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)

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

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

Prerequisites

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

# Verify
wails doctor

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

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

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

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

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

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

Keyboard Shortcuts

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

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

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

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