From star charts to push notifications: a short history of knowing what's overhead
Heavens-Above put satellite predictions online decades before smartphones existed. NASA built its own official app. Here's how satellite tracking got to your pocket — and where SpacePings picks up.
Before push notifications, before smartphones, there was a website: you'd type in your city, and it would hand you a table — rise time, peak time, set time, direction, brightness — for every satellite pass worth watching over the next several nights. That website is Heavens-Above, still online today, still developed and maintained by its original author, Chris Peat, as Heavens-Above GmbH, and hosted by the German Aerospace Center (DLR). It offers daily predictions for the brightest satellites and ten-day predictions for satellites of particular interest — the ISS, Starlink, and others — along with interactive sky charts and 3D orbit visualizations. Sky & Telescope has called it the most popular website for satellite tracking, and it's easy to see why: it's expert-grade data, freely published, run by one person for the community, for longer than most software in this category has existed at all.
The catch with that generation of tool was always the same: you had to go to it. Nothing came to you. If you didn't think to check, you missed the pass.
The app era
The next step was the obvious one — take the same underlying idea and put it on a phone, with alerts layered on top instead of a table you had to remember to check. NASA built its own official entry in this category: Spot the Station, which tracks and notifies users about ISS flyovers using NASA's own trajectory data for the station, updated by flight controllers roughly three times a week. It's free, available worldwide, and — notably — open source, so anyone can see exactly how it works. Independent apps followed the same basic shape: open the app, see a schedule, optionally get an alert.
What this generation mostly didn't change was what got surfaced. A schedule is still a schedule — every geometrically valid pass, whether or not the sky is actually dark enough, whether or not there's a cloud in the way, whether or not the satellite will still be lit by the time it's worth looking. The data got easier to reach. It didn't get more selective.
Where SpacePings picks up
Two things, specifically, that the prediction-table era wasn't built around: pushing only for passes that clear a real quality bar — dark enough sky, bright enough satellite, clear enough forecast — and centering the one moment a table can't capture at all: the exact second a satellite fades into Earth's own shadow, mid-sky, with no horizon to blame. Heavens-Above and NASA's own app both do real, credible orbital work; SpacePings' contribution is narrower and more specific — decide, honestly, whether tonight's pass is worth your time, and if it is, call the one second worth watching for.
Free on iOS — no account needed to check tonight's sky. For the specific, feature-by-feature differences, see how SpacePings compares to Heavens-Above, ISS Detector, and Spot the Station.