feat: add GetRefraction() to refraction module in @observerly/sidera

pkg/refraction/refraction.go

@@ -0,0 +1,44 @@
+/*****************************************************************************************************************/
+
+//	@author		Michael Roberts <michael@observerly.com>
+//	@package	@observerly/sidera
+//	@license	Copyright © 2021-2024 observerly
+
+/*****************************************************************************************************************/
+
+package refraction
+
+/*****************************************************************************************************************/
+
+import (
+	"math"
+
+	"github.com/observerly/sidera/pkg/common"
+)
+
+/*****************************************************************************************************************/
+
+func GetRefraction(
+	target common.HorizontalCoordinate,
+	pressure float64,
+	temperature float64,
+) float64 {
+	alt := target.Altitude
+
+	if alt < 0 {
+		return math.Inf(1)
+	}
+
+	// The pressure, in Pascals:
+	P := pressure
+
+	// The temperature, in Kelvin:
+	T := temperature
+
+	// Get the atmospheric refraction in degrees, corrected for temperature and pressure:
+	R := (1.02 / math.Tan(common.Radians(alt+10.3/(alt+5.11))) / 60) * (P / 101325) * (283.15 / T)
+
+	return R
+}
+
+/*****************************************************************************************************************/

pkg/refraction/refraction_test.go

@@ -0,0 +1,133 @@
+/*****************************************************************************************************************/
+
+//	@author		Michael Roberts <michael@observerly.com>
+//	@package	@observerly/sidera
+//	@license	Copyright © 2021-2024 observerly
+
+/*****************************************************************************************************************/
+
+package refraction
+
+import (
+	"math"
+	"testing"
+
+	"github.com/observerly/sidera/pkg/common"
+)
+
+/*****************************************************************************************************************/
+
+var target = common.HorizontalCoordinate{
+	Altitude: 50.0,
+	Azimuth:  180.0, // For diffraction tests, the azimuthal angle does not matter.
+}
+
+/*****************************************************************************************************************/
+
+func TestRefractionAtTargetBelowHorizon(t *testing.T) {
+	// Test the refraction at a target below the horizon:
+	R := GetRefraction(common.HorizontalCoordinate{
+		Altitude: -10.0,
+		Azimuth:  180.0,
+	}, 101325, 283.15)
+
+	if R != math.Inf(1) {
+		t.Errorf("Expected refraction to be infinite, got %f", R)
+	}
+}
+
+/*****************************************************************************************************************/
+
+func TestRefractionAtTargetAboveHorizon(t *testing.T) {
+	// Test the refraction at a target above the horizon:
+	R := GetRefraction(target, 101325, 283.15)
+
+	if R == math.Inf(1) {
+		t.Errorf("Expected refraction to be finite, got %f", R)
+	}
+
+	if R <= 0 {
+		t.Errorf("Expected refraction to be positive, got %f", R)
+	}
+
+	if R > 1.5 {
+		t.Errorf("Expected refraction to be less than 1.5, got %f", R)
+	}
+}
+
+/*****************************************************************************************************************/
+
+func TestRefractionAtTargetAtHorizon(t *testing.T) {
+	// Test the refraction at a target below the horizon:
+	R := GetRefraction(common.HorizontalCoordinate{
+		Altitude: 0.0,
+		Azimuth:  180.0,
+	}, 101325, 283.15)
+
+	if R <= 0 {
+		t.Errorf("Expected refraction to be positive, got %f", R)
+	}
+
+	if R > 0.5 {
+		t.Errorf("Expected refraction to be less than 1.5, got %f", R)
+	}
+}
+
+/*****************************************************************************************************************/
+
+func TestRefractionAtTargetWithPressure(t *testing.T) {
+	// Test the refraction at a target above the horizon:
+	R := GetRefraction(target, 102325, 283.15)
+
+	if R == math.Inf(1) {
+		t.Errorf("Expected refraction to be finite, got %f", R)
+	}
+
+	if R <= 0 {
+		t.Errorf("Expected refraction to be positive, got %f", R)
+	}
+
+	if R > 1.5 {
+		t.Errorf("Expected refraction to be less than 1.5, got %f", R)
+	}
+}
+
+/*****************************************************************************************************************/
+
+func TestRefractionAtTargetWithTemperature(t *testing.T) {
+	// Test the refraction at a target above the horizon:
+	R := GetRefraction(target, 101325, 286.15)
+
+	if R == math.Inf(1) {
+		t.Errorf("Expected refraction to be finite, got %f", R)
+	}
+
+	if R <= 0 {
+		t.Errorf("Expected refraction to be positive, got %f", R)
+	}
+
+	if R > 1.5 {
+		t.Errorf("Expected refraction to be less than 1.5, got %f", R)
+	}
+}
+
+/*****************************************************************************************************************/
+
+func TestRefractionAtTargetWithPressureAndTemperature(t *testing.T) {
+	// Test the refraction at a target above the horizon:
+	R := GetRefraction(target, 103325, 288.15)
+
+	if R == math.Inf(1) {
+		t.Errorf("Expected refraction to be finite, got %f", R)
+	}
+
+	if R <= 0 {
+		t.Errorf("Expected refraction to be positive, got %f", R)
+	}
+
+	if R > 1.5 {
+		t.Errorf("Expected refraction to be less than 1.5, got %f", R)
+	}
+}
+
+/*****************************************************************************************************************/