EPP

This paper reports, for the first time, observation results of the Coherent Beacon System (CBS) onboard the China Seismo-Electromagnetic Satellite-1 (CSES-1). We describe the CBS, and the Computerized Ionospheric Tomography (CIT) algorithm program is validated by numerical experiment. Two examples are shown, for daytime and nighttime respectively. The Equatorial Ionization Anomaly (EIA) can be seen, and the northern crest core is located at ~20°N in the reconstruction image at 07:28 UTC on 20 July 2018 (daytime). Disturbances are shown in the reconstruction image at 18:40 UTC on 13 July 2018 (nighttime). We find that beacon measurements are more consistent with ionosonde measurements than model results, by comparing N_mF₂ at three sites at Lanzhou, Chongqing, and Kunming; consistency with ionosonde measurements validates beacon measurements. Finally, we have studied Vertical Total Electron Content (VTEC) variations from ground to ~500 km (the height of CSES-1 orbit) and ratios of VTEC between beacon measurements and CODE (Center for Orbit Determination in Europe) data. VTEC variation from ground to ~500 km has a range of 7.2–16.5 TECU for the daytime case and a range of 1.1–1.7 TECU for the nighttime case. The Beacon/CODE ratio of VTEC varies with latitude and time. The mean Beacon/CODE ratio is 0.69 for the daytime case and 0.26 for the nighttime case. The fact that the nighttime case yields lower ratios indicates the higher altitude of the ionosphere during nighttime when the ionosphere is assumed to be a thin layer.