Radio Regulations

Source: the Radio Regulations published by the International Telecommunication Union (ITU).

1.19

WRC-27 · Agenda item 1.19

to consider possible primary allocations in all Regions to the Earth exploration-satellite service (passive) in the frequency bands 4 200-4 400 MHz and 8 400-8 500 MHz, in accordance with Resolution 674 (WRC-23)

Current WP 7C Res. 674 (WRC-23) › 4200–4400 MHz 8400–8500 MHz

Shared frequency bands

Bands this agenda item addresses jointly with other WRC-27 items (CPM Report Table 1). Click a band to open its spectrum page.

8450–8500 MHz

Also studied under: AI 1.15

At a glance Summary & background Regulatory Studies

At a glance Beta

Frequency band

4200–4400 MHz 8400–8500 MHz

Governing resolution

Res. 674 (WRC-23)

Responsible group WP 7C

Agenda-item type Technical

The band and its sensitive neighbours

MOBILE

RADIONAVIGATION

FIXED

SPACE RESEARCH

Blocks group a service with its direction and mode variants; the table names each allocation as the Radio Regulations name it.

Current framework

Services in this band

AERONAUTICAL MOBILE (R)	Primary
Aeronautical radionavigation	Primary
FIXED	Primary
MOBILE except aeronautical mobile	Primary
Space research (space-to-Earth)	Primary

What's being studied — points to watch

No protection claimed

The envisaged passive allocation would come without protection from existing services in the bands or their neighbours (Res. 674) — recognition of the sensing, not a constraint on incumbents.

Radio altimeter safety

4200–4400 MHz carries aircraft radio altimeters, a safety-of-life system; the studies must confirm they remain unaffected.

Deep-space reception

8400–8500 MHz carries space research, including weak deep-space downlinks at 8400–8450 MHz; coexistence must leave them untouched.

Why these bands

Sea-surface brightness temperature is frequency-sensitive, so complementary SST channels must sit within 4–9 GHz (Res. 674) — the choice is set by physics, not convenience.

Preparation timeline

Dec 2023 WRC-23 agenda adopted

Dec 2023 WRC-23 agenda adopted
Dec 2023 CPM 27-1 studies allocated

Dec 2023 CPM 27-1 studies allocated
ITU-R studies 2026

ITU-R studies 2026
ITU-R studies 2027

ITU-R studies 2027
5–15 Apr 2027 CPM 27-2 final report

5–15 Apr 2027 CPM 27-2 final report
RTO Prep meetings 2027

RTO Prep meetings 2027
11–15 Oct 2027 RA-27

11–15 Oct 2027 RA-27
18 Oct–12 Nov 2027 WRC-27

18 Oct–12 Nov 2027 WRC-27

Dec 2023 WRC-23 agenda adopted
Dec 2023 CPM 27-1 studies allocated
ITU-R studies 2026
ITU-R studies 2027
5–15 Apr 2027 CPM 27-2 final report
RTO Prep meetings 2027
11–15 Oct 2027 RA-27
18 Oct–12 Nov 2027 WRC-27

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Source: ITU Radio Regulations, editions of 2008, 2012, 2016, 2020 and 2024. The English, French and Spanish texts are each taken from the official edition in that language, not translated from one another. Sources and citation.