own-tools/pkg/orbitviewer/sgp4_test.go

package orbitviewer

import (
	"math"
	"testing"
	"time"
)

// Standard ISS TLE sample
const (
	testISSName  = "ISS (ZARYA)"
	testISSLine1 = "1 25544U 98067A   24080.56944444  .00014524  00000-0  26388-3 0  9993"
	testISSLine2 = "2 25544  51.6416 195.4568 0004928 120.1234 239.9876 15.49876543445566"
)

func TestParseTLE(t *testing.T) {
	tle, err := ParseTLE(testISSName, testISSLine1, testISSLine2)
	if err != nil {
		t.Fatalf("ParseTLE failed: %v", err)
	}

	if tle.NoradID != 25544 {
		t.Errorf("Expected NoradID 25544, got %d", tle.NoradID)
	}
	if math.Abs(tle.InclinationDeg-51.6416) > 1e-4 {
		t.Errorf("Expected Inclination 51.6416, got %f", tle.InclinationDeg)
	}
	if math.Abs(tle.Eccentricity-0.0004928) > 1e-6 {
		t.Errorf("Expected Eccentricity 0.0004928, got %f", tle.Eccentricity)
	}
}

func TestSGP4Propagation(t *testing.T) {
	tle, err := ParseTLE(testISSName, testISSLine1, testISSLine2)
	if err != nil {
		t.Fatalf("ParseTLE failed: %v", err)
	}

	model, err := NewSGP4Model(tle)
	if err != nil {
		t.Fatalf("NewSGP4Model failed: %v", err)
	}

	// Propagate at epoch (tsince = 0)
	pos, vel, err := model.PropagateMinutes(0)
	if err != nil {
		t.Fatalf("PropagateMinutes(0) failed: %v", err)
	}

	rKm := math.Sqrt(pos.X*pos.X + pos.Y*pos.Y + pos.Z*pos.Z)
	// ISS orbit radius should be around 6700 - 6850 km (altitude 350 - 450 km)
	if rKm < 6650 || rKm > 6900 {
		t.Errorf("Unrealistic orbital radius: %f km", rKm)
	}

	vKmS := math.Sqrt(vel.X*vel.X + vel.Y*vel.Y + vel.Z*vel.Z)
	// Orbital velocity for LEO should be around 7.5 - 7.8 km/s
	if vKmS < 7.2 || vKmS > 8.0 {
		t.Errorf("Unrealistic orbital velocity: %f km/s", vKmS)
	}

	// Propagate 90 minutes (about 1 orbit)
	geo, _, err := model.GeodeticPosition(tle.EpochTime.Add(90 * time.Minute))
	if err != nil {
		t.Fatalf("GeodeticPosition failed: %v", err)
	}

	if geo.Altitude < 350 || geo.Altitude > 460 {
		t.Errorf("Unrealistic altitude after 90 min: %f km", geo.Altitude)
	}
	if geo.Latitude < -55 || geo.Latitude > 55 {
		t.Errorf("Latitude %f exceeds inclination range +/-52 deg by too much", geo.Latitude)
	}
}

func TestLookAnglesAndSun(t *testing.T) {
	// Observer in San Francisco
	obsSF := Geodetic{
		Latitude:  37.7749,
		Longitude: -122.4194,
		Altitude:  0.03, // 30 meters
	}

	// Target directly above observer at 400km altitude
	targetECEF := GeodeticToECEF(Geodetic{
		Latitude:  37.7749,
		Longitude: -122.4194,
		Altitude:  400.0,
	})

	angles := CalculateLookAngles(obsSF, targetECEF)
	if math.Abs(angles.Elevation-90.0) > 0.1 {
		t.Errorf("Expected elevation ~90 deg for overhead satellite, got %f", angles.Elevation)
	}
	if math.Abs(angles.Range-400.0) > 1.0 {
		t.Errorf("Expected range ~400 km, got %f", angles.Range)
	}

	// Test Sun elevation at noon vs midnight
	noonUTC := time.Date(2024, 6, 21, 20, 0, 0, 0, time.UTC) // roughly solar noon in SF (12:00 PDT)
	elNoon := ObserverSunElevation(obsSF, noonUTC)
	if elNoon < 60.0 {
		t.Errorf("Expected high solar elevation at summer solstice noon, got %f", elNoon)
	}

	midnightUTC := time.Date(2024, 6, 21, 8, 0, 0, 0, time.UTC) // midnight in SF
	elMidnight := ObserverSunElevation(obsSF, midnightUTC)
	if elMidnight > -15.0 {
		t.Errorf("Expected negative solar elevation at midnight, got %f", elMidnight)
	}
}

func TestPredictPasses(t *testing.T) {
	tle, err := ParseTLE(testISSName, testISSLine1, testISSLine2)
	if err != nil {
		t.Fatalf("ParseTLE failed: %v", err)
	}

	model, err := NewSGP4Model(tle)
	if err != nil {
		t.Fatalf("NewSGP4Model failed: %v", err)
	}

	obs := Geodetic{
		Latitude:  40.7128, // New York
		Longitude: -74.0060,
		Altitude:  0.01,
	}

	// Predict passes for 5 days starting at epoch
	passes, err := PredictPasses(model, PredictPassesOptions{
		Observer:        obs,
		StartTime:       tle.EpochTime,
		Days:            5,
		MinElevationDeg: 10.0,
		VisibleOnly:     false,
		StandardMag:     -1.8,
	})
	if err != nil {
		t.Fatalf("PredictPasses failed: %v", err)
	}

	if len(passes) == 0 {
		t.Errorf("Expected at least a few passes over 5 days for ISS over NYC, got 0")
	}

	t.Logf("Found %d passes over 5 days", len(passes))
	for i, p := range passes {
		t.Logf("Pass #%d: Start=%s, MaxEl=%.1f deg (%s), End=%s, Dur=%s, Vis=%s, Mag=%.1f",
			i+1, p.Start.TimeFormatted, p.Max.Elevation, p.Max.AzimuthCardinal,
			p.End.TimeFormatted, p.DurationFormatted, p.Visibility, p.EstimatedMag)
	}
}

func TestTiangongNYC(t *testing.T) {
	entry, ok := DefaultCatalog.Get("tiangong")
	if !ok {
		t.Fatalf("Tiangong not in default catalog")
	}

	model, err := NewSGP4Model(entry.TLE)
	if err != nil {
		t.Fatalf("NewSGP4Model failed: %v", err)
	}

	obsNYC := Geodetic{
		Latitude:  40.7128,
		Longitude: -74.0060,
		Altitude:  0.01,
	}

	// 1. All passes
	allPasses, err := PredictPasses(model, PredictPassesOptions{
		Observer:        obsNYC,
		StartTime:       time.Now().UTC(),
		Days:            10,
		MinElevationDeg: 10.0,
		VisibleOnly:     false,
		StandardMag:     -1.0,
	})
	if err != nil {
		t.Fatalf("PredictPasses failed: %v", err)
	}
	t.Logf("Tiangong over NYC - ALL passes: %d", len(allPasses))
	for i, p := range allPasses {
		t.Logf("All pass #%d: Start=%s, MaxEl=%.1f, Vis=%s, Mag=%.1f", i+1, p.Start.Time.Format(time.RFC3339), p.Max.Elevation, p.Visibility, p.EstimatedMag)
	}

	// 2. Visible passes only
	visPasses, _ := PredictPasses(model, PredictPassesOptions{
		Observer:        obsNYC,
		StartTime:       time.Now().UTC(),
		Days:            10,
		MinElevationDeg: 10.0,
		VisibleOnly:     true,
		StandardMag:     -1.0,
	})
	t.Logf("Tiangong over NYC - VISIBLE ONLY passes: %d", len(visPasses))
}