• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.7
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• pp.588-595
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• 2013

Airborne SAR system is the imaging Radar system that is loaded on a manned or unmanned aircraft, which is in charge of high quality image acquisition and moving target detection. This paper describes the operational requirements for the Airborne SAR system and suggests the operational concept to satisfy the requirements. To be specific, it describes the interface with airborne system, state definition and transition, operation mode based on mission definition file, fault management, and data storing and transmission concept. Finally, it gives the ground test results to verify the SAR system operational concept.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.1
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• pp.30-44
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• 2022

The advent of deep learning-based algorithms has facilitated researches on target detection from synthetic aperture radar(SAR) imagery. While most of them concentrate on detection tasks for ships with open SAR ship datasets and for aircraft from SAR scenes of airports, there is relatively scarce researches on the detection of SAR ground vehicle targets where several adverse factors such as high false alarm rates, low signal-to-clutter ratios, and multiple targets in close proximity are predicted to degrade the performances. In this paper, a dataset of ground vehicle targets acquired from TerraSAR-X(TSX) satellite SAR images is presented. Then, both detection and instance segmentation are simultaneously carried out on this dataset based on the deep learning-based Mask R-CNN. Finally, this paper shows the future research directions to further improve the performances of detecting the SAR ground vehicle targets.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.1
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• pp.54-62
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• 2017

For the Earth observation satellite for ISR mission, a satellite constellation can be utilized to observe a specific area periodically and ultimately increase the effectiveness of the mission. The Walker-Delta method was applied to design constellation orbits with four satellites, which could detect abnormal activities in AoI(Area of Interest). To evaluate the effectiveness of the mission, a revisiting time was selected as a key requirement. This paper presents the mission analysis process for four SAR satellites constellation as well as the result of constellation configuration design to meet the requirements. Figure of Merits analysis was performed based on algorithm developed. Finally, it was confirmed that the constellation orbit with four different orbital planes is likely to be appropriate for ISR mission.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.6
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• pp.401-412
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• 2022

In this study, we investigated the design methods of satellite constellations to conduct near-real-time surveillance reconnaissance of the Korean Peninsula. Also, we designed satellite constellations utilizing the Walker-Delta method and repeat-ground-track method, and taking into account the target area and the feasible number of satellites. The constrains of the Electro-Optical and Synthetic Aperture Radar equipment were also considered in performance analysis. As a result, the designed constellation has mean revisit time of less than 30 min which enables near-real-time surveillance reconnaissance of the Korean Peninsula. This research provides the strategy to design the satellite constellation for reconnaissance. Furthermore, it contributes to suggesting an operating strategy for micro-satellites constellation and guidelines for establishing space force.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.4
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• pp.285-293
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• 2020

In this paper, to improve Synthetic Aperture Radar (SAR) image quality, the effect of time synchronization error in the EGI/IMU (Embedded GPS/INS, Inertial Measurement Unit) integrated system is analyzed and state augmentation is applied to compensate it. EGI/IMU integrated system is widely used as a SAR motion measurement algorithm, which consists of EGI mounted to obtain the trajectory and IMU mounted on the SAR antenna. In an EGI/IMU integrated system, a time synchronization error occurs when the clocks of the sensors are not synchronized. Analysis of the effect of time synchronization error on navigation solutions and SAR images confirmed that the time synchronization error deteriorates SAR image quality. The state augmentation is applied to compensate for this and as a result, the SAR image quality does not decrease. In addition, by analyzing the performance and the observability of the time synchronization error according to the maneuver, it was confirmed that the time-variant maneuver such as rotational motion is necessary to estimate the time synchronization error adequately. In order to reduce the influence of the time synchronization error on the SAR image, the time synchronization error must be compensated by performing maneuver changing over time such as a rotation before SAR operation.