All-Sky camera and DMSP satellite orbits (SSUSI/F18) for March 17, 2015, at 18:00 UT. Panel a gives the satellite pass mapped by SSUSI on a log scale with a 2 × 2° latitude and with the encircled locations of the ASC Nyrölä (NYR). Panel b gives a zoom of the satellite pass with the ASC Images inside the encircled locations superimposed to the satellite images in the northern hemisphere. Panel c shows the ASC image from Nyrölä.