===== Apodized Phase Plate coronagraphy (APP) in N-band  =====
<color #ed1c24> APP in the N-band is not a baseline mode, no further work will be done here.</color>

===== Operational procedure =====

==== Preparation ====

  * ETC
  * p2pp kind of OB preparation
  * any special needs?

==== Acquisition ====

  * Templates: [[METIS_acq_APP_N|METIS_acq_APP_N]]

==== Science sequence ====

For HCI observing modes:

  * The target (typically a bright star) is always on-axis and used as the NGS for the SCAO
  * The derotator is always in pupil tracking mode (i.e. pupil is always oriented in the same pre-defined direction)

Sky subtraction:

  * In APP mode, the target will be moved between two predefined positions on the detector (A and B)
  * A single star using the APP generates three PSFs on the detector - two coronagraphic PSFs and a leakage PSF halfway between the two coronagraphic PSFs. In both positions A and B, all three PSFs should be seen. The PSFs at A and B should not interfere with each other.  
  * Offsets between A and B in the N-band will be performed using the CFO-PP2 chopper.
  * Optional small dithers can be included around the positions A and B. 

Template options: 
  * [[METIS_obs_APP_N_AutoChop|METIS_obs_APP_N_AutoChop]]


===== Calibration data =====

++++
Calibration requirements|
  * flatfielding (daytime WCU, not needed daily?; twilight sky flats?)
  * sky background recostruction/subtraction (chop/dither/stare), align frames (dithered/choped exposures)
  * flux calibration (sky atmosphere modeling + one/few standard observations per night?)
  * psf re-construction?
  * provide data cube or "stacked" result?
++++

===== Products =====

  * background-subtracted, flux-calibrated image (cube). Units, e.g., [photons/s/pix]
  * corresponding uncertainties (cube)
  * PSF (cube)

===== Discussion =====
 [[IMG_N_APP_discussion|IMG_N_APP_discussion]] 
