{
  "schema_version": "emberscope_design_spec/v1",
  "design_id": "emberscope-starter-freeform-v1",
  "name": "EmberScope starter-freeform reference design",
  "revision": "2026-06-09",
  "status": "screening_reference_not_fabrication_ready",
  "description": "Current compact folded three-mirror starter-freeform reference exported as a component-level source of truth for diagrams, Blender visualisation, CAD handoff, and automated design gates.",
  "units": {
    "length": "mm",
    "angle": "deg",
    "mass": "kg",
    "wavelength": "um"
  },
  "coordinate_frame": {
    "origin": "M1 vertex for the optical proof-of-concept train",
    "x_axis": "payload lateral axis",
    "y_axis": "folded optical path height axis",
    "z_axis": "nominal entrance-to-primary optical axis",
    "handedness": "right-handed"
  },
  "requirements": {
    "payload_envelope_target_mm": 150.0,
    "mass_budget_kg": 2.0,
    "entrance_aperture_diameter_mm": 40.0,
    "nominal_f_number": 5.0,
    "full_field_deg": 3.0,
    "field_points_deg": [
      0.0,
      0.75,
      1.5
    ],
    "wavelength_um": 11.0,
    "rayleigh_reference_wavelength_um": 10.0,
    "detector_pixel_pitch_um": 17.0,
    "detector_pixels": [
      640,
      512
    ],
    "minimum_edge_throughput": 0.3,
    "prototype_ready_edge_rms_limit_um": 34.0,
    "maximum_freeform_departure_um_screening": 10000.0,
    "required_2x2_pixel_energy_fraction": 0.5
  },
  "performance_evidence": {
    "source": "site/assets/rfs/review-package/current-design/starter_freeform_parameters.json",
    "equivalent_aperture_diameter_mm": 40.0,
    "rayleigh_10um_radius_um": 61.00000000000001,
    "rayleigh_10um_angle_urad": 305.00000000000006,
    "envelope_mm": [
      58.0,
      65.7597028411242,
      72.0
    ],
    "envelope_max_mm": 72.0,
    "mass_proxy_kg": 0.663849400629727,
    "on_axis_rms_spot_um": 6605.114155101264,
    "edge_field_deg": 1.5,
    "edge_rms_spot_um": 4524.285222335228,
    "edge_geo_ee80_radius_um": 5874.23834437924,
    "edge_geo_ee95_radius_um": 6224.973311777451,
    "edge_throughput": 0.38372093023255816,
    "detector_2x2_energy_fraction": null,
    "focus_sanity": {
      "center_error_um": 0.0,
      "normal_angle_deg": 0.0,
      "sensor_rms_um": 6485.040396983787,
      "passes": true
    }
  },
  "components": [
    {
      "id": "payload_envelope_reference",
      "name": "150 mm payload envelope reference",
      "type": "envelope_reference",
      "include_in_optical_envelope": false,
      "geometry": {
        "shape": "box",
        "center_mm": [
          0.0,
          0.0,
          -18.0
        ],
        "size_mm": [
          150.0,
          150.0,
          150.0
        ]
      },
      "purpose": "Reference cube for compact payload packaging checks."
    },
    {
      "id": "entrance_aperture",
      "name": "Entrance aperture",
      "type": "aperture",
      "include_in_optical_envelope": true,
      "geometry": {
        "shape": "circle",
        "center_mm": [
          0.0,
          0.0,
          -46.0
        ],
        "normal": [
          0.0,
          0.0,
          1.0
        ],
        "diameter_mm": 40.0
      },
      "optical": {
        "area_mm2": 1256.6370614359173,
        "equivalent_circular_diameter_mm": 40.0
      }
    },
    {
      "id": "lwir_window_allowance",
      "name": "Serviceable LWIR window allowance",
      "type": "window",
      "include_in_optical_envelope": true,
      "geometry": {
        "shape": "box",
        "center_mm": [
          0.0,
          0.0,
          -52.5
        ],
        "size_mm": [
          48.0,
          48.0,
          2.0
        ]
      },
      "material": {
        "substrate": "TBD LWIR window material",
        "coating": "TBD broadband 8-14 um AR"
      },
      "purpose": "Mechanical and contamination-control allowance; not yet optically powered."
    },
    {
      "id": "stray_light_baffle_allowance",
      "name": "Stray-light baffle allowance",
      "type": "baffle",
      "include_in_optical_envelope": true,
      "geometry": {
        "shape": "cylinder",
        "center_mm": [
          0.0,
          0.0,
          -20.0
        ],
        "axis": [
          0.0,
          0.0,
          1.0
        ],
        "diameter_mm": 48.0,
        "length_mm": 72.0
      },
      "mass_proxy_kg": 0.06,
      "purpose": "First package-level baffle allowance for CAD and clearance checks; final vane geometry remains open."
    },
    {
      "id": "m1_primary",
      "name": "M1 primary",
      "type": "mirror",
      "include_in_optical_envelope": true,
      "position_mm": [
        0.0,
        0.0,
        0.0
      ],
      "orientation": {
        "tip_deg": 5.0,
        "tilt_deg": 0.0
      },
      "surface": {
        "shape_family": "freeform_xy",
        "radius_mm": -133.33333333333334,
        "conic_k": -1.0,
        "diameter_mm": 50.0,
        "rnorm_mm": 20.0,
        "poly_order": 4,
        "poly_coeffs": [
          0.0,
          0.0,
          0.04321311,
          0.0,
          -0.02135484,
          -0.20207849,
          0.21344264,
          0.0,
          0.0425451,
          0.0,
          0.0,
          0.0,
          0.0,
          0.0
        ],
        "max_total_sag_mm": 2.67091406640625,
        "max_freeform_sag_um": 506.59874088875745
      },
      "material": {
        "substrate": "aluminium mirror proxy",
        "coating": "gold or protected metal LWIR reflector TBD"
      },
      "mechanical": {
        "clear_aperture_margin_mm": 2.0,
        "mount_allowance_mm": 3.0
      }
    },
    {
      "id": "m2_secondary",
      "name": "M2 secondary",
      "type": "mirror",
      "include_in_optical_envelope": true,
      "position_mm": [
        0.0,
        8.103581624456748,
        -45.95769514056971
      ],
      "orientation": {
        "tip_deg": -8.0,
        "tilt_deg": 0.0
      },
      "surface": {
        "shape_family": "freeform_xy",
        "radius_mm": 53.33333333333334,
        "conic_k": -2.5,
        "diameter_mm": 32.0,
        "rnorm_mm": 8.0,
        "poly_order": 4,
        "poly_coeffs": [
          0.0,
          0.0,
          0.25642043,
          0.0,
          -0.04233339,
          0.53197315,
          -0.00989257,
          0.0,
          -0.32184185,
          0.0,
          0.0,
          0.0,
          0.0,
          0.0
        ],
        "max_total_sag_mm": 7.60551270251114,
        "max_freeform_sag_um": 4564.242114300641
      },
      "material": {
        "substrate": "aluminium mirror proxy",
        "coating": "gold or protected metal LWIR reflector TBD"
      },
      "mechanical": {
        "clear_aperture_margin_mm": 2.0,
        "mount_allowance_mm": 3.0
      }
    },
    {
      "id": "m3_tertiary",
      "name": "M3 tertiary",
      "type": "mirror",
      "include_in_optical_envelope": true,
      "position_mm": [
        0.0,
        22.71595318409266,
        -15.997893597264142
      ],
      "orientation": {
        "tip_deg": 5.0,
        "tilt_deg": 0.0
      },
      "surface": {
        "shape_family": "freeform_xy",
        "radius_mm": -80.0,
        "conic_k": 0.0,
        "diameter_mm": 36.0,
        "rnorm_mm": 6.0,
        "poly_order": 4,
        "poly_coeffs": [
          0.0,
          0.0,
          0.04982004,
          0.0,
          0.12208412,
          0.32995534,
          -0.12671614,
          0.0,
          -0.14396528,
          0.0,
          0.0,
          0.0,
          0.0,
          0.0
        ],
        "max_total_sag_mm": 7.305875619620306,
        "max_freeform_sag_um": 9050.879339424833
      },
      "material": {
        "substrate": "aluminium mirror proxy",
        "coating": "gold or protected metal LWIR reflector TBD"
      },
      "mechanical": {
        "clear_aperture_margin_mm": 2.0,
        "mount_allowance_mm": 3.0
      }
    },
    {
      "id": "image_sensor",
      "name": "Image sensor / focal plane",
      "type": "sensor",
      "include_in_optical_envelope": true,
      "geometry": {
        "shape": "plane",
        "center_mm": [
          0.3193257296503882,
          26.409414264222555,
          -25.052688441758196
        ],
        "normal": [
          0.2317676546758431,
          0.44974337537021286,
          -0.8625628386133193
        ],
        "x_axis": [
          0.0,
          -0.886706825723299,
          -0.4623321373382032
        ],
        "y_axis": [
          -0.9727711726023028,
          0.10715363515214514,
          -0.20550996138295052
        ],
        "width_mm": 10.88,
        "height_mm": 8.704
      },
      "detector": {
        "pixels": [
          640,
          512
        ],
        "pixel_pitch_um": 17.0,
        "radiometric_raw_required": true
      },
      "mass_proxy_kg": 0.3
    },
    {
      "id": "detector_electronics_allowance",
      "name": "Detector electronics allowance",
      "type": "electronics",
      "include_in_optical_envelope": true,
      "geometry": {
        "shape": "box",
        "center_mm": [
          0.0,
          34.0,
          -31.0
        ],
        "size_mm": [
          42.0,
          2.0,
          32.0
        ]
      },
      "mass_proxy_kg": 0.12,
      "purpose": "Coarse electronics board allowance behind the current focal plane."
    },
    {
      "id": "optical_bench_allowance",
      "name": "Optical bench allowance",
      "type": "structure",
      "include_in_optical_envelope": true,
      "geometry": {
        "shape": "box",
        "center_mm": [
          0.0,
          11.0,
          -24.0
        ],
        "size_mm": [
          58.0,
          4.0,
          56.0
        ]
      },
      "mass_proxy_kg": 0.16,
      "purpose": "First structural allowance tying the three mirror stations to a common datum."
    }
  ],
  "optical_path": [
    "entrance_aperture",
    "m1_primary",
    "m2_secondary",
    "m3_tertiary",
    "image_sensor"
  ],
  "open_engineering_caveats": [
    "The current surface set remains a starter shape demonstration rather than a fabrication-ready prescription.",
    "The detector-energy gate is not yet closed from this source spec; edge RMS remains hundreds of detector pixels.",
    "The baffle, window, electronics, and bench components are package allowances, not detailed mechanical drawings."
  ]
}