==== Daytime wavelength calibration (WCU QCLs) ====
=== Responsible ===
Science Operations

=== Phase ===
Daytime

=== Frequency ===
Once every day (tbc)

=== Purpose ===
Provide an approximate wavelength to pixel transformation for the L and M bands

=== Procedure ===
  * LM band imaging spectrograph and integral-field spectrograph
    * determine absolute wavelength reference / calibrate the WCU QCL source using the WCU HeNe source (tbc)
    * step the WCU QCL source over the desired wavelength range (fine sampling of relevant spectral regions for the LMS, coarse sampling of the full L/M bands for the long-slit spectrograph), take a spectrum at every wavelength position (how many laser lines are visible in a single setting of the QCL? How long does it take to step the QCL through the spectrum?)

=== Pipeline data products ===
  * Wavelength-to-pixel transformation

=== Prepared observing blocks ===
(tbd)

=== Prepared templates ===
(tbd)

=== Pipeline support ===
  * Determine the centroid position of the observed line, e.g. through a Gaussian (tbc) fit to the lines
  * Using the known wavelength of the laser line(s) and the fitted pixel positions, interpolate (and extrapolate) the wavelength to pixel relation for the given setup.

=== Duration ===
  * 30 minutes per spectroscopic setting (low/medium resolution in L) (tbc)
  * tbd minutes for the LMS (depending on how many settings of the LMS need to be calibrated)

=== Prerequisites ===
none

=== Required Accuracy ===
The wavelength accuracy after calibration must be 1/10 of a pixel.

=== Expected Accuracy ===
Applicability of daytime wavelength calibration limited by drifts between daytime and nighttime, also by the accuracy with which the source can be centered in the slit.

=== Notes ===
Our plan is to use this daytime calibration as a first guess for the wavelength calibration and improve it using the telluric absorption or emission lines (see \ref{sec:cals:wavecal_night}).