The Ionospheric Anomaly Monitoring by Magnetometer And Plasma-probe (IAMMAP) is one of the scientific instruments for the Compact Advanced Satellite 500-3 (CAS 500-3) which is planned to be launched by Korean Space Launch Vehicle in 2024. The main scientific objective of IAMMAP is to understand the complicated correlation between the equatorial electro-jet (EEJ) and the equatorial ionization anomaly (EIA) which play important roles in the dynamics of the ionospheric plasma in the dayside equator region. IAMMAP consists of an impedance probe (IP) for precise plasma measurement and magnetometers for EEJ current estimation. The designated sun-synchronous orbit along the quasi-meridional plane makes the instrument suitable for studying the EIA and EEJ. The newly-devised IP is expected to obtain the electron density of the ionosphere with unprecedented precision by measuring the upper-hybrid frequency (fUHR) of the ionospheric plasma, which is not affected by the satellite geometry, the spacecraft potential, or contamination unlike conventional Langmuir probes. A set of temperaturetolerant precision fluxgate magnetometers, called Adaptive In-phase MAGnetometer, is employed also for studying the complicated current system in the ionosphere and magnetosphere, which is particularly related with the EEJ caused by the potential difference along the zonal direction.

1. INTRODUCTION
2. PREVIOUS OBSERVATIONS OF EQUATORIALIONIZATION ANOMALY (EIA) AND EQUATORIALELECTRO-JET (EEJ)
    2.1 Neutral-Plasma Interaction in the Dayside Ionosphere
    2.2 Equatorial Ionization Anomaly (EIA) Observation usingDetection of Electro-Magnetic Emissions Transmitted fromEarthquake Regions (DEMETER)
    2.3 Equatorial Electro-Jet (EEJ) Observation using SWARM
    2.4 Issues of Previous Observations and Suggestions forthe Improved Mission Design
3. IAMMAP INSTRUMENT DESIGN ANDPROTOTYPE TEST RESULTS
    3.1 IAMMAP Configuration
    3.2 Impedance Probe Design and Prototype Test Results
    3.3 Adaptive In-Phase MAGnetometer (AIMAG) Designand Prototype Test Results
4. SUMMARY AND CONCLUSIONS
ACKNOWLEDGMENTS
ORCIDs
REFERENCES

• Kwangsun Ryu(Satellite Technology Research Center, KAIST, Daejeon 34141, Korea) Corresponding author
• Seunguk Lee(Satellite Technology Research Center, KAIST,Department of Astronomy and Space Science, Chungbuk National University)
• Chang Ho Woo(Satellite Technology Research Center, KAIST, Daejeon 34141, Korea)
• Junchan Lee(Satellite Technology Research Center, KAIST, Daejeon 34141, Korea)
• Eunjin Jang(Satellite Technology Research Center, KAIST, Daejeon 34141, Korea)
• Jaemin Hwang(Satellite Technology Research Center, KAIST, Daejeon 34141, Korea)
• Jin-Kyu Kim(Satellite Technology Research Center, KAIST, Daejeon 34141, Korea)
• Wonho Cha(Satellite Technology Research Center, KAIST, Daejeon 34141, Korea)
• Dong-guk Kim(Satellite Technology Research Center, KAIST, Daejeon 34141, Korea)
• BonJu Koo(Satellite Technology Research Center, KAIST, Daejeon 34141, Korea)
• SeongOg Park(Satellite Technology Research Center, KAIST, Daejeon 34141, Korea)
• Dooyoung Choi(Department of Astronomy and Space Science, Chungbuk National University, Chungju 28644, Korea)
• Cheong Rim Choi(Department of Astronomy and Space Science, Chungbuk National University, Chungju 28644, Korea)