What is the IRS in remote sensing

This lexicon is available on DVD with extensive additional material.


Engl. Akron. For Inter-Agency Space Debris Coordination Committee; an international association of space agencies to exchange current research results and develop preventive measures. For Germany, DLR ensures that the requirements decided there are met in current German projects.

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Engl. Acronym for I.nfrared A.tmospheric S.ounding I.interferometer; probing instrument on the METOP series; the probing Michelson interferometer is used to create temperature, water vapor and other trace gas profiles of the atmosphere, as well as to determine the sea surface temperature and cloud properties. The soundings are made twice a day for the entire atmosphere.


Left: The instrument includes a spectrometer that breaks down the light radiation emitted by the atmosphere and enables observation of the atmospheric chemistry.

Right: The temperature of the troposphere and the lower stratosphere is measured under cloud-free conditions, as is the humidity of the troposphere. IASI also measures the degree of cloud cover as well as the temperature and air pressure at the cloud upper limit. Likewise, the total amount of O3 measured, also the content of CO, CO4 and N2O.


The IASI is a measuring instrument that provides very precise, vertically resolved data on the composition of the atmosphere. The instrument includes a spectrometer that breaks down the light radiation emitted by the atmosphere and enables observation of the atmospheric chemistry. The aim is to calculate and track the existing amounts of trace gases such as ozone, methane or carbon monoxide on a global level. A central component of the IASI is a periodically moving mirror that generates an interference pattern from which the atmospheric data you are looking for can be derived. IASI also includes an image generator that works with the spectrometer to locate the probing points.

The temperature of the troposphere and the lower stratosphere is measured under cloud-free conditions with a vertical resolution of 1 km in the lower troposphere, a horizontal resolution of 25 km and an accuracy of 1 Kelvin. The humidity of the troposphere is also measured under cloud-free conditions, with a vertical resolution of 1-2 km in the lower troposphere, a horizontal resolution of 25 km and an accuracy of 10%. IASI also measures the degree of cloud cover as well as the temperature and air pressure at the cloud top.

The total amount of ozone is measured under cloud-free conditions, with a horizontal resolution of 25 km and an accuracy of 5%, as well as the content of CO, CO4 and N2O, integrated over the entire column with an accuracy of 10% and a horizontal resolution of 100 km.

Strong eruption of volcanic gases and ash in Chile

This picture shows the huge cloud of sulfur dioxide that was ejected from the Chilean volcanic complex Puyehue-Cordón Caulle, about 600 km south of Santiago. After being inactive for over 50 years, a series of earthquakes heralded the start of this great eruption. On June 4, 2011, a 4 km long crevice opened and sent a cloud of ash and gas up 10 km. Several thousand people were evacuated after a 50 cm thick layer of ash and pumice rained down and covered a large area. Airports in Chile and Argentina had to close.
The image was generated on June 6th from IASI data from the MetOp-A satellite. It represents the SO2-Concentration in the entire vertical column of air. Strong westerly winds (area of ​​the 'Roaring Forties') drove the cloud far out into the South Atlantic. The sharp change in direction to N is explained by a pronounced pressure system.

Eruptions of volcanoes often - as happened here - produce electrically charged air currents, which trigger violent thunderstorms and thus give the natural event a special drama.

See also the picture gallery Chile volcano eruption - in pictures (The Guardian 2011)

Sources: ESA / Survivalangel

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Operation IceBridge was a 2009-2016 NASA mission for airborne monitoring of changes in the polar ice. It didn't end until the end of 2019. The detailed three-dimensional images are intended to contribute to a better understanding of the processes that connect the polar regions with the global climate system.
IceBridge deployed a highly specialized fleet of research aircraft and state-of-the-art instruments to study the annual changes in sea ice thickness, glaciers, ice shelves and ice sheets. In addition, IceBridge collects important data that is needed to predict the reaction of the polar ice to climate changes and the resulting rise in sea levels. The flights over Greenland took place from March to May, those over Antarctica from October to November. Additional smaller observation flights in other parts of the world were also part of the IceBridge campaign.

IceBridge also closes the temporal observation gap of the polar regions that arose between NASA's ICESat satellite missions. ICESat-1, which has been in space since 2003, failed in 2009, ICESat-2 did not start work until 2018. In this respect, IceBridge's observations are of crucial importance for data continuity.

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ICESat / ICESat-2

Engl. Acronym for I.ce, C.loud and land E.levation Satellite; NASA earth observation mission to determine the height of ice sheets and their changes, to create height profiles of clouds and aerosols as well as to determine land topography, height of vegetation cover and sea ice thickness has now ended. The Geoscience Laser Altimeter System (GLAS) was the only instrument on board the satellite. ICESat has been in its inclined, non-sun-synchronous orbit (inclination 94 °) at an altitude of 600 km since January 2003. Its orbital time was 97 minutes and its repetition cycle was 183 days. The satellite was in operation until 2009.

The second generation of the laser altimeter mission (ICESat-2) started on September 15, 2018. In contrast to ICESat, the instrument Advanced Topographic Laser Altimeter System (ATLAS) of the new satellite emit six laser pulses - not just one. Using the time it takes for the impulses to come back to the satellite, scientists can calculate the height of ice sheets, glaciers and vegetation on earth and observe changes with unprecedented levels of detail.

Scientists will be able to combine the new ice-related data with measurements taken from a variety of other satellites and instruments, helping research uncover hidden relationships between ice and other marine and atmospheric phenomena such as wind, current, temperature, precipitation and more . The main scientific task of ICESat-2 is to collect data in order to be able to estimate the annual changes in height of the ice sheets in Greenland and Antarctica with an accuracy of up to 4 mm.

Infographic illustrating the key technological and scientific objectives of ICESat-2

ICESat-2 continues to record ice height measurements begun by NASA's previous ICESat mission. ICESat's ice height measurements continued through the agency's annual Operation IceBridge, which began in 2009 and continued through 2019. ICESat-2 data will be available to the public through the National Snow and Ice Data Center. The engineers at NASA Goddard built and tested the ATLAS instrument and are leading the ICESat-2 mission for NASA's Science Mission Directorate. Northrop Grumman designed and built the satellite bus, installed the instrument, and tested the completed satellite.


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Engl. Acronym for I.onospheric Connection Explorer; Satellite mission of NASA's explorer program to study changes in the terrestrial ionosphere. The two-year mission is scheduled to start in October 2019. The planned approximately circular orbit of the spacecraft at an altitude of 575 km is inclined 27 degrees to the Earth's equator. This orbit enables observation of the ionosphere in the area of ​​the equator.

ICON examines the forces that are in conflict with one another in the dynamic ionosphere: space weather with its solar winds and the earth's climate system. The few gases in this layer are anything but calm, as a mixture of neutral and charged particles flow through them in powerful winds. These winds can vary on a wide variety of time scales, depending on the terrestrial seasons, the warming and cooling occurring during the day, and incoming solar radiation bursts.

ICON has four instruments: Two ultraviolet radiation spectrographs come from UC Berkeley. They are used to detect light in extreme (EUV) and far (FUV) ultraviolet for determining plasma density. The MIGHTI (M.ichelson I.interferometer for Global Hhigh resolution imaging of the Thermosphere and I.onosphere) called interferometer is primarily used to collect data on wind speed and temperature in the high atmosphere and is supplied by the Virginia Marine Research Laboratory (NRL). The measuring device for the speed, temperature and number of ions (Ion velocity meter, ION) was created in Dallas at the University of Texas (UT Dallas).

With ICON, the aim is to learn to understand the processes in this layer, which is important for radio signals, as changes in it can lead to serious disruptions in communication and GPS signals.

ICON explores the boundary between earth and space

Left: NASA's Ionospheric Connection Explorer (ICON) satellite, which will investigate the boundary of space: that dynamic zone high in our atmosphere where terrestrial weather from below meets space weather from above.

Right: Clouds of red, green, and yellow light - known as airglow - can be seen in this video at the edge of the earth, captured from the International Space Station. Full length and resolution video at NASA Goddard Media Studios.

Source: NASA

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See International Council for Science


Engl. Acronym for I.nstantaneous F.ield Of V.iew, German current field of view, observed surface element, too Opening angle; The measure of spatial resolution is the size of the area that was included in a numerical value (DN value, digital number) is implemented. The IFOV (A) is the solid angle and determines the smallest unit to be resolved. IFOV is typically measured in mrad (milliradians). The unit mrad describes small parts of a solid angle (see Fig. Below).

At a certain time, the energy of the surface (B) is measured at a height above ground (C) with the solid angle (A). The IFOV is multiplied by the height above ground and results in the smallest unit to be resolved (resolution cell). The features or areas to be observed must be the same size or larger than the IFOV in order to be detected. This applies to homogeneous surfaces. Linear or punctiform objects with a different spectral behavior (higher reflectivity) to their surroundings can also be "seen" in smaller units than the IFOV.
The entire recording is divided into pixels. The size of the pixels does not have to correspond to the spatial resolution. The spatial resolution of the ERS-1/2 was, for example, 25 m, but the pixel size was 12.5 m.

Instantaneous Field of View

The degree of recognizable details on the earth's surface depends on the spatial resolution. The spatial resolution is essentially determined by the instantaneous field of view (IFOV). The IFOV (A) is the solid angle (specified in mrad) and determines the smallest unit to be resolved.

Source: Natural Resources Canada


See (The) Integrated Global Atmospheric Chemistry Observations


See International Geosphere-Biosphere Program


Engl. Acronym for I.ntegrated Global Observing S.strategy; Organizational framework supported by space agencies and governments that unites the most important satellite systems and surface-based systems for global environmental observations of the atmosphere, oceans and land surfaces.
In the meantime, the goals and tasks of IGOS are being continued by the Group on Earth Observations.

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IHS system

Engl. IHS color model; syn. HSV, HSB, HIS system; Term for color systems that define a color by its lightness (intensity), Hue (Hue) and color saturation (saturation) define.

The intensity I shows the differences in brightness in an image, the values ​​are between black and white. They do not contain any color information. The hue H indicates the dominant wavelength of the color. The saturation S describes the purity of the color.

These elements are described in a cylinder in which the color is removed from the base area. The angle (starting from 0 °) is used as a measure for the respective color (see color coordinate circle). The color saturation is sketched through the distance from the cylinder axis and the intensity of the color is applied to the cylinder axis itself, which is also the achromatic straight line (since no angle leads away from the 0 ° line).

IHS cylinder in cross section

The IHS model is a cylinder in shape. The position of a color in this cylinder is indicated by the coordinates I, H and S.

"Hue" is understood to mean the name of the color or, more precisely, the respective position in the spectrum. Each spectral gradation is a color in the IHS model. The angle coordinate is specified as the size; the range is logically from 0 to 360.

Saturation is understood to be the intensity of the respective hue, i.e. strong or pale. The strong tones are on the edge of the cylinder, the paler ones on the inside. The range is from 0 to 100.

The "brightness" corresponds, so to speak, to the height of the cylinder. It indicates whether there is white, black or gray in the middle of the cylinder diameter. The range also goes from 0 to 100.

The figure shows a cross-section of the IHS cylinder. The color point marked with a square has the coordinates H = 0, S = 0 and I = 0. The values ​​for H and S are shown in the circle, the size I on the bar next to it.

Source: copyshop-tips

The IHS color model is mainly used in remote sensing.

IHS transformation

The IHS transformation is used to improve color rendering. The data of spectral channels can be modified in other ways than by additive color mixing. The multispectral data is transformed into the IHS color space.


Engl. Acronym for I.maging I.nfrared R.adiometer, imaging infrared radiometer


From Greekeikōn '(pronounced eikona) for 'image'; The world's first commercial satellite with a spatial resolution of less than one meter in the panchromatic range and four meters in the multispectral range (three channels in the visible spectrum and one in the near infrared). Each picture shows an area of ​​at least 11 × 11 km with a resolution of up to 82 cm. Strips 11 km wide and many hundreds of km long can also be recorded.

The satellite orbits the earth at an altitude of 681 km 14 times a day with an orbit inclination of 98.1 °. It is thus in a sun-synchronous orbit and flies over the equator with each orbit at 10:30 a.m. local solar time.
The expected service life is 5-7 years. The satellite was initially owned and operated by Space Imaging, which was later taken over by Orbimage, which in turn was merged into the new GeoEye company. GeoEye has since merged with DigitalGlobe through takeover.

Goosenecks of the San Juan River, Utah

The San Juan River formed a series of tight loops in this section of the river, which resemble goosenecks. The river covers just 1.6 km as the crow flies over a length of 8 km.During the slow uplift of the rock, a canyon over 300 m deep was created, on the walls of which rock that is several million years old was exposed.

Ikonos from GeoEye took this picture on May 9, 2004.
The Goosenecks State Park offers spectacular views of the Goosenecks, the shape of which is known in geomorphology entrenched or incised meanders designated.

Source: NASA EarthObservatory / Goosenecks State Park

IKONOS-1 started on April 27, 1999, but was lost at the start. The structurally identical IKONOS-2 satellite was originally scheduled to launch in 2000. After this failure, IKONOS-2 was renamed IKONOS and finally launched into orbit on September 24, 1999. The launch took place in each case with an Athena-2 rocket from Vandenberg Air Force Base in California. IKONOS has been out of service since March 2015.

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Engl. Acronym for I.mproved L.in the B A.tmospheric S.pectrometer-II; Instrument on ADEOS-II for monitoring the stratospheric ozone content in high latitudes. It has not been operational since the satellite went down in 2003.

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Engl. For "picture"; in remote sensing the term for any kind of pictorial representation of an object with the help of electromagnetic energy, regardless of which wavelengths or which remote sensing technology was used for its recording and storage. An" image "can be analog (film) or digital.

Digital images are typically made up of pixels. A pixel is the smallest unit of an image and has a precisely defined position, so digital data technology uses discrete values. In contrast, an analog system uses a continuous series of values ​​to represent data.

Well-known examples include remote sensing data such as satellite data, scanner data, and photographs. An image is usually stored as a raster data set of binary or whole values ​​that represent the intensity of the reflected light, the radiated heat or other values ​​of the electromagnetic spectrum.
See also analog picture, digital picture

Image enhancement

Engl. For Image enhancement, look there


A satellite instrument that records and locates data from the earth and its atmosphere. The data from imagers are converted into images by computers and are therefore also referred to as imaging sensors.
Most imagers are passive sensors because they only pick up the reflected or emitted radiation from objects. Imagers are mainly used to obtain structural information of the variables that do not have continuous distributions. These are e.g. clouds or ground characteristics. The spatial resolution is generally better than 10 km. Many imagers have multiple wavelength channels with a typical bandwidth of 10 percent. A classic example of an imager is the ETM + on Landsat-7, whose spatial resolution is up to 15 m. From the images in the visible at 0.5 micrometers and in the near infrared, the spatial structure of the reflected radiation can be used to distinguish between fields, towns, mountains and rivers. Often, information from different channels is merged into color representations. In the case of passive systems, the terms Imaging radiometer or Scanning radiometer common.

Imagers that use radar systems are called active sensors because they emit microwaves and measure the radar echo reflected from the 'illuminated' object.

Imagery Intelligence (IMINT)

See picture explanation

Image spectometry

Remote sensing using instruments that often have hundreds of detectors that record narrowly within the electromagnetic spectrum. In principle, they register within the visible and near infrared section of the spectrum.


See Remote Sensing Methodology Institute

Indian Remote Sensing Satellite (IRS)


indirect transformation

Engl. indirect method of transformation, French method indirecte de la transformation; according to DIN 18716 a "method in which the gray values ​​for the pixels of the output image are determined by means of the inverse transformation equation in the input image".

Inertial Navigation System (INS)

Engl. For inertial navigation system, often used in combination with GPS.


Data that is combined and integrated in order to recognize something from it for a specific purpose, ie "meaningful" data. Data alone is not necessarily information, but rather a collection of facts from which information can be obtained with knowledge and transformation rules. However, both terms are often used synonymously.
In our sense, one can speak of information when an answer is given to a specific question that increases the level of understanding of the questioner and enables him to come closer to a certain goal. (Bartelme 2000)

According to De Lange (2020), the term information in computer science includes a message together with its meaning for the recipient.


Until the end of 2010, Astrium was an independent subsidiary with companies in Germany, France and the United Kingdom. One of Infoterra's main tasks was the commercial use of the data obtained from the TerraSAR-X radar satellite. Since January 2011 Infoterra has been operating together with SPOT Image under the name Astrium Geo-Information Services. The renaming and restructuring of the entire Airbus group led to the Geo-Intelligence portfolio within Airbus Defense and Space in 2014.

Infrared Space Observatory (ISO)

Scientific mission of the ESA for infrared astronomy with a space telescope for the infrared range of 2.4-240 µm. As a space observatory above the earth's atmosphere, ISO was able to observe celestial objects even at wavelengths that cannot be used from the earth due to the absorption of the atmosphere. ISO moved in a highly eccentric earth orbit with an orbital time of 24 hours. ISO was active from 1995 to 1998.

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Infrared image

Representation of an object through the pictorial representation of the infrared radiation emitted or reflected by the object.

The satellite's infrared (IR) sensor detects electromagnetic radiation in "thermal IR", at wavelengths between 10 and 12 micrometers (about 20 times longer than the wavelength of visible light). The intensity of the IR radiation reaching the satellite depends on the heat of the object that is emitting this radiation.

The most intense radiation comes from regions where the ground or ocean is warm. Such regions with intense emission are shown as dark gray tones. The IR radiation emitted by clouds in the upper atmosphere, where it is very cold, is much less intense. These regions of low intensity of the IR emission are shown in the IR photo as white and light gray.

So high clouds are white. Low clouds, with temperatures close to the surface, are often medium gray. The surface and oceans in the lower latitudes appear dark gray. On a sunny afternoon, the country heats up so much that it appears almost black.

Satellite image of Europe with METEOSAT-10 (April 26, 2020, 6 UTC)

An HRV image is created in this image with the help of the METEOSAT-10 satellite (High Resolution Visible) shown in the visible range of the spectrum combined with an infrared channel (range 10.8 µm). It shows the region of Central Europe in a high resolution of 1.5 km.

The letters indicate important cities. The numbers indicate the latitude and longitude circles, marked by the small black crosses.

The HRV channel covers the spectral range between 0.4 - 1.1 μm with a broadband radiometer. The HRV frequency band focuses on capturing the surface (clouds or cloud-free areas). Primarily convective structures (thunderstorm cells) should be recorded.

Since the HRV channel cannot reproduce any information at night due to the darkness, the HRV image is provided as a combined image. At night, IR channels cover the area that is not illuminated by the sun, so that you can see a smooth transition between the HRV and IR channels, especially during twilight times.

Source: DWD

Since IR is continuously emitted from the earth and clouds, it is possible to obtain IR satellite images even when the scene is not lit by the sun (and thus to construct image loops that extend over a full 24 hours). In contrast to this, satellite images in the visible range, which are based on the sunlight that is reflected towards the satellite, can only be obtained during the daylight hours.

Infrared satellite images provide a temperature image of the earth or cloud surface. When the sky is cloudless, the temperature of the earth's surface is shown. If there are clouds, the image provides the temperature of the cloud upper limit. What is below remains hidden in this picture.

Animated infrared satellite images of severe weather and tornado events

In April 2011, massive storm systems repeatedly swept across the southern United States, causing violent storms and tornadoes. This animation of the weather satellite GOES-East follows the development and the trajectory of the storm system from its formation over the Great Plains to reaching the western Atlantic in the period from April 14-17, 2011.
The underlying infrared images are colored using image processing in order to clarify the storm intensity. The darkest orange / red tones represent the highest, and therefore coldest, upper cloud limits. These areas are characterized by high levels of precipitation and high storm intensity. A second series of tornadoes occurred in the last third of April 2011, bringing the total number of the series to 160 and killing approximately 300 people.
Click on graphic to start the animation. Allow blocked content!

Source: NOAA

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Infrared film

Photographic film that is sensitized to the near infrared range of the electromagnetic spectrum, i.e. the range between 700 and 900 nm. Advantages of infrared films are better penetration of haze and the highlighting of bodies of water and wetlands. Furthermore, deciduous and coniferous trees can be clearly distinguished from one another and, especially with color infrared films, sick, dying or stressed vegetation is easier to see.
Infrared films are offered as

  • Black and white filmsthat are more or less sensitive in the infrared range. The visible light is completely or largely (red filter) switched off by camera filters. A typical effect is an extremely dark sky and a white coloration of the leaves (wood effect).
  • Color films (engl. color infrared film, CIR), the color rendering of which shows “wrong colors”, i.e. the colors shown do not correspond to the perception of the human eye, but the infrared areas are “translated” into those of visible light (so-called false color film). Such materials are used in aerial photographs, for example for mapping forest damage and in aerial archeology, and more rarely in the artistic field.

The color infrared film consists of three photographic layers sensitized for the primary colors green and red as well as for near infrared. For better visualization of the infrared component, the radiation in this wavelength range is shown in red, red light in green and green light in blue. The color infrared color film is used, among other things, as photogrammetric recording material for the interpretation of aerial photographs. Due to strong differences in albedo in the panchromatic and near infrared range of the electromagnetic spectrum, Color infrared aerial photographs especially the vegetation differentiated by different shades of red.

Infrared radiation (IR)

Engl. infrared radiation, French rayonnement infrarouge; according to DIN 18716 it is "optical and thermal radiation whose wavelength is greater than that of visible radiation". IR radiation is electromagnetic radiation with a wavelength ranging from approx. 0.7 to 1,000 micrometers (µm). This corresponds to a frequency range from 300 GHz to 400 THz.

This is above the visible and below the microwave radiation. Most of the energy emitted or reflected by the earth and its atmosphere is in the infrared range. Infrared radiation is generated almost entirely through intramolecular processes. Three-atom gases such as water vapor, carbon dioxide and ozone absorb infrared radiation and play an important role in the propagation of infrared radiation in the atmosphere.

The most important natural source of infrared radiation is the sun. Infrared radiation accounts for around 50 percent of the solar radiation that reaches the ground. In addition, the earth warmed up by solar radiation emits infrared radiation.

Heat balance of the earth

The infrared radiation emitted by the earth is absorbed by the natural and artificial gases contained in the atmosphere, such as water, carbon dioxide, ozone, methane and chlorofluorocarbons (CFC). This leads to an additional warming of the earth. This process is of crucial importance for the earth's heat balance and thus also for global warming (climate change).

Discovery by William Herschel in 1800

The German astronomer William Herschel first discovered or demonstrated infrared radiation in 1800. He split sunlight into its spectral parts with a prism and found an invisible but warming region beyond the red, i.e. longest-wave range of visible light Radiation. The ability to heat substances is still used today to detect infrared radiation.

"Warm" bodies emit infrared radiation

Every "warm" body (body temperature above absolute zero of approx. -273 ° C) emits infrared radiation. The amount of energy emitted and the wavelength distribution of the radiation depend on the temperature of the body. The warmer a body is, the more energy it emits in the form of IR radiation and the shorter the wavelength of the radiation.

Area of ​​IR within
of the electromagnetic spectrum

The infrared range of the spectrum covers the wavelength range from about 0.7 μm to 100 μm - more than 100 times as wide as the visible part! The infrared range can be divided into two categories based on its radiation properties - the reflected IR and the emitted or thermal IR.
The radiation in the reflected IR range is used for remote sensing purposes in a way that is very similar to the radiation in the visible range. The reflected IR covers wavelengths from around 0.7 μm to 3.0 μm. The thermal IR range is very different from the visible and reflected IR range, as this energy is essentially the radiation emitted from the earth's surface in the form of heat. Thermal IR includes wavelengths from around 3.0 μm to 100 μm.

Source: Natural Resources Canada

Infrared cameras and night vision devices

With the help of so-called infrared cameras, it is possible to make infrared radiation visible. Infrared cameras can be used, for example, for non-contact temperature measurement. However, its use as a so-called night vision device is better known. This takes advantage of the fact that every "warm" body emits infrared radiation.

Remote sensing instruments detect this radiation. The same applies to signals that are sent out by a satellite and reflected back to it.
The chemical surface properties and vegetation cover can be measured in the visible and near-infrared spectral range. In the mid-infrared, geological formations can be detected thanks to the absorption properties that depend on the silicate structures. In the far infrared, emissions from the atmosphere and the earth's surface provide information about air and soil temperatures as well as about water vapor and other trace components of the atmosphere. Since infrared data is based on temperature conditions rather than visible radiation, the data can be collected day and night.

In general, IR radiation is important for determining surface temperatures, for classifying clouds and for determining the atmospheric structure (stratification, temperature and concentration profiles).

Classification of the infrared spectral range

The terms and limits are not clearly defined as in the visible area and are partly determined by applications or special physical phenomena, which is why there are several different definitions.The International Commission on Illumination (CIE) and DIN propose the division into three bands: IR-A, IR-B and IR-C. The definition with the designations NIR, MIR and FIR follows ISO 20473.

Temperature to Vienna in K
Areas of application / comments
near infrared
  • Short-wave part of the NIR range, 780 nm limit due to the human sense of sight adapted to the solar spectrum.
  • Photographic infrared (ColorInfraRed, CIR) is 0.7 to 1.0 µm: photographic film can record this wave range.
  • Since healthy vegetation reflects very intensely in this area, so-called false-color infrared (air) images are preferably used for vegetation studies.
  • long wave part of the NIR range
  • the limitation is due to the water absorption at 1450 nm.
mid infrared
  • Range of thermal radiation at terrestrial temperatures
far infrared
  • The atmosphere absorbs strongly here, at the border to the microwave range the cosmic 3-Kelvin radiation is just visible.

In a compilation of different sources, infrared radiation is divided into:

  • near infrared (NIR for engl. near infrared): 0.7 - 1.4 µm
    • including photographic infrared, 0.7 - 1.0 µm: photographic film can record this wave range. Since healthy vegetation reflects very intensely in this area, so-called false-color infrared (air) images are preferably used for vegetation studies.
  • medium infrared mid IR)
  • short-wave IR (SWIR for engl. short wavelength IR): 1.4-3 µm
  • medium wave infrared (MWIR for engl. mid wavelength IR): 3 - 8 µm
  • thermal infrared (TIR for engl. thermal infrared): 8 μm to 13 μm
  • Thermal infrared (TIR for engl. thermal infrared): 5 μm to 50 μm
  • long wave IR (LWIR for engl. long wavelength IR): 8-15 µm
  • far infrared (FIR for engl. far infrared): 15-1000 µm

The designations are not always as clearly defined as for the visible area. As a consequence, attention must be paid to every radiometer and every publication what the designation of a spectral range means in terms of wavelength, wavelength range or measurement channel.


See SEOSAT-Ingenio


Engl. orbital inclination, French inclinaison(d'orbite); In the case of satellite orbits, denotes the angle by which the orbital plane of the satellite is inclined to the plane of the equator. The deviation of the plane of the orbit from the equatorial plane is counted in degrees from zero to 180 and denoted by 'i' in orbital equations. A geostationary orbit, in which a satellite orbits directly over the equator, has an orbit inclination of zero degrees. A polar orbit that guides a satellite over the North and South Poles has an orbit inclination of 90 degrees. An inclined orbit between zero and 90 degrees, on which a satellite runs in the same direction as the earth's rotation, is called a prograd. In a retrograde (retrograde) orbit, a satellite orbits the earth from east to west, i.e. counter to the earth's rotation. The inclination of the orbit is between 90 and 180 degrees.

The inclination is one of the 6 parameters, the so-called Kepler elements, which are necessary to describe a satellite orbit.

Inclination of a satellite orbit, here from GPS satellitesSource: kowoma


Port. Acronym for I.nstituto Nacional De P.esquisas E.spaciais; Brazilian space agency.

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Engl. Acronym for Interferometric S.ynthetic A.perture R.adar, German Radar interferometry; This active method uses phase differences that are detected when the signals coming back from the site are received with two antennas arranged next to each other. Object heights and thus digital terrain models can be derived from these phase differences using complex computational processes. When recording from an airplane, the distance between the antennas is a few decimeters. The use of this technique at satellite height requires greater distances. For this reason, a 60 m long boom was used for the Shuttle Radar Topography Mission to obtain interferometric SAR data from a large part of the earth's surface from a height of around 230 km. Since the area only has to be overflown once, this procedure is called single-pass interferometry.
With InSAR, the phase values ​​of corresponding pixels of two SAR images recorded at different times can also be compared in order to measure distance differences of a fraction of a wavelength (cm). The trajectories are slightly offset, with only one antenna recording each time. This repeat-pass method has the disadvantage that intermittent changes that affect the surface roughness, such as wind conditions or rainfall, affect the radar echo and falsify the calculated terrain heights.
Areas of application for radar interferometry are the detection of changes in the earth's surface in the mm and cm range (glaciers, volcanism, landslides, earthquakes, subsidence, etc.) as well as the measurement of ocean currents.

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Engl. Acronym forIndianGeostationary multi-function Satellite; Indian weather satellite system, additionally with communication and search and rescue tasks.

The latest INSAT-3D was launched in 2013 from Kourou. It is located at an altitude of 36,000 km above the equator at 82 ° E in a geostationary orbit. The three-axis stabilized satellite is equipped with a six-channel imaging system, an atmosphere measuring device with 19 channels (18 infrared and one channel in the visible range) and a system from the international search and rescue system COSPAS-SARSAT and supplies meteorological data such as weather images and data to distribute temperature, humidity and ozone content of the atmosphere.

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in situ (exploration, measurement)

Lat. For in the right place, engl. in-situ measurement, French mesure on the site; The term here refers to the acquisition of information about an object or an appearance with the help of an instrument which, in contrast to remote sensing, is in direct physical contact or in the immediate vicinity of the object or object being examined. Typical in-situ measurement methods are gas chromatography or mass spectroscopy.

In situ ceptometer for measurement
the leaf area index (LAI)

Measurement of reflectance with
a spectroradiometer

Positioning with a
Trimble GPS device

in situ information acquisition

The term refers to measurements made at the actual location of the observed object or material or in close contact with it.

The sensor can be in physical contact with the object to be measured or immersed in it (e.g. temperature sensor, ground salinity meter), 'on-site measurement'. Alternatively, the sensor can detect a certain type of energy that is reflected or radiated from the target object (e.g., spectrometry, macro photography, near photogrammetry), 'close up' or 'proximal exploration, measurement'.

Sources: Jensen 2009; CCRS

In (in situ) atmospheric research, almost all available aircraft have been used so far:

  • Tethered balloons (summit height 1000 m, load capacity a few 10 kg), with which one can perform excellent long-lasting meteorological and air-chemical investigations in the planetary boundary layer.
  • Kites and hang gliders (v a few m / s, summit height a few 1000 m, load capacity a few kg), which have already been used for the undisturbed measurement of the actinic radiation flux as a function of cloud cover and atmospheric aerosol load.
  • Airships (Zeppeline) (flight height some 1000 m, carrying capacity some 1000 kg, range some 1000 km), which only since recent times of atmospheric research are available
    stand. Their advantage is their variable speed, which makes Lagrange experiments possible. In these experiments, the airship is moved over the ground at exactly the same wind speed as the ambient air, so that the airship is always surrounded by the same air mass.
  • Airplanes (v a few 100 m / s, summit height <21 km), which are used for a variety of research purposes. Smaller aircraft are mostly used for local and regional environmental monitoring, but also for investigations into mesoscale dynamics, cloud formation, radiation balance and photochemistry in the lowest atmosphere. Larger and more powerful aircraft, on the other hand, are mainly used to investigate processes of regional and hemispherical importance, such as B. intercontinental and interhemispheric transport of air pollutants, photochemistry, microphysics, and transport of ozone in the upper troposphere and lower stratosphere or the formation of the ozone hole. Large aircraft also have the advantage that they can use many measuring devices and thus measure a large number of atmospheric parameters at the same time, which greatly improves the synergetic interpretation of the measurements.
    A particularly interesting application here is the use of regular commercial aircraft. As part of the CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) project, in-situ measurements of air-chemically and climatically relevant atmospheric trace substances are carried out on Lufthansa scheduled flights.
    The Russian GEOPHYSICA and the American ER-2, both of which were formerly used for espionage purposes, also represent a special class of research aircraft. Both aircraft are characterized by their high summit height (<21 km), with which the otherwise difficult to reach, but photochemically and climatically significant uppermost troposphere and lower stratosphere (15-21 km) can be reached. These aircraft were used, among other things, very successfully to investigate the chemical and dynamic processes that lead to the formation of the stratospheric ozone hole in the Antarctic spring, or to investigate the climatically important tropical upper troposphere and lower stratosphere.
  • Soaring unmanned drones (summit height 22 km, range up to 25,000 km, v = 100 m / s, typical load capacity <500 kg) used by NASA to research the dynamics and photochemistry of the difficult-to-reach subtropical and tropical tropopause regions and the lower stratosphere ( 15-22 km) have recently been used. In contrast to high-altitude research aircraft, drones have a much greater range and deployment time, which means that very remote areas over the Pacific or Antarctica can be easily and safely reached and examined.
  • Balloons: Small balloons (carrying capacity a few kg, summit height up to 35 km) are used by many weather services for regular meteorological monitoring of the lower and middle atmosphere. Large balloons (summit height up to 45 km, range up to 5 orbits the earth, load capacity <2 t, v some 10 m / s), however, are often used for researching the stratospheric ozone layer.
  • Rockets (carrying capacity <1t, summit height a few 100 km, flight time a few 10 minutes), which have so far mainly been used to investigate the atmosphere above the summit height of the balloons (> 45 km, i.e. in the upper stratosphere, mesosphere, thermosphere and exosphere) . Their advantage lies in their high possible peak height, which means that atmospheric regions that cannot be reached with other methods can be investigated.

In the Copernicus program, all data not obtained from space fall under the term “in-situ” data. They are collected by the individual member states and, in some cases, coordinated with one another. Special licenses and interfaces are agreed for the use of this data. The in-situ component is coordinated by the European Environment Agency (EEA) on behalf of the European Commission.

In-situ data for the Copernicus program comes from meteorological sensors, weather balloons, sea buoys and river level probes, or from aerial surveys with remote sensing instruments. Digital topographic maps and elevation models, orthophoto mosaics, protected area cadastre, the road network as well as thematic maps (forest, settlement structure, waterway network, etc.) and statistical maps (population distribution, etc.) are included in the in-situ data.

According to the European INSPIRE directive, these in situ data are gradually linked to the common European spatial data infrastructure.

In Germany, you can search for and use spatial data (geodata) from the federal, state and local authorities in the GDI-DE geoportal. Eurostat and the EEA offer additional, Europe-wide data free of charge. Examples of this are the in-situ data sets of the Digital Surface Model of Europe (EU-DEM) and the Lucas project from Eurostat.

The central contact point for information on the Copernicus in-situ data, the conditions of use and access options is the in-situ data website of the European Commission.


See global radiation


Engl. Acronym for Instructure for Spatial I.nformation in the E.uropean community; an initiative of the European Commission with the aim of providing geospatial services and data uniformly across Europe online via the Internet. In order to achieve this goal, Directive 2007/2 / EC of the European Parliament and of the Council for the creation of a spatial data infrastructure within the European Union came into force on May 15, 2007.

The implementation of the directive will facilitate the cross-border use of spatial data, for example on addresses, properties, transport networks or protected areas. In practice, INSPIRE requires a uniform description of the spatial data and its provision on the Internet, with services for search, visualization and download. The data itself must also be available in a uniform format.

Topics in Annexes I to III of the INSPIRE Directive



Source: European Parliament and the Council of the European Union [2007]

Geodata sets affected by INSPIRE are currently being identified at the federal, state and local levels on the basis of the subject areas and made generally usable according to the specified, uniform technical standards.

All geodata that can be used via INSPIRE web services are also made available within Germany via the Internet as part of the Germany geodata infrastructure. INSPIRE thus not only benefits Europe, but is also an important step towards networking the administration in Germany. Both science and economy as well as the citizens benefit from this.

In addition, Europe is making important and coordinated contributions to the Copernicus and INSPIRE joint activities Systems global earth observation system (GEOSS).

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Remote Sensing Technology Institute (IMF)

The Remote Sensing Technology Institute, which is part of the DLR's Earth Observation Center (EOC), and the German Remote Sensing Data Center (DFD) form the competence center for earth observation in Germany. It is represented at the DLR sites in Oberpfaffenhofen near Munich, Berlin-Adlershof and Neustrelitz in Mecklenburg-Western Pomerania. The IMF conducts research and development in the field of remote sensing technologies. Algorithms, methods and processing systems (so-called processors) for the extraction of geographic information from remote sensing data are being developed. The IMF thus contributes to the optimal use of modern remote sensing sensors for current scientific and social issues. The processors will be integrated into the payload ground segments of the DFD and the industry for national and international earth observation missions.

The IMF has three technological priorities:

Scientific and experimental procedures as well as operational processors are developed. For national, European and international missions, these processors are integrated into the reception and processing chains of the DFD or industrial partners. The IMF operates the EOC's airborne optical sensor suite. The calibration and spectrometry laboratories of the IMF provide the basis for the best possible use of remote sensing data.

Finally, with its remote sensing expertise, the institute contributes to the conception of new sensor systems and earth observation missions.

A particular concern is the training of young scientists. In the DLR_School_Lab, schoolchildren are introduced to topics related to earth observation, bachelor and master theses can be carried out "hands-on" in current projects and attractive scientific questions can be dealt with in doctoral theses.IMF scientists teach at universities, the director of the institute heads a chair at the Technical University of Munich. The institute is certified according to ISO9001: 2008.

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Often syn. to sensor; an instrument in the field of remote sensing encompasses the entire system including optics and data readout.
An instrument collects information about an object or a phenomenon within the current field of view of the sensor system without being in direct contact with it. It is located on a suborbital or on a satellite platform.

Measurements using remote sensing instruments

A remote sensing instrument registers information about an object or a phenomenon without being in direct contact with it, depending on the opening angle of the sensor in the observed surface element (instantaneous-field-of-view, IFOV).

The sensor is located on a suborbital platform or on a satellite.

An instrument or sensor usually consists of optics, detectors, and electronics that pick up radiation and convert it into other forms. This can be a specific pattern (image, profile, etc.), a warning, a control signal or another signal.

Sources: Jensen 2009; Kramer 2002

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Engl. Acronym for International Gamma-R.ay A.strophysics L.aboratory; ESA's gamma-ray observatory for tracking down massive events in the universe. It will study explosions, radiation, the formation of elements, black holes and other exotic objects during the mission, which is expected to last 5 years. Integral is the first space observatory that can simultaneously observe objects in the range of gamma rays, X-rays and visible light. Preferred targets for observation are violent explosions, so-called gamma-ray bursts, powerful phenomena such as supernova explosions and areas of the universe in which black holes are suspected.

The payload on Integral consists of four instruments. An imaging sensor provides the sharpest gamma ray images to date. A spectrometer determines the energy of the gamma rays very precisely. Two other instruments help identify the sources of gamma rays, they are an X-ray monitor and an optical camera. To reduce costs, the payload was placed on a service module that is identical to that of XMM-Newton.

Integral was launched with a Proton rocket, Russia's largest launcher, on October 17, 2002 from the Baikonur Cosmodrome (Kazakhstan). The powerful rocket was required to propel the heavy spacecraft into its elliptical and unusually high Earth orbit, which is necessary for the scientific success of the mission.

The closest point to the earth is 9,000 km (increasing to 13,000 km after 5 years), the furthest at 153,000 km. Like the shape of the orbit, the inclination of the orbit changes significantly over the five years. The high and eccentric orbit with an orbit time of 72 hours enables long and uninterrupted observations with an almost constant background outside the earth's proton and electron belt, because the satellite spends most of its time on its orbit beyond 60,000 km.

Integral is a decidedly international mission in which all member states of the ESA plus the USA, Russia, the Czech Republic and Poland are involved.
The successful mission has been extended several times, currently until December 31, 2022.

Left: Test phase for the 5 m high and 4 t heavy satellite Integral in the vacuum chamber of the European Space Research and Technology Center in Noordwijk, NL, before launch with a Russian Proton rocket.

Right: Integral on its mission to detect gamma rays outside the Earth's atmosphere. Gamma rays are more powerful than the X-rays used for medical purposes. Fortunately, the earth's atmosphere acts as a shield against this dangerous cosmic radiation. At the same time, this means that gamma rays of cosmic origin can only be detected with the help of satellites.

Source: ESA

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(The) Integrated Global Atmospheric Chemistry Observations (IGACO)

International program for long-term observation of the chemical composition of the atmosphere with the help of integrated, ground- and space-based measurements. The data collected within the framework of IGOS should be made available to the largest possible group of users.

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Integrated Multi-satellite Retrievals for GPM (IMERG)

German about Integrated multi-satellite data retrieval for GPM; an integrated precipitation data product from NASA, created from satellite data from the Global Precipitation Measurement (GPM) program and data from precipitation measuring stations. For this purpose, a special algorithm was developed, with the help of which the data for the entire globe can be compared, merged and interpolated in real time.

Historically and in the foreseeable future, passive microwave sensors (PMW) provide the lion's share of the relatively accurate satellite-based precipitation estimates. These are only available from platforms in low earth orbits (LEO). With the help of IMERG it is possible to compensate for the limited data acquisition from individual LEO satellites by including as many LEO satellites as possible in the system. Then the data from infrared sensors on geosynchronous satellites is added. Finally, data from precipitation stations are used to ensure the important regionalization and to correct errors in the satellite estimates.

The system processes the data several times for each observation period, initially in order to obtain a quick overview estimate. Subsequent runs with further data input then always give better results, until a version that can also be used for science is available in a last step.

The GPM core satellite of the GPM mission serves - like the TRMM satellite before - for calibration and evaluation for all PMW and IR precipitation products that are integrated in IMERG.

Click on graphic for YouTube animation

France's Flooding Rains Examined by NASA’s IMERG

Eastern France experienced unusually heavy rainfall in the month of 2018, and NASA satellite data helped identify the location of the greatest rainfall.

The French national weather agency has issued orange flood warnings across much of France. Frequent rains have resulted in widespread flooding along the Seine that flows through Paris. Flooding in Paris was similar to that of the June 2016 flood, when the water level reached more than 6 meters.

The IMERG data on the amount of rain, which were added up in the period from January 17 to 25, 2018, showed the highest amounts of precipitation along the Seine east of Paris. These IMERG estimates suggest that the area where the Seine flows towards Paris experienced total rainfall of more than 180 mm.Source: NASA

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