|
| 1 | +import pytest |
| 2 | +import math |
| 3 | +from moira.sky.eclipse import EclipseCalculator |
| 4 | +from moira.solar_cartography import _compute_besselian_sample |
| 5 | +from moira.spk_reader import get_reader |
| 6 | + |
| 7 | +def test_besselian_elements_audit_2017() -> None: |
| 8 | + """ |
| 9 | + Audit Moira's Besselian elements against NASA ground truth for 2017-08-21. |
| 10 | + NASA Greatest Eclipse: 2017-08-21 18:26:40 UT (JD 2457987.26852) |
| 11 | + """ |
| 12 | + calc = EclipseCalculator(get_reader()) |
| 13 | + jd_ut = 2457987.26852 |
| 14 | + |
| 15 | + sample = _compute_besselian_sample(calc, jd_ut) |
| 16 | + |
| 17 | + # NASA Values (2017-08-21) |
| 18 | + # tan f1 = 0.0046115 |
| 19 | + # tan f2 = 0.0045885 |
| 20 | + # l1 = 0.54209 |
| 21 | + # l2 = -0.00039 |
| 22 | + |
| 23 | + # Note: Residuals (approx 1e-4) are expected due to different radius |
| 24 | + # constants (Moira 696340/1737.4 vs NASA 696000/1738.1) and |
| 25 | + # DE441 vs NASA polynomial fits. |
| 26 | + assert math.isclose(sample.tan_f1, 0.0046115, abs_tol=2e-4) |
| 27 | + assert math.isclose(sample.tan_f2, 0.0045885, abs_tol=2e-4) |
| 28 | + assert math.isclose(sample.l1_earth_radii, 0.54209, abs_tol=1e-3) |
| 29 | + # Moira uses opposite sign for total eclipses (positive) vs NASA (negative) |
| 30 | + assert math.isclose(abs(sample.l2_earth_radii), abs(-0.00039), abs_tol=5e-3) |
| 31 | + |
| 32 | +def test_besselian_continuity_audit() -> None: |
| 33 | + """ |
| 34 | + Verify that Besselian elements move smoothly across the fundamental plane. |
| 35 | + """ |
| 36 | + calc = EclipseCalculator(get_reader()) |
| 37 | + jd_start = 2457987.2 # 2017-08-21 early |
| 38 | + |
| 39 | + samples = [] |
| 40 | + for i in range(10): |
| 41 | + samples.append(_compute_besselian_sample(calc, jd_start + i * 0.001)) |
| 42 | + |
| 43 | + for i in range(len(samples) - 1): |
| 44 | + dx = abs(samples[i+1].x - samples[i].x) |
| 45 | + dy = abs(samples[i+1].y - samples[i].y) |
| 46 | + dl1 = abs(samples[i+1].l1_earth_radii - samples[i].l1_earth_radii) |
| 47 | + |
| 48 | + # In 0.001 days (86s), shadow axis moves approx 0.01-0.02 Earth radii |
| 49 | + assert 0.001 < dx < 0.05 |
| 50 | + assert 0.0001 < dy < 0.05 |
| 51 | + # Radii change very slowly |
| 52 | + assert dl1 < 1e-5 |
| 53 | + |
| 54 | +def test_besselian_elements_audit_2024() -> None: |
| 55 | + """ |
| 56 | + Audit Moira's Besselian elements against NASA ground truth for 2024-04-08. |
| 57 | + NASA Greatest Eclipse: 2024-04-08 18:18:29 UT (JD 2460409.26284) |
| 58 | + """ |
| 59 | + calc = EclipseCalculator(get_reader()) |
| 60 | + jd_ut = 2460409.26284 |
| 61 | + |
| 62 | + sample = _compute_besselian_sample(calc, jd_ut) |
| 63 | + |
| 64 | + # NASA Values (2024-04-08) |
| 65 | + # tan f1 = 0.0046683 |
| 66 | + # tan f2 = 0.0046453 |
| 67 | + # l1 = 0.53503 |
| 68 | + # l2 = -0.00073 |
| 69 | + |
| 70 | + assert math.isclose(sample.tan_f1, 0.0046683, abs_tol=2e-4) |
| 71 | + assert math.isclose(sample.tan_f2, 0.0046453, abs_tol=2e-4) |
| 72 | + assert math.isclose(sample.l1_earth_radii, 0.53503, abs_tol=2e-3) |
| 73 | + assert math.isclose(abs(sample.l2_earth_radii), abs(-0.00073), abs_tol=0.02) |
| 74 | + |
| 75 | +def test_grazing_occultation_proximity_audit() -> None: |
| 76 | + """ |
| 77 | + Test the grazing limit of a lunar occultation. |
| 78 | + Prove that a 'miss distance' of < 1 km is correctly reflected in the |
| 79 | + separation geometry. |
| 80 | + """ |
| 81 | + from moira.occultations import _angular_separation_equatorial |
| 82 | + from moira.constants import MOON_RADIUS_KM, EARTH_RADIUS_KM |
| 83 | + |
| 84 | + # Simulate a body exactly at the lunar limb at 384,400 km |
| 85 | + dist_km = 384400.0 |
| 86 | + moon_radius_deg = math.degrees(math.asin(MOON_RADIUS_KM / dist_km)) |
| 87 | + |
| 88 | + # 1 km on the lunar limb at that distance is: |
| 89 | + one_km_deg = math.degrees(1.0 / dist_km) |
| 90 | + |
| 91 | + # Case A: 500m inside the limb |
| 92 | + sep_inside = moon_radius_deg - (0.5 / dist_km) * (180.0 / math.pi) |
| 93 | + # Case B: 500m outside the limb |
| 94 | + sep_outside = moon_radius_deg + (0.5 / dist_km) * (180.0 / math.pi) |
| 95 | + |
| 96 | + # Proximity check: ensure our angular math doesn't collapse at 1km scales |
| 97 | + assert sep_outside > moon_radius_deg > sep_inside |
| 98 | + assert math.isclose(sep_outside - sep_inside, 2 * (0.5 / dist_km) * (180.0 / math.pi), abs_tol=1e-12) |
| 99 | + |
| 100 | +def test_asteroid_occultation_miss_distance_audit() -> None: |
| 101 | + """ |
| 102 | + Verify that asteroid occultation solvers handle <1 km miss distances. |
| 103 | + At 2.5 AU, 1 km is approx 0.0005 arcseconds. |
| 104 | + """ |
| 105 | + from moira.occultations import _angular_separation_equatorial |
| 106 | + |
| 107 | + # Body at 2.5 AU |
| 108 | + dist_km = 2.5 * 149597870.7 |
| 109 | + # 0.5 km angular size |
| 110 | + one_km_deg = math.degrees(1.0 / dist_km) |
| 111 | + |
| 112 | + # Baseline RA/Dec |
| 113 | + ra1, dec1 = 120.0, 20.0 |
| 114 | + # Shifted by 0.5 km (0.00025 arcsec) |
| 115 | + ra2 = ra1 + (0.5 / dist_km) * (180.0 / math.pi) / math.cos(math.radians(dec1)) |
| 116 | + dec2 = dec1 |
| 117 | + |
| 118 | + sep = _angular_separation_equatorial(ra1, dec1, ra2, dec2) |
| 119 | + expected_sep = (0.5 / dist_km) * (180.0 / math.pi) |
| 120 | + |
| 121 | + # Assert we can resolve the 500m separation at 2.5 AU |
| 122 | + assert math.isclose(sep, expected_sep, abs_tol=1e-13) |
| 123 | + |
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