• Journal of Astronomy and Space Sciences
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• v.34 no.4
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• pp.271-280
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• 2017

This study presents the application of satellite laser ranging (SLR) to orbit determination (OD) of high-Earth-orbit (HEO) satellites. Two HEO satellites are considered: the Quasi-Zenith Satellite-1 (QZS-1), a Japanese elliptical-inclinedgeosynchronous-orbit (EIGSO) satellite, and the Compass-G1, a Chinese geostationary-orbit (GEO) satellite. One week of normal point (NP) data were collected for each satellite to perform the OD based on the batch least-square process. Five SLR tracking stations successfully obtained 374 NPs for QZS-1 in eight days, whereas only two ground tracking stations could track Compass-G1, yielding 68 NPs in ten days. Two types of station bias estimation and a station data weighting strategy were utilized for the OD of QZS-1. The post-fit root-mean-square (RMS) residuals of the two week-long arcs were 11.98 cm and 10.77 cm when estimating the biases once in an arc (MBIAS). These residuals were decreased significantly to 2.40 cm and 3.60 cm by estimating the biases every pass (PBIAS). Then, the resultant OD precision was evaluated by the orbit overlap method, yielding three-dimensional errors of 55.013 m with MBIAS and 1.962 m with PBIAS for the overlap period of six days. For the OD of Compass-G1, no station weighting strategy was applied, and only MBIAS was utilized due to the lack of NPs. The post-fit RMS residuals of OD were 8.81 cm and 12.00 cm with 49 NPs and 47 NPs, respectively, and the corresponding threedimensional orbit overlap error for four days was 160.564 m. These results indicate that the amount of SLR tracking data is critical for obtaining precise OD of HEO satellites using SLR because additional parameters, such as station bias, are available for estimation with sufficient tracking data. Furthermore, the stand-alone SLR-based orbit solution is consistently attainable for HEO satellites if a target satellite is continuously trackable for a specific period.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.31.3-31.3
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• 2008

Satellite laser ranging (SLR) system which measures the round trip time of laser to satellites is one of the important techniques in space geodesy. SLR system gives a powerful tool to determine the precise orbit of satellites, the center of mass of the Earth, and etc because it provides instantaneous range measurements of millimeter level precision. China Transportable Ranging Observation System (TROS) was built in 1999 and other four SLR stations were founded in China. TROS has been upgraded to the new electronic system capable of KHz ranging since last year, and succeeded in KHz SLR technology. TROS has been operated in KASI headquarter for research of space geodesy since August 2008, which will be operated for 12 months by August 2009. Now ISCEA and KASI keep strong relationship in SLR field.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2010.04a
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• pp.43-44
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• 2010

We present the analysis of space geodetic technique observation, Satellite Laser Ranging (SLR), to LAGEOS1 and LAGEOS2 for the definition of the Terrestrial Reference Frame (TRF). The data were analyzed in 7day arcs during about 9 years (2000/01/10 ~ 2008/12/29) using NASA Goddard's GEODYN/SOLVE II software. The comparison of the coordinates between ITRF2005 and TRF solutions determined in this work shows that there is no significant bias.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.4
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• pp.370-377
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• 2011

Korea Astronomy and Space Science Institute(KASI) has been developing one mobile SLR system since 2008 named as ARGO-M. Control logic in real-time laser ranging and data processing for normal point from the ranging data are key elements in the operation system of ARGO-M. KASI operation system team performed software logic analysis and related operations for SLR observation with help of Graz SLR station in Austria. This paper describes the algorithm required for SLR operation based on the method in Graz station. We figured out the essential logic for SLR operation and the remedy for the observation quality enhancement through this study.

• Journal of Astronomy and Space Sciences
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• v.27 no.2
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• pp.135-144
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• 2010

In this paper, we present the result of preliminary design of tracking mount for ARGO-M which is a movable satellite laser ranging (SLR) system developed by Korea Astronomy and Space Science Institute (KASI). The tracking mount consists of a couple of core parts such as driving motors, encoders and bearings, and the requirements of each parts are determined on the basis of the technical consideration. 2D and 3D models for tracking mount were preliminarily designed using the selected core parts. In order to evaluate the validity of the preliminarily design, the simulator to test the elevation axis was designed and manufactured. The test to check the tracking performance and system accuracy of the simulator was performed, and it was confirmed that the preliminary design meets the operating specifications. Additionally, it was found that the repetitive errors and hysteresis errors need to be improved by the additional control algorithm.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.367-368
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• 2009

• Proceedings of the Optical Society of Korea Conference
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• 2005.07a
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• pp.320-321
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• 2005

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.34.2-34.2
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• 2008

The batch least square filter is widely used for ground estimations. However, in orbit determination (OD) under inaccurate initial conditions and few measurement data the performance by the batch least square filter can lead an unstable results. To complement weak part of the batch filter, the batch unscented transformation without any linearization process is developed by ACL (Astrodynamics and Control Laboratory) in YONSEI University. In this paper, the batch unscented transformation is introduced and applied to satellite orbit determination using Satellite Laser Ranging (SLR) data. Only range of the satellite measured from ground tracking stations is used for measurement data. The results of simulation test are compared with those of the weighted batch least square filter for various initial states errors (position and velocity). Simulation results show that the batch unscented transformation is comparable or slightly superior to batch least square filter in the orbit determination.

• Journal of Astronomy and Space Sciences
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• v.30 no.4
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• pp.269-277
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• 2013

In this study, we present results of precise orbital geodetic parameter estimation using satellite laser ranging (SLR) observations for the International Laser Ranging Service (ILRS) associate analysis center (AAC). Using normal point observations of LAGEOS-1, LAGEOS-2, ETALON-1, and ETALON-2 in SLR consolidated laser ranging data format, the NASA/GSFC GEODYN II and SOLVE software programs were utilized for precise orbit determination (POD) and finding solutions of a terrestrial reference frame (TRF) and Earth orientation parameters (EOPs). For POD, a weekly-based orbit determination strategy was employed to process SLR observations taken from 20 weeks in 2013. For solutions of TRF and EOPs, loosely constrained scheme was used to integrate POD results of four geodetic SLR satellites. The coordinates of 11 ILRS core sites were determined and daily polar motion and polar motion rates were estimated. The root mean square (RMS) value of post-fit residuals was used for orbit quality assessment, and both the stability of TRF and the precision of EOPs by external comparison were analyzed for verification of our solutions. Results of post-fit residuals show that the RMS of the orbits of LAGEOS-1 and LAGEOS-2 are 1.20 and 1.12 cm, and those of ETALON-1 and ETALON-2 are 1.02 and 1.11 cm, respectively. The stability analysis of TRF shows that the mean value of 3D stability of the coordinates of 11 ILRS core sites is 7.0 mm. An external comparison, with respect to International Earth rotation and Reference systems Service (IERS) 08 C04 results, shows that standard deviations of polar motion $X_P$ and $Y_P$ are 0.754 milliarcseconds (mas) and 0.576 mas, respectively. Our results of precise orbital and geodetic parameter estimation are reasonable and help advance research at ILRS AAC.

• Journal of Astronomy and Space Sciences
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• v.36 no.2
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• pp.97-103
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• 2019

An automated signal-acquisition method for the NASA's space geodesy satellite laser ranging (SGSLR) system is described as a selection of two system parameters with specified probabilities. These parameters are the correlation parameter: the minimum received pulse number for a signal-acquisition and the frame time: the minimum time for the correlation parameter. The probabilities specified are the signal-detection and false-acquisition probabilities to distinguish signals from background noise. The steps of parameter selection are finding the minimum set of values by fitting a curve and performing a graph-domain approximation. However, this selection method is inefficient, not only because of repetition of the entire process if any performance values change, such as the signal and noise count rate, but also because this method is dependent upon system specifications and environmental conditions. Moreover, computation is complicated and graph-domain approximation can introduce inaccuracy. In this study, a new method is proposed to select the parameters via a conditional equation derived from characteristics of the signal-detection and false-acquisition probabilities. The results show that this method yields better efficiency and robustness against changing performance values with simplicity and accuracy and can be easily applied to other satellite laser ranging (SLR) systems.