Evaluate calibration recipes for ADC
E.g. see email Joost 2020/04/01:
I promised to send over the publications by Pathak et al. where they use the deformable mirror on the Subaru SCExAO instrument to measure the residual dispersion after the ADC (which actually is in front of the DM for this instrument). They are able to improve the ADC position from an initial positioning error of 6.2 mas to <1 mas in H-band. Likely, a similar observation run has to be done with the ADC for MICADO, to at the least check if the ADC correction algorithm works sufficiently well.
In short the process is as follows:
- The set the shape of the DM to a sinusoidal pattern in both x and y direction to create artificial speckles around the PSF core.
- The ADC is set in its initial position
- By drawing lines between the speckles a radiation centre is determined.
- If there is no dispersion the radiation centre and the PSF core will be in the same location.
- If there is dispersion, then the radiation center and the PSF core will be in a (slightly) different position and the ADC performance can be improved.
In the first paper Pathak et al. discuss the concept and first results, in the second paper they discuss the results of the closed loop dispersion control that they set up using the internal Near IR camera (low pixel count, high time resolution).