Overpass Predictor preview
Work out when a radar satellite can actually image a spot on the ground — and when to have a corner reflector standing there. Your browser pulls the orbital elements from Celestrak itself and does all the propagation, so nothing about where you look reaches my server. The basemap tiles come from Esri.
Opportunity, not tasking. Public orbital elements tell you when a satellite can see a place. They say nothing about whether anyone pointed it there. Nothing here is a guarantee that an image exists.
A radar satellite cannot photograph what is directly beneath it. Synthetic aperture radar has to squint to one side, or it cannot tell a return on the left from the same-range return on the right. So the ground a pass can actually image is two bands offset either side of its track, with a blind zone underneath.
The imaging window this page talks about is incidence 20° to 45° — the overlap of ICEYE’s performant / time-dominant tasking ranges and a conservative cut of Umbra’s agility. That is a working sensor window, not a derived constant. How far those bands sit off the track is not a fixed 190–500 km: it is solved from this satellite’s altitude on the local earth radius, so a 520 km bird and a 650 km bird do not share a ribbon.
A pass directly overhead is still useless. Incidence
is the angle the beam makes with the local vertical where it lands. That
comes from the earth-centre / satellite / site triangle — this
pass’s altitude and the slant range to you — not from
90 − elevation. Look angle at the satellite is
smaller than incidence because Earth is curved; they meet only at nadir.
A satellite at 89° elevation is still about 1° incidence and
cannot image you. Every pass is listed. The one inside 20–45°
is called out and drawn on the map.
Why a corner reflector. A trihedral corner reflector returns radar energy straight back the way it came, so it lights up as a bright point against dark ground. Useful for marking a location, checking that an image was actually collected, or calibrating. It has roughly a 3 dB beamwidth of about 40° full width — hold aim within roughly ±20° of boresight — so the aiming azimuth in the tasking order is a setup instruction rather than trivia.
The desktop tool adds ATAK data packages, macOS notifications, a menu-bar watcher, and cross-checking predictions against what a commercial archive actually captured. This page is the geometry and the timing.