What is an orbital slot?
An orbital slot is a designated position on the geostationary arc — the equatorial circle at 35,786 km altitude where satellites appear stationary relative to Earth. Each slot is defined by its longitude (e.g., 19.2°E for the Astra satellite cluster over Europe) and is associated with specific frequency band allocations. Because geostationary orbit is a unique physical resource, the number of usable slots in prime coverage positions is finite — particularly over densely populated regions like North America, Europe, and Asia-Pacific where demand is highest.
ITU allocation and national filing
Orbital slots are managed internationally by the ITU Radio Regulations. National administrations file for slots on behalf of their licensed operators and coordinate with other administrations to avoid interference. Priority is established by filing date: the administration that completed coordination first has regulatory priority (the 'first come, first served' principle). This has motivated some nations — particularly developing countries with equatorial positions — to file for many more slots than they can actually use, creating a 'paper satellite' filing backlog that the ITU has attempted to address with milestone requirements.
Commercial value
Prime GEO orbital slots have significant commercial value — an operator with a strategic slot (e.g., 28.2°E serving the UK/Ireland DTH market) has a competitive advantage that new entrants cannot easily replicate. Orbital slots are sold, leased, and included in satellite operator acquisitions. The Eutelsat acquisition of OneWeb, for example, was partly motivated by Eutelsat's desire to retain its strategic GEO slot portfolio while adding LEO broadband capability. The value of specific slots depends on coverage footprint, spectrum rights, and existing antenna pointing databases among the user population.