What's Over You Right Now

The Next Hour Over You

Pick a spot above and the page works out which satellites cross your sky in the next hour, and shows all of them moving over the globe. Your location stays on your device.

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How It Works

We build digital twins of space vehicles and the sensors that look at them. This page is the smallest version of that chain: public orbital data in, a standard propagator, a position you can check against the sky. All of the arithmetic runs in your browser.

• Orbital data. CelesTrak's GP data for the space stations, the brightest satellites, Earth observation and the TDRS relays, about 330 objects once an object listed twice is counted once and docked modules are folded into their station. Starlink, more than ten thousand objects, loads after the globe is up. This site keeps a copy of it, saved when the site was last published. Once that copy is more than a day old, your browser asks CelesTrak for fresh data and keeps it for six hours. After a declined Starlink request it waits two hours before asking again, and uses the site's copy meanwhile. If nothing can be reached, a small set bundled with the page stands in, and the page always says which data it is using and how old it is. The GPS satellites load the first time you open the GPS walkthrough.
• Propagation. SGP4, through satellite.js, in a background thread. Passes: 10 second steps from 30 seconds ago to 60 minutes ahead. Each run of samples above the horizon is one pass, rise and set are interpolated and the peak is refined to one second. Starlink is searched at 60 second steps and only the count above your horizon and the three highest passes are kept. Positions for the globe are computed once a second. Between updates each icon moves along its own velocity, which stays within a few kilometres of the true path over a minute.
• Look angles. The position is rotated into Earth-fixed coordinates and turned into azimuth and elevation at your spot, taken at sea level.
• Sunlit. A low precision sun position, good to about a hundredth of a degree, and a cylindrical Earth shadow. The flag appears only for objects in the visual group, and only while they are in sunlight with the sun more than six degrees below your horizon. The same sun direction places the day and night line on the globe, with no twilight band.
• The globe. NASA's Blue Marble and city lights maps on a sphere, in an Earth-fixed frame: the camera moves and satellites move over a still Earth. The icons are not to scale, a real satellite would be far smaller than a pixel. Altitude is height above the WGS84 ellipsoid, speed is the inertial speed. The red ring around your spot is the horizon for an object at 550 km, drawn for one altitude only.
• Follow a packet. One request from a Starlink dish to a website and back, hop by hop: up to the Starlink broadband satellite highest in your sky right now, across laser links when no gateway is in reach, down to a gateway, fiber to Starlink's point of presence, then to the server. Every distance and light travel time comes from the satellites' live positions. The direct-to-cell satellites, which serve phones, are left out. Starlink doesn't publish which satellite, gateway, laser route or point of presence carries a given request, so those are likely picks, and the steps say so.
• Laser mesh. Starlink doesn't publish which of its satellites are linked by laser, so the mesh is a model: each satellite linked to the nearest one ahead in its own orbit plane and the nearest in the plane beside it, three links at most, one for each of a satellite's three lasers. The race and ride along use the same model. The pulses running along the links are decoration, not traffic.
• Coverage map. How many Starlink broadband satellites are at least 25 degrees up, the lowest a Starlink dish uses, at the centre of every one-degree square of the Earth, counted again every ten seconds.
• Race. Fiber runs the great circle between the two places at two thirds of the speed of light, its speed in glass, so its time is a floor: real cables run longer. Starlink takes the shortest path for light through the mesh, up from a satellite at least 25 degrees up over one place and down to one over the other. The geostationary packet bounces off a satellite 35,786 km up, or two of them through a ground station when no one satellite is in view of both. Switching and queueing delays are left out of all three.
• Ride along. The camera follows the satellite's track, a point every ten seconds joined into a smooth curve. The satellites are drawn far bigger than they are, and the dishes a Starlink beams to are made up, spots on populated land in its view.
• How GPS finds you. The real GPS satellites, propagated like the rest. The spheres and circles are drawn on the ground for clarity: a receiver solves in three dimensions, for its position and its clock error together.
• Left out. No atmospheric refraction, no brightness estimate, no terrain. Zero degrees here is the geometric horizon, and a pass that peaks at ten degrees will be behind the trees for most people.

Orbital data from CelesTrak, originally from USSPACECOM via Space-Track.org. Place names from GeoNames, CC BY 4.0. Earth maps from NASA. Every source and license is on the Credits page.