MEPD (Medium Energy Particle Detector) on the NEXTSat-1
In-situ observations using spacecraft have accumulated various information such as magnetic field intensity, energies, and fluxes of different species of charged particles, frequencies and densities of fluidic plasma and of its waves to formulate geomagnetic storms perceived through the abrupt increase of ring currents and subsequent decrease of magnetic field intensity. Specifically, energetic charged particle detectors are often utilized to measure the energies and fluxes in the range of a few keV to a few MeV within a few microseconds to a few seconds.
Medium Energy Particle Detector (MEPD) is an instrument capable of measuring energy distribution of electrons, protons, and neutrals in the energy range of 20 ~ 400 keV with 6.25 keV linear or 2~24.32 keV pseudo-log energy resolution, 1~128 Hz cadence, and 106~108/cm2∙sr∙sec∙keV dynamic range of incident fluxes. The apparatus consists of two identical telescopes, each with a field of view of 15º x 70º, with orthogonal placement for the detection of different pitch angles. MEPD produces spectral data by incrementing a number of detected particles with respect to individual energy channels divided into 64 bins.
The energy-channel relation of the instrument is calibrated referring to distinct peak energy lines emitted from well-known radioisotopes. Further tests to verify the time resolution, dynamic range adjustment and particle separation are performed. MEPD is one of the suite instrument built in Instruments for the Study of Space Storms (ISSS) measuring both space radiation and plasma aboard the Next Generation Small Satellite-1 (NEXTSAT-1). NEXTSat-1 is a low-altitude sun-synchronous orbit satellite with a scheduled mission launch date in the year 2017 when the solar activity is near the maximum or in the declining phase of the 24th cycle. This research summarizes the design, development review and test results of the energetic charged particle detector for the research of geomagnetic storm.