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 NASA GIBS Blue Marble, footprint + groundtrack overlay, satellite SVG icon for tracked sat
• 📡 Polar plot — az/el pass track with AOS/LOS markers, current position animation
• 🕐 Pass prediction — 24h upcoming passes, Max El, duration, quality rating, single sat or full watchlist view
• 📻 Doppler correction — automatic TX/RX frequency correction via FlexRadio 8600 TCP API, configurable RX/TX slices
• 🔄 Rotor control — Az/El or Az-only commands to PstRotator via UDP XML protocol
• 🛰️ TLE management — parallel fetch from Celestrak + PE0SAT, merged with deduplication, local cache fallback
• 🔊 AOS voice alerts — Windows TTS announcement at AOS for all watchlist satellites, configurable voice
• 📋 Satellite frequency database — 40+ satellites with nominal frequencies, auto-applied on selection
• 🔍 Watchlist — persistent satellite selection with alphabetical sorting and duplicate prevention

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Architecture

SatMaster/
├── main.go                    # Wails entry point
├── app.go                     # App struct, Wails bindings, position loop, tracking
├── wails.json                 # Wails project config
│
├── backend/
│   ├── tle/
│   │   └── manager.go         # Parallel TLE fetch (Celestrak + PE0SAT), merge, cache, parse
│   │
│   ├── propagator/
│   │   └── engine.go          # SGP4 propagation (akhenakh/sgp4), 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 events, AOS voice alert engine
    ├── stores/satstore.js      # Svelte stores + localStorage persistence
    ├── lib/
    │   ├── wails.js            # Wails Go call bridge + dev stubs
    │   ├── utils.js            # Formatting helpers (freq, az, el, range, etc.)
    │   ├── satdb.js            # Satellite frequency database (40+ sats)
    │   └── maidenhead.js       # Maidenhead locator ↔ lat/lon conversion
    └── components/
        ├── StatusBar.svelte    # Top bar: clock, sat data, Doppler, SOUND/DOPPLER/ROTATOR toggles
        ├── SatSelector.svelte  # Left sidebar: watchlist, frequencies, track toggles, sat info
        ├── WorldMap.svelte     # Leaflet map, sat markers, SVG icon, footprint, groundtrack
        ├── PolarPlot.svelte    # SVG polar az/el plot
        ├── PassesPanel.svelte  # Pass list + detail + embedded polar plot
        └── SettingsPanel.svelte # QTH, FlexRadio, PstRotator, slices, voice alerts, 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:

slice t 0 145.800000    # Set RX slice frequency (MHz)
slice t 1 145.200000    # Set TX slice frequency (MHz)
slice s 0 mode=FM       # Set slice mode

• Connect: Settings → FlexRadio → enter IP → Connect
• RX slice (downlink) defaults to Slice A (index 0), TX to Slice B (index 1)
• Configurable in Settings → FlexRadio → Satellite Slices
• Doppler correction fires every second during active tracking
• Dead-band: 1 Hz — updates only sent when shift exceeds threshold
• Track Freq/Mode button is disabled if satellite has no known frequencies

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PstRotator — Protocol Notes

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

<PST><AZIMUTH>180</AZIMUTH></PST>
<PST><AZIMUTH>180</AZIMUTH><ELEVATION>45</ELEVATION></PST>

• Configure in PstRotator: Setup → UDP Server → Port 12000
• Az-only or Az+El mode configurable in Settings → PstRotator → Rotor Mode
• Dead-band: 5° Az and El to prevent rotor hunting
• Elevation clamped to [0°, 90°] — no negative elevation commands sent
• ResetDeadband() called when Track Azimuth is enabled to force immediate move

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TLE Data

• Primary source: https://celestrak.org/NORAD/elements/gp.php?GROUP=amateur&FORMAT=tle
• Secondary source: http://tle.pe0sat.nl/kepler/amateur.txt
• Both sources fetched in parallel and merged — Celestrak takes priority on duplicates, PE0SAT contributes satellites not present in Celestrak
• Cache: %LOCALAPPDATA%\SatMaster\satmaster_tle_cache.txt (Windows)
• Bundled fallback: ISS, AO-7, AO-27, SO-50, FO-29, RS-44 (always available offline)
• TLE age shown in status bar; use Settings → TLE Data → Refresh TLE to force update

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Pass Prediction

• Step: 10s (30s when satellite below -15° elevation)
• AOS/LOS bisection precision: 1 second
• Horizon: passes below configured Min El are filtered from the list
• 24-hour prediction window
• Passes panel: single satellite view or full watchlist view

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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

Range rate is computed by finite difference (2-second interval) on the SGP4 position.

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AOS Voice Alerts

SatMaster announces AOS for all watchlist satellites using Windows TTS (Web Speech API).

• Announcement format: "AOS [satellite name] is rising. Pass will last for X minutes."
• Toggle: StatusBar → 🔊 SOUND ON/OFF
• Voice selection: Settings → Voice Alerts → TTS Voice dropdown
• Recommended voices: Microsoft David or Microsoft Zira (English)
• To install English voices: Windows Settings → Time & Language → Speech → Add voices → English (United States)

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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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Satellite Frequency Database

Built-in frequency database (frontend/src/lib/satdb.js) covers 40+ satellites including:

Satellite	Type	Downlink	Uplink
ISS	FM	437.800 MHz	145.990 MHz
SO-50	FM	436.795 MHz	145.850 MHz
AO-91	FM	145.960 MHz	435.250 MHz
RS-44	Linear	435.640 MHz	145.965 MHz
AO-73	Linear	145.960 MHz	435.140 MHz
FO-29	Linear	435.850 MHz	145.950 MHz
QO-100	Linear	10489.750 MHz	2400.250 MHz
TEVEL2-1…9	FM	436.400 MHz	145.970 MHz
…	…	…	…

Frequencies are auto-applied when a satellite is selected. Multiple frequency entries per satellite are supported (e.g. ISS has FM voice + APRS).

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Future Enhancements

• Multiple satellite tracking (split-screen polar)
• Audio squelch mute between passes
• Log4OM integration for contact logging
• Export pass schedule to CSV/PDF
• Linux/macOS rotor backend