958. The information sent back from its radiation detector led to the discovery of the Earth's Van Allen radiation belts.
The TIROS-1 spacecraft, launched on April 1, 1960 as part of NASA's TIROS (Television Infrared Observation Satellite) Program, sent back the first television footage of weather patterns to be taken from space.
As of 2008, more than 150 Earth observation satellites were in orbit, recording data with both passive and active sensors and acquiring more than 10 terabits of data daily.Most Earth observation satellites carry instruments that should be operated at a relatively low altitude. Altitudes below 500-600 kilometers are in general avoided, though, because of the significant air-drag at such low altitudes making frequent orbit reboost maneuvres necessary. The Earth observation satellites ERS-1, ERS-2 and Envisat of European Space Agency as well as the MetOp spacecraft of EUMETSAT are all operated at altitudes of about 800 km. The Proba-1, Proba-2 and SMOS spacecraft of European Space Agency are observing the Earth from an altitude of about 700 km. The Earth observation satellites of UAE, DubaiSat-1 & DubaiSat-2 are also placed in Low Earth Orbits (LEO) orbits and providing satellite imagery of various parts of the Earth.To get (nearly) global coverage with a low orbit it must be a polar orbit or nearly so. A low orbit will have an orbital period of roughly 100 minutes and the Earth will rotate around its polar axis with about 25 deg between successive orbits, with the result that the ground track is shifted towards west with these 25 deg in longitude. Most are in sun-synchronous orbits.
Spacecraft carrying instruments for which an altitude of 36000 km is suitable sometimes use a geostationary orbit. Such an orbit allows uninterrupted coverage of more than 1/3 of the Earth. Three geostationary spacecraft at longitudes separated with 120 deg can cover the whole Earth except the extreme polar regions. This type of orbit is mainly used for meteorological satellites.IRS-1A
IRS-1A was the first remote sensing mission undertaken by the Indian Space Research Organization (ISRO). It was a part-operational, part-experimental mission to develop Indian expertise in satellite imagery.Imagery intelligence
Imagery intelligence (IMINT) is an intelligence gathering discipline which collects information via satellite and aerial photography.
IMINT is a subset of intelligence collection management which is a subset of intelligence cycle management. IMINT is complemented by non-imaging MASINT electro-optical and radar sensors.Meteosat
The Meteosat series of satellites are geostationary meteorological satellites operated by EUMETSAT under the Meteosat Transition Programme (MTP) and the Meteosat Second Generation (MSG) program.
The MTP program was established to ensure the operational continuity between the end of the successful Meteosat Operational Programme in 1995 and Meteosat Second Generation (MSG), which came into operation at the start of 2004 using improved satellites. The MSG program will provide service until the MTG (Meteosat Third Generation) program takes over.NASA Earth Observatory
NASA Earth Observatory is an online publishing outlet for NASA which was created in 1999. It is the principal source of satellite imagery and other scientific information pertaining to the climate and the environment which are being provided by NASA for consumption by the general public. It is funded with public money, as authorized by the United States Congress, and is part of the EOS Project Science Office located at Goddard Space Flight Center.
As of 2006 NASA Earth Observatory has won the Webby People's Voice Award in Education three times. There were a series of publicized images issued by the website in 2008, including imagery of clouds streaming over the Caspian Sea, dust storms curling off the coast of Morocco, the crumbling of the Wilkins Ice Shelf, Hurricane Bertha, and others.NASA WorldWind
WorldWind is an open-source (released under the NOSA license and the Apache 2.0 license) virtual globe. It was first developed by NASA in 2003 for use on personal computers and then further developed in concert with the open source community since 2004. As of 2017, a web-based version of WorldWind is available online. An Android version is also available.The original version relied on .NET Framework, which ran only on Microsoft Windows. The more recent Java version, WorldWind Java, is cross platform, a software development kit (SDK) aimed at developers and, unlike the old .NET version, not a standalone virtual globe application in the style of Google Earth. The SDK includes a suite of basic demos, available at goworldwind.org. The WorldWind Java version was awarded NASA Software of the Year in November 2009. The program overlays NASA and USGS satellite imagery, aerial photography, topographic maps, Keyhole Markup Language (KML) and Collada files.
On May 3, 2019, WorldWind will be suspended and all servers will be unavailable after that date. The SDK will still be available on Github, but without any technical support. Community-based mitigation efforts for dealing with the shutdown are available at WorldWindEarth.Outflow (meteorology)
Outflow, in meteorology, is air that flows outwards from a storm system. It is associated with ridging, or anticyclonic flow. In the low levels of the troposphere, outflow radiates from thunderstorms in the form of a wedge of rain-cooled air, which is visible as a thin rope-like cloud on weather satellite imagery or a fine line on weather radar imagery. Low-level outflow boundaries can disrupt the center of small tropical cyclones. However, outflow aloft is essential for the strengthening of a tropical cyclone. If this outflow is undercut, the tropical cyclone weakens. If two tropical cyclones are in proximity, the upper level outflow from the system to the west can limit the development of the system to the east.RapidEye
RapidEye AG was a German geospatial information provider focused on assisting in management decision-making through services based on their own Earth observation imagery. The company operated a five-satellite constellation producing 5-meter resolution imagery that was designed and implemented by MacDonald Dettwiler (MDA) of Richmond, Canada.
Today, RapidEye refers to the constellation of 5 earth observation satellites owned and operated by Planet Labs.Reconnaissance satellite
A reconnaissance satellite or intelligence satellite (commonly, although unofficially, referred to as a spy satellite) is an Earth observation satellite or communications satellite deployed for military or intelligence applications.
The first generation type (i.e., Corona
and Zenit) took photographs, then ejected canisters of photographic film which would descend back down into Earth's atmosphere. Corona capsules were retrieved in mid-air as they floated down on parachutes. Later, spacecraft had digital imaging systems and downloaded the images via encrypted radio links.
In the United States, most information available is on programs that existed up to 1972, as this information has been declassified due to its age. Some information about programs prior to that time is still classified, and a small amount of information is available on subsequent missions.
A few up-to-date reconnaissance satellite images have been declassified on occasion, or leaked, as in the case of KH-11 photographs which were sent to Jane's Defence Weekly in 1984.SPOT (satellite)
SPOT (French: Satellite Pour l’Observation de la Terre, lit. "Satellite for observation of Earth") is a commercial high-resolution optical imaging Earth observation satellite system operating from space. It is run by Spot Image, based in Toulouse, France. It was initiated by the CNES (Centre national d'études spatiales – the French space agency) in the 1970s and was developed in association with the SSTC (Belgian scientific, technical and cultural services) and the Swedish National Space Board (SNSB). It has been designed to improve the knowledge and management of the Earth by exploring the Earth's resources, detecting and forecasting phenomena involving climatology and oceanography, and monitoring human activities and natural phenomena. The SPOT system includes a series of satellites and ground control resources for satellite control and programming, image production, and distribution. Earlier satellites were launched using the European Space Agency's Ariane 2, 3, and 4 rockets, while SPOT 6 and SPOT 7 were launched by the Indian PSLV.SkySat
SkySat is a constellation of sub-meter resolution Earth observation satellites owned by Planet Labs, providing imagery, high-definition video and analytics services. Planet acquired the satellites with their purchase of Terra Bella (formerly Skybox Imaging), a Mountain View, California-based company founded in 2009 by Dan Berkenstock, Julian Mann, John Fenwick, and Ching-Yu Hu, from Google in 2017.UNOSAT
UNOSAT was established in 2001 as an operational, technology-intensive programme of the United Nations Institute for Training and Research (UNITAR). UNOSAT provides satellite imagery analysis and capacity development to the UN system, UN member states, and its partners. The programme's work supports evidence-based decision making for peace, security and resilience. UNOSAT products are used in response to humanitarian crises and for implementation of the 2030 Agenda for Sustainable Development.
The UNOSAT team is mainly composed of GIS and imagery analysts, remote sensing experts, geologists, hydrogeologists and hydrologists, supported by IT engineers, programmers, and management experts.
UNOSAT is headquartered at The European Organization for Nuclear Research (CERN) in Geneva, Switzerland with regional presence in Bangkok, Nairobi and N’Djamena.