The wide-angle Polarimetric Camera (PolCam) onboard South Korea’s first lunar orbiter, Danuri, is a pioneering instrument designed to conduct the first global polarimetric and high-phase-angle survey of the Moon. Precise geometric calibration is critical for this mission, particularly due to PolCam’s highly oblique viewing geometry, which introduces significant topographic distortion. We present a comprehensive on-orbit geometric calibration that relies on 160,256 tie points derived from matching features between PolCam images and the well-orthorectified global map of the Kaguya Multiband Imager (MI). This dataset allows us to address two fundamental challenges: (1) the accurate reconstruction of the observation time for each line of an observation strip via a simple linear model, and (2) the refinement of the precise camera model, geometric model for PolCam optics. Our optimization method for these two challenges transforms the 2D image coordinates of identified features into 3D lunar coordinates and minimizes the reprojection error against the reference coordinates provided by the Kaguya MI map. From the refined observation time and camera model, we compute the precise longitude, latitude, and elevation of each pixel of an observed image. These estimated 3D coordinates are then used to generate orthorectified images, the final product of the geometric calibration. The resulting calibration achieves a geometric precision comparable to that of previous lunar orbiters and establishes the foundational framework necessary to produce geometrically-corrected data products of PolCam.

The study on the efficiency improvement of qualification procedures for low Earth orbit (LEO) satellites analyzed the differences between the European ECSS and the American NASA standards. ECSS allows flexible test tailoring to accommodate project-specific requirements, whereas NASA enforces strict standardized procedures to ensure high reliability. Additionally, ECSS prioritizes cost efficiency, while NASA emphasizes reliability. In terms of application scope, NASA focuses on private-sector collaborations, whereas ECSS is centered on cooperative projects within Europe. Based on this comparative analysis, this study proposes a qualification framework for Korean LEO satellites, categorizing 18 qualification test items into mandatory and optional groups. This approach is expected to enhance the reliability, performance, and stability of satellite systems. Therefore, the proposed Korean qualification test sequence should be implemented and incorporated into national defense standards. This will strengthen the systematic structure of the qualification process while maximizing efficiency in terms of testing time and cost.

The emergence of global internet access from the low Earth orbit (LEO) comes with cybersecurity vulnerabilities. Under international space law regimes, the concept of cybersecurity in outer space remains ambiguous. Furthermore, cyberattacks affecting the era’s thoroughly segregated computer space systems were unimagined. Cyber borders are not the same as physical borders. Cyberspace does not admit the demarcation of territorial sovereignty, as it is not based on physical location, and assigning territorial sovereignty to cyberspace is time-consuming. This research proposes the concept of a multi-stakeholder international legal regime for space cybersecurity, as establishing cybersecurity standards and risk management mechanisms necessitates technical measures and a regulatory framework. International cooperation is the only way to provide a fully coordinated approach to cyberspace protection which is consistent with the fundamental premise of international cooperation and collaboration in space.

본 연구의 목적은 중학교 영재 학생들이 수행한 증거 기반 추론의 특징을 조사하는 것이었다. 연구를 위한 자료는 수도권에 위치한 한 대학교의 영재 교육원에서 중학교 영재 학생들이 비대면 방식으로 진행한 탐구 과제를 통해 수집되었다. 학생들에게 수성의 최대 이각을 관측한 자료를 제공하고 이 자료를 이용하여 수성의 공전 궤도를 작도하게 하였다. 또, 작도 전에 수성의 궤도에 대한 자신의 가설을 진술하게 하였으며 작도 결과를 증거로 삼아 수성 궤도의 모양을 추론하게 하였다. 학생들이 제출한 보고서의 내용을 분석하여 수성의 공전 궤도 모양에 관한 판단 유형을 5가지로 분류하고 가설 및 증거에 관한 추론 유형을 4가지로 분류한 후, 판단 유형에 따른 증거 기반 추론의 특징을 정리하였다. 분석 결과를 토대로, 증거 기반 추론에서는 증거에 대한 적절한 해석이 중요하고, 이론과 증거의 조화가 핵심적인 역할을 하며, 복수의 가설을 상정하는 것이 유리할 수 있음을 논의하였고, 지구과학 교육을 위한 시사점을 제안하였다.

We study the pseudo-synchronous orbital motion of a binary system on the main sequence. The equations of the pseudo-synchronous orbit are derived up to O(e4) where e is the eccentricy of the orbit. We integrate the equations to present their solutions. The theoretical results are applied to the evolution of the orbit and spin of the binary star Y Cygni, which has a current eccentricity of e0 = 0.142. We tabulate our numerical results for the evolution of the orbit and spin per century. The numerical results for the semi-major axes and rotational angular velocities in the evolutional time scales of three stages (synchronization, circularization, and collapse time scale) are also tabulated. Synchronization is achieved in about 5 × 103 years followed by circularization lasting about 1 × 105 years before decaying in 2 × 105 years.

In this study, I calculate the past and future dynamical states of the Earth-Moon system by using modified Lambeck’s formulae. I find that the ocean tidal effect must have been smaller in the past compared to its present amount. Even though the Moon is already in the spin-orbit synchronous rotational state, my calculation suggest that it will not be in geostationary rotational state in the next billion years or so. This is due to the associated Earth’s obliquity increase and slow retardation of Earth’s spin and lunar orbital angular velocities. I also attempt to calculate the precessional period of the Earth in the future. To avoid uncertainties in the time scale, the future state is described by using the Earth-Moon distance ratio as independent parameter. Effects due to solar tidal dissipation are included in all calculations.

카울라에 의해 완성되었던 인공위성궤도이론과 케플러의 법칙을 다시 다루었다. 카울라의 원문에서는 생략되었던 부분을 포함한 모든 수식유도과정을 상세히 기술하였다. 특히 15개의 독립적인 라그랑지 괄호들을 계산하는 데에 변환행렬의 직교성을 사용하여, 간결성과 명확성을 이루었다. 여러 중간단계에서 중요한 물리적인 개념들에 대한 설명도 추가하였다. 카울라의 개념적 오류 한 개를 정정하였다.