Orbit Determination Using SLR Data for STSAT-2C: Short-arc Analysis

김영록,박은서,Daniel Kucharski1,임형철 한국우주과학회 2015 Journal of Astronomy and Space Sciences Vol.32 No.3

In this study, we present the results of orbit determination (OD) using satellite laser ranging (SLR) data for the Science and Technology Satellite (STSAT)-2C by a short-arc analysis. For SLR data processing, the NASA/GSFC GEODYN II software with one year (2013/04 – 2014/04) of normal point observations is used. As there is only an extremely small quantity of SLR observations of STSAT-2C and they are sparsely distribution, the selection of the arc length and the estimation intervals for the atmospheric drag coefficients and the empirical acceleration parameters was made on an arc-to-arc basis. For orbit quality assessment, the post-fit residuals of each short-arc and orbit overlaps of arcs are investigated. The OD results show that the weighted root mean square post-fit residuals of short-arcs are less than 1 cm, and the average 1-day orbit overlaps are superior to 50/600/900 m for the radial/cross-track/along-track components. These results demonstrate that OD for STSAT-2C was successfully achieved with cm-level range precision. However its orbit quality did not reach the same level due to the availability of few and sparse measurement conditions. From a mission analysis viewpoint, obtaining the results of OD for STSAT-2C is significant for generating enhanced orbit predictions for more frequent tracking.

Confirmation of gravitationally induced attitude drift of spinning satellite Ajisai with Graz high repetition rate SLR data

Kucharski, D.,Kirchner, G.,Otsubo, T.,Lim, H.C.,Bennett, J.,Koidl, F.,Kim, Y.R.,Hwang, J.Y. The Committee by Pergamon Press] ; Elsevier Scienc 2016 ADVANCES IN SPACE RESEARCH Vol.57 No.4

<P>The high repetition rate Satellite Laser Ranging system Graz delivers the millimeter precision range measurements to the corner cube reflector panels of Ajisai. The analysis of 4599 passes measured from October 2003 until November 2014 reveals the secular precession and nutation of Ajisai spin axis due to the gravitational forces as predicted by Kubo (1987) with the periods of 35.6 years and 116.5 days respectively. The observed precession cone is oriented at RA = 88.9 degrees, Dec = -88.85 degrees (32000) and has a radius of 1.08 degrees. The radius of the nutation cone increases from 1.32 degrees to 1.57 degrees over the 11 years of the measurements. We also detect a draconitic wobbling of Ajisai orientation due to the 'motion' of the Sun about the satellite's orbit. The observed spin period of Ajisai increases exponentially over the investigated time span according to the trend function: T= 1.4 92277.exp(0.0148388. Y) [s], where Y is in years since launch (1986.6133), RMS = 0.412 ms. The physical simulation model fitted to the observed spin parameters proves a very low interaction between Ajisai and the Earth's magnetic field, what assures that the satellite's angular momentum vector will remain in the vicinity of the south celestial pole for the coming decades. The developed empirical model of the spin axis orientation can improve the accuracy of the range determination between the ground SLR systems and the satellite's center-of-mass (Kucharski et al., 2015) and enable the accurate attitude prediction of Ajisai for the laser time-transfer experiments (Kunimori et al., 1992). (C) 2015 COSPAR. Published by Elsevier Ltd. All rights reserved.</P>

Tropical Pacific response to 20th century Atlantic warming

Kucharski, F.,Kang, I.-S.,Farneti, R.,Feudale, L. AGU AMERICAN GEOPHYSICAL UNION 2011 Geophysical research letters Vol.38 No.3

Atlantic forcing of Pacific decadal variability

Kucharski, F.,Ikram, F.,Molteni, F.,Farneti, R.,Kang, I. S.,No, H. H.,King, M. P.,Giuliani, G.,Mogensen, K. Springer Science + Business Media 2016 Climate dynamics Vol.46 No.7

<P>This paper investigates the Atlantic Ocean influence on equatorial Pacific decadal variability. Using an ensemble of simulations, where the ICTPAGCM ('SPEEDY') is coupled to the NEMO/OPA ocean model in the Indo-Pacific region and forced by observed sea surface temperatures in the Atlantic region, it is shown that the Atlantic Multidecadal Oscillation (AMO) has had a substantial influence on the equatorial Pacific decadal variability. According to AMO phases we have identified three periods with strong Atlantic forcing of equatorial Pacific changes, namely (1) 1931-1950 minus 1910-1929, (2) 1970-1989 minus 1931-1950 and (3) 1994-2013 minus 1970-1989. Both observations and the model show easterly surface wind anomalies in the central Pacific, cooling in the central-eastern Pacific and warming in the western Pacific/Indian Ocean region in events (1) and (3) and the opposite signals in event (2). The physical mechanism for these responses is related to a modification of the Walker circulation because a positive (negative) AMO leads to an overall warmer (cooler) tropical Atlantic. The warmer (cooler) tropical Atlantic modifies the Walker circulation, leading to rising (sinking) and upper-level divergence (convergence) motion in the Atlantic region and sinking (rising) motion and upper-level convergence (divergence) in the central Pacific region.</P>

A method to calculate zero-signature satellite laser ranging normal points for millimeter geodesy - a case study with Ajisai

Kucharski, Daniel,Kirchner, Georg,Otsubo, Toshimichi,Koidl, Franz TERRA SCIENTIFIC PUBLISHING COMPANY 2015 EARTH PLANETS AND SPACE Vol.67 No.1

Attitude and Spin Period of Space Debris Envisat Measured by Satellite Laser Ranging

Kucharski, Daniel,Kirchner, Georg,Koidl, Franz,Cunbo Fan,Carman, Randall,Moore, Christopher,Dmytrotsa, Andriy,Ploner, Martin,Bianco, Giuseppe,Medvedskij, Mikhailo,Makeyev, Andriy,Appleby, Graham,Suzuk IEEE 2014 IEEE transactions on geoscience and remote sensing Vol.52 No.12

<P>The Environmental Satellite (Envisat) mission was finished on April 8, 2012, and since that time, the attitude of the satellite has undergone significant changes. During the International Laser Ranging Service campaign, the Satellite Laser Ranging (SLR) stations have performed the range measurements to the satellite that allowed determination of the attitude and the spin period of Envisat during seven months of 2013. The spin axis of the satellite is stable within the radial coordinate system (RCS; fixed with the orbit) and is pointing in the direction opposite to the normal vector of the orbital plane in such a way that the spin axis makes an angle of 61.86° with the nadir vector and 90.69° with the along-track vector. The offset between the symmetry axis of the retroreflector panel and the spin axis of the satellite is 2.52 m and causes the meter-scale oscillations of the range measurements between the ground SLR system and the satellite during a pass. Envisat rotates in the counterclockwise (CCW) direction, with an inertial period of 134.74 s (September 25, 2013), and the spin period increases by 36.7 ms/day.</P>

Spin Axis Precession of LARES Measured by Satellite Laser Ranging

Kucharski, Daniel,Hyung-Chul Lim,Kirchner, Georg,Otsubo, Toshimichi,Bianco, Giuseppe,Joo-Yeon Hwang IEEE 2014 IEEE geoscience and remote sensing letters Vol.11 No.3

<P>Satellite laser ranging (SLR) is an efficient technique to measure spin parameters of the fully passive satellite LARES. Analysis of the laser range measurements gives information about the spin rate of the spacecraft and the orientation of its spin axis. A frequency analysis applied to the SLR data indicates an exponential increase of the satellite's spin period: T = 11.7612 ·exp(0.00293327 ·D) , RMS = 0.115 s, where D is in days since launch. The initial spin period of LARES is calculated from the spin observations during the first 30 days after launch and is equal to T<SUB>0</SUB> = 11.7131, RMS = 0.073 s. The spin axis of the satellite is precessing around the initial coordinates of right ascension RA<SUB>initial</SUB> = 186.5<SUP>°</SUP>, RMS<SUB>RA</SUB> = 3.1<SUP>°</SUP>, and Declination Decinitial = - 73.0<SUP>°</SUP>, RMS<SUB>Dec</SUB> = 0.7<SUP>°</SUP> (J2000 inertial reference frame), with a period of 211.7 days. The precession of the spin axis may be responsible for the observed oscillation of the slowing down rate: the spin half-life period (the time after which the spin period has doubled) varies between 209 and 267 days. The measured spin parameters of LARES are compared-and show good agreement-with the theoretical predictions given by the satellite spin model. Information about the spin parameters of LARES is necessary for the accurate modeling of the forces and torques that are affecting the orbital motion of the satellite.</P>

Orbit Determination Using SLR Data for STSAT-2C: Short-arc Analysis

Young-Rok Kim,Eunseo Park,Daniel Kucharski,Hyung-Chul Lim 한국우주과학회 2015 Journal of Astronomy and Space Sciences Vol.32 No.3

In this study, we present the results of orbit determination (OD) using satellite laser ranging (SLR) data for the Science and Technology Satellite (STSAT)-2C by a short-arc analysis. For SLR data processing, the NASA/GSFC GEODYN II software with one year (2013/04 – 2014/04) of normal point observations is used. As there is only an extremely small quantity of SLR observations of STSAT-2C and they are sparsely distribution, the selection of the arc length and the estimation intervals for the atmospheric drag coefficients and the empirical acceleration parameters was made on an arc-to-arc basis. For orbit quality assessment, the post-fit residuals of each short-arc and orbit overlaps of arcs are investigated. The OD results show that the weighted root mean square post-fit residuals of short-arcs are less than 1 cm, and the average 1-day orbit overlaps are superior to 50/600/900 m for the radial/cross-track/along-track components. These results demonstrate that OD for STSAT-2C was successfully achieved with cm-level range precision. However its orbit quality did not reach the same level due to the availability of few and sparse measurement conditions. From a mission analysis viewpoint, obtaining the results of OD for STSAT-2C is significant for generating enhanced orbit predictions for more frequent tracking.

Vacuum Carburizing System for Powdered Metal Parts & Components

Kowakewski Janusz,Kucharski Karol 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1

Powdered metal parts and components may be carburized successfully in a vacuum furnace by combining carburizing technology VacCarb™ with a hi-tech control system. This approach is different from traditional carburizing methods, because vacuum carburizing is a non-equilibrium process. It is not possible to set the carbon potential as in a traditional carburizing atmosphere and control its composition in order to obtain a desired carburized case. This paper presents test results that demonstrate that vacuum carburizing system VacCarb™ carburized P.M. materials faster than traditional steel with acceptable results. In the experiments conducted, PM samples with the lowest density and open porosity showed a dramatic increase in the surface carbon content up to 2.5%C and a 3 times deeper case. Currently the boost-diffusion technique is applied to control the surface carbon content and distribution in the case. In the first boost step, the flow of the carburizing gas has to be sufficient to saturate the austenite, while avoiding soot deposition and formation of massive carbides. To accomplish this goal, the proper gas flow rate has to be calculated. In the case of P.M. parts, more carbon can be absorbed by the part’s surface because of the additional internal surface area created by pores present in the carburized case. This amount will depend on the density of the part, the densification grade of the surface layer and the stage of the surface - “as machined” or “as sintered”. It is believed that enhanced gas diffusion after initial evacuation of the P.M. parts leads to faster carburization from within the pores, especially when pores are open - surface “as sintered” and interconnected - low density. A serious problem with vacuum carburizing is delivery of the carbon in a uniform manner to the work pieces. This led to the development of the different methods of carburizing gas circulation such as the pulse/pump method or the pulse/pause technique applied in SECO/WARWICK’s VacCarb™ Technology. In both cases, each pressure change may deliver fresh carburizing atmosphere into the pores and leads to faster carburization from within the pores. Since today’s control of vacuum carburizing is based largely on empirical results, presented experiments may lead to better understanding and improved control of the process.

Interannual rainfall variability and ECMWF‐Sys4‐based predictability over the Arabian Peninsula winter monsoon region

Abid, Muhammad Adnan,Kucharski, Fred,Almazroui, Mansour,Kang, In‐,Sik John WileySons, Ltd 2016 Quarterly journal of the Royal Meteorological Soci Vol.142 No.694

<P>Interannual winter rainfall variability and its predictability are analysed over the Arabian Peninsula region by using observed and hindcast datasets from the state-of-the-art European Centre for Medium-Range Weather Forecasts (ECMWF) seasonal prediction System 4 for the period 1981-2010. An Arabian winter monsoon index (AWMI) is defined to highlight the Arabian Peninsula as the most representative region for the Northern Hemispheric winter dominating the summer rainfall. The observations show that the rainfall variability is relatively large over the northeast of the Arabian Peninsula. The correlation coefficient between the Nino3.4 index and rainfall in this region is 0.33, statistically significant at the 90% level, suggesting potentially some modest predictability, and indicating that El Nino increases and La Nina decreases the rainfall. Regression analysis shows that upper-level cyclonic circulation anomalies that are forced by El Nino Southern Oscillation (ENSO) are responsible for the winter rainfall anomalies over the Arabian region. The stronger (weaker) mean transient-eddy activity related to the upper-level trough induced by the warm (cold) sea-surface temperatures during El Nino (La Nina) tends to increase (decrease) the rainfall in the region. The model hindcast dataset reproduces the ENSO-rainfall connection. The seasonal mean predictability of the northeast Arabian rainfall index is 0.35, statistically significant at the 95% level. It is shown that the noise variance is larger than the signal over the Arabian Peninsula region, which tends to limit the prediction skill. The potential predictability is generally increased in ENSO years and is, in particular, larger during La Nina compared to El Nino years in the region. Furthermore, central Pacific ENSO events and ENSO events with weak signals in the Indian Ocean tend to increase predictability over the Arabian region.</P>