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Phoebe

Ask Phoebe

Ask about seeing a satellite from a city, in plain English. For example:

Each question is answered on its own, so name the satellite and the city every time.

Answered by Claude (Anthropic) from Phoebe’s data. Don’t include personal details.

About Phoebe

Phoebe answers one question: when should I go outside, and will I actually see it? Satellites are only visible when they are sunlit against a dark sky, so Phoebe combines orbital data, the Sun’s position and the cloud forecast for your city. Sky apps are best for spotting a satellite once you’re outside; Phoebe tells you when to go out and where to look.

How it works

Once a day Phoebe downloads the latest orbital data for every active satellite. The dots on the globe are calculated in your browser every second; pass predictions are calculated on Phoebe’s server. Both use SGP4, the standard model for this kind of orbital data.

The viewing rating comes from the hourly cloud forecast for the time of the pass: good up to 25% cloud cover, fair up to 50%, and poor above that.

Ask Phoebe answers questions in plain English using Claude, an AI model by Anthropic, which looks up passes, satellites and forecasts with Phoebe’s own data. Before an answer is shown, every time and number in it is checked against that data; if anything doesn’t match, you see the pass data instead of the answer.

When a pass counts as visible

A pass is shown only when all three are true at the same moment:

  • the satellite is at least 10° above your horizon,
  • the satellite is in sunlight, not in Earth’s shadow, and
  • your sky is dark enough: the Sun is at least 6° below the horizon.

That’s why visible passes come in stretches: for days at a time the satellite only crosses your sky in daylight, or in Earth’s shadow in the middle of the night.

How the predictions were checked

Phoebe’s ISS predictions were compared with Heavens-Above, a long-running satellite prediction site. For Chicago in October 2026, all 11 visible passes matched, and every appear, highest and disappear time (33 in all) was within 2 seconds. Both agreed that Austin had no visible ISS passes that week.

Predictions get less accurate as orbital data ages, so they’re best within a few days. Phoebe is for planning when to look up, not for navigation or safety decisions.

Your location and privacy

Phoebe has no accounts and doesn’t store where you are.

  • “Use my location” is rounded to about 1 km in your browser before it’s used anywhere, and the page’s address only ever holds a city or those rounded coordinates.
  • City search sends what you type to Open-Meteo (along with your IP address, like any web request).
  • The cloud forecast sends the place’s rounded coordinates to Open-Meteo, which keeps server logs, possibly including them, for up to 90 days.
  • Ask Phoebe sends your question to Phoebe’s server and to Anthropic to answer it, and the place you name to Open-Meteo to find it, so don’t include personal details.
  • Phoebe counts anonymous events (for example, that a pass list was shown) and reports errors, never with your place, coordinates, IP address or anything you typed.

Data and credits

  • Orbital data from CelesTrak.
  • Weather data and city search by Open-Meteo.com (CC BY 4.0).
  • City locations based on GeoNames (CC BY 4.0).
  • Earth image from the three-globe project by Vasco Asturiano (MIT License).
  • Predictions checked against Heavens-Above.

Who made Phoebe

Phoebe was built by Garick Mendez, a software engineer in Austin, Texas. Feedback is welcome: reach me through the contact form on garickm.com, or browse the source code on GitHub.