OscarWatch

OscarWatch is still in development

Desktop satellite tracking for amateur radio operators. OscarWatch shows where AMSAT spacecraft are, predicts passes over your station, works out Doppler-corrected uplink and downlink frequencies, and can drive your rotator and radio during a pass — all from one map-centred window.

TLEs and the transponder frequency database are published from tle.oscarwatch.org (TLEs, transponder database).

Who is this for?

Licensed amateurs working VHF/UHF satellites: FM cubesats (SO-50, ISS, …), linear transponders (RS-44, FO-29, …), and similar modes. You should already be comfortable with pass times, azimuth, elevation, and Doppler; OscarWatch handles the maths and optional hardware control so you can focus on the contact.

You do not need to be a programmer to use published builds.

What OscarWatch does

• Map and sky plot — subpoint, ground track, footprint, and a polar view from your QTH; optional DX station marker and live Az/El at a remote grid for the focused satellite
• Pass list — upcoming passes with max elevation and time-to-AOS; sidebar scrolls on smaller windows
• Frequency panel — transponder modes from a built-in database, live uplink/downlink with Doppler, RX offsets (separate for Voice and CW on linear SSB), and CTCSS (access/arm tones). Keyboard shortcuts: help/keyboard-shortcuts.html (Ctrl+W, numpad + / − for RX offset, S for solo map view, map arrows, etc.)
• Optional automation — serial rotator tracking and radio CAT (Doppler, satellite/split layout, tones) during a pass
• Optional extras — voice “satellite rising” alerts, pass WAV recording, Cloudlog frequency sync

OscarWatch does not decode telemetry or replace your logging software; it is a pass-tracking and station-assist tool for the shack or field.

Getting started

Download

Pre-built packages for Windows, macOS, and Linux are on the Releases page (see Cross-platform publish for platform names). Extract the archive for your OS and run OscarWatch.

macOS (first install): release builds are not code-signed or notarized. macOS may block the app or bundled native libraries on first use:

1. OscarWatch — if Finder says the app “cannot be opened”, right-click OscarWatch → Open once, or use System Settings → Privacy & Security → Open Anyway.
2. Pass recording — if you use automatic WAV capture, macOS may also ask you to allow **libportaudio.dylib** (in runtimes/osx-*/native/ inside the app folder). Approve it the same way when prompted.
3. Microphone — allow microphone access when you first enable recording in Settings.

These prompts are usually one-time per install. Tracking, passes, and radio/rotator control work without pass recording if you skip step 2.

To build from source instead, see Build and run below.

First-time setup

1. Open Settings → Station and enter your latitude, longitude, and grid square.
2. Satellites → Select satellites — enable the spacecraft you plan to work.
3. Satellites → Refresh TLEs — refresh at least once per operating day (or enable auto-update under Settings → Tracking).
4. If you use a rig or rotator: Settings → Radio and Settings → Rotator — set COM ports (rig and rotator must use different ports).
5. Click a satellite on the map or in the pass list to focus it — live az/el and frequencies apply to the focused pass.

During a pass

1. Confirm the correct transponder mode in the frequency panel on the map (e.g. FM voice, Mode B USB/LSB). On linear SSB modes, use Voice / CW in the panel title bar (or Ctrl+W) — see frequencies help.
2. Watch azimuth and elevation in the sidebar — point your antenna there (or let the rotator track if enabled).
3. Set your radio from the Radio / Sat columns in the overlay, or enable CAT so OscarWatch updates frequencies for Doppler.
4. On FM satellites, pick the correct CTCSS tone when access and arm are both listed.

Standby (browsing only)

Press Standby in the sidebar when you are only planning or browsing: the rotator parks, CAT pauses, and accidental tracking stops. Press Resume before a real pass. While in Standby, menu Rotator opens manual az/el control for a quick contact between passes.

Operator guide

Plain-language help ships with the app: Help → Operator guide (also in the [help/](help/) folder). Topics include quick start, frequencies, TLEs, pass planning, radio/rotator setup, recording, and troubleshooting.

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Features

• World map — equirectangular Earth texture with satellite subpoint, ground track, footprint overlays (optional motion arrows), your QTH, and an optional remote DX station grid marker
• Sky plot — polar view of satellite azimuth/elevation relative to your station; click to focus; expand/collapse state is remembered
• TLE catalog — fetched from https://tle.oscarwatch.org/, cached under %AppData%/OscarWatch/
• TLE auto-update — manual refresh, on startup (if stale), or every 6 hours while running (Settings → Tracking)
• Satellite picker — choose which spacecraft to track
• Pass predictions — upcoming passes with TCA (time of closest approach / max elevation), min-elevation and min-duration filters
• Pass planner — multi-station profiles (home / portable), pass quality filters, and .ics calendar export for contest or field-day planning
• Mutual pass finder — find passes visible from two stations at once (Passes → Mutual pass finder)
• DX station monitor — enter a remote Maidenhead grid on the map; see where that station is and live azimuth/elevation for the focused satellite from their QTH (compact draggable overlay)
• Live telemetry — azimuth, elevation, range, and altitude updated every second (UTC)
• Voice announcements — optional spoken “rising” alerts when a satellite crosses a configurable elevation while ascending (e.g. “Alpha Oscar Zero Seven is rising”); Settings → Voice
• Pass recording — optional automatic WAV capture from a line-in or USB audio device while the focused satellite is above configurable elevation thresholds; Settings → Recording. Files save to %AppData%/OscarWatch/recordings/ by default as {sat-name}-{yy}-{MM}-{dd}-{HH}-{mm}.wav (UTC). A red REC badge appears on the pass row while recording.
• Doppler frequencies — draggable overlay on the world map with transponder modes from the satellite database, live radio/sat uplink & downlink, RX offsets (separate stored values for Voice and CW on linear SSB), CTCSS (access/arm), and Voice/CW toggle for linear SSB (header buttons + Ctrl+W; CAT/Cloudlog follow Settings → Radio → Linear CW: keep receive in USB/LSB)
• Transponder database editor — Satellites → Manage transponder database… (add satellites from your TLE catalog or a custom name, Import/Export JSON, edit modes); Satellites → Update transponder database… merges published modes from tle.oscarwatch.org/satellite_database.json (new entries added with your consent; local edits kept on conflicts unless you accept remote). See documents/satellite-database.md
• Radio CAT — doppler tracking, satellite/split setup, Main/Sub VFOs, uplink CTCSS where supported; Settings → Radio (see Supported hardware)
• Rotator control — serial pass tracking, manual park, and manual rotator (az/el dialog in Standby for quick contacts between passes); Settings → Rotator (see Supported hardware)
• Cloudlog — optional Radio API v2 uplink/downlink when tracking (Settings → Cloudlog)
• Appearance — light, dark, or system theme (sky plot adapts; world map image stays light); optional footprint motion arrows on the map

Supported hardware

OscarWatch talks to rigs and rotators over serial CAT (COM port on Windows, device path on Linux/macOS). Rig and rotator must use different ports.

Radios

Radio	Protocol	Notes
ICOM IC-910	CI-V	Cross-band: satellite mode, Main/Sub, Sub uplink CTCSS. Receive-only (uplink 0): SAT off, downlink on Main
ICOM IC-9100	CI-V	Same as IC-9700; default CI-V address 7C
ICOM IC-9700	CI-V	Same layout as IC-910
Yaesu FT-847	Yaesu CAT	Satellite mode, SAT RX/TX VFOs, doppler, uplink CTCSS
Kenwood TS-2000	Kenwood ASCII CAT	Beta — SATL via CAT; auto FA/FB band swap; linear CW uplink in SATL; TRACE off via CAT
Dummy rig	—	No serial I/O; for UI and doppler testing without a radio

All tracked rigs: linear NOR/REV doppler, interactive Main VFO tuning on USB/LSB/CW (Sub uplink deferred briefly after dial moves on Main/Sub rigs), TX/RX offset spinners, configurable CAT thresholds and pause.

More rigs: see TODO.md and building radio drivers.

Rotators

Controller	Protocol	Notes
Yaesu GS-232	GS-232	Yaesu rotators and many GS-232 clones
EasyComm	EasyComm II	SPID, M2, and other EasyComm-compatible controllers

Pass tracking when elevation is above the track-start threshold; manual Park in the sidebar; manual rotator in Standby (menu Rotator… — set az/el, Rotate, Stop, Park for a quick contact without resuming pass tracking). Azimuth range 360° or 450° (e.g. G-5500). On 450° rotators, optional smart azimuth chooses 361–450° commands for the shortest path across north (Settings → Rotator). Optional calibration offsets correct pass tracking and manual moves; park uses your configured park az/el exactly.

More controllers: building rotator drivers.

Settings

Open Settings from the menu. Tabs:

Tab	Purpose
Station	Display name, latitude/longitude, Maidenhead grid square, altitude ASL
Tracking	Minimum pass elevation, prediction window, TLE auto-update, transponder database check on startup
Appearance	Light / dark / system theme; footprint motion arrows on/off
Voice	Enable announcements, trigger elevation (default −3°), voice selection, test button
Recording	Automatic pass WAV capture, input device, start/stop elevation, output folder, test clip
Rotator	Type (GS-232 / EasyComm), COM port, 360°/450° azimuth, smart 450°, park, track-start elevation, calibration offsets
Radio	Rig type, COM port, region (Icom), CI-V address, linear CW receive mode (USB/LSB vs CW on both VFOs), Doppler CAT thresholds (FM default 350 Hz, SSB/CW default 50 Hz — see help), pause CAT
Cloudlog	Base URL, API key, radio name, test connection; posts SAT uplink/downlink when tracking

Settings are stored in %AppData%/OscarWatch/settings.json.

Planned work is listed in TODO.md. Transponder database merge/sync is documented in documents/satellite-database.md.

Voice announcements (platform notes)

Platform	Text-to-speech
Windows	Built-in (System.Speech)
macOS	Built-in (/usr/bin/say)
Linux	Requires espeak-ng (preferred) or spd-say on PATH

If TTS is unavailable, the Voice tab shows a notice and announcements are skipped.

Pass recording (platform notes)

Audio capture uses PortAudio (via PortAudioSharp2). Native runtimes are included in published builds for Windows x64, macOS (Intel/Apple Silicon), and Linux x64/ARM64.

Platform	Notes
Windows	Select your radio interface or sound card input in Settings → Recording
macOS	Core Audio devices; see macOS (first install) if libportaudio.dylib is blocked; grant microphone permission when prompted
Linux	Requires PulseAudio or ALSA; install libasound2 / PulseAudio as needed for your distro

WAV files are uncompressed (~5 MB/min mono at 44.1 kHz). Use an external tool if you need MP3 later.

Settings location

File	Path
Settings	%AppData%/OscarWatch/settings.json
Recordings	%AppData%/OscarWatch/recordings/
TLE cache	%AppData%/OscarWatch/tle-cache.txt
Transponder DB (user)	%AppData%/OscarWatch/satellite_database.json
Transponder DB (remote)	tle.oscarwatch.org/satellite_database.json
Logs	%AppData%/OscarWatch/logs/ (daily rolling oscarwatch-YYYYMMDD.log, 14 days retained)

Open the recordings or log folder from Help → Open recordings folder or Help → Open logs folder. Unhandled crashes and rig/rotator/CAT errors are written to logs (not API keys).

Contributing

Pull requests are welcome when they add something valuable to the core of OscarWatch — bug fixes, rig or rotator drivers, tracking behaviour, operator-facing features, and transponder database entries (new satellites/modes or corrections with a credible source). For larger changes, open an issue first so direction can be agreed before you invest time in a big diff.

Transponder data is also published at tle.oscarwatch.org/satellite_database.json; see documents/satellite-database.md.

Support

OscarWatch is free and open source. If you find it useful, you can support ongoing development via GitHub Sponsors or PayPal. If you donate, please let Peter know your callsign so you can be thanked.

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For developers

Requirements

• .NET 10 SDK

Build and run

dotnet build OscarWatch.slnx
dotnet run --project OscarWatch/OscarWatch.csproj

For lower memory use, prefer Release (-c Release). Debug builds include Avalonia diagnostics overhead.

dotnet run -c Release --project OscarWatch/OscarWatch.csproj

Cross-platform publish

GitHub Actions

Publish runs on a version tag (v*) or a manual workflow dispatch. It builds and tests on Linux, then publishes installable packages per platform.

Artifacts:

Artifact	Runtime
OscarWatch-win-x64	Windows x64
OscarWatch-osx-arm64	macOS Apple Silicon
OscarWatch-osx-x64	macOS Intel
OscarWatch-linux-x64	Linux x64
OscarWatch-linux-arm64	Linux ARM64 (Raspberry Pi 64-bit OS)

• Manual run: Actions → Publish → Run workflow
• Release: git tag v1.0.0 && git push origin v1.0.0 → GitHub Release with all archives

Local publish

# Windows
dotnet publish OscarWatch/OscarWatch.csproj -c Release -r win-x64 --self-contained

# macOS (Apple Silicon)
dotnet publish OscarWatch/OscarWatch.csproj -c Release -r osx-arm64 --self-contained

# macOS (Intel)
dotnet publish OscarWatch/OscarWatch.csproj -c Release -r osx-x64 --self-contained

# Linux x64
dotnet publish OscarWatch/OscarWatch.csproj -c Release -r linux-x64 --self-contained

# Raspberry Pi (64-bit OS)
dotnet publish OscarWatch/OscarWatch.csproj -c Release -r linux-arm64 --self-contained

Publish profiles are under OscarWatch/Properties/PublishProfiles/ (e.g. dotnet publish -p:PublishProfile=win-x64).

Project structure

Project	Role
OscarWatch.Core	Models, TLE parser, settings, Maidenhead grid, orbit interfaces, voice/phonetics
OscarWatch.Orbit	OrbitTools adapters, pass predictor, ground geometry
OscarWatch	Avalonia UI

Developer documentation

• documents/ — how to add radio and rotator drivers (IRigDriver, IRotatorDriver); satellite transponder database (remote updates, merge policy, schema)
• help/ — operator HTML help (bundled with the app)
• docs/ACCESSIBILITY.md — UI contrast, colour-blind-safe tracking colours, keyboard

Orbit propagation

Uses OrbitTools Public Edition via Zeptomoby.OrbitTools.Orbit (non-commercial). For commercial use or the Track Library (pass engine, iso-elevation footprints), obtain a Professional license.

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License

Copyright © 2026 Peter Goodhall (MM9SQL).

OscarWatch is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License v3.0 or later (AGPL-3.0-or-later). See LICENSE.md for the full license text.

If you run a modified version as a network service, AGPL requires making the corresponding source available to users who interact with it over the network.

Third-party components (OrbitTools, Avalonia, TLE sources, map imagery, etc.) have their own licenses — see CREDITS.md and the Orbit propagation section above.

Credits

See CREDITS.md.

Supporters

Donors who have helped fund development are listed in supporters.md.