# Configuration

## CalibrationConfig

Pipeline-level configuration controlling mode, PWV fitting strategy,
and feature flags.

**Source:** `cal-core/src/config.rs`

```{eval-rst}
.. list-table::
   :header-rows: 1
   :widths: 22 12 12 54

   * - Field
     - Type
     - Default
     - Description
   * - ``obs_mode``
     - ObsMode
     - Auto
     - Observation mode (auto-detected if Auto)
   * - ``pwv_source``
     - PwvSource
     - FitGridRefine
     - PWV retrieval strategy
   * - ``pwv_initial_guess``
     - f64
     - 1.0
     - Initial PWV guess for fitting (mm)
   * - ``pwv_grid_min``
     - f64
     - 0.001
     - Minimum PWV in grid search (mm)
   * - ``pwv_grid_max``
     - f64
     - 10.0
     - Maximum PWV in grid search (mm)
   * - ``pwv_grid_steps``
     - usize
     - 100
     - Number of grid search points
   * - ``pwv_per_pixel``
     - bool
     - false
     - Fit PWV independently per pixel
   * - ``clip_tsys``
     - f64
     - 200.0
     - Bad channel T_rec threshold multiplier (K)
   * - ``clip_counts``
     - f64
     - 0.01
     - Minimum hot-cold count ratio
   * - ``eta_fss``
     - f64
     - 1.0
     - Forward scattering efficiency
   * - ``eta_mb``
     - f64
     - 1.0
     - Main beam efficiency
   * - ``gain_el_correction``
     - f64
     - 1.0
     - Elevation-dependent gain correction
   * - ``n_threads``
     - Option
     - auto
     - Rayon thread pool size
   * - ``physics``
     - PhysicsConstants
     - KalibrateCompat
     - Physics constants precision
   * - ``dbs_adhesive``
     - bool
     - false
     - Enable DBS adhesive beam coupling for OtfChopped mode
   * - ``gain_interpolate``
     - u8
     - 0
     - Gain drift correction level (0=off, 2=correct ON, 3=correct ON+OFF)
   * - ``skydiff``
     - u32
     - 0
     - SKY-DIFF diagnostic depth (0=off, N=diff against N most recent OFFs)
   * - ``skychopdiff``
     - bool
     - false
     - SKYCHOPDIFF diagnostic: chop-phase diffs of the sky in chopped scans
```

## CalibrationParams

Instrument-level calibration parameters that travel with every scan.
Groups per-instrument values with per-load thresholds and physics mode,
eliminating loose `f64` parameters from pipeline function signatures.

Constructed via `CalibrationParams::from_config(config, foeff, gain_image)`.

**Source:** `cal-core/src/config.rs`

```{eval-rst}
.. list-table::
   :header-rows: 1
   :widths: 22 12 12 54

   * - Field
     - Type
     - Default
     - Description
   * - ``foeff``
     - f64
     - 0.97
     - Forward efficiency (eta_fss)
   * - ``gain_image``
     - f64
     - 0.5
     - Image sideband gain ratio (0.0--1.0); signal gain = 1 - gain_image
   * - ``clip_tsys``
     - f64
     - 200.0
     - T_sys clipping threshold for bad channel detection (K)
   * - ``clip_counts``
     - f64
     - 0.01
     - Minimum hot-cold count ratio for bad channel detection
   * - ``physics``
     - PhysicsConstants
     - KalibrateCompat
     - Physical constants mode
```

`CalibrationLoad` constructors (`new`, `new_with_load_temps`) accept
`&CalibrationParams` rather than separate `foeff`/`gain_image`/`physics`
arguments.

## ObsMode

```{eval-rst}
.. list-table::
   :header-rows: 1
   :widths: 25 25 50

   * - Variant
     - CLI value
     - Description
   * - ``Auto``
     - ``auto``
     - Auto-detect from data
   * - ``TotalPower``
     - ``totalpower``, ``tp``
     - Position-switched ON/OFF
   * - ``OtfTotalPower``
     - ``otf``, ``otf_totalpower``
     - On-the-fly scanning
   * - ``OtfChopped``
     - ``otf-chopped``
     - OTF with dual beam switch (OTFSWA/OTFSWB)
   * - ``FrequencySwitch``
     - --
     - Stubbed: frequency-switched reference
   * - ``BeamSwitch``
     - --
     - Stubbed: standalone beam-switched reference
```

## PwvSource

```{eval-rst}
.. list-table::
   :header-rows: 1
   :widths: 25 75

   * - Variant
     - Description
   * - ``FitGridRefine``
     - Grid search (100 points) + Newton refinement (5 iterations)
   * - ``FitLM``
     - Levenberg-Marquardt least-squares (fallback)
   * - ``External(f64)``
     - Fixed PWV value in mm (no fitting)
```

## PhysicsConstants

```{eval-rst}
.. list-table::
   :header-rows: 1
   :widths: 25 30 45

   * - Variant
     - :math:`h/k_B`
     - Notes
   * - ``Exact``
     - SI 2019, f64
     - Full precision
   * - ``KalibrateCompat``
     - 0.047995 K/GHz, f32 truncation
     - **Default** -- legacy parity mode
```