Geostationary Slot Coordination — 2D Ring Simulator

GEO Slot Traffic

Starting operators 8

ITU coordination arc 2.0°

Ring rotation speed 1.0×

Ring status

Satellites in ring

Tightest gap

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Worst-case C/I

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Pairs interfering

How it works

The Outer Space Treaty (1967) never defines a mechanism for allocating the geostationary belt or managing traffic on it — that job fell to the ITU's Radio Regulations, a first-come-first-served coordination process built around one number: angular separation on the ring.

GEO radius:      42,164 km  (period = 1 sidereal day)
Off-axis gain:   G(θ) ≈ 29 − 25·log₁₀(θ)  dBi   [ITU-R S.580 envelope, 1°≤θ≤7°]
Carrier/Interf.: C/I(θ) ≈ G_main − G(θ)
Coordination trigger: C/I below ~26 dB → operators must formally coordinate
(the model crosses 26 dB near θ≈1.3°, so the traditional 2° arc keeps ~4.5 dB of margin)

θ is the angular gap between two satellites as seen from a ground antenna. A dish that is sharply focused on the wanted satellite still picks up some signal from any neighbor within a few degrees — how much is set by the antenna's off-axis sidelobe pattern.
Below the coordination arc (2° is the traditional C-band figure; some Ku-band and NGSO-adjacent filings now squeeze closer), the interfering signal's carrier-to-interference ratio drops below the threshold operators need for a clean downlink — the pair turns red on the ring and a beam is drawn between them.
File a coordinated slot respects the current arc and drops the new satellite into the widest open gap. Squeeze in a paper satellite ignores it — mimicking an operator that files a "paper" slot to claim spectrum rights before it has a real payload, the practice the OST's silence on space traffic left no clear brake on.
Drag any satellite dot around the ring yourself — the C/I readouts and the curve below update live as you move it, exactly as they would if that operator relocated its longitude slot.
The ring itself rotates with Earth beneath it (once per sidereal day, ~23h56m) — a true geostationary satellite never moves relative to the ground station it serves; rotation is cosmetic here and never changes the angular gaps or C/I.

Coordinated satellite Interfering pair (C/I below threshold)

drag a satellite to move it