해상 위성 및 무인기 합성개구레이더(SAR) 기반 잠수함 수중 항적(Internal Wave Wake) 해수면 마이크로파 변조 패턴 실시간 역추적 C# SIMD 필터

3. Zero-Allocation C# SIMD SAR 후류 역추적 필터 구현

SAR 2D 밝기 매트릭스를 입력받아 내부파 패킷 파장과 V자형 꼭지점을 추출하고 잠수함 3차원 운동 벡터를 도출하는 C# .NET 9.0 엔진입니다.

using System;
using System.Runtime.CompilerServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;

namespace ZeliDesk.Defense.SarSubmarineWake
{
    public readonly ref struct SarTileTelemetry
    {
        public readonly float StripeWavelengthMeters; // Peak spatial period
        public readonly float WakeApexAngleDeg;        // V-shape half angle
        public readonly float PeakNrcsModulationDb;    // dB contrast (+/- 2.5 dB)
        public readonly float SeaPycnoclineDepthM;    // Oceanographic thermocline
        public readonly float DensityContrastRatio;    // Delta rho / rho ~ 0.0025

        public SarTileTelemetry(float lambda, float angle, float nrcsDb, float pycDepth, float dRho)
        {
            StripeWavelengthMeters = lambda;
            WakeApexAngleDeg = angle;
            PeakNrcsModulationDb = nrcsDb;
            SeaPycnoclineDepthM = pycDepth;
            DensityContrastRatio = dRho;
        }
    }

    public ref struct SubmarineWakeEstimate
    {
        public float EstimatedSpeedKnots;
        public float EstimatedDepthMeters;
        public float SubmarineHeadingDeg;
        public float DisplacementTonnageEstimate;
        public bool ConfirmedInternalWakeContact;
    }

    public static class SubmarineSarWakeInversionEngine
    {
        private const float Gravity = 9.80665f;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void InvertSubmarineKinematics(
            in SarTileTelemetry telemetry,
            float radarAzimuthDeg,
            ref SubmarineWakeEstimate output)
        {
            // 1. Calculate Internal Gravity Wave Phase Speed c0
            // c0 = sqrt(g * (delta_rho / rho) * h1) for h1 << h2
            float h1 = MathF.Max(10.0f, telemetry.SeaPycnoclineDepthM);
            float c0 = MathF.Sqrt(Gravity * telemetry.DensityContrastRatio * h1);

            // 2. Submarine Speed from Wake Mach Angle: sin(theta) = c0 / U_sub
            float thetaRad = telemetry.WakeApexAngleDeg * (MathF.PI / 180.0f);
            float sinTheta = MathF.Sin(thetaRad);

            if (sinTheta < 0.05f || sinTheta > 0.95f)
            {
                output.ConfirmedInternalWakeContact = false;
                return;
            }

            float uSubMps = c0 / sinTheta;
            float uSubKnots = uSubMps * 1.94384f; // Convert m/s to knots
            output.EstimatedSpeedKnots = uSubKnots;

            // 3. Submarine Depth Estimation from Soliton Amplitude & NRCS Contrast
            // Deeper submarine produces weaker surface velocity gradient
            // delta_sigma / sigma ~ A * exp(-2 * k_IW * Z_sub)
            float kIw = 2.0f * MathF.PI / MathF.Max(50.0f, telemetry.StripeWavelengthMeters);
            float contrastLinear = MathF.Pow(10.0f, telemetry.PeakNrcsModulationDb / 10.0f);

            // Invert depth: Z_sub = -ln(contrast / base) / (2 * k_IW)
            float rawDepth = MathF.Log(MathF.Max(0.1f, 8.5f / contrastLinear)) / (2.0f * kIw);
            float clampedDepth = Math.Clamp(rawDepth + h1 * 0.5f, 25.0f, 400.0f);
            output.EstimatedDepthMeters = clampedDepth;

            // 4. Heading Alignment
            output.SubmarineHeadingDeg = radarAzimuthDeg + telemetry.WakeApexAngleDeg;

            // 5. Tonnage from Wavelength & Energy
            // Displacement ~ f(lambda_IW^2 * amplitude)
            float tonnage = (telemetry.StripeWavelengthMeters * telemetry.StripeWavelengthMeters) * 0.12f;
            output.DisplacementTonnageEstimate = Math.Clamp(tonnage, 1200.0f, 18000.0f);

            output.ConfirmedInternalWakeContact = (contrastLinear > 1.25f && uSubKnots > 3.0f && uSubKnots < 35.0f);
        }
    }
}