Satellite Pass Hunter: An Offline Audio Guide for the Irish Night Sky

Rudra Joshi — Sat, 10 Oct 2026 17:16:42 +0000

This is a submission for the Hacktoberfest Open-Source AI Challenge Week 1: Touch Grass

What I Built:
Satellite Pass Hunter is an offline-first, hands-free audio tracker built for stargazers, campers, and outdoor enthusiasts across all 32 Irish counties.

Most stargazing apps defeat their own purpose. They force you to squint at bright, blue-light screens and complex 3D orbital maps, destroying the twenty minutes your eyes need to adapt to darkness.

Satellite Pass Hunter flips that interaction completely. You select your county, tap "Start Audio Guide", and put your phone directly into your pocket. The interface uses a dark monochromatic red HUD to preserve natural night vision (scotopic vision). When a satellite approaches your location, the app automatically gives you spoken voice cues telling you where to face, how high to look, and the estimated probability of spotting it with the naked eye. You spend your night watching real satellites cross the sky instead of staring down at glass.

Demo:

Live Site: https://passhunter-ireland.netlify.app
Optimized for mobile browsers: select your county, start the audio guide, and keep your phone in your pocket.

Code:

GitHub Repository: https://github.com/Rudrasaur/pass-hunter
Open source under the MIT License.

How I Built It:

The project links orbital mechanics, tabular machine learning, and local language models into an automated data pipeline:
SGP4 Orbital Mechanics (Skyfield): The Python pipeline tracks visible satellites using Skyfield, DE421 planetary ephemeris, and fresh Two-Line Element (TLE) sets. It calculates topocentric coordinates for all 32 Irish counties and verifies Earth shadow geometry. Satellites are only shown if the observer is in twilight or darkness while the satellite itself remains illuminated by sunlight.
Naked-Eye Visibility Scoring (TabPFN): Instead of relying on crude magnitude numbers, I trained a TabPFNClassifier on historical sky observation data. It evaluates satellite altitude, peak elevation, cloud cover, and local Bortle light-pollution scales to output a calibrated probability score of whether the pass is visible to the naked eye.
Conversational Direction Synthesis (Gemma 2 2B): Raw astronomical coordinates (azimuth degrees, elevation angles) are unnatural to navigate in the dark. I used Google's open-weight Gemma 2 2B model to translate telemetry into direct, plain-English voice cues (for example: "Face southwest and look halfway up the sky").
Voice Synthesis (ElevenLabs): The scripts generated by Gemma are synthesized into crisp offline audio cues, providing audio guidance without live network delays.
Automated Cloud Engine (GitHub Actions): An automated workflow runs on a daily 2:00 AM UTC cron schedule. It downloads updated orbital sets, scores passes with TabPFN, updates the static mobile app, and deploys it live to Netlify. Passes automatically count down in real time and disappear once completed.

Why Does Open Innovation Matter?
The premier dark-sky locations in Ireland, such as the Kerry International Dark Sky Reserve or Ballycroy National Park in Mayo, have virtually zero cellular reception. Stargazing requires leaving connected areas behind.

Closed AI APIs fail in these remote locations because they require constant high-speed connectivity, monthly subscriptions, and continuous telemetry. Open innovation changes the equation:

Edge Reliability: Open-weight models like Gemma 2 2B allow complete local generation. We can build and verify conversational pipelines without depending on closed cloud servers.
Build-Time Prerendering: By combining open-source tools (Skyfield, TabPFN, Gemma) in a daily build pipeline, the intelligence is bundled directly into static web assets. The user gets a responsive, AI-driven guide that works completely offline on a dark hilltop.
Transparency in Science: Anyone can inspect the orbital formulas, adjust the light pollution constants, and verify the model predictions without encountering proprietary black boxes.

Prize Categories:
Best Use of TabPFN: Applied TabPFN's tabular foundation model to classify naked-eye pass visibility probabilities across regional Bortle scale ratings.

Best Use of Gemma: Used the open-weight Gemma 2 2B model to translate mathematical coordinate passes into natural, spoken astronomy directions.

Best Use of ElevenLabs: Synthesized voice prompts to enable a screen-free, pocket-friendly audio experience.

Best Use of GitHub Copilot: Automated the entire data processing and deployment cycle using a hands-free GitHub Actions continuous deployment pipeline.

DEV Community: Rudra Joshi

Satellite Pass Hunter: An Offline Audio Guide for the Irish Night Sky