Study on the impact of the potential variation in the CSES satellite platform on Langmuir probe observations

The Langmuir Probe (LAP) onboard China Seismo-Electromagnetic Satellite (CSES-01) operates by applying a sweeping bias-voltage (V) to its probe and measuring the resulting current (I). Plasma parameters are subsequently derived from the analysis of the current-voltage (I-V) characteristic curves. The sweeping bias-voltage (V) is referenced to the satellite platform's ground potential (Vg). A negative shift in Vg beyond the range of the sweeping bias-voltage can lead to incomplete I-V curves, thereby affecting the accuracy of LAP measurements. Over the past five years, the gradual drift in Vg on the CSES-01 satellite has caused observable disturbances in LAP data, particularly during ascending orbits around 02:00 local time. To mitigate the impact of Vg drift on LAP measurements, the range of the bias-voltage sweeping has been adjusted several times. This study analyzes five years of plasma density and temperature data from CSES-01's ascending orbits to investigate the influence of Vg variations on LAP observations and to evaluate the effectiveness of adjusting the bias-voltage sweeping range by comparing with the simultaneous Swarm-B measurements and IRI model predictions. The results demonstrate that, despite Vg drift, accurate observational data can still be obtained through the adjustments of the bias-voltage sweeping range. The latitudinal profiles, global distribution structures, and long-term temporal trends of electron density (Ne) and electron temperate (Te) accurately reflect the actual variations in the ionosphere. Notably, due to the bias-volatage adjustments, only a small fraction of the measurements is affected by Vg shifting. These findings provide valuable insights for effectively utilizing CSES-01 plasma data in scientific research. Furthermore, the identified issues and their solutions offer a critical reference for the design, development, and operation of similar Low-Earth-Orbit (LEO) satellites and Langmuir probes, ensuring their optimal performance and scientific reliability.