Footprints of (blue) the Arase and (red) the POES-15 satellites during the EEP event #1 on July 24–25, 2018, in the AACGM coordinate. The mapped altitude is 100 km for both satellites. The magnetic local times are calculated at 0000 UT. The footprints of the Arase and the POES satellites were traced using the T96 model. The black circle indicates the all-sky field of view at Syowa Station, assuming a 10° elevation angle and an emission altitude of 110 km. Plus signs show the 8×8 beam directions of the imaging riometer, projected at 90 km altitude.