GEO belt

How to read this board

Read this first. Public elements place a satellite at GEO only to within tens of kilometres, so no separation under about 50 km is claimed, and a listed pair may be farther apart or closer than shown. Operators also place satellites close together on purpose, including across companies by agreement, and a servicing vehicle docked to its client shows as 0 km. Close approaches by inspection satellites are what this board is meant to show. A short list of satellites with a published inspection or servicing role is labelled, with sources; every other pair is shown as having no listed role.

Every active object in the geosynchronous belt, from public orbital elements: where it is, which are moving, which changed their orbit, and which sit close to a satellite of another owner. It shows proximity and behaviour. It never states intent.

Method

• Data. CelesTrak's active geosynchronous group (GP elements in OMM format) and its catalogue records for owner and object type, taken once or twice a day by the daily run, within CelesTrak's usage policy. The elements are USSPACECOM basic SSA data, which Space-Track allows to be redistributed and used in published analysis with citation.
• Longitude. The sub-satellite longitude from the mean elements, carried to a common time with two-body motion. Good to a few tenths of a degree, which is tens of kilometres at GEO.
• Classes. Station-kept: drift under 0.1° a day and inclination under 1°. Inclined: drift under 0.1° a day, inclination 1° or more (often older satellites saving fuel). Drifting: 0.1° a day or more.
• Close. Objects within 100 km of each other at the common time, with positions from SGP4 (the standard model for public elements, as on the globe; from 31 Oct 2026). Two-body motion, used before, drifted by up to about 100 km for elements more than a week old. CelesTrak's owner codes are often a country, so pairs with the same code are counted, not listed, unless one has a listed role. Elements older than 3 days are flagged beside the pair.
• Manoeuvres. Between consecutive snapshots: the drift rate changed by more than 0.02° a day, the inclination by more than 0.02°, or the longitude is more than 0.15° from where the earlier elements put it at the later time (by the same orbit motion, so an inclined orbit's daily swing isn't counted). A change is routine station-keeping when the satellite isn't drifting before or after. Inclined satellites still trim their drift to hold their longitude, so that is routine too. A change to their inclination isn't, because they aren't held north–south. Everything else is listed first: a satellite that started or stopped drifting, or a drifting one whose drift rate changed. The dates are those of the two element sets; the change happened somewhere between them. Snapshots began on 26 Oct 2026.
• Globe. Every object near GEO from Space-Track, placed with satellite.js (SGP4, the standard model for public orbital elements) in the Earth-fixed frame, so a satellite holding its slot hangs still over its longitude. Tracks show what the published elements said at each time: each element set is propagated only until the next one, so manoeuvres show where they happened. The dashed line is the next 48 hours predicted from the latest elements, which a manoeuvre would break. The line-of-sight circle is where the satellite stands above the chosen elevation: geometry, not a beam footprint. A hypothetical beam (in the panel, for one selected satellite) is a model: a circular main lobe whose gain falls as −3(ψ/ψ½)² dB with the angle ψ from boresight (ψ½ is half the −3 dB beamwidth; the form ITU-R S.1528 gives after ITU-R S.672), with a beamwidth of about 70λ/D degrees for a dish of diameter D at wavelength λ. The −3, −6 and −10 dB contours are projected onto the Earth from the satellite's position, so they stretch where the beam meets the Earth at a slant. It shows where a beam of that size could reach, for example where an uplink would need to be; it is not the satellite's real coverage. Published footprints aren't drawn: operators' coverage maps and collections such as SatBeams don't allow redistribution, and US filings' beam files are still to be checked (the Sources page records each). A footprint file you hold (KML or GeoJSON) can be drawn on the globe: it is read in your browser and never uploaded. Libraries: three.js and satellite.js (MIT); coastlines from Natural Earth (public domain).
• Globe tools. Look from a city or any point (type latitude, longitude or click the Earth): each satellite's elevation, bearing and range from there (WGS84, sea level), and for a satellite holding its longitude, the next sun-outage seasons, worked out as on the Sun outages page. Sun and the Earth's shadow draws the sun's direction, the point beneath it and the day–night line (a low-precision solar ephemeris, about 0.01°), and in red the part of the belt inside the Earth's shadow, modelled as a cylinder one Earth radius wide; the shadow reaches the belt only in the weeks around the equinoxes. Relative motion (select two) gives their separation over the history window and the next 48 hours, and the second one's offset from the first: radial (up), along-track (ahead in its orbit) and cross-track, from the first one's position and its velocity relative to the stars. Closest objects over time (select one) finds the five objects of any owner or type that come nearest in the same span. Board findings rings the board's close pairs, its orbit changes other than station-keeping and its arrivals and departures. Each comes with a CSV. All of it uses the same positions as the globe, so it carries the same error of tens of kilometres; in particular an inclined satellite swings north and south each day, so its separation from a neighbour can change by hundreds of kilometres within hours.
• Callouts. Automatic highlights of behaviour worth a look, from the last 14 days: C1 close to another owner's satellite (under 100 km on some hour of a day), C2 approaching (three daily falls, ending under 200 km), C3 parked beside another owner (stopped after a manoeuvre within 0.5° of a station-kept satellite of another owner), C4 heading for an occupied slot, C5 an orbit change by an object with a listed role, C6 arrived in the protected zone, C7 retired to the graveyard, C8 went quiet. Each rule was frozen in writing with a list of published cases before it was run, then scored on four months of history and seven older cases: C3 to C7 found most of their cases at a few callouts a week and show by default; C1 and C2 found theirs but fire hundreds of times a week, mostly when inclined satellites pass near another owner's satellite once a day, and C8 missed its one case, so those three stay off unless you switch them on. Callouts describe behaviour, never intent; the scores and every miss are in the validation file.
• Region. Everything Space-Track lists with a mean motion of 0.9 to 1.1 revolutions a day and an eccentricity under 0.3. The protected zone is the IADC geosynchronous protected region: perigee and apogee within 200 km of 35,786 km altitude, and inclination 15° or less. The graveyard is everything above it. Each day's list is compared with the day before: newly catalogued (launched within the last year), back in the public catalogue, entered the zone, raised to the graveyard, lowered below the zone, left the zone, dropped out of the list, and, for payloads in the zone, no new public elements for over 7 days. A satellite missing from public data hasn't necessarily stopped working: some are simply not published.
• Owners are CelesTrak's codes: CIS is Russia and the former Soviet states, PRC China, ITSO Intelsat, EUTE Eutelsat, SES SES.

Orbital data: USSPACECOM (space-track.org) via CelesTrak, and from space-track.org directly for the region and its arrivals and departures; basic SSA data, redistributed with citation. Region code: tools/geo_region.py. Code: tools/geo.py. Data file: geo.json.