Minimize Glossary

A list of terms and acronyms in use on the Earth Watching website.


Advanced Along-Track Scanning Radiometer, AATSR, is an instrument carried aboard the Envisat satellite. The instrument has a wide lens, allowing it to perform accurate measurements of the atmosphere, and views a location from two different angles. The primary objective of AATSR was to take measurements of the Sea Surface Temperature, but could also be used for a wide variety of environmental observations.


Advanced Synthetic Aperture Radar, ASAR, is an instrument carried aboard the Envisat satellite. It provides a more advanced form of sensing than the standard SAR instrument, allowing it to operate in a wider variety of modes.

Change Detection

An application of Remote Sensing, Change Detection utilises satellite data over a period of time to track changes to a location or object. An example of Change Detection is tracking Deforestation.


ESA's flagship Earth observation satellite, Envisat was launched in 2002. The largest Earth observation satellite yet, Envisat carried ten instruments to perform a variety of observations of the Earth's environment. This was accomplished successfully until contact was lost with the satellite in April 2012.
Envisat on Earthnet Online


The European Remote Sensing satellites 1 and 2 were launched in 1991 and 1995 respectively. The two craft observed the Earth with four instruments on ERS-1 and five on ERS-2 until their retirement in 2000 and 2011.
ERS on Earthnet Online


The European Space Agency, ESA is a multi-national organisation tasked with coordinating Europe's space activities and conducting research into new technologies derived from those activities.
ESA website

Interferometry / InSAR

SAR Interferometry (InSAR) is an application of remote sensing. Interferometry is the process of combining waves, most commonly electromagnetic, to study and compare the combined result. InSAR uses the same principle with SAR images, combining two or more images to study the result. This is used for, among others, topography and change detection.

Landsat 5

A NASA Earth-observing satellite, Landsat 5 was launched in 1984. Equipped with two sensors, Landsat 5 was designed to obtain imagery of the Earth's surface.
Landsat imagery is made available to the Earth Watching website through ESA's Third Party Missions, with agreements in place between NASA and ESA.
Landsat website


Medium Resolution Imaging Spectrometer, MERIS, is an instrument carried aboard the Envisat satellite. The instrument is composed of five cameras which acquire data that is then used in concert to create 2D images. While MERIS' primary objective was ocean observation, it was also used for atmospheric and land observations.


Multi-temporal imaging is an application of Remote Sensing that involves taking two or more satellite images and combining them. This process thus highlights changes between the images over different dates.

Polarimetry / PolInSAR

Polarimetry is a method of measuring and interpreting polarised waves, such as electromagnetic or visible light. This enables analysis of an object or location. PolInSAR is an application of Remote Sensing that builds on SAR Interferometry, combining SAR images to study the result. It is possible to create 3D images from this data.

Remote Sensing

In this context, satellite remote sensing is the process of obtaining information about a location from a satellite in orbit. It is therefore remote because the sensor at no time is in physical contact with the location in question.


Synthetic Aperture Radar, SAR, is a form of Remote Sensing. SAR instruments use an antenna to target a location with pulses of radio waves. The echoes that are received from these radio waves can then be used to map the topography of an area. Due to this method, SAR instruments can acquire data of a location regardless of the weather or time of day.

Thematic Mapper

The Thematic Mapper (TM) is an instrument carried aboard the Landsat 5 satellite. It is capable of obtaining multi-spectral imagery in visible and infrared bands. This instrument was switched-off in May 2012.