Software of Slit-Viewing Camera Module for IGRINS (Immersion GRating INfrared Spectrograph)

We developed an observation control software for the IGRINS (Immersion Grating Infrared Spectrograph) silt-viewing camera module, which points the astronomical target onto the spectroscopy slit and sends tracking feedbacks to the telescope control system. The point spread function (PSF) is not always symmetric. In addition, bright targets are easily saturated and shown as a donut shape. It is not trivial to define and find the center of the asymmetric PSF especially on a slit mask. We made a center balancing algorithm (CBA) following the concept of median. The CBA derives the expected center position along the slit-width axis by referencing the stray flux ratios of both upper and lower sides of the slit. We compared efficiencies of the CBA and those of a two-dimensional Gaussian fitting (2DGA) through simulations from observation images in order to evaluate the center finding algorithms. Both of the algorithms are now applied in observation and users can select the algorithm.