Explain how 'unintended' satellite emissions differ from licensed transmissions, and why current spectrum regulation may fail to protect radio astronomy.

A recent study under the SNIFFLES monitoring programme, published in Monthly Notices of the Royal Astronomical Society, tracked Starlink, OneWeb and China's Guowang satellites for about 376 hours. It found some signals 100 billion times brighter than typical cosmic sources [1]. Its main lesson is that licensing what a satellite transmits does not control everything it emits.

How unintended emissions differ from licensed transmissions

• Intended (licensed): deliberate transmissions in assigned bands, such as Starlink's direct-to-cell signals [1]. Their frequency and timing are known, so they can be coordinated and filtered.
• Unwanted: by-products of the transmitter itself, such as harmonics at multiples of the transmission frequency [1].
• Unintended: stray radiation from onboard electronics like power converters and computers, not from the antenna [1]. These parts have no assigned frequency, so no licence condition covers them.
• Design trait, not a fault: one Starlink version showed emissions in about 77% of observations [1]. Once a satellite is launched, this cannot be fixed.

Why current spectrum regulation may fail

• Rules built around transmitters: protection depends on ITU interference thresholds (Rec. ITU-R RA.769) and spectrum masks. Yet signals exceed these thresholds by many orders of magnitude even when transmitters comply with their masks [2].
• Rules written for single systems: the regime was built on single-system assumptions. Thousands of LEO satellites now create aggregate interference [2].
• Science cannot change frequency: OneWeb's 1,613.19 MHz emission overlaps the hydroxyl line used to study star-forming gas [1]. A spectral line cannot be moved, and signals that overload the receiver cannot be filtered out by software.
• Remote sites no longer shield: radio-quiet zones keep out noise from the ground, but LEO satellites pass overhead. Australia's remote Mopra and ATCA telescopes still recorded them [1].
• Jurisdiction gap: satellites in space fall under other states' regulators [2]. Constellations licensed by different states [1] pass over every observatory, including India's GMRT.
• Soft law only: the UN COPUOS Dark and Quiet Skies process has produced recommendations, not binding obligations [3].

Unintended emissions are a hardware-level externality that frequency-based licences were never designed to catch. IN-SPACe and DoT could require pre-launch emission testing as part of satellite authorisation. India could also run SNIFFLES-style monitoring at GMRT and press for binding hardware emission limits at WRC-27 and COPUOS, building on the Dark and Quiet Skies recommendations [3]. Satellite connectivity can then grow while the radio sky stays a shared scientific commons.