Low-energy ion data (E < 25 keV/q) acquired by the Kaguya spacecraft were used to study ions originating near the lunar surface when the Moon was in the terrestrial magnetotail lobe. We focus on three intervals during which Kaguya detected these ions at different altitudes: similar to 100 km on 15 October 2008, similar to 50 km on 9 April 2009, and a descent from similar to 60 to similar to 30 km on 9 May 2009. In each interval, the strongly enhanced fluxes of lunar-origin ions exhibited a band structure spanning less than 100 eV/q to similar to 1,000 eV/q, with pitch angles from 30 degrees to 140 degrees. To understand where and how cold lunar-origin ions (<1 eV) are energized to the observed energy levels, we conducted test-particle simulations. The simulations indicate that these ions can reach energies of similar to 300 eV through multiple reflections from the lunar photoelectron sheath, and are further accelerated by the motional electric field, increasing their energies from several hundred eV to similar to 1,000 eV, consistent with Kaguya observations.

Abstract Observing the polarization of the lunar regolith is essential for obtaining detailed information about the composition and characteristics of lunar soil. Observations conducted via lunar orbiters facilitate polarization measurements over wide areas; however, achieving very high‐resolution imaging requires either a large optical system or a narrow field of view, both of which complicate observations under varying incident angle conditions. Furthermore, when the lunar surface is imaged at high resolution, the emission angle can vary significantly due to the slope and orientation of local terrain features such as craters and hills. This variability is particularly pronounced in young craters, where steep slopes near the rim result in emission angles that are nearly horizontal. In addition, unlike ground‐based observations, orbital systems can observe the same region at various times and from different angles, resulting in significant variation in the off‐plane angle between the satellite, the target area, and the Sun. Consequently, the Sun, target, and detector may not align linearly on the lunar surface. In this study, we measured the degree of polarization of the JSC‐1A lunar soil simulant at various incident, reflection, and off‐plane angles to examine how the polarizer angle changes under different conditions. The results show that even at the same phase angle, the degree of polarization varies significantly with incident and off‐plane angles, indicating that these geometric factors must be considered for accurate interpretation of polarization measurements. These measurements are expected to aid in identifying critical factors for accurately interpreting polarization data obtained from the lunar surface.

Search coil magnetometers (SCMs) are widely used in space science missions to measure time-varying magnetic fields. However, conventional SCM designs often increase sensor mass and electronic power consumption in order to meet mission-specific sensitivity requirements. This study presents the design and ground-based test results of a space search coil magnetometer (SSCM) concept aimed at reducing sensor mass and electronic power consumption while maintaining practical system operability for platform-constrained missions. Mass reduction was achieved by adopting a rolling-sheet core configuration. In addition, printed circuit board (PCB)-based interconnections between segmented windings were implemented to improve the reproducibility of assembly and mechanical robustness without additional structural complexity. Power reduction was achieved by employing an application-specific integrated circuit (ASIC)-based sensor amplifier and a compact control electronic unit implemented as a modular stack with a 1U CubeSat standard board form factor. Performance tests confirmed the stable operation of the integrated sensor–electronics chain over the target measurement band. The system-level noise-equivalent magnetic induction (NEMI) measured under laboratory conditions was 33 fT/√Hz at 1 kHz. Environmental tests including vibration and thermal cycling were performed to further verify the structural safety and functional stability of the sensor assembly under space-relevant conditions. The proposed SSCM architecture provides a practical approach for implementing low-mass and low-power magnetic field instruments for platform-constrained space missions.

The Korea Pathfinder Lunar Orbiter (KPLO) spacecraft utilizes the KPLO Magnetometer (KMAG) payload, a three-fluxgate magnetometer array mounted on a 1.2 m boom, to measure crustal and induced lunar magnetic fields. The short boom length exposes the magnetometers to intricate, multi-source stray magnetic fields. These interference signals include a low-frequency, 20 nT peak-to-peak signal from the solar panels and batteries as the spacecraft transitions between sunlight and darkness during certain orbital phases. These stray magnetic fields impede the analysis of lunar magnetic anomalies with magnitudes up to 3 nT at a 100 km altitude. Additionally, downlink issues during the mission's initial stages occasionally resulted in data gaps of up to 12 min (approximately 13% of the orbit) in several orbits. To overcome these data quality challenges, we present a comprehensive three-component method: (a) the Recurrent Forecasting Multichannel Singular Spectrum Analysis (M-SSA) algorithm interpolates data gaps, (b) Wavelet-Adaptive Interference Cancellation for Underdetermined Platforms (WAIC-UP) removes stray magnetic fields from the continuous magnetometer measurements, and (c) the Removal Algorithm for Magnetometer Environmental Noise (RAMEN) gradiometry algorithm corrects low-frequency trends not observed by WAIC-UP. We demonstrate the efficacy of our approach by comparing the results with contemporaneous magnetic field measurements from the lunar-orbiting ARTEMIS-P1 spacecraft and lunar crustal magnetic field maps from the Lunar Prospector and Kaguya missions. This integrated application of M-SSA, WAIC-UP, and RAMEN enables KMAG to reliably investigate lunar magnetic fields despite non-dipolar spacecraft interference and intermittent data gaps.

The mission-assisting anisotropic magnetoresistive sensor (MAMS) module is one of the components supporting the operation of the lunar surface magnetometer (LSMAG), one of the Korean candidate payloads for the Commercial Lunar Payload Services (CLPS) program. LSMAG uses fluxgate magnetometers (FGMs), which have a 0.2 nT resolution and ± 2,000 nT measurement range. For the scientific analysis of LSMAG data, four types of additional mission-assisting functions are required: strong magnetic field measurement, lander noise detection, offset calibration signal generation, and attitude information provision. To perform these functions, the MAMS module utilizes anisotropic magnetoresistive (AMR) sensors (HMC1001/1002), an accelerometer (ADXL355), and an artificial magnetic field generating circuit. The AMR sensors have a larger measurement range than FGMs. Therefore, these sensors are suitable for measuring strong magnetic fields and the lander’s noise signal, making them applicable for noise-removal techniques. The MAMS module also includes an accelerometer (ADXL355) to measure the attitude of the LSMAG boom and features an artificial field-generating function to determine the sensor offset. The MAMS module passed functional and space environmental tests to verify its performance. The AMR sensors have a 20 nT resolution and ± 80,000 nT range, while the accelerometer has a 6 mg resolution and ± 2 g range under Earth conditions. This module includes its own microcontroller unit and supports a wide input voltage range and standard RS485 universal asynchronous receiver/transmitter (UART) communication. We expect the MAMS module to not only play an essential role in supporting LSMAG data calibration and operation, but also to be used in various future space science exploration missions.

We analyze data acquired by the Kaguya satellite on 14 October 2008 when the Moon was in the terrestrial magnetotail lobe to gain new insight into the energization of ions originating from the Moon. The Moon-originating ions were detected over a broad range of latitudes from -80 degrees to 50 degrees above the Moon's dayside at similar to 100 km altitude. The fluxes of the Moon-originating ions were observed at energies from similar to 50 to similar to 1,000 eV. Additionally, these ions exhibited a wide distribution pitch angle spanning from similar to 45 to 90 degrees. The energy levels of ions originating from the Moon show rapid changes, either increasing or decreasing by a factor of similar to 10 within 8 min without the solar zenith angle dependence. Such rapid energy changes were observed over the highland regions. These observations are discussed in light of possible acceleration mechanisms of Moon-originating ions, including temporal and spatial effects. The Moon-originating ions are distributed over a broad range of latitudes from -80 degrees to 50 degrees The median peak energy of Moon-originating ions does not show a significant dependence on the solar zenith angle between 0 degrees and 60 degrees The energy of the Moon-originating ions shows a sudden rise or drop by a factor of similar to 10 in 8 min over the highland regions

The formation of lunar crustal magnetic anomalies is not well understood, and most anomalies are not associated with any obvious geologic features. To investigate further, we studied lunar craters from 100 to 400 km in diameter (totaling 305 craters) that may have demagnetized the crust. We find that the four craters Chaplygin, Keeler, Gauss, and Fermi are highly likely to have demagnetized the crust, based on our statistical methods. We modeled the magnetic source of these craters as a simple hole in a thin magnetized plate, representing the destruction of a surficial magnetized layer (Hypothesis 1). Alternatively, we also simulated the impact demagnetization of deeper-seated magnetism in the crust by shock and temperature (Hypothesis 2). Some interior magnetization remains unexplained under both hypotheses, but the destruction of a pre-existing surficial layer of magnetized material is consistent with the location of the peak in each crater's magnetic field. We also find three of the craters are inversely correlated with remotely sensed iron, further supporting our interpretation that the craters demagnetized a surficial layer. The four craters are located on magnetized ejecta deposits from the South Pole-Aitken, Orientale, and Crisium basins. Hence, these four craters further support the hypothesis that large provinces of magnetized material on the Moon arise from hot impact ejecta that cooled in a dynamo field.

A search coil magnetometer (SCM) is a common equipment to observe energy transmission and vibrations in space physics, enabling measurements across a wide frequency range of up to tens of kilohertz. This study proposes the designs of a magnetic core that allows a low-mass sensor and improves its performance: a rod core, sheet-stacked core, and rolling-sheet core. Subsequently, the performance of each sensor was investigated. The sheet-stacked core using the cobalt-based alloy exhibited the highest sensitivity, although it exhibited instability beyond 20 kHz. In contrast, the rod and rolling-sheet core sensors demonstrated stability in the magnetic field measurements (10 Hz–40 kHz). Moreover, the noise equivalent magnetic induction (NEMI) of the rod- and rolling-sheet core sensors were 0.014 pT Hz–1/2 and 0.012 pT Hz–1/2 at 1 kHz, respectively. The rolling-sheet core with high relative permeability achieved a mass reduction of over three times that of the rod core while exhibiting sufficient sensitivity.

The Korean Pathfinder Lunar Orbiter (KPLO)-MAGnetometer (KMAG) consists of three triaxial fluxgate sensors (MAG1, MAG2, and MAG3) that measure the magnetic field around the Moon. The three sensors are mounted in the order MAG3, MAG2, and MAG1 inside a 1.2 m long boom, away from the satellite body. Before it arrived on the Moon, we compared the magnetic field measurements taken by DSCOVR and KPLO in solar wind to verify the measurement performance of the KMAG instrument. We found that there were artificial disturbances in the KMAG measurement data, such as step-like and spike-like disturbances, which were produced by the spacecraft body. To remove spacecraft-generated disturbances, we applied a multi-sensor method, employing the gradiometer technique and principal component analysis, using KMAG magnetic field data, and confirmed the successful elimination of spacecraft-generated disturbances. In the future, the proposed multi-sensor method is expected to clean the magnetic field data measured onboard the KPLO from the lunar orbit.

The Korea Pathfinder Lunar Orbiter (KPLO), the first South Korea lunar exploration probe, successfully arrived at the Moon on December, 2022 (UTC), following a 4.5-month ballistic lunar transfer (BLT) trajectory. Since the launch (4 August, 2022), the KPLO magnetometer (KMAG) has carried out various observations during the trans-lunar cruise phase and a 100 km altitude lunar polar orbit. KMAG consists of three fluxgate magnetometers capable of measuring magnetic fields within a ± 1,000 nT range with a resolution of 0.2 nT. The sampling rate is 10 Hz. During the originally planned lifetime of one year, KMAG has been operating successfully while performing observations of lunar crustal magnetic fields, magnetic fields induced in the lunar interior, and various solar wind events. The calibration and offset processes were performed during the TLC phase. In addition, reliabilities of the KMAG lunar magnetic field observations have been verified by comparing them with the surface vector mapping (SVM) data. If the KPLO’s mission orbit during the extended mission phase is close enough to the lunar surface, KMAG will contribute to updating the lunar surface magnetic field map and will provide insights into the lunar interior structure and lunar space environment.

The Sun-Earth Lagrange point L4 is considered as one of the unique places where the solar activity and heliospheric environment can be observed in a continuous and comprehensive manner. The L4 mission affords a clear and wide-angle view of the Sun-Earth line for the study of the Sun-Earth and Sun-Moon connections from he perspective of remote-sensing observations. In-situ measurements of the solar radiation, solar wind, and heliospheric magnetic field are critical components necessary for monitoring and forecasting the radiation environment as it relates to the issue of safe human exploration of the Moon and Mars. A dust detector on the ram side of the spacecraft allows for an unprecedented detection of local dust and its interactions with the heliosphere. The purpose of the present paper is to emphasize the importance of L4 observations as well as to outline a strategy for the planned L4 mission with remote and in-situ payloads onboard a Korean spacecraft. It is expected that the Korean L4 mission can significantly contribute to improving the space weather forecasting capability by enhancing the understanding of heliosphere through comprehensive and coordinated observations of the heliosphere at multi-points with other existing or planned L1 and L5 missions.

Electromagnetic ion cyclotron (EMIC) waves generated by hot anisotropic (T ⊥ > T ∥ ) protons (∼10–100 keV), play an important role in accelerating cold (<1 eV) protons (H + ) and helium (He + ) ions in the magnetosphere. Using a hybrid code with parameters found in the inner magnetosphere, we examine when and how cold H + and He + ions are energized by EMIC waves. Hybrid simulations show that the energization of the cold particles occurs in two steps. In the first step, EMIC waves, which are linearly excited in the early stage of the simulation, interact with cold H + and He + ions, resulting in energization mostly in the direction perpendicular to the background magnetic field. The energization in this step is mainly contributed by enhanced bulk motion of these ions as a result of the linear response, consistent with recent observations in the inner magnetosphere. In the second step, nonlinear evolution of energized cold H + and He + ions are confirmed in the parallel direction, which is seen after about 200 proton gyroperiods (∼8.5 s). Throughout the simulation run, cold He + ions are much more energized in the perpendicular direction than in the parallel direction. However, the cold protons are more energized in the parallel direction than in the perpendicular direction after 500 proton gyroperiods (∼21.3 s). By comparing recent observations and the present simulation results, we suggest that the cold particle energization by EMIC waves occurs at an early stage of wave generation when the nonlinear evolution of EMIC waves is not dominant in the inner magnetosphere.

In space exploration, instruments measuring magnetic fields require magnetic cleanliness because it helps to distinguish the magnetic field generated by the spacecraft from the ambient field. A spacecraft has its own DC and AC magnetic fields generated by the current flow and residual moments of the spacecraft instruments. Therefore, analysis and testing are required in the development phase. The Korea Pathfinder Lunar Orbiter (KPLO) carries the KPLO Magnetometer (KMAG) instrument to observe magnetic fields on the lunar surface and the space environment around the Moon. To verify the magnetic cleanliness of the KPLO, we analyzed the magnetic field generated by it. We used the positional information and the magnetic dipole moments of twenty-five instruments, with which the KPLO is equipped. The analysis method was a Python program using magpylib. Finally, the worst-case analysis results showed that the spacecraft field around the magnetometer is less than 700 nT, which is the KMAG magnetic cleanliness requirement. (C) 2021 COSPAR. Published by Elsevier B.V.

CubeSat is a satellite platform that is widely used not only for earth observation but also for space exploration. CubeSat is also used in magnetic field investigation missions to observe space physics phenomena with various shape configurations of magnetometer instrument unit. In case of magnetic field measurement, the magnetometer instrument should be far away from the satellite body to minimize the magnetic disturbances from satellites. But the accommodation setting of the magnetometer instrument is limited due to the volume constraint of small satellites like a CubeSat. In this paper, we investigated that the magnetic field interference generated by the cube satellite was analyzed how much it can affect the reliability of magnetic field measurement. For this analysis, we used a reaction wheel and Torque rods which have relatively high-power consumption as major noise sources. The magnetic dipole moment of these parts was derived by the data sheet of the manufacturer. We have been confirmed that the effect 논문 Received: January 10, 2022 Revised: January 26, 2022 Accepted: January 28, 2022 Corresponding author : Ho Jin Tel : +82-31-201-3865 E-mail : benho@khu.ac.kr Copyright © 2022 The Korean Space Science Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. ORCID Hye Jeong Jo https://orcid.org/0000-0003-1966-052X Ho Jin https://orcid.org/0000-0002-1773-8234 Hyeonhu Park https://orcid.org/0000-0002-5487-776X Khan-Hyuk Kim https://orcid.org/0000-0001-8872-6065 Yunho Jang https://orcid.org/0000-0002-8483-4218 Woohyun Jo https://orcid.org/0000-0003-0178-230X 우주과학임무를 위한 큐브위성 자기장 청결도 분석 42 | https://doi.org/10.52912/jsta.2.1.41 of the residual moment of the magnetic torque located in the middle of the 3U cube satellite can reach 36,000 nT from the outermost end of the body of the CubeSat in a space without an external magnetic field. In the case of accurate magnetic field measurements of less than 1 nT, we found that the magnetometer should be at least 0.6 m away from the CubeSat body. We expect that this analysis method will be an important role of a magnetic cleanliness analysis when designing a CubeSat to carry out a magnetic field measurement. 핵심어 : 초소형위성, 자기 청결도, 자기장 측정기, 우주과학, 자기장

Although electromagnetic ion cyclotron (EMIC) waves are commonly observed in the magnetosphere and are believed to energize background cold ions, it is not clear whether EMIC waves play a significant role in determining spacecraft potential change. In this paper, we present two strong He‐band EMIC wave events observed by the Van Allen Probe‐B spacecraft inside the plasmasphere. One event occurred on 11 March 2016 when the spacecraft was on the dayside, and the other occurred on 9 October 2016 when the spacecraft was in the postmidnight sector. When a strong He‐band EMIC wave activity was detected, low‐energy ion flux enhancements occurred nearly simultaneously with the EMIC wave power enhancements. Both events presented in this study are clearly unique in that He‐band wave power and enhanced proton flux are extremely high. During the wave activity interval, we found that the spacecraft charged more positively without a significant change in the ambient electron density. We discuss whether low‐energy ions energized by EMIC waves can contribute to the spacecraft potential change.

Polarimetric measurements of the lunar surface from lunar orbit soon will be available via Wide-Field Polarimetric Camera (PolCam) onboard the Korea Pathfinder Lunar Orbiter (KPLO), which is planned to be launched in mid 2022. To provide calibration data for the PolCam, we are conducting speckle polarimetric measurements of the nearside of the Moon from the Earth???s ground. It appears that speckle imaging of the Moon for scientific purposes has not been attempted before, and there is need for a procedure to create a ???lucky image??? from a number of observed speckle images. As a first step of obtaining calibration data for the PolCam from the ground, we search for the best sharpness measure for lunar surfaces. We then calculate the minimum number of speckle images and the number of images to be shift-and-added for higher resolution (sharpness) and signal-to-noise ratio.

Van Allen Probe A observed strongly enhanced hydrogen (H+) band electromagnetic ion cyclotron (EMIC) waves lasting >6 hr without helium (He+) band EMIC wave activity outside the plasmasphere on 23 February 2014. During the H‐band EMIC wave interval, multiharmonic toroidal waves were detected by the spacecraft. We estimated the local mass density using the observed toroidal wave frequencies and background electron number density. It was found that the average ion mass is close to 1. This indicates that the protons are the dominant ion species for the H‐band wave interval. From these observations, we suggest that the cold ion composition plays a major role in determining the spectral properties of EMIC waves. We also observed low‐energy He+ ion flux enhancements associated with the H‐band EMIC waves in the direction perpendicular to the background magnetic field. We discuss how the H‐band waves energize the low‐energy He+ ions in the perpendicular direction.

Kplo-MAGnetometer (KMAG) is one of the scientific instruments of Korea Pathfinder Lunar Orbiter (KPLO) set to be launched in 2022. Its objectives are magnetic field investigation and technical demonstration near the surface of the Moon. Specifically, it will investigate the lithospheric magnetism of the Moon and measure the electromagnetic wave properties near the lunar surface. It consists of three fluxgate magnetometers on a 1.2 m long boom, which is relatively shorter than the boom used in other missions. The three magnetometers are included for scientific measurements, redundancy checks, and multi-sensor technical investigation. The magnetometers and an inner Anisotropic Magneto-Resistive sensor perform simultaneous sampling to correct for the magnetic field interference caused by the spacecraft. The fully integrated flight model assembly showed that the magnetometer noise level was less than 30 pT Hz −1/2 at 1 Hz and stability was within ±0.2 nT at the 10 Hz sampling rate. This paper describes the configuration and performance of the KMAG using the multi-sensing method. KPLO, THEMIS-ARTEMIS spacecraft, and Commercial Lunar Payload Service modules will be in their operational phase simultaneously. Therefore, the KMAG will be able to contribute to multi-site in-situ measurements of the lunar magnetic field. We expect that the KMAG will provide an up-to-date lunar observation data set and an opportunity to perform the multi-sensor observation.

The Van Allen Probe A spacecraft observed strong ∼0.5‐Hz helium (He + ) band and weak ∼0.8‐Hz hydrogen (H + ) band EMIC waves on April 17, 2018, at L = ∼4.5–5.2, in the dawn sector, near the magnetic equator, and close to the plasmapause. We examined low‐energy ion fluxes observed by the Helium Oxygen Proton and Electron (HOPE) instrument onboard Van Allen Probe A during the wave interval and found that low‐energy He + flux (<10 eV) enhancements occur nearly simultaneously with He‐band and H‐band EMIC wave power enhancements in a direction mostly perpendicular to the background magnetic field without significant low‐energy H + and O + flux variations. We suggest that cold He + ions (<1 eV) are preferentially and transversely heated up 10 eV through the interaction with EMIC waves inside the plasmasphere. The low‐Earth orbit spacecraft observed localized precipitations of energetic protons in the upper ionosphere at subauroral latitudes near the magnetic field footprint of Van Allen Probe A. Our observations provide a clear evidence that EMIC waves play an important role in the overall dynamics in the inner magnetosphere, contributing to the high‐energy particle loss and low‐energy particle energization.