Europe approves radio astronomy protection rules over Iridium and US objections

Europe's Electronic Communications Committee (ECC) has approved a Recommendation on licensing mobile satellite service systems that interfere with radio astronomy, rejecting formal requests from Iridium and the US Department of State to cancel the draft. Romania was the only administration to oppose publication on the record.

The approval came despite claims from the operator and Washington that no current evidence of a problem exists. Germany countered at the meeting with new measurements showing Iridium's daytime emissions still exceed protection limits — by an average of 3 dB for one orbital group of satellites and 8 dB for another.

What does the new Recommendation say?

The ECC, part of the European technical agency CEPT, met earlier this month and adopted guidance for national regulators authorising or renewing licences for mobile satellite service (MSS) systems transmitting to the ground in the 1613.8–1626.5 MHz range of the L-band.

The text urges regulators to consider licence provisions that let them limit which satellites user terminals may communicate with. Regulators "may also consider" restricting downlinks to 1621.35–1626.5 MHz, further from the protected band, and requiring "a radioastronomy protection mode, or equivalent mitigation". Where non-compliance "cannot be resolved at national level", CEPT administrations should jointly assess it and "discuss a collective action".

Why does the band matter?

Iridium operates 66 low Earth orbit satellites providing voice and data to ships, aircraft, governments and emergency services, transmitting at frequencies around 1618–1626 MHz. Just below sits 1610.6–1613.8 MHz, reserved for radio astronomy, where telescopes observe very low emissions from hydroxyl molecules around giant and supergiant stars. Even small amounts of leaking energy can ruin the data. ITU Radio Regulations (footnote 5.372) prohibit MSS stations from causing harmful interference in the band.

The problem is long-standing. In 1998, Iridium signed an agreement with the European Science Foundation's Committee on Radio Astronomy Frequencies committing to meet international protection levels by 2006. Those levels were never met; Germany's Leeheim monitoring station recorded exceedances of up to 26 dB. Iridium's second-generation constellation, launched from 2017, included a "radio astronomy protection mode", which the company later dropped, citing conflicts with safety-of-life traffic. At the request of the Czech Republic, France, Germany, Liechtenstein and Switzerland, CEPT opened a work item in February 2025, handled by satellite project team FM44.

What are the opponents' arguments?

Iridium said it "supports the protection of radio astronomy" but argued the Recommendation "should not be approved, revised, or retained as a CEPT deliverable". Its case rests on a single, resolved German matter concerning the Effelsberg telescope and "outdated measurement results" from Leeheim: "No current measurements were presented."

It called its Effelsberg mitigation "targeted and dynamic" — lower channels restricted, users moved to higher frequencies only when particular satellites approach the site — and warned a blanket Europe-wide limit would degrade service "well beyond what is needed". Squeezing traffic into fewer channels could raise transmit power and increase leakage into the protected band.

The US State Department took a similar line, saying the draft "appears to go beyond general RAS-protection guidance by identifying a single U.S.-licensed MSS operator" and that the record does not show "a current CEPT-wide harmful-interference problem". It pointed to the US model of coordination with the National Science Foundation, warned that limiting Iridium to 1621.35–1626.5 MHz would reduce capacity and resilience for maritime and aeronautical safety communications, and noted Iridium "has filing priority at the ITU in the band at issue". The submission followed Iridium's April FCC filing claiming the process "would unfairly target Iridium, a US-licensed operator" — an "overstatement", according to Globalstar, the band's only other operator, which holds a French ITU filing and is unaffected.

Did Germany's data change minds?

Germany answered the "no current measurements" claim with an information paper summarising the first two of this year's three Leeheim campaigns, run by regulator BNetzA in March–April and July–August 2026 using "exactly the procedures defined within ECC".

"The situation has not changed since 2024 after Iridium introduced some amendments," the paper said. Night-time levels are "just within acceptable limits". The highest daytime peak was 4,000 Jansky from a single satellite in August, matching the highest 2025 reading.

Notably, the data also undermines the proposed fix: in recent measurements, Iridium's visible downlinks "only occupied frequencies above 1621.35 MHz" and the protection mode was in use — yet daytime emissions still exceeded protection levels.

What happens next?

The final text has softened through several edits; a June draft would have made the frequency limit and protection mode mandatory. The Recommendation itself concedes the situation "has improved following improvements by the concerned satellite operator in 2024". The Netherlands successfully pushed for language "neutral with respect to satellite systems".

Ownership changes add uncertainty: Rocket Lab is set to acquire Iridium, while Amazon is buying Globalstar, including its European L-band licences. How the new owners handle the no-interference rule remains an open question.