[P-EM09] Space Weather and Space Climate

[PEM09-P16] Improvement of bias current subtraction for Himawari-8/SEDA-e observation

*Tsutomu Nagatsuma¹, Kaori Sakaguchi¹ (1.National Institute of Information and Communications Technology)

Keywords:Space Weather, High Energy Electron, Intercalibration

Space environment data acquisition monitor (SEDA) onboard Himawari-8 has been operating since Nov. 2014. SEDA has two sensors. One is high energy electron sensor (SEDA-e) and the other is high energy proton sensor (SEDA-p). SEDA-e measures internal charging currents produced from high energy electrons (from 0.1 to 4.5 MeV) collected by 8 plates arranged in a stack. Electron fluxes are estimated from the charging currents. Since the charging currents are quite small, it needs to be amplified by operational amplifier. This means that bias current is contaminated as a offset of particle flux. Therefore, we need to remove the bias current effect. To subtraact the bias current effect, we use empirical model based on the pre-flight measurements. The empirical model of bias current is a function of temperature. This works well for the beginning of Himawari-8/SEDA observation. However, the background flux level tends to be increase as time goes on especially for higher energy channels. Using long period of high energy electron flux and temperature data of the sensor, we try to estimate the optimal bias current as a function of temperature. In this presentation, we will introduce initial trial for improving bias current subtraction for SEDA-e observation and evaluate the quality of data using intercalibration of GOES/SEISS data.