• Journal of Space Technology and Applications
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• v.1 no.1
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• pp.23-32
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• 2021

The high-level Space Situational Awareness (SSA) objective is to provide to the users dependable, accurate and timely information in order to support risk management on orbit and during re-entry and support safe and secure operation of space assets and related services. Therefore the risk assessment for the re-entry of space objects should be managed nationally. In this research, the Software for Re-Entry Prediction of space objects (SREP) was developed for national SSA system. In particular, the rate of change of the drag coefficient is estimated through a newly proposed Drag Scale Factor Estimation (DSFE), and is used for high-precision orbit propagator (HPOP) up to an altitude of 100 km to predict the re-entry time and position of the space object. The effectiveness of this re-entry prediction is shown through the re-entry time window and ground track of space objects falling in real events, Grace-1, Grace-2, Tiangong-1, and Chang Zheng-5B Rocket body. As a result, through analysis 12 hours before the final re-entry time, it is shown that the re-entry time window and crash time can be accurately predicted with an error of less than 20 minutes.

• The Korean Journal of Air & Space Law and Policy
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• v.29 no.1
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• pp.199-236
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• 2014

This paper analyses from the perspective of distributive justice the legal mechanisms for international allocation of orbital slots, which are of co-owned nature and thereby limited natural resources in outer space. The allocative function is delegated to the International Telecommunication Union. The Radio Regulation, amongst such other legal instruments as the Constitution and Convention, by which the ITU and contracting States thereof abides, dictates how the orbital positions are distributed. Thus, the RR is thoroughly reviewed in the essay. The mechanisms are in a broad sense categorized into two systems: 'a posteriori system' where the 'first come, first served' principle prevails; and 'a priori system' designed to foster the utilisation of the slots by those who lack space resources and are, in especial, likely to be marginalised under the former system. The argument proceeds on the premise that a posteriori system places the under-resourced States in unfavourable positions in the securement of the slots. In contrast with this notion, seven factors were instantiated for an assertion that the degradation of the distributive justice derived from the 'first come, first served' rule, which lays the foundation for the system, could be either mitigated or counterbalanced by the alleged exceptions to the rule. However, the author of this essay argues for counterevidences against the factors and thereby demonstrating that the principle still remains as an overwhelming doctrine, posing a threat to the pursuit of fair allocation. The elements he set forth are as in the following: 1) that the 'first come, first served' principle only applies to assignments capable of causing harmful interferences; 2) the interoperability of the principle with the 'rule of conformity' with the all the ITU instruments; 3) the viability of alternative registrations, as an exception of the application of the principle, on the condition of provisional and informational purposes; 4) another reference that matters in deciding the priority: the types of services in the TFA; 5) the Rule of Procedure H40 proclaiming a ban on taking advantage of coming first to the Register; 6) the technical factors and equity-oriented norms under international and municipal laws along with; 7) the changes of 'basic characteristics' of registered assignments. The second half of this essay illustrates by examining the relevant Annexes to the Regulation that the planned allocation, i.e., a priori system, bear the structured flaws that hinder the fulfillment of the original purpose of the system. The Broadcasting and Fixed Satellite Systems are the reviewed Plans in which the 'first come, first served' principle re-emerges in the end as a determining factor to grant the 'right to international recognition' to administrations including those who has not the allotted portions in the Plan.

• Korean Journal of Remote Sensing
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• v.14 no.3
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• pp.277-284
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• 1998

To establish a monthly data collection planning for the Ocean Scanning Multispectral Imager (OSMI), we have examined the global patterns of three impacting factors: pigment concentration, cloud cover, and sun glint. Other than satellite mission constraints (e.g., duty cycle), these three factors are considered critical for the OSMI data collection. The Nimbus-7 Coastal Zone Color Scanner (CZCS) monthly mean products and the International Satellite Cloud Climatology Project (ISCCP) monthly mean products (C2) were used for the analysis of pigment concentration and cloud cover distributions, respectively. And the monthly-simulated patterns of sun glint were produced by performing the OSMI orbit prediction and the calculation of sun glint radiances at the top-of-atmosphere (TOA). Using monthly statistics (mean and/or standard deviation) of each factor in the above for a given 10$^{\circ}$ latitude by 10$^{\circ}$ longitude grid, we generated the priority map for each month. The priority maps of three factors for each month were subsequently superimposed to visualize the impact of three factors in all. The initial results illustrated that a large part of oceans in the summer hemisphere was classified into the low priority regions because of seasonal changes of clouds and sun illumination. Sensitivity tests for different sets of classifications were performed and demonstrated the seasonal effects of clouds and sun glint to be robust.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.363-373
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• 2000

It is necessary to employ the interpolation technique to resolve problems, which are associated with the characteristic locus in time-distance space, in the unsteady analysis of pipe flow. Various interpolation methods such as linear timeline interpolation, linear spaceline interpolation, wave speed adjustment, cubic spaceline interpolation and cubic timeline interpolation have been suggested and tested to investigate the interpolation error. Performance of various interpolation techniques was evaluated both a single pipeline and a complex one. The range of error was calculated as the courant number varied between 0 and 1 in a single pipeline. Reorganization of computational element and proper selection of interpolation method are found to be prerequisites for the effective computation of unsteady analysis.

• Cartoon and Animation Studies
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• s.33
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• pp.271-291
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• 2013

Cartoons exhibit contents and images and deliver them to readers by repeating frames. Frames embody the cross sectional factors of space-time, and the repetition of frames makes those cross sectional factors into a continuous flow. The gutter, which exists between frames, takes the role to make the continuous flow link smoothly, and at the beginning stage of the gutter, the operating of the gutter was usually passive by the frame meanings. However, the gutter is not just a medium for linking the frames, but is an efficient participation device for creating new expression methods of cartoon organization. By producing new directing methods for cartoon organization, the distinctive functions of the gutter have been kept alive with cartoon history. The distinctive functions of the gutter can be divided largely into transition function, reminiscence function, speech balloon function, pen function, and decorative function. And those functions perform actively as direct expression method of the gutter. When those functional methods are expressed by the author's intention and the frequency of them is generalized according to described contents, using each author's individual differences can suggest direction for new directing organization of cartoons.

• Aerospace Engineering and Technology
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• v.7 no.2
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• pp.58-66
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• 2008

In the space environment, many other things to design electronic circuits should be considered with respect to commercial circuit design. The first thing is that electronics in space are likely to be exposed to radiation effects and the second thing is that it is impossible to repair or replace electronic parts after once spacecraft was launched. In this severe situation, very strict and tight worst case analysis conditions should be applied to the electronics in space environment to do its own function well without any problems during the overall mission period. So this paper summarizes worst case input conditions and methods which are specified in the ESA Worst Case Analysis Specification (ECSS-Q-30-01A) and proposes the results of Worst Case Analysis for one simple electronic circuit which is implemented at a real On-Board Computer in the Low Earth Orbit Satellite.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.12
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• pp.1207-1215
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• 2008

Satellite generates a complex electromagnetic noise by conducted and radiated coupling effect of the various electrical instruments. This noise may cause serious problems on the satellite system. To minimize the electromagnetic coupling effects and maintain the system safety margin, system noise reduction technique should be applied from the beginning of the system design. The COMS system is evaluated by measuring the conducted noise on system electrical power leads at PSR(Power Supply Regulator) and verifying a 6 dB system safety margin under the complex noise environment with current injection. The radiated noise due to the complex transmit antenna configuration is evaluated by integrating all unit-level RE measurement results, and the RF compatibility between spacecraft and launch vehicle is analyzed with the above estimations. This paper describes the COMS EMC compatibility analysis with respect to each unit level EMC test results, and RF compatibility analysis between spacecraft and launch vehicle. The analyzed results will be reflected on FM(Flight Model) EMC test.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.1
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• pp.151-158
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• 1992

Topographic mapping from economic SPOT stereo imagery than aerial photographs has become possible. Many of authors have studied the possibility of base map revisions and the accuracy of results. They have concluded that the SPOT image is suitable for 1/50,000 to 1/100,000 topographic map. For topographic map, orthophoto and DTM generation from SPOT imagery, accurate exterior orientation parameters are needed. But since the geometric characteristic of SPOT image is dynamic linear array imagery, the conventional bundle adjustment for photogrammetry can not be directly applied. Reliability is the ability to detect gross error, which is called the internal reliability, and the effect of non-detectable gross error on the results of exterior orientation, which is called the external reliability. This paper shows how the reliability of SPOT imagery depends on the different coordinate systems, presentations of coordinate for flight direction, orders of exterior orientation parameters and distribution of control points, and thus analyses the theoretical reliability of the exterior orientation, which can provide a basis for the planning of SPOT projects.

• Journal of Astronomy and Space Sciences
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• v.26 no.4
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• pp.439-450
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• 2009

Recurrent enhancements of relativistic electron events at geosynchronous orbit (GREEs) were observed in 2006. These GREE enhancements were associated with high-speed solar wind streams coming from the same coronal hole. For the first six months of 2006, the occurrence of GREEs has 27 day periodicity and the GREEs were enhanced with various flux levels. Several factors have been studied to be related to GREEs: (1) High speed stream, (2) Pc5 ULF wave activity, (3) Southward IMF Bz, (4) substorm occurrence, (5) Whistler mode chorus wave, and (6) Dynamic pressure. In this paper, we have examined the effectiveness about those parameters in selected periods.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1613-1618
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• 2012

The wheel bearing is one of the important parts in a vehicle for translating power and bearing weight. When it is mounted on the knuckle by using bolts, the distortion of the outer ring including the seal mounting point and raceway occurs. In this study, a numerical analysis was performed to analyze the distortion of the outer ring by using a finite element method. The commercial software MSC.MARC was used for this purpose. Elastoplastic and contact analysis were carried out to compute the clamping behavior of the outer ring, bolts, and knuckle. Because the concavity on the flange of the outer ring affects the deformation, its effect was considered. To verify the reliability of this study, the roundness of the outer ring was measured. The experimental results were comparatively in agreement with the computational results.