Satellite Pass: Doppler Shift & Elevation Tracker — 2D Orbital-Plane View

Every low-Earth-orbit satellite pass is a race against the clock and against physics: the satellite is moving several kilometres per second relative to any fixed ground station, so the carrier frequency a receiver locks onto is never quite the one the satellite transmits. This 2D companion looks straight down the satellite's own orbital plane — Earth and the orbit both render as clean circles, so you can see exactly how the ground station's position (offset by the pass's miss angle) traces out the changing slant range, elevation and radial velocity that drive the Doppler shift. A live strip chart traces the Doppler S-curve underneath the orbit view: positive on approach, exactly zero at closest approach, negative as the satellite recedes over the horizon. Adjust the orbit altitude, how close the ground track passes overhead, and the downlink band to see how each one reshapes the curve that real satellite ground stations track and compensate for during every single pass. Drag to pan the view and scroll or pinch to zoom in on the geometry.