A total solar eclipse passed over the continental United States from the west to the east coast on 21 August 2017. Measurements made by more than 2200 ground-based GNSS (Global Navigation Satellite System) receivers observed a significant decrease in ionospheric total electron content (TEC). Meanwhile, radio occultation soundings from the LEMUR2-LYNSEY-SYMO satellite record a double-peaked feature in the scanned TEC profile. A reproduction of the double-peaked feature on the TEC profile shows that the solar eclipse depresses the electron density and simultaneously tilts the ionosphere. This study, in turn, indicates the combination of the International Reference Ionosphere model and the GNSS TEC is a powerful tool for observing ionospheric space weather.