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All Journal Indonesian Journal of Geography
Nizam Ahmad
Indonesian National Institute of Aeronautics and Space (LAPAN)
Earth & Planetary Sciences

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Numerical Simulation of Spacecraft Charging Attributed to Ionospheric Plasma in Polar and Equatorial Environment Nizam Ahmad; Hideyuki Usui
Indonesian Journal of Geography Vol 52, No 1 (2020): Indonesian Journal of Geography
Publisher : Faculty of Geography, Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (22.772 KB) | DOI: 10.22146/ijg.50564

Abstract

The presence of spacecraft in ionospheric plasma can change plasma properties, vice versa plasma can lead to charge buildup on spacecraft. The level of charging, through electric potential of spacecraft, initially depends on plasma density. However, simulations done on four LEO satellites, i.e. ERS 1, MIDORI, ASCA and FUSE 1, showed that charging level depends on plasma electron temperature rather than plasma density which satisfied the Boltzmann’s relation in the absence of high-energy electrons from aurora. The higher the plasma electron temperature the more spacecraft exposed to negative charging. It is assumed that plasma ions and electrons are collisionless or in Maxwellian distribution. It is found that there is no strong relation between density and charging level. Furthermore, there exists insignificant different of charging between polar and equatorial satellites. It means that the placement of satellite in polar or equatorial region, as long as the presence of auroral electrons is excluded, will suffer similar level of charging which is less than 5V (negative). Since spacecraft are exposed to negative charge, electric field generated by spacecraft potential, together with mesothermal motion effects, deflects ion trajectory into donwstream region leading to ion void region. The ion density is reduced compared to electron density, but there is no significant different of ion void feature between polar and equatorial satellites.and capacity building of beneficiaries. 
Preliminary Determination of Footprint Area of Uncontrolled Space Debris: Case Study of Tiangong-1 Space Station Nizam Ahmad; Elisa Fitri
Indonesian Journal of Geography Vol 53, No 2 (2021): Indonesian Journal of Geography
Publisher : Faculty of Geography, Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/ijg.54247

Abstract

Indonesia is an archipelagic country consisting of 16,056 islands and covering a vast area around 5,120km x 1,760km. With the largest coastline in the world, Indonesia is vulnerable to the fall of human-made objects from space. Furthermore, the space objects placed at polar and equatorial regions pass over the equatorial region, including Indonesia, more frequently around 4 and 9 times a day, successively depending on their altitudes. Due to the significant probability of the passages, determining the footprint of falling space objects (debris) is mandatory. Therefore, this study examines the demise of Tiangong 1 as a case study. First, trajectory propagation was carried out to track the re-entry point resulting in an estimated footprint area of around 2,632 km x 2,698 km over the Sothern Pacific Ocean.  Second, a mathematical formulation in Astrodynamics was applied to engage a series of assumptions, which led to a more cramped footprint area of around 193km x 12km over a small portion of the South Pacific Ocean. Since the orbital prediction is fraught with great uncertainty, it was very likely that the Tiangong-1 debris fell over the Southern Pacific Ocean of the order of thousands of kilometers.
Co-Authors Elisa Fitri Hideyuki Usui