What do remote sensing satellites do

Its impossible to miss in the right-hand image below as a reddish mark, whereas in the standard RGB image on the left, the fire scar is not even recognizable. Credit: NASA. Once data are processed into imagery with varying band combinations, they can aid in resource management decisions and disaster assessment; the imagery just needs to be interpreted.

Different land cover types can be discriminated more readily, by using image classification algorithms. Image classification uses the spectral information of each individual pixel. A program using image classification algorithms can automatically group the pixels in what is called an unsupervised classification.

Maps or imagery can also be integrated into a geographical information system GIS and then each pixel can be compared with other GIS data, such as census data. Satellites also often carry a variety of sensors measuring biogeophysical parameters, such as sea surface temperature, nitrogen dioxide or other atmospheric pollutants, winds, aerosols, and biomass. These parameters can be evaluated through statistical and spectral analysis techniques.

To aid in getting started with applications-based research using remotely-sensed data, Data Pathfinders provide a data product selection guide focused on specific science disciplines and application areas, such as those mentioned above.

Learn Backgrounders What is Remote Sensing? What is Remote Sensing? Orbits There are three primary types of orbits in which satellites reside: polar; non-polar, low-Earth orbit, and geostationary. A spacecraft in a geostationary orbit. Observing with the Electromagnetic Spectrum Electromagnetic energy, produced by the vibration of charged particles, travels in the form of waves through the atmosphere and the vacuum of space. Diagram of the Electromagnetic Spectrum Some waves are absorbed or reflected by elements in the atmosphere, like water vapor and carbon dioxide, while some wavelengths allow for unimpeded movement through the atmosphere; visible light has wavelengths that can be transmitted through the atmosphere.

Credit: Jeannie Allen The primary source of the energy observed by satellites, is the Sun. Often, when energy is absorbed, it is re-emitted, usually at longer wavelengths. For example, the energy absorbed by the ocean gets re-emitted as infrared radiation. Sensors Sensors, or instruments, aboard satellites and aircraft use the Sun as a source of illumination or provide their own source of illumination, measuring the energy that is reflected back.

Credit: NASA Applied Remote Sensing Training Program Passive sensors include different types of radiometers instruments that quantitatively measure the intensity of electromagnetic radiation in select bands and spectrometers devices that are designed to detect, measure, and analyze the spectral content of reflected electromagnetic radiation.

Most passive systems used by remote sensing applications operate in the visible, infrared, thermal infrared, and microwave portions of the electromagnetic spectrum. These sensors measure land and sea surface temperature, vegetation properties, cloud and aerosol properties, and other physical properties.

Resolution Resolution plays a role in how data from a sensor can be used. Data Processing, Interpretation, and Analysis Remote sensing data acquired from instruments aboard satellites require processing before the data are usable by most researchers and applied science users.

Creating Satellite Imagery Many sensors acquire data at different spectral wavelengths. Image Interpretation Once data are processed into imagery with varying band combinations, they can aid in resource management decisions and disaster assessment; the imagery just needs to be interpreted. Know the scale — there are different scales based on the spatial resolution of the image and each scale provides different features of importance.

For example, when tracking a flood, a detailed, high-resolution view will show which homes and businesses are surrounded by water. The wider landscape view shows which parts of a county or metropolitan area are flooded and perhaps where the water is coming from. An even broader view would show the entire region—the flooded river system or the mountain ranges and valleys that control the flow.

A hemispheric view would show the movement of weather systems connected to the floods. Look for patterns, shapes and textures — many features are easy to identify based on their pattern or shape. For example, agricultural areas are very geometric in shape, usually circles or rectangles. Straight lines are typically manmade structures, like roads or canals. True- or natural-color images are basically what we would see with our own eyes if looking down from space.

Water absorbs light so typically it appears black or blue; however, sunlight reflecting off the surface might make it appear gray or silver. Sediment can affect water color, making it appear more brown, as can algae, making it appear more green. Bare ground is usually some shade of brown; however, it depends on the mineral composition of the sediment. Urban areas are typically gray from the extensive concrete. Ice and snow are white, but so are clouds.

Consider what you know — having knowledge of the area you are observing aids in the identification of these features.

Coastal applications: Monitor shoreline changes, track sediment transport, and map coastal features. Data can be used for coastal mapping and erosion prevention.

Ocean applications: Monitor ocean circulation and current systems, measure ocean temperature and wave heights, and track sea ice. Data can be used to better understand the oceans and how to best manage ocean resources. Hazard assessment: Track hurricanes, earthquakes, erosion, and flooding.

Data can be used to assess the impacts of a natural disaster and create preparedness strategies to be used before and after a hazardous event. It weighs approximately 2, kg and had a design life of five years. HJ - 1C. HJ-1C has a mass of kg and a sun-synchronous orbit at an altitude of km. The local time of the orbital descending node is Globally, the United States was the first country to develop high-resolution Earth observation systems.

Other countries such as Israel, France, and India have only one or two of these satellites each. Currently, China has no high-resolution satellites. According to the China Geographic Surveying and Mapping Information and Innovation Report , although China has achieved success in satellite remote sensing technology, it is still behind in high-resolution civilian remote sensing satellite technology and its commercial applications.

Additionally, the development of GF-1 helped improve the capability for independent development of high-resolution satellites, and enhanced the self-sufficiency of high-resolution remote sensing data.

The design life of GF-1 is five to eight years Ding On April 28, , GF-1 began imaging and sending data. The first batch of images included four types: 2 m panchromatic, 8 m multispectral, 16 m multispectral, and 2 m panchromatic fused with 8 m multispectral. GF-8 is an optical remote sensing satellite used in land surveying, urban planning, land delineation, highway and railway network design, crop yield estimation, disaster prevention and reduction, and other fields.

The satellite can provide pictures with a ground pixel resolution of less than 1 m. It will be used in land surveying, urban planning, road network design, agriculture, and disaster prevention and relief.

It was the nd flight of the Long March rocket series. It can spot an oil tanker at sea using the CMOS camera, and features the best imaging capability among global high-orbit remote sensing satellites. It will be used for disaster prevention and relief, surveillance of geological disasters and forest disasters, and meteorological forecasting. The GF-6 satellite has a similar function to the GF-1 satellite but has better cameras, and its high-resolution images can cover a large area of the Earth, according to the State Administration of Science, Technology and Industry for National Defence.

GF-6 can observe the nutritional content of crops and help estimate the yields of crops such as corn, rice, soybeans, cotton and peanuts.

Its data will also be applied in monitoring agricultural disasters such as droughts and floods, evaluation of agricultural projects and surveying of forests and wetlands. Microsatellites are a new type of satellite that is low-cost and has a short development time and more flexible operation than conventional spacecraft that are heavy, costly, and time-consuming to develop. The spatial and temporal resolutions of Earth observation can be significantly improved using a distributed constellation of microsatellites.

As a result, microsatellites are becoming more widely used around the world. SJ-9A is equipped with a high-resolution multispectral camera with a panchromatic resolution of 2. SJ-9B carries longwave infrared focal plane components for optical imaging with a resolution of 73 m.

A series of scientific experiments such as space measurement, environmental monitoring, and Earth observation have been carried out in space with the support of the Shenzhou spacecraft. The Shenzhou spacecraft have accelerated the development of Earth observation technology in China.

The system includes one optical remote sensing satellite, two satellites for video imaging and another for testing imaging techniques. By , the plans indicate a satellite orbital constellation capable of a min update. The SuperView-1 01 and 02 satellites were launched by one rocket on December 28, , and two better performing satellites will be launched in the future to comprise four 0.

The Lishui-1 satellites, developed by the privately owned Zhejiang Lishui Electronic Technology Co Ltd, are commercial remote sensing satellites that were launched by an LM solid-fuel rocket from the Jiuquan Satellite Launch Center in northwest China on November 10, The company plans to build a constellation of up to 80 to commercial satellites to obtain images of the Earth and data to serve business purposes. It carried next-generation SAR and optical sensors with a ground resolution of 18 m.

During satellite operation, SAR transmits more than 1, microwave pulse signals per second to the surface and receives signals reflected from the ground with the same antenna. The optical sensor is composed of a VNIR radiometer and a shortwave infrared radiometer, and Earth observation is carried out in eight wavebands.

The PALSAR-2 has three modes: 1 Spotlight mode—the most detailed observation mode with 1 by 3 m resolution 25 km observation width ; 2 Strip Map mode—a high-resolution mode with the choice of 3, 6 or 10 m resolution observation widths of 50 or 70 km ; and 3 ScanSAR mode—a broad area observation mode with observation widths of or km and resolution of or 60 m, respectively. Resourcesat is part of the Indian remote sensing satellite system. The first of the Resourcesat satellites, Resourcesat, was launched on October 17, This series is used for disaster forecasting, agriculture, water resources, forest and environment monitoring, infrastructure development, geological exploration, and mapping services.

LISS-4 has a spatial resolution of 5. The Resurs-F series of satellites are tasked with monitoring crop growth, ice cover, landforms, and other features. They also undertake scientific research missions. For example, the two Resurs-F1 satellites launched in May and July were passive atmospheric research satellites, 70 mm in diameter and 78 kg in mass, that were used to study the density of the upper atmosphere.

The two satellites also carried scientific instruments from other countries for scientific experiments. Equipped with a passive remote sensor, the MK-4 camera can record images on three separate pieces of film and perform imaging in any three of the following six spectral bands: 0. The satellite can be used for mapping, environmental monitoring, and geographic surveys. The Resurs-O series of satellites were mainly used in geology, cartography, fire detection, ice detection, hydrology, and agriculture.

They were designed and manufactured by the then National Institute of Electronics in the former Soviet Union. At present, ocean satellites are the primary means of marine environment monitoring, making their development a necessity. These satellites can conduct global surveys of fisheries, scientifically estimate fishery potential, and provide a basis for the development of fishery policies. Furthermore, they can effectively and affordably measure the marine gravity field to provide an understanding of submarine tectonics and oil and gas reserves, and assist in developing offshore oil fields.

According to the research objectives of the EOS and ESE, the period from to the present is the comprehensive oceanographic observation stage in the development of ocean remote sensing.

The first satellite of the next-generation international Earth observation satellite system, Terra EOS-AM1 , was launched on December 18, , marking the beginning of a new era of human observation of Earth. Both Terra and Aqua are equipped with a Moderate Resolution Imaging Spectroradiometer MODIS that has 36 wavebands ranging from visible to thermal infrared light, nine of which can be used for ocean color remote sensing.

The Jason program was proposed to meet the requirements for establishing a global marine observation system and the demands of oceanic and climatological research. Launched on June 27, , Seasat-1 operated on orbit for days and stopped working on October 10, , due to an electrical system fault. It was launched to demonstrate global monitoring technologies including the observation of oceanic dynamics and satellite orbit characteristics and to provide oceanographic data for the development and application of an operational ocean dynamics monitoring system.

The satellite carried only one remote sensing instrument, SeaWiFS, which could monitor ocean color, generate multispectral images of the land and sea surface, and analyze the impacts of ocean color changes on the global environment, atmosphere, carbon cycle, and other ecological cycles.

SeaWiFS consisted of optical remote sensors and an electronic module, and the satellite covered the global ocean area once every two days. The successful launch of the first meteorological satellite, Meteosat, in marked the beginning of the implementation of the European Earth Observation Program EOP. The main task of Meteosat was to monitor the atmosphere over Europe and Africa.

The GOCE moved on a low, nearly-circular, twilight sun-synchronous orbit. Due to its energy supply, trial operation, gradiometer calibration, orbital adjustment and other reasons, the time period for scientific observation was only twelve months.

The original plan was to extend the mission by ten months and increase the observation tasks accordingly Floberghagen et al. The goal of the GOCE mission was to provide a high-precision, high-resolution static Earth gravity model Bouman et al.

Such models can be obtained based on the gravity gradient and GPS tracking data. The specific goals were to: determine global gravity anomalies with a precision of 1 mGal, determine the global geoid with a precision of 1—2 cm, and fulfil these goals with a spatial resolution above km half-wavelength Visser ; Gooding et al. Its mission is to monitor and investigate marine environments and obtain dynamic ocean environment parameters including sea surface wind, wave height, ocean current, and sea surface temperature.

HY-2A also provides data for the prewarning and forecasting of disastrous sea conditions, and offers supportive services for the prevention and mitigation of marine disasters, protection of marine rights and interests, development of marine resources, protection of the marine environment, marine scientific research, and national defense.

Generally, modern ocean satellites have an accurately determined sun-synchronous orbit, use a variety of remote sensors for measurement, and adopt a comprehensive remote sensing platform. It functions on a circular near-polar sun-synchronous orbit km above Earth, and continuously provides effective IRS-P4 services Gohil et al. The observation data from OceanSat-2 are applied to new areas of ocean research such as tornado trajectory prediction, coastal area mapping, and atmospheric research.

The OCM and ROSA provide several geophysical parameters such as suspended sediment, yellow matter, phytoplankton, sea surface temperature SST , sea wind, sea conditions, significant wave height, and atmospheric profiles derived from GPS radio occultation. The radar is designed to provide detailed information for sea ice, land ice, and climate studies, and the radar images can be used in fields such as oceanography, agriculture, forestry, hydrology, geology, and geography and to provide real-time ice surveillance of the Arctic ocean.

It fills a wide variety of roles, including in sea ice mapping and ship routing, iceberg detection, agricultural crop monitoring, marine surveillance for ship and pollution detection, terrestrial defense surveillance and target identification, geological mapping, land use mapping, wetlands mapping, and topographic mapping. Meteorological satellites have become an indispensable part of the basic and strategic resources for national economic and social development in countries across the world.

As the problems of environmental pollution, resource shortages, and natural disasters become increasingly worse, the role of meteorological satellites in weather forecasting, environmental monitoring, and disaster mitigation and prevention has become more important than ever.

Since the launch of its first meteorological satellite in April , the United States has developed two series of meteorological satellites: geostationary meteorological satellites and polar-orbiting meteorological satellites. The DMSP satellite series uses two data transmission modes: direct reading mode and storage mode. The former can transmit data to the ground station in real time and the latter transmits the data stored in the satellite-borne magnetic tape unit to the ground station when the satellite is flying over it.

Daytime and nighttime cloud imaging, land surface and sea surface temperature sensing. With a quantization level of 13 bits, the instrument has 20 channels and a resolution of AMSU can sound temperature and humidity on cloudy days, sound precipitation on the land and sea, recognize sea ice and determine its scope, and sound soil moisture to a certain degree. ERBS is used to observe incident solar shortwave radiation, solar shortwave radiation reflected to outer space, and longwave radiation transmitted from the Earth-atmosphere system.

SBUV is used to measure the total amount and vertical distribution of ozone. The instrument detects the — nm band and measures two aspects: the ultraviolet backscatter of the atmosphere in the O 3 absorption band and the ultraviolet radiation of the Sun. The European meteorological satellite program began in The second-generation Meteosat satellites entered Phase A system design phase before and entered Phase B sample satellite development phase soon after. Phase C was developed as the launch and implementation phase, and Phase D was the postlaunch application and improvement phase.

To acquire day-and-night visible light, infrared cloud imagery, snow and ice cover, vegetation, ocean color, sea surface temperature, etc. For high-resolution picture transmission HRPT , the bit rate is 0.

FY - 1C. Its design life was two years. A series of technical measures were taken that led to improvements in the product quality, adaptability to space environments, and system reliability. FY - 1D. Fourteen technical improvements were made that led to improved stability. FY-1D functioned normally for ten years, exceeding its design life and completing all tasks.

It is no longer in operation. FY - 3A. These features enabled the country to obtain global, all-weather, three-dimensional, quantitative, multispectral data on atmospheric, land surface, and sea surface characteristics.

FY - 3B. FY-3B is the second satellite in the FY-3 meteorological satellite series. FY-3B is useful for accurate monitoring and numerical forecasting of rainstorms in southern China that usually occur in the afternoon. The satellite had a design life of three years but is still operating in orbit. It replaced FY-3A to operate, after undergoing tests, in a morning orbit with FY-2B, which is in an afternoon orbit, to provide temporal resolution of global observation data of up to six hours.

The FY-3C missions primarily include Earth surface imaging and atmospheric sounding, and its observational data will be used in weather forecasting, and in monitoring of natural disasters and ecological and environmental factors.

Compared with FY-3A and FY-3B, the payload on board FY-3C features 12 sensing instruments, including a visible infrared radiometer, a microwave scanning radiometer, a microwave temperature sounder MWTS , a microwave humidity sounder MWHS , a microwave imager, and a medium resolution imaging spectrometer. The satellite is designed to provide weather forecasts in medium- and long-range numerical weather prediction NWP models, enabling high-impact weather forecasting up to a week in advance, and alleviate the impacts of natural disasters on the economy and society and improve livelihood.

FY-2A had a three-channel scanning radiometer and a design life of three years at a stable spinning altitude. The satellite began to have issues after working for three months and then worked intermittently, only operating for six to eight hours each day. Ultimately, FY-2A failed to meet the requirements for commercial meteorological services.

The first original cloud image was received on July 6. FY-2B only had a three-channel scanning radiometer and a design life of three years in a stable spinning altitude. It functioned in orbit for less than eight months before a problem occurred with one of the components on board the satellite; from then onward, the signals it sent back were too weak to receive.

Ultimately, FY-2B failed to meet the requirements for commercial meteorological services. FY-2C was the first commercial-use satellite in the FY-2 meteorological satellite series.

Four days after it was positioned, adjustments were made to the ground application system to technically coordinate it with the satellite. FY-2C could observe changes in sea surface temperature, and one of its channels was designed for measuring 3. It was possible to use spectral channels to observe ground heat sources to promptly discover forest fires in remote and desolate places, monitor their situation, and predict their development trends. FY-2D was the fourth satellite in the FY-2 meteorological satellite series.

It was launched using an LM-3A rocket at on December 8, After 1, s of flying, it successfully separated from the rocket, entering into a large elliptical transfer orbit with a perigee altitude of km, apogee altitude of 36, km, and inclination of At on December 9, the apogee engine was ignited for orbital transfer, and secondary separation was successfully completed.

After four batches of orbit trimming, the satellite was positioned at an altitude of 36, km above the equator at It is currently no longer in operation. FY-2F boasted flexible capability for scanning specific regions with a high temporal resolution and could monitor disastrous weather conditions such as typhoons and severe convections.

The space environment monitor continuously monitored solar X-rays and the flow of high-energy protons, electrons, and heavy particles, and the data were used for space weather monitoring, forecasting, and early warning services.

During flood season, the double-satellite observation mode allowed for spinning the satellite, enabling it to provide a cloud picture every fifteen minutes. This intensified observation mode played a key role in monitoring disastrous weather systems such as typhoons, rainstorms, thunderstorms, and small- and medium-scale local convective systems. The FY-2 meteorological satellite series played a crucial role in combating heavy rain, freezing snow, and other extreme weather events.

The satellites also provided assistance in the Wenchuan earthquake relief operations and in providing meteorological services for the Beijing Olympics and Paralympics. Based on the technology of FY-2 F satellite, the FY-2G satellite was improved by reducing infrared stray radiation, uplifting the observation frequency for the blackbody, and improving the telemetry resolution of optical components.

These improvements increase the retrieval accuracy of FY-2G satellite quantitative products and enhance the quantitative application of satellite data products. FY-2H was launched on June 5, It can provide favorable observation perspectives and custom-made high-frequency subregional observation for countries and regions such as western Asia, central Asia, Africa, and Europe.

Equipped with a scanning radiometer and a space environment monitor, FY-2H can supply data for dozens of remote sensing products such as cloud images, clear sky atmospheric radiation, sand and dust, and cloud motion wind CMW for weather prediction, disaster warning, and environmental monitoring, enriching the data sources for global NWP models. FY - 4A. FY-4A was launched on December 11, , as the first Chinese second-generation geostationary meteorological satellite.

Four new instruments are on board the latest independently developed weather satellite, namely, an advanced geosynchronous radiation imager AGRI , a geosynchronous interferometric infrared sounder GIIRS , a lightning mapping imager LMI and a space environment package SEP. FY-4A is the first satellite in China that can capture lightning. The onboard Lightning Mapping Imager enables this function. It is the first geostationary optical remote sensing instrument in China and has filled the gap in terms of lightning observation and satellite-borne detection.

FY-4A can detect lightning over China and neighboring areas and take lightning pictures per second. By real-time and consecutive observation of lightning, it can aid in observation and tracking of severe convective weather and provide early warning for lightning disasters. Since Japan launched its first geostationary meteorological satellite, GMS-1, in , it has put five geostationary meteorological satellites into orbit.

The satellite can obtain information about winds below and above clouds, and detect sea surface temperature distribution. INSAT is a multiagent multitarget satellite system and is one of the largest satellite systems in Asia.

INSAT provides services such as domestic long-distance communication, meteorological and Earth observation data relay, augmented television receiver national direct satellite broadcasting, TV education, rural communications, meteorology, and disaster alarms. Most of the previous three generations of satellites do not function in sun-synchronous orbit.

However, the fourth-generation of satellites is known to work in a sun-synchronous orbit. In March , it launched its first-generation polar-orbiting meteorological satellite: Meteor The first generation consisted of 31 satellites Meteor launched from to , most of which had an orbital inclination of The second generation Meteor-2 comprised 24 satellites launched after In most cases, two or three satellites were simultaneously operating on orbit, with an orbital inclination of The third-generation Meteor-3 polar-orbiting meteorological satellites were launched in A problem occurred with the attitude control after launch, but the satellite resumed working after some remedial measures were taken.

Looking back on the past five decades of spaceborne remote sensing, every step along the way has been based on the national backgrounds and political and economic conditions of each country.

During this period of development, the purpose of Earth observation shifted from single-field surveying toward serving the demands of the overall development of human society Guo Since entering the period of globalization, remote sensing technologies have developed into a complete system Guo et al.

All of the aforementioned satellite programs have clearly defined services. The European GMES program covers the six service fields of land, ocean, emergency management, security, atmosphere, and climate change Veefkind et al. In addition, Russia, Japan, India, and some other countries have issued strategic plans for Earth observation, forming systems with their own characteristics. In addition, some companies such as DigitalGlobe are planning to deploy new high-resolution satellites and trying to enter the microsatellite field.

The planned satellites have also been extended from optical to meteorological and radar satellites.