RIQ FCa : No Distortion map in IMG-N-CVC

[astronomyk]

https://jira.eso.org/browse/MET-2133

DRL-D : Tab. 4 (p.30)

The IMG-N-CVC doesn't make use of a distortion map?

@gotten @oczoske - is this right? If so, why? (more for my understanding). Because of the chop-nod cycle?

[hugobuddel]

Interesting. Table 4, "Overview of required calibrations per instrument mode." is taken verbatim from the Calibration Plan, there the column is called "Distortion & plate-scale" and indeed the only minus sign there is for IMG_N_CVC.

However, we totally ignore that in the DRLD and apply the distortion correction the same way in the LM and N band everywhere. So something seems off somewhere.

I couldn't quickly see why there is no check mark in that cell in the Calibration Plan; perhaps we should know that first.

[gotten]

Bit of a mystery why it is a dash in the table (same seen in Tab 6-1 of the 1057 operational concepts doc ?). At some point you should correct for distortion if you want proper rectified data. Either a mistake in the table or the authors of the calibration plan know something we don't know (about the practical implementation of distortion correction while chopping between three coronagraphs). I can make wild guesses about thermal background spatial structures here but perhaps easier to ask.

To be confirmed with @rvboekel and @Rumpelstil ?

[gotten]

Replied to RIX with similar story. Expecting action item on me.

[hugobuddel]

Yes we've confirmed this afternoon with @Rumpelstil that there should be distortion correction for the N band.

Distortion correction and (absolute?) astrometry in general was originally not planned for the N band, but later agreed to do it anyway. The tables will be updated.

The astrometric calibration was also missing in the PIP spec, #251, it will be added there too.

Sorry for updating this issue too late to affect your answer. I'll add a comment.