KPF DRP Overview

The KPF DRP processes raw KPF spectra and associated data products stored in the Level 0 (L0) files into reduced spectra (L1) and radial velocities and other final data products associated with individual observations (L2). The KPF DRP operates within the WMKO DRP Framework using recipes to specify the algorithms applied and config files to specify parameters associated with the processing. A summary of the main recipe used to process KPF data products is below.

Main Recipe

Level 0 to 2D

  1. Remove the overscan region from each amplifier region

  2. Stitch amplifier regions into a single image (per CCD)

  3. Subtract master bias (per CCD)

  4. Subtract scaled master dark (per CCD)

  5. Apply master flat (per CCD)

  6. Apply bad-pixel mask (per CCD)

2D to Level 1

  1. Spectral Extraction

    1. Map the orderlet locations using a rectified master flat.

    2. Extract each order and orderlet using a weighted sum. The weights are determined from the rectified flat.

    3. Reject outliers by comparing the cross-dispersion profile in each column to that expected in a scaled master flat.

    4. Subtract background by measuring the inter-order light.

    5. Copy wavelength solution from the day’s master ThAr or LFC frames.

    6. Calculate photon-weighted midpoint for each order from the exposure meter spectral timeseries.

  2. Ca H&K Spectrometer Spectra

    1. Subtract master bias

    2. Subtract scaled master dark

    3. Spectral Extraction

    4. Apply default wavelength solution to extracted spectra

Level 1 to Level 2

  1. Compute Cross-correlation functions (CCFs) with binary masks

  2. Compute RVs per order and per orderlet from fitting CCF peaks

  3. Compute reweighted RVs based on information content per order

  4. Compute and correct for the barycentric RV using the photon-weighted midpoints.

Wavelength Solution Recipes

ThAr

  1. Step 1

  2. Step 2

  3. Step 3

  4. …

LFC

  1. Step 1

  2. Step 2

  3. Step 3

  4. …

Etalon

  1. Step 1

  2. Step 2

  3. Step 3

  4. …

Master Construction Recipes

The DRP also creates ‘master’ files that are stacks of particular observations of a particular type (e.g., darks, bias, flats). The DRP also has a set of ‘quick-look’ recipes to produce diagnostic plots and measurements.