Mechanical design and vibration analysis/test of Instrument for Space Storm Study(ISSS)

Abstract

The Instruments of Study for Space Science payload (ISSS) is to be flown as a secondary payload on board the Next Generation Small (NEXTSat-1) series of Korea, a microsatellite scheduled for launch in 2017 into the polar orbit. It consists of Space Radiation Detectors (SRD) and Space Plasma Detectors (SPD). SRD will measure the ring current and radiation belt particles in the subauroral regions and it is structured based on two instruments: Medium Energy Particle Detector (MEPD) and High Energy Particle Detector (HEPD). SPD will measure the ionospheric ions and electrons in the middle and low latitude regions and it is composed of three conventional instruments: a Langmuir Probe (LP), a Retarding Potential Analyzer (RPA), and an Ion Drift Meter (IDM). Hence, the ISSS consists of five instruments, MEPD, HEPD, LP, RPA, and IDM and these instruments will be utilized for collecting space environment data. The ISSS weighs about 13kg and its structure has structural frames of which material is aluminum 7075 T6. Moreover, the ISSS contains six large ($116 \times 136.5mm^{2}$) and six small ($88 \times 88mm^{2}$) electrical circuit boards and 13 bunches of harnesses are connected in the ISSS. Due to flexibility of electrical circuit boards, sinusoidal and random loads could cause fracture of electrical segments attached in the circuit boards in the payload structure. The harnesses could provoke vibrations which collide with payload structure. Furthermore, it distorts with electrical signals and provoke signal noise. Thus, the electrical signals have to be protected because science payload have to calculate sensitive data. For these reasons, the structural analysis was performed to ensure robust against disturbances during launch. Since stability of satellite structure have to be ascertained, vibration properties of the ISSS were exactly tested through environmental tests and analyzed by Finite Elements Analysis (FEA) softwares. There are seven kinds of loads on structure including, natural frequency, steady state (semi-steady) acceleration, sine excitation, acoustic noise, transient loads, shock loads, and temperature. However, steady state, acceleration, transient loads, shock loads, and temperature have no relevance to vibration, and acoustic load do not provokes deformation on the ISSS which has no large surfaces. Therefore, in case of the ISSS, modes and sinusoidal, and random loads were considered as verified properties due to geometrical structure of the ISSS. Modal analysis was analyzed by ANSYS and NASTRAN softwares and environmental tests were conducted in accordance with test requirement written by Satellite Technology Research Center (SATREC).