Korea Aerospace Research Institute Research Articles

New smart twisting active rotor (STAR): pretest predictions

AbstractA Mach-scaled model rotor with an active twist capability is in preparation for a wind tunnel test in the large low-speed facility of the German-Dutch wind tunnel (DNW) with international participation by the German Aerospace Center (DLR), US Army Combat Capabilities Development Command (DEVCOM) Aviation & Missile Center, National Aeronautics and Space Administration, French Aerospace Lab (ONERA), Korea Aerospace Research Institute, Konkuk University, Japan Aerospace Exploration Agency, Glasgow University, and DNW. To get the maximum benefit from the test and the most valuable data within the available test time, the tentative test matrix was covered by predictions of the partners, active twist benefits were evaluated, and support was provided to the test team to focus on the key operational conditions.

Korea Pathfinder Lunar Orbiter (KPLO) Operation: From Design to Initial Results

Korea Pathfinder Lunar Orbiter (KPLO) is South Korea’s first space exploration mission, developed by the Korea Aerospace Research Institute. It aims to develop technologies for lunar exploration, explore lunar science, and test new technologies. KPLO was launched on August 5, 2022, by a Falcon-9 launch vehicle from cape canaveral space force station (CCSFS) in the United States and placed on a ballistic lunar transfer (BLT) trajectory. A total of four trajectory correction maneuvers were performed during the approximately 4.5-month trans-lunar cruise phase to reach the Moon. Starting with the first lunar orbit insertion (LOI) maneuver on December 16, the spacecraft performed a total of three maneuvers before arriving at the lunar mission orbit, at an altitude of 100 kilometers, on December 27, 2022. After entering lunar orbit, the commissioning phase validated the operation of the mission mode, in which the payload is oriented toward the center of the Moon. After completing about one month of commissioning, normal mission operations began, and each payload successfully performed its planned mission. All of the spacecraft operations that KPLO performs from launch to normal operations were designed through the system operations design process. This includes operations that are automatically initiated post-separation from the launch vehicle, as well as those in lunar transfer orbit and lunar mission orbit. Key operational procedures such as the spacecraft’s initial checkout, trajectory correction maneuvers, LOI, and commissioning were developed during the early operation preparation phase. These procedures were executed effectively during both the early and normal operation phases. The successful execution of these operations confirms the robust verification of the system operation.

ShadowCam Instrument and Investigation Overview

ShadowCam is a National Aeronautics and Space Administration Advanced Exploration Systems funded instrument hosted onboard the Korea Aerospace Research Institute (KARI) Korea Pathfinder Lunar Orbiter (KPLO) satellite. By collecting high-resolution images of permanently shadowed regions (PSRs), ShadowCam will provide critical information about the distribution and accessibility of water ice and other volatiles at spatial scales (1.7 m/pixel) required to mitigate risks and maximize the results of future exploration activities. The PSRs never see direct sunlight and are illuminated only by light reflected from nearby topographic highs. Since secondary illumination is very dim, ShadowCam was designed to be over 200 times more sensitive than previous imagers like the Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC). ShadowCam images thus allow for unprecedented views into the shadows, but saturate while imaging sunlit terrain.

KARI and NASA JSC Collaborative Endeavors for Joint Korea Pathfinder Lunar Orbiter Flight Dynamics Operations: Architecture, Challenges, Successes, and Lessons Learned

This paper outlines the collaborative efforts between the Korea Aerospace Research Institute (KARI) and the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) for the Flight Dynamics (FD) operation of the Korea Pathfinder Lunar Orbiter (KPLO). From the outset of the KPLO program, the joint KARI KPLO FD team and NASA JSC Flight Operations Directorate (FOD) have devoted significant time and effort towards ensuring the mission’s success. This paper begins by introducing the aims and scope of the collaborative work, followed by a detailed description of the efforts made between the KPLO FD team and JSC FOD. This includes the top-level concept, interface architecture, test results, established operation procedures/timeline, and the summary of the joint rehearsal conducted. Finally, the paper discusses the challenges and lessons learned from this journey, particularly from the practical FD operational perspectives. Thanks to the joint team’s collaborative efforts, KPLO has successfully entered lunar orbit and is performing its mission exceptionally well. The joint experience has fostered mutual trust between KARI and NASA JSC, serving as a foundation for further cooperation and collaboration. The efforts and outcomes described in this work will provide valuable insights to experts worldwide who are willing to foster similar international collaborations in the future.

Lessons Learned from Korea Pathfinder Lunar Orbiter Flight Dynamics Operations: NASA Deep Space Network Interfaces and Support Levels

On Aug. 4, 2022, at 23:08:48 (UTC), the Korea Pathfinder Lunar Orbiter (KPLO), also known as Danuri, was launched using a SpaceX Falcon 9 launch vehicle. Currently, KPLO is successfully conducting its science mission around the Moon. The National Aeronautics and Space Administration (NASA)’s Deep Space Network (DSN) was utilized for the successful flight operation of KPLO. A great deal of joint effort was made between the Korea Aerospace Research Institute (KARI) and NASA DSN team since the beginning of KPLO ground system design for the success of the mission. The efficient utilization and management of NASA DSN in deep space exploration are critical not only for the spacecraft’s telemetry and command but also for tracking the flight dynamics (FD) operation. In this work, the top-level DSN interface architecture, detailed workflows, DSN support levels, and practical lessons learned from the joint team’s efforts are presented for KPLO’s successful FD operation. Due to the significant joint team’s efforts, KPLO is currently performing its mission smoothly in the lunar mission orbit. Through KPLO cooperative operation experience with DSN, a more reliable and efficient partnership is expected not only for Korea’s own deep space exploration mission but also for the KARI-NASA DSN joint support on other deep space missions in the future.

Kompsat-5 Image Data Provision and Quality Management

The Korea Aerospace Research Institute is conducting continuous quality management to provide reliable Kompsat-5 SAR image products to users. In this paper, the Kompsat-5 satellite operation, data processing, quality management, and data provision were described. The operation and image mode characteristics of the Kompsat-5 satellite from the image point of view were described, and the classification and characteristics of image products provided to users were explained. In addition, image data acquisition, quality index measurement, and its results are described for quality management of SAR images. Finally, it explains how to search for and order Kompsat image product through the ARIRANG system to quickly provide users with image products whose quality has been confirmed through quality management. Kompsat product can be searched and ordered from the ARIRANG Satellite Search and Order System (https://ksatdb.kari.re.kr/arirang/).

GEO-KOMPSAT-2A/2B AMI/GOCI-II/GEMS Data & Products

Two geostationary satellites developed by the Korea Aerospace Research Institute and currently in operation are the GEO-KOMPSAT-2A (GK-2A) and the GEO-KOMPSAT-2B (GK-2B). The main instruments mounted on these satellites are the Advanced Meteorological Imager (AMI), the Geostationary Ocean Color Imager (GOCI-II) and the Geostationary Environment Monitoring Spectrometer (GEMS). This paper briefly introduced the GK-2A and GK-2B programs including measurement principles and elements of the instruments. Moreover, the data formats, operational products, and applications are summarized.

KOMPSAT Optical Image Data Provision and Quality Management

Korea Aerospace Research Institute (KARI) is conducting continuous quality control to provide reliable optical image products to various users. This paper describes KOrea Multi-Purpose SATellites (KOMPSAT-3 and KOMPSAT-3A) characteristics, operation, and image collection mode in order to enhance satellite image application. Also, image product of the satellites and quality management of the image product are described in this paper. The KOMPSAT-3 launched in 2012 and KOMPSAT-3A launched in 2015 collected many imageries around the world and provide them to users through web. Users can search for images through web catalog and order new imaging task. The KOMPSAT images provided under the KARI control is expected to be great help for earth observation and satellite image application enhancement.

Structural Considerations for Generating and Handling LTP Report Segments from an Interoperability Testing

Delay- and disruption-tolerant networking (DTN) technology is increasingly being considered for deep space exploration missions. In particular, DTN is being considered for trunk-line communications between ground and lunar elements of the Artemis program. Licklider transmission protocol (LTP) is a DTN protocol that supports reliable data transmission within a network and, as such, functions as a necessary “convergence-layer” protocol in the architecture. Korea Aerospace Research Institute (KARI) has recently developed an LTP reference implementation and performed an interoperability test with the National Aeronautics and Space Administration (NASA)’s Interplanetary Overlay Network (ION) DTN software. The test revealed that there can be significant variation in issuing report segments and data segment retransmission, which can lead to errors or malfunction during LTP transaction. This paper presents the results of the interoperability test between different implementations of LTP together with some implementation considerations suggested by the results to overcome the issues of the interoperability among different LTP implementations.

KOMPSAT-5 GNSS Radio Occultation Data Operations

The Korea Aerospace Research Institute launched KOMPSAT-5 on August 22, 2013, and has been operating for 10 years. KOMPSAT-5 has SAR (Synthetic Aperture Radar) for earth observation missions, and collects data necessary for earth atmosphere analysis through GNSS RO (Radio Occultation) receivers. RO data can be used for numerical weather forecast model based on temperature, pressure, and humidity by calculating the vertical distribution of atmospheric information. As a part of the Korea-US science and technology cooperation, KARI has been providing RO data of KOMPSAT-5 to the United States NOAA (National Oceanic and Atmospheric Administration) in near-real time since 2018. To this end, KARI receives telemetry data from the satellite about 12 times a day using 3 ground stations from Daejeon, Alaska in the U.S., and Sodankyla in Finland. The pre-processed data is being provided to both the UCAR (University Corporation for Atmospheric Research) in the U.S. and the KASI (Korea Astronomy and Space Science Institute). In this paper, radio occlusion data of KOMPSAT-5 is introduced, and system configuration, operation concepts for providing near-real time data and its application are also presented.

국방우주력 발전을 위한 해상기반 우주영역인식체계 활용방안 연구

In the era of space exploration, all-round efforts at the national level for the development of space power are continuing. Until now, Korea's space situation awareness has been led by three institutions: the Korea Astronomy & Space Science Institute, the Korea Aerospace Research Institute, and the Republic of Korea Air Force. So far there has been no discussion on maritime-based space awareness system. Currently, these institutions have raised the level of awareness of the space situation around the Korean Peninsula to a significant level through their own efforts. However, land-based space situation awareness that covers only over the Korean Peninsula reveals various limitations. First, omnidirectional search is impossible, and second, land-based radar requires high power for long-distance search, so there is an adverse effect on the human body due to high-power radio wave radiation. Third, since it is operated in a fixed position, it is less efficient than the radar operated at sea, so it is vulnerable to a surprise attack from the enemy. Contrary to the limitations of land-based SDA assets, sea-based SDA assets have the following advantages. First, it can be free from the burden of infrastructure construction, and second, it is not necessary to construct additional facilities for the radar system, so it is possible to reduce costs in connection with the facility construction problem. Third, the mobility of the detection coverage is guaranteed as it is not fixed in maritime usage. Such maritime-based SDA power can utilize the assets already possessed by the navy, and there are parts that need to be newly developed for better SDA in the future. Compared to the ground-based SDA system, which is difficult to properly build and requires a lot of budget, utilizing the 10 Aegis and KDDX ships that the Navy will have in the 2030s could be a very attractive option for the reinforcement of space power in Korea, where resources and time are limited.

AI Dataset for Road Detection using KOMPSAT Images

Information on shape and type of road present in an optical image of satellite is useful for digital mapping and monitoring of road changes. Processing and structuring optical image data collected from payloads mounted on KOMPSAT 3 and 3A can accelerate the development of road detection algorithms and the extraction of road information using them. In particular, if it is built with a learning dataset for AI (Artificial Intelligence) prepared to apply deep learning technology, the latest artificial intelligence technology in the field of computer science can be spun off to the field of satellite image-based road detection to attempt a wide range of analysis. Korea Aerospace Research Institute constructed an image dataset for AI learning using satellite optical images with Korean companies, and this paper explains the type and size of datasets along with examples of the use of the dataset. The established data can be used through the website, aihub.or.kr.

초소형위성의 폐기 기동을 위한 항력 증대 장치 개발

In this paper, we described the development of a drag augmentation device for nanosatellite. Recently, space industry has entered the New Space era, and barriers to entry into Low Earth Orbit (LEO) for artificial objects such as small rockets and nanosatellite mega constellations have been significantly lowered. As a result, the number of space debris is increasing exponentially, and it is approaching as a major threat to satellite currently in operation as well as satellites to be launched in near future. To prevent this, international organizations like Inter-Agency Space Debris Coordination Committee (IADC) have been proposed space debris mitigation guidelines. The Korea Aerospace Research Institute (KARI) conducted KARI Rendezvous & Docking demonstration SATellite (KARDSAT) project, the first nanosatellites for rendezvous and docking technology demonstration in Korea, and we also developed drag augmentation device for KARDSAT Target nanosatellite that complied with the international guideline of post-mission disposal.

Sequential convex programming approach for real-time guidance during the powered descent phase of mars landing missions

• The main contribution of this study is the development of a new sequential-convex-programming-based technique that can periodically update the real-time guidance solution in consideration of the minimum-fuel Mars powered descent guidance problem with free final time. • To illustrate the validity of the proposed strategy for on-board real-time applications, an on-board test was conducted using the GR740, which is the processor of choice for the next-generation on-board computers of the European Space Agency (ESA) and Korea Aerospace Research Institute (KARI). • To assess the performance of the strategy, numerical simulations were conducted under various conditions. • Furthermore, the results of Monte Carlo simulations revealed that the proposed strategy is adequately robust against environmental and systematic disturbances. An on-board guidance generation approach for Mars pinpoint landing has been developed based on sequential convex programming. To optimize the flight time in the formulation, a discretized form of the landing problem was constructed under the conditions of linearized states, controls, and time increment between consecutive time steps. To implement this strategy in real time, on-board demonstrations were conducted with the GR740, which is the next-generation on-board processor of choice for the European Space Agency. The total number of time steps was determined based on the results of these demonstrations. The numerically simulated results also indicate that the solution obtained via the proposed strategy is close to the optimized GPOPS-II solution under the condition of no disturbance. Even under disturbances such as navigation errors, initial prediction errors, and perturbation forces, the proposed strategy ensures that the spacecraft reaches its target position with near-optimal fuel consumption.

Practical Algorithms on Lunar Reference Frame Transformations for Korea Pathfinder Lunar Orbiter Flight Operation

This technical paper deals the practical transformation algorithms between several lunar reference frames which will be used for Korea pathfinder lunar orbiter (KPLO) flight operation. Despite of various lunar reference frame definitions already exist, use of a common transformation algorithm while establishing lunar reference frame is very important for all members related to KPLO mission. This is because use of slight different parameters during frame transformation may result significant misleading while reprocessing data based on KPLO flight dynamics. Therefore, details of practical transformation algorithms for the KPLO mission specific lunar reference frames is presented with step by step implementation procedures. Examples of transformation results are also presented to support KPLO flight dynamics data user community which is expected to give practical guidelines while post processing the data as their needs. With this technical paper, common understandings of reference frames that will be used throughout not only the KPLO flight operation but also science data reprocessing can be established. It is expected to eliminate, or at least minimize, unnecessary confusion among all of the KPLO mission members including: Korea Aerospace Research Institute (KARI), National Aeronautics and Space Administration (NASA) as well as other organizations participating in KPLO payload development and operation, or further lunar science community world-wide who are interested in KPLO science data post processing.

The Formation of Korean Satellite Development Program:The Case Study of SaTReC and SaTReC-I

This study examines how the Korean satellite development program was established in Korean society and expanded its boundaries through tracking the history of KAIST Satellite Technology Research Center (SaTReC) from 1989 to 2013. Based on documentary analysis, I argue that the Korean satellite development program was started by an autonomous research group, SaTReC, and evolved into a governmentled program. This process is divided into four periods based on the boundaries of the Korean satellite development program: 1989-1993, 1994-1999, 2000-2005, and 2006-2013. Although the role of SaTReC was reduced in the Korean satellite development program, the Korean satellite development program expanded its boundaries from SaTReC to the Government and Korea Aerospace Research Institute (KARI), to industry, and finally to other countries and the public. New actors of the Korean satellite development program raised according to the expansion of boundaries. This study shows that the Korean satellite program continuously has expanded its boundaries to find its position in society under environmental change and provides insights for the future of the Korean satellite development program in the new era.

Overview of the Flight Dynamics Subsystem for Korea Pathfinder Lunar Orbiter Mission

Korea’s first lunar mission, the Korea Pathfinder Lunar Orbiter (KPLO), aims to launch in mid-2022 via the Space-X Falcon-9 launch vehicle. For the successful flight operation of KPLO, the Korea Aerospace Research Institute (KARI) has designed and developed the Flight Dynamics Subsystem (FDS). FDS is one of the subsystems in the KPLO Deep-Space Ground System (KDGS), which is responsible for the overall flight dynamics-related operation. FDS is currently successfully implemented and meets all of the requirements derived from the critical design phases. The current work addresses the design and implementation results for the KPLO FDS. Starting from overviews on KPLO payloads, bus systems, and mission trajectory characteristics, a review on KDGS is also treated briefly. Details on the design philosophy, unique characteristics, and functionalities of all six different modules nested inside the FDS with its Graphical User Interface (GUI) design are discussed. Moreover, efforts currently devoted to the flight operation preparation of the KPLO are summarized, including many collaborative works between KARI and the National Aeronautics and Space Administration (NASA) teams.

창정 5B호 발사체의 재진입 시점 예측 분석

This paper represents a reentry time prediction analysis of CZ-5B rocket-body in China, subject to analysis of the Inter-Agency Space Debris Coordination Committee Reentry (IADC) reentry test campaign conducted in May 2021. Predicting the reentry of space objects is difficult to accurately predict due to the lack of accurate physical information about target, and uncertainty in atmospheric density. Therefore, IADC conducts annual re-entry campaigns to verify analysis techniques by each agency, and the Korea Aerospace Research Institute has also participated in them since 2015. Ballistic coefficient estimation method proposed to predict target reentry time and the result confirmed the difference of 73 seconds, which confirms the accuracy of the proposed method.

Aerodynamic analysis and static stability analysis of Manned/unmanned distributed propulsion aircrafts using actuator methods

The development of personal aerial vehicles (PAVs) using electric power distributed propulsion methods is rapidly growing. As the aerodynamic performance and flight stability characteristics can be significantly affected by multiple-propeller operation, aerodynamic analysis reflecting the power-on effect is required for design/development. Simulating all propellers using the general computational fluid dynamics is inefficient in terms of computational time and cost. Therefore, this study evaluates the practicality of actuator methods in the aerodynamic analysis of two aircrafts with multiple propellers: a quad tilt propeller (QTP) unmanned aerial vehicle (UAV) and an optionally piloted personal air vehicle (OPPAV) of the Korea Aerospace Research Institute (KARI). The normal and side forces generated by the propellers under various angle of attack and sideslip angle conditions are found to be the most contributing factors to the deterioration in the aircraft longitudinal and directional static stabilities, respectively. The forces and moments generated by the propellers are found to make both longitudinal and directional stabilities of the QTP UAV unstable. However, the OPPAV appears to remain stable state even with the operating propellers. We conclude that actuator methods, being computationally efficient in terms of cost, time, and accuracy, possess great potential for aerodynamic analysis in various related industries.

The spatial data of paddy rice classification over Northeast Asia using COMS geostationary satellite

The Korea Aerospace Research Institute (KARI) estimated paddy rice classification maps over Northeast Asia using the Cheonian geostationary orbiting satellite (COMS: Communication, Ocean and Meteorological Satellite) data. In the case of classification map of rice paddy, it is not only used as input data for estimating rice yield, but also for various fields such as agriculture, weather, climate change, bio energy, and ecology. The spatial resolution of the classified rice map is 500 m, and the classification map was estimated yearly temporal resolution from 2011 to 2017. The spatial coverage of the classification map was the Northeast Asia with the latitude 25 ° N ~ 47 ° N and the longitude 115 ° E ~ 145 ° E as shown in Fig. 1 including Heilongjiang Sheng, Jilin Sheng, and Liaoning Sheng. In this classification map of paddy rice, it was calculated by applying geostationary orbiting satellites based on value-added products from Geostationary Ocean Color Imager (GOCI). In this study, we additionally used MODIS Land Surface Water Indices (LSWI) to support rice classification by considering the physical characteristics of rice cultivation area in the transplanting season. Basically, the radiance value of the top of atmosphere (TOP) observed in GOCI satellite was corrected to the surface reflectance at the top of the canopy through radiative transfer model. After that, NDVI, which can reflect the time series growth characteristics of rice, was estimated first. In addition, the MODIS LSWI index was used to determine the rice cultivation area with the NDVI in Northeast Asia by reflecting the water characteristics of the rice cultivation area during the transplanting period. More details of validation results for this algorithm can be found in previous studies.