Yashvi-Sharma · Nov 5, 2026 · Oct 30, 2026 · Oct 30, 2026
diff --git a/ZShooter_v2/ZShooter_ALTDETECT.yaml b/ZShooter_v2/ZShooter_ALTDETECT.yaml
@@ -46,3 +46,5 @@ properties:
   dark_k: 0.006388888888888889  # 23 e/hour/pixel
   excess_noise_factor_k: 1.0
   avalanche_gain_k: 1
+  x_size_k: 2048
+  y_size_k: 2048
diff --git a/ZShooter_v2/ZShooter_ALTDETECT4k.yaml b/ZShooter_v2/ZShooter_ALTDETECT4k.yaml
@@ -0,0 +1,50 @@
+# Alternative detector engineering package; optical prescription is unchanged.
+object: detector
+alias: DET
+name: zshooter_alternative_detectors_4k
+properties:
+  detector_mode: SPEC_ALTDETECT4K
+  detector_type_b: CCD
+  ron_b: 2.5
+  dark_b: 0.0005555555555555556  # 2 e/hour/pixel
+  qe_class_b: SpectralQuantumEfficiency
+  qe_kwargs_b:
+    filename: detector_specs/ccd_uv_enhanced_TER.dat
+  detector_type_g: CCD
+  ron_g: 2.5
+  dark_g: 0.0005555555555555556  # 2 e/hour/pixel
+  qe_class_g: SpectralQuantumEfficiency
+  qe_kwargs_g:
+    filename: detector_specs/ccd_ml_uv_enhanced_TER.dat
+  detector_type_r: CCD
+  ron_r: 2.5
+  dark_r: 0.0005555555555555556  # 2 e/hour/pixel
+  qe_class_r: SpectralQuantumEfficiency
+  qe_kwargs_r:
+    filename: detector_specs/ccd_ml2_uv_enhanced_hirho_TER.dat
+  detector_type_yj: H2RG
+  pixel_size_yj: 0.018
+  pixel_scale_yj: 0.1884654  # Same 10.4703 arcsec/mm camera plate scale
+  usable_well_yj: 60000
+  ron_yj: 6.0
+  dark_yj: 0.006388888888888889  # 23 e/hour/pixel
+  excess_noise_factor_yj: 1.0
+  avalanche_gain_yj: 1
+  detector_type_h: H2RG
+  pixel_size_h: 0.018
+  pixel_scale_h: 0.1884654  # Same 10.4703 arcsec/mm camera plate scale
+  usable_well_h: 60000
+  ron_h: 6.0
+  dark_h: 0.006388888888888889  # 23 e/hour/pixel
+  excess_noise_factor_h: 1.0
+  avalanche_gain_h: 1
+  detector_type_k: H4RG
+  pixel_size_k: 0.010
+  pixel_scale_k: 0.104703  # Same 10.4703 arcsec/mm camera plate scale
+  usable_well_k: 60000
+  ron_k: 6.0
+  dark_k: 0.006388888888888889  # 23 e/hour/pixel
+  excess_noise_factor_k: 1.0
+  avalanche_gain_k: 1
+  x_size_k: 4096
+  y_size_k: 4096
diff --git a/ZShooter_v2/ZShooter_DET.yaml b/ZShooter_v2/ZShooter_DET.yaml
@@ -124,6 +124,8 @@ properties :
     plate_scale_yj: 10.4703
     plate_scale_h: 10.4703
     plate_scale_k: 10.4703
+    x_size_k: 2048
+    y_size_k: 2048
 #    tapered_qe_example:
 #      enabled: False
 #      description: >
@@ -320,7 +322,7 @@ effects :
         detector: "!DET.detector_type_h"
 
   - name: detector_k
-    description: Single 2k x 2k detector for ZShooter_v2 K arm
+    description: Single detector for ZShooter_v2 K arm
     include: True
     class: DetectorList
     kwargs:
@@ -331,8 +333,8 @@ effects :
           id: [5]
           x_cen: [0.0]
           y_cen: [0.0]
-          x_size: [2048]
-          y_size: [2048]
+          x_size: ["!DET.x_size_k"]
+          y_size: ["!DET.y_size_k"]
           pixel_size: ['!DET.pixel_size_k']
           angle: [0.0]
           gain: [1.0]

diff --git a/ZShooter_v2/default.yaml b/ZShooter_v2/default.yaml
@@ -69,6 +69,15 @@ mode_yamls:
     - ZShooter_DET.yaml
     - ZShooter_ALTDETECT.yaml
 
+- object: instrument
+  alias: OBS
+  name: SPEC_ALTDETECT4K
+  description: "Editable alternative detector engineering package"
+  yamls:
+    - ZShooter_SPEC.yaml
+    - ZShooter_DET.yaml
+    - ZShooter_ALTDETECT4k.yaml
+
 - object: instrument
   alias: OBS
   name: IMAGER

diff --git a/ZShooter_v2/tests/test_detector_modes.py b/ZShooter_v2/tests/test_detector_modes.py
@@ -0,0 +1,27 @@
+from pathlib import Path
+
+import numpy as np
+import pytest
+import scopesim as sim
+
+
+@pytest.mark.parametrize('mode,detector_type,pitch,size', [('SPEC', 'LmAPD', .015, 2048), ('SPEC_ALTDETECT', 'H2RG', .018, 2048), ('SPEC_ALTDETECT4K', 'H4RG', .010, 4096)])
+def test_k_detector_mode_reaches_geometry_and_readout_metadata(monkeypatch, mode, detector_type, pitch, size):
+    root = Path(__file__).resolve().parents[2]
+    monkeypatch.setitem(sim.rc.__config__, '!SIM.file.local_packages_path', str(root))
+    commands = sim.UserCommands(use_instrument='ZShooter_v2', set_modes=[mode], properties={'!OBS.mjdobs': 60310.25})
+    ignore = ['atmo_transmission', 'continuum_emission', 'airglow_and_interline_continuum', 'adc_residuals']
+    for document in commands.yaml_dicts:
+        if 'effects' in document:
+            document['effects'] = [effect for effect in document['effects'] if effect['name'] not in ignore]
+    train = sim.OpticalTrain(commands)
+    assert train.cmds['!DET.detector_mode'] == mode
+    detector, = train.detector_managers[5]
+    header = detector._native_header
+    assert header['DETMODE'] == mode
+    assert header['DETTYPE'] == detector_type
+    assert (header['NAXIS1'], header['NAXIS2']) == (size, size)
+    np.testing.assert_allclose(abs(header['CDELT1D']), pitch)
+    np.testing.assert_allclose(abs(header['CDELT2D']), pitch)
+    traces = train['trace_list_analytical'].spectral_traces
+    assert len([trace for trace in traces.values() if trace.meta['image_plane_id'] == 5]) == 8
diff --git a/ZShooter_v2/traces/echelle_trace_parameters.dat b/ZShooter_v2/traces/echelle_trace_parameters.dat
@@ -39,4 +39,4 @@ g        1              1                85    30   430         650       18000
 r        2              2                56    20   650         980       18000       65.6               225           270                        4.46     0.7                   10.4703       10              !DET.pixel_size_r       2048    4096        50.150       625           10            x              14.10            -6.00    -2.867205            -5.372810    1500    1250    0.5306
 yj       3              3                80    23   960         1340      18000       65.6               225           270                        4.46     0.7                   10.4703       10              !DET.pixel_size_yj       2048    2048        24.000       350           10            x              10.90            -5.00    -0.441923            -3.921145    1500    1250    0.5306
 h        4              4                51    10   1470        1830      18000       65.6               225           270                        4.46     0.7                   10.4703       10              !DET.pixel_size_h       2048    2048        24.000       300           10            x              13.70            -6.10    -2.474361            -4.610933    1500    1250    0.5306
-k        5              5                38    8    1990        2450      18000       65.6               225           270                        4.46     0.7                   10.4703       10              !DET.pixel_size_k       2048    2048        24.000       270           10            x              16.80            -6.50    -0.621554            -5.307695    1500    1250    0.5306
+k        5              5                38    8    1990        2450      18000       65.6               225           270                        4.46     0.7                   10.4703       10              !DET.pixel_size_k       !DET.x_size_k    !DET.y_size_k        24.000       270           10            x              16.80            -6.50    -0.621554            -5.307695    1500    1250    0.5306