What’s Happening

In 2025, the European Space Agency (ESA) and the ITU signed a joint statement, first revealed at Mobile World Congress, committing to collaboration on radio spectrum sustainability. This includes shared efforts in defining best practices for interference management, data sharing about spectrum usage, responsible use of spectrum by satellite systems, and protections against harmful interference. ESA CSC

Additionally, this cooperation is part of a broader ITU effort to monitor and mitigate spectrum congestion and spectral pollution. Given the increasing density of NGSOs and SmallSats, ESA and ITU are working together on studies and guidance for administrations and operators to ensure spectrum resources remain usable and interference risks are minimized. These efforts do not yet have binding treaty force but are expected to inform national implementation and future ITU-R study group outputs.

Why It Matters

While the joint statement is not itself a regulation, it signals where regulatory pressure is increasing. SmallSat operators will face greater expectations for demonstrating spectrum hygiene, i.e., showing that signals stay within intended bands, that spurious emissions are controlled, and that spectrum sharing does not degrade services. Moreover, administrations may start to adopt ESA-ITU best practices into their domestic regulations, leading to variation but also increasing compliance demands in multiple jurisdictions.

For CubeSat projects, this means spectrum planning must include more rigorous technical guardbanding, filter design, emission mask verification, and possibly more conservative link margins. Also, operators should anticipate that administrations may require spectrum usage reporting, monitoring of interference events, and possibly remediation obligations. In short, the regulatory “soft law” is shifting toward requiring proactivity in spectrum management, not just reactive compliance.

Implications for SmallSat / CubeSat Operators

Operators will need to embed spectrum sustainability into mission design. That means selecting components and RF architectures with low out-of-band emissions, diligent calibration of transmit power, and more careful anticipation of cumulative interference from multiple satellites. Testing and documentation of spectral masks and spurious emissions will become more important. There is also likely to be pressure on greater coordination or sharing of spectrum usage data (e.g., telemetry of RF usage) with administrations or third parties.

Another implication is that mission risk assessments and compliance reports may need to include spectrum sustainability metrics: how much interference margin exists, how likely your transmissions are to cause interference with other services, and whether your signal will degrade over time or across thermal/environmental stress.

Finally, as administrations incorporate ESA-ITU guidelines into national licensing or spectrum oversight, CubeSat operators operating in multiple countries will need to manage compliance across different jurisdictions that may have different thresholds or interpretations of these best practices.

Deep Dive Scenarios

Scenario: A multi-country CubeSat provider planning global coverage
If operating in Europe, Africa, or Asia, the provider must ensure its emissions and filter design match the best practices expected by both ESA and national telecommunications authorities, possibly meaning tighter spectral masks than prior designs. Also, the operator may need to report signal usage, conduct regular spectral scans, or provide evidence of non-interference.

Scenario: Academic institution testing new RF payloads
For a university CubeSat with a high-power experimental transmitter, it may now be harder to obtain licenses in jurisdictions that have adopted ESA-ITU guidance, unless the institution can demonstrate emission control and spectrum sustainability. Early engagement with national regulatory bodies about their expectations will be crucial.

Checklist for SmallSat / CubeSat Operators

• Evaluate RF front-end and filter designs to ensure compliance with recommended emission masks.
• Incorporate spectrum sustainability metrics in mission planning: interference margin, spurious emissions, spectral leakage.
• Maintain test reports and verification data for spectral emissions under different environmental conditions.
• Engage with administrations early to understand national adoption of ESA-ITU guidelines.
• Put in place spectrum usage monitoring and logging capabilities.