Ryan Malloy
425a6357cc
Project scaffold for decoding Apollo USB signals: - 2287.5 MHz downlink with PM/FM modulation - 1.024 MHz BPSK subcarrier (PCM telemetry) - 1.25 MHz FM subcarrier (voice) - 128-word PCM frames at 50 fps Based on NAA Course A-624 Study Guide (1965) and Virtual AGC.
83 lines
2.6 KiB
Markdown
83 lines
2.6 KiB
Markdown
# gr-apollo
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GNU Radio 3.10+ out-of-tree module for decoding **Apollo Unified S-Band (USB)** telecommunications signals.
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## Overview
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The Apollo Unified S-Band system was the primary communication link between the spacecraft and Earth during the Apollo missions (1967-1972). This module implements GNU Radio blocks to decode these signals, enabling:
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- Reception of Apollo-era recordings
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- Integration with the [Virtual AGC](https://www.ibiblio.org/apollo/) emulator
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- Educational exploration of 1960s space communications
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## Signal Specifications
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| Parameter | Value |
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|-----------|-------|
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| Downlink Frequency | 2287.5 MHz |
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| Uplink Frequency | 2106.40625 MHz |
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| Coherent Ratio | 240/221 |
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| PM Peak Deviation | 0.133 rad (7.6°) |
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| PCM Subcarrier | 1.024 MHz BPSK |
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| PCM Bit Rate | 51.2 kbps (high) / 1.6 kbps (low) |
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| Voice Subcarrier | 1.25 MHz FM |
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| Frame Length | 128 words × 8 bits @ 50 fps |
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## Installation
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```bash
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# Using uv (recommended)
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uv pip install -e .
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# Install GRC blocks
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cp grc/*.yml ~/.local/share/gnuradio/grc/blocks/
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```
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## Signal Chain
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```
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RF 2287.5 MHz
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│
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▼
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┌─────────────┐
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│ Carrier PLL │ ◄── 240/221 coherent recovery
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└─────────────┘
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│
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▼
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┌─────────────┐
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│ PM Demod │ ◄── 0.133 rad peak deviation
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└─────────────┘
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│
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├────────────────────┬──────────────────┐
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▼ ▼ ▼
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┌──────────┐ ┌──────────┐ ┌──────────┐
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│ 1.024MHz │ │ 1.25 MHz │ │ Ranging │
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│ BPSK │ │ FM │ │ PRN │
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└──────────┘ └──────────┘ └──────────┘
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│ │
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▼ ▼
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┌──────────┐ ┌──────────┐
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│ PCM Sync │ │ Voice │
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│ 51.2kbps │ │ 300-3kHz │
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└──────────┘ └──────────┘
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│
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▼
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┌──────────┐
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│ 128-word │
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│ Demux │
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└──────────┘
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│
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▼
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Telemetry
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```
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## References
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- [Virtual AGC Project](https://www.ibiblio.org/apollo/)
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- [NASA Technical Reports](https://ntrs.nasa.gov/)
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- NAA Course A-624: Telecommunication Systems Study Guide (1965)
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## License
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MIT
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