Effect of atomic oxygen exposure on spacecraft charging properties 衛星帯電物性に及ぼす原子状酸素曝露の影響
Effect of atomic oxygen exposure on spacecraft charging properties
Noor Danish Ahrar Mundari
ヌール ダニッシュ アラール ムンダリ
九州工業大学博士学位論文（要旨） 学位記番号:工博甲第311号 学位授与年月日:平成23年3月25日
Spacecraft surface charging can lead to arcing and a loss of electrical power generation capability of solar panel, or even loss of a satellite. The charging problem may be further aggravated by the atomic oxygen (AO) exposure in Low Earth Orbit (LEO), which modifies the surface of materials like, Polyimide, Teflon, anti-reflective coating, cover glass, etc., used on satellite surface. These affect material properties, such as resistivity, secondary electron emissivity, photo emission, which govern the charging behaviour. These properties are crucial input parameters for spacecraft charging analysis.This research develops a new facility at KIT, based on a novel technique for generating atomic oxygen flux involving laser induced breakdown of molecular oxygen. High velocity AO in an evacuated nozzle is formed, where laser beam breakdowns molecular oxygen into AO injected through a pressurized pulse valve into the nozzle. The energy of AO is measured using Time of flight (TOF) technique. The generated AO flux is measured using Quartz Crystal Microbalance (QCM). The Mass Flow Controller (MFC) inserted in oxygen gas supply line measures the net amount of gas being injected through pulse valve. The spectral analysis of AO production wavelength (777.6nm) is detected using a spectrometer. The relative abundance of generated species is observed using a Quadrupole Mass Analyzer System (QMAS). The developed facility produces AO of velocity 8～14 kms-1 having the flux in the order of 1018 atoms/m2/shot. This flux is used to expose spacecraft surface materials for extended period of 10 years at 800 km, equivalent to exposure of satellite surface materials to atomic oxygen fluence for the normal lifetime of the satellite in orbit.This thesis develops a new method and facility for the measurement of resistivity of atomic oxygen exposed polyimide by using surface charge decay method. The resistivity measurement is performed in vacuum using the charge storage decay method at room temperature, which is considered most appropriate for measuring the resistivity for space application. The mathematical formulation and experimental facility are indigenously developed to measure resistivity as per space requirement. We introduce a new method to measure surface and volume resistivity together, which can be further improved to measure the secondary electron characteristics. The results show that the surface resistivity increases and the volume resistivity remains almost the same for the AO exposure fluence of 5.4x1018atoms cm-2 on polyimide film.
九州工業大学博士学位論文 学位記番号:工博甲第311号 学位授与年月日:平成23年3月25日
1. Introduction|2. AO exposure facility and atomic oxygen characterisation|3. Resistivity measurement facility of insulator and mathematical formulation|4. Results and Discussion|5. Summary