SatMaster — F4BPO Satellite Tracker

Amateur satellite tracking application with Doppler correction for FlexRadio 8600 and rotor control via PstRotator.

Stack: Go + Wails v2 + Svelte
Platform: Windows (primary), Linux/macOS (compilable)

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Features

• 🗺️ World map — real-time satellite positions on Leaflet dark map, footprint overlay
• 📡 Polar plot — az/el pass track with AOS/LOS markers, current position animation
• 🕐 Pass prediction — 24h upcoming passes, Max El, duration, quality rating
• 📻 Doppler correction — automatic TX/RX frequency correction via FlexRadio 8600 TCP API
• 🔄 Rotor control — Az/El commands to PstRotator via UDP XML protocol
• 🛰️ TLE management — auto-fetch from tle.oscarwatch.org with local cache fallback

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Architecture

SatMaster/
├── main.go                    # Wails entry point
├── app.go                     # App struct, Wails bindings, position loop
├── wails.json                 # Wails project config
│
├── backend/
│   ├── tle/
│   │   └── manager.go         # TLE fetch (oscarwatch.org), cache, parse, lookup
│   │
│   ├── propagator/
│   │   └── engine.go          # SGP4 propagation, az/el, pass prediction
│   │
│   ├── doppler/
│   │   └── calculator.go      # Doppler shift computation (range rate → Hz correction)
│   │
│   ├── flexradio/
│   │   └── client.go          # FlexRadio SmartSDR TCP API (port 4992)
│   │
│   └── rotor/
│       └── pstrotator.go      # PstRotator UDP XML protocol (port 12000)
│
└── frontend/src/
    ├── App.svelte              # Root layout, Wails event subscriptions
    ├── stores/satstore.js      # Svelte stores for all app state
    ├── lib/
    │   ├── wails.js            # Wails Go call bridge + dev stubs
    │   └── utils.js            # Formatting helpers (freq, az, el, etc.)
    └── components/
        ├── StatusBar.svelte    # Top bar: clock, sat data, Doppler, connections
        ├── SatSelector.svelte  # Left sidebar: search + quick-select + full list
        ├── WorldMap.svelte     # Leaflet map with sat markers + footprints
        ├── PolarPlot.svelte    # SVG polar az/el plot
        ├── PassesPanel.svelte  # Pass list + detail + embedded polar plot
        └── SettingsPanel.svelte # QTH, frequencies, FlexRadio, rotor, TLE

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Prerequisites

# Go 1.21+
# Node.js 18+
# Wails v2
go install github.com/wailsapp/wails/v2/cmd/wails@latest

# Verify
wails doctor

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Setup & Build

# 1. Clone / copy project
cd SatMaster

# 2. Download Go dependencies
go mod tidy

# 3. Install frontend deps
cd frontend && npm install && cd ..

# 4. Development mode (hot reload)
wails dev

# 5. Production build (single .exe)
wails build
# → build/bin/SatMaster.exe

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FlexRadio 8600 — Protocol Notes

SatMaster uses the SmartSDR TCP API on port 4992.

Commands sent:

C1|slice set 0 freq=145.800000    # Set RX frequency (MHz)
C2|transmit set freq=145.200000   # Set TX frequency (MHz)

• Connect: Settings → FlexRadio 8600 → enter IP → Connect
• The active slice index is 0 (Slice A) by default
• Doppler correction fires every second during active tracking
• Dead-band: updates only sent when shift exceeds ~10 Hz

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PstRotator — Protocol Notes

SatMaster sends UDP XML to PstRotator on port 12000 (default).

<PST><CMD>SET</CMD><AZ>180.0</AZ><EL>45.0</EL></PST>

• Configure in PstRotator: Setup → UDP Server → Port 12000
• Dead-band: 0.5° Az and El to prevent rotor hunting
• Elevation is clamped to [0°, 90°] — no negative elevation commands sent

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TLE Data

• Primary source: https://tle.oscarwatch.org/nasabare.txt
• Fallback: Celestrak SOCRATES
• Cache: %LOCALAPPDATA%\SatMaster\satmaster_tle_cache.txt (Windows)
• Bundled fallback: ISS, AO-7, AO-27, SO-50 (always available)
• TLE age shown in status bar; highlighted orange if > 48h

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Pass Prediction

• Step: 10s (30s when satellite below -15° elevation)
• AOS/LOS bisection precision: 1 second
• Horizon: passes below 5° Max El are filtered from the list
• 24-hour prediction window

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Doppler Formula

f_corrected_down = f_nominal × (1 - v_range / c)
f_corrected_up   = f_nominal / (1 - v_range / c)

where:
  v_range = range rate in km/s (+ = receding, - = approaching)
  c       = 299792.458 km/s

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Keyboard Shortcuts

Key	Action
M	Switch to Map tab
P	Switch to Passes tab
S	Switch to Settings tab

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Adding More Satellites

The app loads all satellites from the TLE feed (~2000+ amateur sats from OscarWatch). Use the search box in the satellite selector to find any satellite by name or NORAD catalog number.

Common amateur satellites available:

• ISS (ZARYA) — 145.800 MHz FM voice
• AO-7 — 145.975 MHz / 29.502 MHz linear transponder
• AO-27 — 145.850 MHz FM
• SO-50 — 436.795 MHz FM
• RS-44 — 435.640 MHz / 145.935 MHz linear
• PO-101 (Diwata-2) — 437.500 MHz FM
• XW-2A/B/C/D — CW/linear transponders
• CAS-4A/B — linear transponders

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Future Enhancements

• Ground track on world map (lat/lon per pass point)
• Multiple satellite tracking (split-screen polar)
• Audio squelch mute between passes
• Log4OM integration for contact logging
• Satellite database with nominal frequencies auto-loaded
• AOS/LOS audio alert
• Export pass schedule to CSV/PDF