The Ionospheric Plasma and Electrodynamics Instrument (IPEI) is a joint project of the National Space Program Office of the Republic of China, the University of Texas at Dallas, The National Central University, and the National Chiao-Tung University. The IPEI sensors consist of an ion-trap (IT), a pair of ion drift meters (IDM), and a retarding potential analyzer (RPA). The instrument is designed to measure the ion density, temperature, and drift velocity in order to study the large-scale electrodynamics, plasma distribution, and the small-scale plasma structure in the low-latitude ionosphere with emphasis on the equatorial region above Taiwan. The high-resolution measurements will enable detailed studies of equatorial bubbles, Rayleigh-Taylor instability, the ExB drift instability, and the Perkins instability.