Revised Point-spread Functions for the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory

Abstract We present revised point-spread functions (PSFs) for the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. These PSFs provide a robust estimate of the light diffracted by the meshes holding the entrance and focal plane filters and the light that is diffusely scattered over the detector by the microroughness of the mirrors. We first calibrate the diffracted light using flare images. Our modeling of the diffracted light provides reliable determinations of the mesh parameters and finds that about 24%–33% of the collected light is diffracted, depending on the AIA channel. Then, we fit the diffuse scattered light using partially lunar-occulted images. We find that the diffuse scattered light can be modeled as a superposition of two power-law functions that scatter light over the entire detector. The amount of diffuse scattered light ranges from 10% to 35%, depending on the AIA channel. In total, AIA diffracts and diffusely scatters about 37%–55% of the collected light over the detector. When correcting for this, bright image regions increase in intensity by about 30%, dark image regions decrease by up to 90%, and the associated differential emission measure analysis of solar features is affected accordingly. Finally, we compare the image reconstructions using our new PSFs to those from the AIA team and B. Poduval et al. We find that our PSFs outperform the others, better correcting for the flare diffraction pattern and far more accurately predicting long-distance scattered light in lunar occultations.