{"abstract":"Irradiance projection becomes negative when the sun is behind the panel.","category":"Solar tracker geometry","checks":7,"contract":"Panel tilted by tilt degrees from horizontal, facing pan_az (clockwise from north). zenith = 90 - sun_el. cos(aoi) = cos(zen)cos(tilt) + sin(zen)sin(tilt)cos(sun_az - pan_az), clamped to [-1, 1]. Return [aoi degrees rounded 3, max(cos aoi, 0) rounded 4, 'front' or 'back'], or [None, 0.0, 'night'] when sun_el <= 0.","contract_signature":"tilt, pan_az, sun_az, sun_el","evaluation_group":"w2-solar_tracker_geometry-fixed-panel-incidence","failed_approach":"Taking the absolute value credits rear-side sun to the front face.","family":"w2-solar_tracker_geometry-fixed-panel-incidence-back-side-projection","id":"FA-93406","implementations":{"attempt":{"sha256":"7df7b772bdebde3ede30703a2b7721222c8712eca676eb5d0aa852f5932fb408","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(tilt, pan_az, sun_az, sun_el):\n    if sun_el <= 0:\n        return [None, 0.0, 'night']\n    zen = math.radians(90 - sun_el)\n    t = math.radians(tilt)\n    c = math.cos(zen) * math.cos(t) + math.sin(zen) * math.sin(t) * math.cos(math.radians(sun_az - pan_az))\n    c = max(-1.0, min(1.0, c))\n    aoi = math.degrees(math.acos(c))\n    side = 'front' if c >= 0 else 'back'\n    return [round(aoi, 3), round(abs(c), 4), side]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[['boundary: sun on horizon', [30, 180, 180, 0], [None, 0.0, 'night']],\n  ['normal: sun normal to panel', [30, 180, 180, 60], [0.0, 1.0, 'front']],\n  ['boundary: sun behind vertical panel', [90, 180, 0, 20], [160.0, 0.0, 'back']],\n  ['regression: back-side projection', [30, 135, 0, 10], [101.408, 0.0, 'back']],\n  ['regression: back-side projection (partial repair)', [90, 180, 30, 20], [144.469, 0.0, 'back']],\n  ['control 1', [0, 180, 225, -5], [None, 0.0, 'night']],\n  ['control 2', [0, 135, 150, 45], [45.0, 0.7071, 'front']]],\n [['boundary: sun on horizon', [30, 180, 180, 0], [None, 0.0, 'night']],\n  ['normal: sun normal to panel', [30, 180, 180, 60], [0.0, 1.0, 'front']],\n  ['boundary: sun behind vertical panel', [90, 180, 0, 20], [160.0, 0.0, 'back']],\n  ['regression: back-side projection', [90, 180, 30, 75], [102.953, 0.0, 'back']],\n  ['regression: back-side projection (partial repair)', [25, 180, 60, 10], [92.907, 0.0, 'back']],\n  ['control 1', [60, 225, 270, 20], [41.716, 0.7465, 'front']],\n  ['control 2', [20, 90, 0, 89], [20.024, 0.9395, 'front']]],\n [['boundary: sun on horizon', [30, 180, 180, 0], [None, 0.0, 'night']],\n  ['normal: sun normal to panel', [30, 180, 180, 60], [0.0, 1.0, 'front']],\n  ['boundary: sun behind vertical panel', [90, 180, 0, 20], [160.0, 0.0, 'back']],\n  ['regression: back-side projection', [90, 90, 200, 30], [107.229, 0.0, 'back']],\n  ['regression: back-side projection (partial repair)', [20, 180, 30, 10], [97.384, 0.0, 'back']],\n  ['control 1', [60, 90, 135, 30], [38.709, 0.7803, 'front']],\n  ['control 2', [45, 270, 60, 89], [45.868, 0.6963, 'front']]],\n [['boundary: sun on horizon', [30, 180, 180, 0], [None, 0.0, 'night']],\n  ['normal: sun normal to panel', [30, 180, 180, 60], [0.0, 1.0, 'front']],\n  ['boundary: sun behind vertical panel', [90, 180, 0, 20], [160.0, 0.0, 'back']],\n  ['regression: back-side projection', [25, 270, 100, 3], [111.604, 0.0, 'back']],\n  ['regression: back-side projection (partial repair)', [10, 180, 60, 3], [92.015, 0.0, 'back']],\n  ['control 1', [45, 180, 315, 0], [None, 0.0, 'night']],\n  ['control 2', [30, 90, 225, 45], [68.754, 0.3624, 'front']]],\n [['boundary: sun on horizon', [30, 180, 180, 0], [None, 0.0, 'night']],\n  ['normal: sun normal to panel', [30, 180, 180, 60], [0.0, 1.0, 'front']],\n  ['boundary: sun behind vertical panel', [90, 180, 0, 20], [160.0, 0.0, 'back']],\n  ['regression: back-side projection', [90, 270, 150, 45], [110.705, 0.0, 'back']],\n  ['regression: back-side projection (partial repair)', [30, 270, 90, 10], [110.0, 0.0, 'back']],\n  ['control 1', [45, 180, 0, 75], [60.0, 0.5, 'front']],\n  ['control 2', [45, 225, 270, -5], [None, 0.0, 'night']]]]\nfor label, args, expected in fixtures[N-1]:\n    check(label, solve(*args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"1e32841279b0f0be1d2be54ecf4f9996fb77aa3846c5812a59414ccf14f37149","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(tilt, pan_az, sun_az, sun_el):\n    if sun_el <= 0:\n        return [None, 0.0, 'night']\n    zen = math.radians(90 - sun_el)\n    t = math.radians(tilt)\n    c = math.cos(zen) * math.cos(t) + math.sin(zen) * math.sin(t) * math.cos(math.radians(sun_az - pan_az))\n    c = max(-1.0, min(1.0, c))\n    aoi = math.degrees(math.acos(c))\n    side = 'front' if c >= 0 else 'back'\n    return [round(aoi, 3), round(c, 4), side]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[['boundary: sun on horizon', [30, 180, 180, 0], [None, 0.0, 'night']],\n  ['normal: sun normal to panel', [30, 180, 180, 60], [0.0, 1.0, 'front']],\n  ['boundary: sun behind vertical panel', [90, 180, 0, 20], [160.0, 0.0, 'back']],\n  ['regression: back-side projection', [30, 135, 0, 10], [101.408, 0.0, 'back']],\n  ['regression: back-side projection (partial repair)', [90, 180, 30, 20], [144.469, 0.0, 'back']],\n  ['control 1', [0, 180, 225, -5], [None, 0.0, 'night']],\n  ['control 2', [0, 135, 150, 45], [45.0, 0.7071, 'front']]],\n [['boundary: sun on horizon', [30, 180, 180, 0], [None, 0.0, 'night']],\n  ['normal: sun normal to panel', [30, 180, 180, 60], [0.0, 1.0, 'front']],\n  ['boundary: sun behind vertical panel', [90, 180, 0, 20], [160.0, 0.0, 'back']],\n  ['regression: back-side projection', [90, 180, 30, 75], [102.953, 0.0, 'back']],\n  ['regression: back-side projection (partial repair)', [25, 180, 60, 10], [92.907, 0.0, 'back']],\n  ['control 1', [60, 225, 270, 20], [41.716, 0.7465, 'front']],\n  ['control 2', [20, 90, 0, 89], [20.024, 0.9395, 'front']]],\n [['boundary: sun on horizon', [30, 180, 180, 0], [None, 0.0, 'night']],\n  ['normal: sun normal to panel', [30, 180, 180, 60], [0.0, 1.0, 'front']],\n  ['boundary: sun behind vertical panel', [90, 180, 0, 20], [160.0, 0.0, 'back']],\n  ['regression: back-side projection', [90, 90, 200, 30], [107.229, 0.0, 'back']],\n  ['regression: back-side projection (partial repair)', [20, 180, 30, 10], [97.384, 0.0, 'back']],\n  ['control 1', [60, 90, 135, 30], [38.709, 0.7803, 'front']],\n  ['control 2', [45, 270, 60, 89], [45.868, 0.6963, 'front']]],\n [['boundary: sun on horizon', [30, 180, 180, 0], [None, 0.0, 'night']],\n  ['normal: sun normal to panel', [30, 180, 180, 60], [0.0, 1.0, 'front']],\n  ['boundary: sun behind vertical panel', [90, 180, 0, 20], [160.0, 0.0, 'back']],\n  ['regression: back-side projection', [25, 270, 100, 3], [111.604, 0.0, 'back']],\n  ['regression: back-side projection (partial repair)', [10, 180, 60, 3], [92.015, 0.0, 'back']],\n  ['control 1', [45, 180, 315, 0], [None, 0.0, 'night']],\n  ['control 2', [30, 90, 225, 45], [68.754, 0.3624, 'front']]],\n [['boundary: sun on horizon', [30, 180, 180, 0], [None, 0.0, 'night']],\n  ['normal: sun normal to panel', [30, 180, 180, 60], [0.0, 1.0, 'front']],\n  ['boundary: sun behind vertical panel', [90, 180, 0, 20], [160.0, 0.0, 'back']],\n  ['regression: back-side projection', [90, 270, 150, 45], [110.705, 0.0, 'back']],\n  ['regression: back-side projection (partial repair)', [30, 270, 90, 10], [110.0, 0.0, 'back']],\n  ['control 1', [45, 180, 0, 75], [60.0, 0.5, 'front']],\n  ['control 2', [45, 225, 270, -5], [None, 0.0, 'night']]]]\nfor label, args, expected in fixtures[N-1]:\n    check(label, solve(*args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":"Deterministic stipulated toy contract for teaching; no claim of conformance with any standard, vendor protocol or production controller. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"w2-solar_tracker_geometry-fixed-panel-incidence-back-side-projection","generated_at":"2026-09-29T14:51:54.903208+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Single-axis and dual-axis solar trackers turn a sun direction into actuator commands; a sign, frame or limit mistake points a whole plant away from the sun or into a mechanical stop.","root_cause":"The projection factor is not clipped at zero.","sha256":"a9a3f5af24ab94bab198d55346534278ac7a57d897ce8ee730a4e540f1013df7","title":"Fixed panel angle of incidence: back-side projection · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":42.22,"exit_code":1,"observations":[{"actual":[null,0.0,"night"],"check":"boundary: sun on horizon","expected":[null,0.0,"night"],"passed":true},{"actual":[0.0,1.0,"front"],"check":"normal: sun normal to panel","expected":[0.0,1.0,"front"],"passed":true},{"actual":[160.0,0.9397,"back"],"check":"boundary: sun behind vertical panel","expected":[160.0,0.0,"back"],"passed":false},{"actual":[101.408,0.1978,"back"],"check":"regression: back-side projection","expected":[101.408,0.0,"back"],"passed":false},{"actual":[144.469,0.8138,"back"],"check":"regression: back-side projection (partial repair)","expected":[144.469,0.0,"back"],"passed":false},{"actual":[null,0.0,"night"],"check":"control 1","expected":[null,0.0,"night"],"passed":true},{"actual":[45.0,0.7071,"front"],"check":"control 2","expected":[45.0,0.7071,"front"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary: sun on horizon\", \"actual\": [null, 0.0, \"night\"], \"expected\": [null, 0.0, \"night\"], \"passed\": true}, {\"check\": \"normal: sun normal to panel\", \"actual\": [0.0, 1.0, \"front\"], \"expected\": [0.0, 1.0, \"front\"], \"passed\": true}, {\"check\": \"boundary: sun behind vertical panel\", \"actual\": [160.0, 0.9397, \"back\"], \"expected\": [160.0, 0.0, \"back\"], \"passed\": false}, {\"check\": \"regression: back-side projection\", \"actual\": [101.408, 0.1978, \"back\"], \"expected\": [101.408, 0.0, \"back\"], \"passed\": false}, {\"check\": \"regression: back-side projection (partial repair)\", \"actual\": [144.469, 0.8138, \"back\"], \"expected\": [144.469, 0.0, \"back\"], \"passed\": false}, {\"check\": \"control 1\", \"actual\": [null, 0.0, \"night\"], \"expected\": [null, 0.0, \"night\"], \"passed\": true}, {\"check\": \"control 2\", \"actual\": [45.0, 0.7071, \"front\"], \"expected\": [45.0, 0.7071, \"front\"], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.369,"exit_code":1,"observations":[{"actual":[null,0.0,"night"],"check":"boundary: sun on horizon","expected":[null,0.0,"night"],"passed":true},{"actual":[0.0,1.0,"front"],"check":"normal: sun normal to panel","expected":[0.0,1.0,"front"],"passed":true},{"actual":[160.0,-0.9397,"back"],"check":"boundary: sun behind vertical panel","expected":[160.0,0.0,"back"],"passed":false},{"actual":[101.408,-0.1978,"back"],"check":"regression: back-side projection","expected":[101.408,0.0,"back"],"passed":false},{"actual":[144.469,-0.8138,"back"],"check":"regression: back-side projection (partial repair)","expected":[144.469,0.0,"back"],"passed":false},{"actual":[null,0.0,"night"],"check":"control 1","expected":[null,0.0,"night"],"passed":true},{"actual":[45.0,0.7071,"front"],"check":"control 2","expected":[45.0,0.7071,"front"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary: sun on horizon\", \"actual\": [null, 0.0, \"night\"], \"expected\": [null, 0.0, \"night\"], \"passed\": true}, {\"check\": \"normal: sun normal to panel\", \"actual\": [0.0, 1.0, \"front\"], \"expected\": [0.0, 1.0, \"front\"], \"passed\": true}, {\"check\": \"boundary: sun behind vertical panel\", \"actual\": [160.0, -0.9397, \"back\"], \"expected\": [160.0, 0.0, \"back\"], \"passed\": false}, {\"check\": \"regression: back-side projection\", \"actual\": [101.408, -0.1978, \"back\"], \"expected\": [101.408, 0.0, \"back\"], \"passed\": false}, {\"check\": \"regression: back-side projection (partial repair)\", \"actual\": [144.469, -0.8138, \"back\"], \"expected\": [144.469, 0.0, \"back\"], \"passed\": false}, {\"check\": \"control 1\", \"actual\": [null, 0.0, \"night\"], \"expected\": [null, 0.0, \"night\"], \"passed\": true}, {\"check\": \"control 2\", \"actual\": [45.0, 0.7071, \"front\"], \"expected\": [45.0, 0.7071, \"front\"], \"passed\": true}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}