Page 32 - Turning digital technology innovation into climate action

Turning digital technology innovation into climate action

Figure 7: Global Observing System (GOS)

Box 3: Space-based Earth monitoring systems
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Spaceborne Earth monitoring & observation systems and their crucial impacts

The ITU Radiocommunication Sector (ITU–R) Study Group 7 deals with science services.
These include the Earth exploration-satellite and meteorological-satellite services with
systems for passive and active spaceborne remote sensing, which enable scientists to obtain
important data about the Earth and its atmosphere. The systems used for these purposes
have far-reaching effects for everyone on the planet. The data are being used to study and
monitor climate change, assist meteorologists in predicting the weather, and monitor a
wide variety of natural hazards.
Spaceborne active sensors are instruments that help in this regard by obtaining data
through the transmission and reception of radio waves. They are basically radar systems
on spaceborne platforms. There are five types of active sensors, each having its own specific
purpose. The synthetic aperture radar (SAR) is used to obtain topographical data of the
Earth’s surface. Altimeters are used to measure the precise height of the ocean surface.
Scatterometers are primarily used to determine the wind direction and speed at the ocean
surface. Precipitation radars are used to determine rainfall rates and the three-dimensional
structure of the rainfall. And cloud profile radars are used to measure cloud cover and
structure over the Earth’s surface.

Spaceborne passive sensors are very sensitive receivers known as radiometers that
measure the electromagnetic energy emitted and scattered by the Earth, and the chemical
constituents in its atmosphere. These very sensitive receivers require protection from
radio-frequency interference in order to be able to make their requisite measurements.
Passive remote sensing instruments operating on Earth observation satellites are looking
down at the Earth’s surface and atmosphere, and are susceptible to interference from

5 ITU News Magazine. ‘Monitoring Our Changing Planet.’ International Telecommunication Union (ITU), 2019, www .itu
.int/ en/ itunews/ Documents/ 2019/ 2019 -01/ 2019 _ITUNews01 -en .pdf.

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