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Earth observation

Spectrum for Earth observations – A global challenge for ITU members

Philippe Tristant is Frequency Manager at Meteo France and EUMETNET. From 2005 to 2010, he chaired the Steering Group on Radio Frequency Coordination of the World Meteorological Organization (WMO) Commission for Basic systems and is still a member of this group.

Information about climate, climate change, weather, precipitation, pollution and disasters is critically important for the global community. Earth observation activities make it possible to provide this information, which is required for daily and long-term weather forecasts, studies of climate change, protection of the environment, economic development, and safety of life and property.

Earth observation applications are totally dependent on radio frequencies to measure and collect the data upon which analyses, predictions and warnings are based, and to disseminate this information to governments, policy-makers, disaster management organizations, commercial interests and the general public.

These applications are spread over the whole spectrum – from a few kHz to several hundred GHz – and make use of a large variety of radio technologies and services provided from the ground, in situ or from space. It is therefore not surprising to see agenda items related to Earth observation at all world radiocommunication conferences (WRCs).

Protecting “passive bands”

Among the many applications, the case of “passive bands” used for satellite remote sensing under the Earth exploration satellite service needs to be highlighted. The impressive progress made in recent years in weather and climate analysis and forecasts, including warnings for the dangerous weather phenomena (heavy rain, storms, cyclones) that affect all populations and economies, is to a great extent attributable to these “passive” observations and their incorporation in numerical models.

These applications, essential for meteorology and climate monitoring, involve the measurement of natural radiation at very low power levels and in frequency bands uniquely determined by physical properties (for example, molecular resonance). Low levels of interference (from in-band or out-of-band interferers) can degrade the effectiveness of passive sensors. Compatibility with the Earth exploration satellite service (passive) hence needs to be very carefully studied to avoid any risk of harmful interference that would render the corresponding bands unusable and definitively lost for the Earth observation community.

Earth Observations at WRC-12

A number of items on the WRC-12 agenda are of direct interest to the Earth observation and meteorological communities. In particular, the conference will consider:


  • agenda item 1.6 – identifying relevant bands for satellite remote passive sensing between 275 and 3000 GHz;

  • agenda item 1.8 – potential out-of-band emission limits for the fixed service in order to ensure protection of the 86-92 GHz Earth exploration satellite service (passive) band;

  • agenda item 1.15 – allocation of parts of the spectrum between 3 and 50 MHz for oceanographic radars;

  • agenda item 1.16 – allocation of spectrum below 20 kHz for lightning detection applications;

  • agenda item 1.24 – possible extension of the existing primary allocation to the meteorological satellite service (MetSat) in the band 7 750-7 850 MHz to the band 7 850–7 900 MHz.


Raising awareness of the importance of Earth observation

WRC-12 will also consider agenda item 8.1.1c, which aims to enhance recognition of the importance of Earth observations and to increase administrations’ knowledge and understanding of the use and benefits of related applications. This item stems from Resolution 673 (WRC-07), and is not requesting any new allocation for, or protection to, services related to Earth observation.

For years, most members of the ITU Radiocommunication Sector (ITU-R) erroneously considered Earth observation radio applications to be unimportant, seeing Earth observations as being of scientific interest to just a few countries.

A lot of work has been performed in ITU-R since WRC-07 to respond to Resolution 673. Two Recommendations have been adopted: ITU-R RS.1859 on “Use of remote sensing systems for data collection to be used in the event of natural disasters and similar emergencies”; and ITU-R RS.1883 on “Use of remote sensing systems in the study of climate change and the effects thereof”. And two reports have been published: the ITU-D report on “Utilization of ICT for disaster management, resources and active and passive space-based sensing systems as they apply to disaster and emergency relief situations”; and Report ITU-R RS.2178 on “The essential role and global importance of radio-spectrum use for Earth observations and for related applications”.

These important reference documents show that:

  • Earth observation data are shared among all countries – generally at no cost – and directly benefit every citizen.

  • The societal value of Earth observations outweighs the economic value of the radio-spectrum being sought.

  • Most of this societal value relates to preventing mass loss of life or threats to socio-political stability and security.


Regional interest in Earth observation activities

Chart 1

All regions now recognize the need to maintain and improve Earth observation capabilities. Europe has been at the forefront of these activities with its Global Monitoring for Environment and Security programme. Europe also launched the initiative that resulted in the Group on Earth Observation (GEO), an intergovernmental organization that to date comprises 87 countries worldwide and more than 60 international organizations.

GEO is now leading a worldwide effort to build a Global Earth Observation System of Systems (GEOSS) to provide comprehensive and coordinated observations that will be transformed into vital information for the benefit of all within 9 different societal benefits (see chart).

GEO recognizes radio frequency protection as being critically important, in particular in frequency bands where passive sensing measurements are performed. This was clearly stated in the Cape Town Declaration issued by the Earth Observation Ministerial Summit in November 2007.

Because of their complexity, the processes and phenomena that occur on Earth need to be observed continuously and over an extended time-frame. Also, the increasingly sophisticated observation instruments involve research and development efforts usually over a very long period of time. Earth observation activities therefore require the long-term availability and protection of radio frequencies to safeguard and secure these essential activities.

The Earth observation and meteorological communities sincerely hope that all ITU-R members will understand the use, benefits and requirements of Earth observation activities, and will give due consideration to proposals under WRC-12 agenda item 8.1.1c to improve recognition of the essential role and global importance of Earth observation radiocommunication applications.

Taking the long view

A number of new challenges in frequency management will obviously be considered at future WRCs, and one should hope that an understanding of the importance of Earth observation will not only prevail during the discussions among ITU-R members at WRC-12, but will also continue beyond that conference.

The frequency bands allocated to, and used for, Earth observation are to a great extent shared with other radiocommunication services. As far as they go, the current conditions are satisfactory and should remain in place. The protection of purely “passive bands” covered by No. 5.340 of the Radio Regulations will require an increasing level of care and consideration. Clearly, future trends will probably lead to adding more and more new radio services in a spectrum that is already congested. This is bound to lead to an increase in cases of adjacent band potential interference and will justify the need to duly regulate unwanted emissions in the “passive bands”.

The 1 400-1 427 MHz band is an example of a case in point. WRC-07 considered its protection from unwanted emissions produced by a large number of radio services but failed to agree on regulating the unwanted emissions – only recommended levels were proposed. In 2009, the European Space Agency (ESA) launched the Soil Moisture and Ocean Salinity (SMOS) satellite with a single instrument operating in this frequency band, and found that operations were experiencing unexpectedly high levels of interference (see map). If the situation in this 1 400–1 427 MHz frequency band does not improve in the future, the possibility of using the band will be definitively lost for the Earth observation community, and with it the corresponding data that cannot be retrieved in other frequency bands.

More generally, avoiding the loss of essential data is the rationale for the strong involvement of the Earth observation and meteorological communities in the frequency management process. The global challenge for ITU members in the future is summed up in the simple ITU statement made at Cancún in December 2010 during the United Nations Climate Change Conference: “No spectrum, no global observations!”



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Updated: 2018-09-24