ASTRA ATC Models
Fine-tuned models for Singapore military air traffic control, built for two training simulators:
- astra/ - ASTRA, the ATC training simulator (ASR and display formatter)
- par/ - the Precision Approach Radar (PAR) talkdown simulator (ASR)
The ASTRA and PAR models were developed separately for their own phraseology and callsigns, so they are not a single model: use the ASTRA ASR for ASTRA and the PAR ASR for PAR. Future work may train one ASR model that handles both.
astra/
ASR/whisper/ Whisper Large v3 (legacy CTranslate2 backend)
ASR/parakeet/ Parakeet-TDT 0.6B v2 (NeMo checkpoint)
LLM/ Qwen3-1.7B display formatter (legacy)
par/
ASR/ Parakeet-TDT 0.6B v2 (NeMo .nemo)
ASTRA
Pipeline
Audio --> VAD (Silero) --> ASR (Whisper or Parakeet) --> Rule Formatter --> Display Text
"camel climb flight level zero nine zero"
"CAMEL climb FL090"
The production pipeline uses a deterministic rule-based formatter instead of the legacy LLM formatter.
Models
astra/ASR/whisper/ - Whisper Large v3 (Legacy CTranslate2 backend)
Fine-tuned for Singapore military ATC speech. Uses CTranslate2 float16 format for fast inference with faster-whisper.
| Metric | Value |
|---|---|
| WER | 0.66% |
| Base model | openai/whisper-large-v3 |
| Size | 2.9 GB |
| Runtime | faster-whisper / CTranslate2 |
astra/ASR/parakeet/ - Parakeet-TDT 0.6B v2 (NeMo checkpoint)
Fine-tuned NeMo Parakeet model for Singapore military ATC speech. Published as a raw checkpoint together with the tokenizer artifacts required to restore it.
| Metric | Value |
|---|---|
| Validation WER | 0.72% |
| Base model | nvidia/parakeet-tdt-0.6b-v2 |
| Size | 7.0 GB |
| Runtime | nemo_toolkit[asr] |
astra/LLM/ - Qwen3-1.7B Display Formatter (Legacy)
Legacy. Superseded by the deterministic rule formatter. Retained for reference only.
Converts normalized ASR output into structured ATC display text.
| Metric | Value |
|---|---|
| Exact match | 100% (161/161) |
| Base model | unsloth/Qwen3-1.7B |
| Size | 3.3 GB |
Architecture
Audio --> VAD (Silero) --> ASR backend --> Post-processing --> Rule Formatter --> Display Text
| Component | Technology | Notes |
|---|---|---|
| VAD | Silero VAD | Shared frontend for both ASR backends |
| ASR (legacy) | Whisper Large v3 (CTranslate2) | Lower-memory legacy backend |
| ASR (current NeMo path) | Parakeet-TDT 0.6B v2 | Fine-tuned NeMo checkpoint |
| Formatter | Deterministic rules | Converts normalized speech to ATC display text |
Domain
Singapore military ATC covering Tengah and Paya Lebar operations, military phraseology, 100+ callsigns, and approach / recovery / emergency traffic.
Training History
ASR
| Run | WER | Base | Key Change |
|---|---|---|---|
| ct2_run5 | 0.48% | jacktol/whisper-large-v3-finetuned-for-ATC | Initial fine-tune |
| ct2_run6 | 0.40% | jacktol/whisper-large-v3-finetuned-for-ATC | +augmentation, weight decay |
| ct2_run7 | 0.24% | jacktol/whisper-large-v3-finetuned-for-ATC | Frozen encoder, +50 real recordings |
| ct2_run8 | 0.66% | openai/whisper-large-v3 | Full retrain from base, enhanced augmentation |
| parakeet_atc | 0.72% | nvidia/parakeet-tdt-0.6b-v2 | NeMo fine-tune with ATC radio augmentation, best checkpoint at epoch 76 |
LLM
| Run | Accuracy | Key Change |
|---|---|---|
| llm_run3 | 98.1% (Qwen3-8B) | QLoRA 4-bit, 871 examples |
| llm_run4 | 100% (Qwen3-1.7B) | bf16 LoRA, 1,915 examples with ASR noise augmentation |
Quick Start
Whisper ASR
from faster_whisper import WhisperModel
model = WhisperModel("./astra/ASR/whisper", device="cuda", compute_type="float16")
segments, info = model.transcribe("audio.wav", language="en", beam_size=5)
text = " ".join(seg.text.strip() for seg in segments)
Parakeet ASR
See astra/ASR/parakeet/README.md for the NeMo restore example and tokenizer artifact requirements.
PAR
par/ASR/ - Parakeet-TDT 0.6B v2 (NeMo .nemo)
Fine-tuned for PAR talkdown speech: fast, clipped controller calls and pilot replies. Self-contained .nemo, so no
tokenizer artifacts are needed. Details, results per test set and training stats in par/ASR/README.md.
| Metric | Value |
|---|---|
| PAR held-out WER | 0.17% |
| Base model | nvidia/parakeet-tdt-0.6b-v2 |
| Size | 2.5 GB |
| Runtime | nemo_toolkit[asr] |
Download
# Full repo
huggingface-cli download aether-raid/astra-atc-models --local-dir ./models
# ASTRA Whisper ASR only
huggingface-cli download aether-raid/astra-atc-models --include "astra/ASR/whisper/*" --local-dir ./models
# ASTRA Parakeet ASR only
huggingface-cli download aether-raid/astra-atc-models --include "astra/ASR/parakeet/*" --local-dir ./models
# ASTRA LLM only (legacy)
huggingface-cli download aether-raid/astra-atc-models --include "astra/LLM/*" --local-dir ./models
# PAR ASR only
huggingface-cli download aether-raid/astra-atc-models --include "par/ASR/*" --local-dir ./models