[feat](trx-noaa): add NOAA APT satellite image decoder

New trx-noaa crate: FFT-based Hilbert transform (rustfft) for 2400 Hz
AM demodulation, sync A detection via cross-correlation, line assembly
at 4160 Hz, and JPEG output via the image crate.

- trx-core: NoaaImage type, DecodedMessage::NoaaImage variant,
  noaa_decode_enabled/noaa_decode_reset_seq on RigState/RigSnapshot,
  AUDIO_MSG_NOAA_IMAGE = 0x16
- trx-server: DecoderHistories::noaa, run_noaa_decoder task (activates
  on noaa_decode_enabled, auto-finalises after 30 s silence), saves
  JPEGs to ~/.cache/trx-rs/noaa/<YYYY-MM-DD_HH-MM-SS>.jpg, forwards
  events over TCP audio channel and history replay

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-core/src/audio.rs

@@ -66,6 +66,8 @@ pub const AUDIO_MSG_VCHAN_BW: u8 = 0x13;
 pub const AUDIO_MSG_FT4_DECODE: u8 = 0x14;
 /// Server → client: FT2 decoded message (JSON `DecodedMessage::Ft2`).
 pub const AUDIO_MSG_FT2_DECODE: u8 = 0x15;
+/// Server → client: NOAA APT image complete (JSON `DecodedMessage::NoaaImage`).
+pub const AUDIO_MSG_NOAA_IMAGE: u8 = 0x16;
 
 /// Maximum payload size for normal messages (1 MB).
 const MAX_PAYLOAD_SIZE: u32 = 1_048_576;

src/trx-core/src/decode.rs

@@ -28,6 +28,8 @@ pub enum DecodedMessage {
     Ft2(Ft8Message),
     #[serde(rename = "wspr")]
     Wspr(WsprMessage),
+    #[serde(rename = "noaa_image")]
+    NoaaImage(NoaaImage),
 }
 
 impl DecodedMessage {
@@ -40,6 +42,7 @@ impl DecodedMessage {
             Self::Cw(m) => m.rig_id = Some(id),
             Self::Ft8(m) | Self::Ft4(m) | Self::Ft2(m) => m.rig_id = Some(id),
             Self::Wspr(m) => m.rig_id = Some(id),
+            Self::NoaaImage(m) => m.rig_id = Some(id),
         }
     }
 
@@ -52,6 +55,7 @@ impl DecodedMessage {
             Self::Cw(m) => m.rig_id.as_deref(),
             Self::Ft8(m) | Self::Ft4(m) | Self::Ft2(m) => m.rig_id.as_deref(),
             Self::Wspr(m) => m.rig_id.as_deref(),
+            Self::NoaaImage(m) => m.rig_id.as_deref(),
         }
     }
 }
@@ -203,6 +207,23 @@ pub struct Ft8Message {
     pub message: String,
 }
 
+/// A completed NOAA APT satellite image, saved to disk as a JPEG.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct NoaaImage {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub rig_id: Option<String>,
+    /// UTC timestamp (milliseconds since epoch) of pass start (first decoded line).
+    pub pass_start_ms: i64,
+    /// UTC timestamp (milliseconds since epoch) when the image was finalised.
+    pub pass_end_ms: i64,
+    /// Number of decoded image lines.
+    pub line_count: u32,
+    /// Absolute filesystem path to the saved JPEG file.
+    pub path: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub ts_ms: Option<i64>,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct WsprMessage {
     #[serde(skip_serializing_if = "Option::is_none")]

src/trx-core/src/rig/state.rs

@@ -46,6 +46,8 @@ pub struct RigState {
     #[serde(default)]
     pub wspr_decode_enabled: bool,
     #[serde(default)]
+    pub noaa_decode_enabled: bool,
+    #[serde(default)]
     pub cw_auto: bool,
     #[serde(default)]
     pub cw_wpm: u32,
@@ -77,6 +79,8 @@ pub struct RigState {
     pub ft2_decode_reset_seq: u64,
     #[serde(default, skip_serializing)]
     pub wspr_decode_reset_seq: u64,
+    #[serde(default, skip_serializing)]
+    pub noaa_decode_reset_seq: u64,
 }
 
 /// Mode supported by the rig.
@@ -159,6 +163,7 @@ impl RigState {
             ft4_decode_enabled: false,
             ft2_decode_enabled: false,
             wspr_decode_enabled: false,
+            noaa_decode_enabled: false,
             cw_auto: true,
             cw_wpm: 15,
             cw_tone_hz: 700,
@@ -172,6 +177,7 @@ impl RigState {
             ft4_decode_reset_seq: 0,
             ft2_decode_reset_seq: 0,
             wspr_decode_reset_seq: 0,
+            noaa_decode_reset_seq: 0,
         }
     }
 
@@ -231,6 +237,7 @@ impl RigState {
             ft4_decode_enabled: snapshot.ft4_decode_enabled,
             ft2_decode_enabled: snapshot.ft2_decode_enabled,
             wspr_decode_enabled: snapshot.wspr_decode_enabled,
+            noaa_decode_enabled: snapshot.noaa_decode_enabled,
             filter: snapshot.filter,
             spectrum: None, // spectrum flows through /api/spectrum, not persistent state
             vchan_rds: None, // vchan RDS flows through /api/spectrum, not persistent state
@@ -241,6 +248,7 @@ impl RigState {
             ft4_decode_reset_seq: 0,
             ft2_decode_reset_seq: 0,
             wspr_decode_reset_seq: 0,
+            noaa_decode_reset_seq: 0,
         }
     }
 
@@ -278,6 +286,7 @@ impl RigState {
             ft4_decode_enabled: self.ft4_decode_enabled,
             ft2_decode_enabled: self.ft2_decode_enabled,
             wspr_decode_enabled: self.wspr_decode_enabled,
+            noaa_decode_enabled: self.noaa_decode_enabled,
             filter: self.filter.clone(),
             spectrum: self.spectrum.clone(),
             vchan_rds: self.vchan_rds.clone(),
@@ -489,6 +498,8 @@ pub struct RigSnapshot {
     #[serde(default)]
     pub wspr_decode_enabled: bool,
     #[serde(default)]
+    pub noaa_decode_enabled: bool,
+    #[serde(default)]
     pub cw_auto: bool,
     #[serde(default)]
     pub cw_wpm: u32,