Search

Accepted: 2016-04-14, 資料番号: SA1160049000

著者人数: 16名, 資料番号: SA1004954000

Accepted: 2014-06-25, 資料番号: SA1140142000

The SELENE mission, consisting of three separate satellites that use different terrestrial-based tracking systems, presents a unique opportunity to evaluate the contribution of these tracking systems to orbit determination precision. The tracking data consist of four-way Doppler between the main orbiter and one of the two sub-satellites while the former is over the far side, and of same-beam differential VLBI tracking between the two sub-satellites. Laser altimeter data are also used for orbit determination. The contribution to orbit precision of these different data types is investigated through orbit overlap analysis. It is shown that using four-way and VLBI data improves orbit consistency for all satellites involved by reducing peak values in orbit overlap differences that exist when only standard two-way Doppler and range data are used. Including laser altimeter data improves the orbit precision of the SELENE main satellite further, resulting in very smooth total orbit errors at an average level of 18 m. The multi-satellite data have also resulted in improved lunar gravity field models, which are assessed through orbit overlap analysis using Lunar Prospector tracking data. Improvements over a pre-SELENE model are shown to be mostly in the along-track and cross-track directions. Orbit overlap differences are at a level between 13 and 21 m with the SELENE models, depending on whether 1-day data overlaps or 1-day predictions are used.

資料番号: PA1110080000

著者人数: 34名, Accepted: 2010-04-22, 資料番号: SA1002890000

著者人数: 15名, Accepted: 2010-08-03, 資料番号: SA1002891000

アストロダイナミクスシンポジウム (2009年7月30-31日. 宇宙航空研究開発機構宇宙科学研究本部)), Workshop on JAXA Astrodynamics and Flight Mechanics, 2009 (July 30-31, 2009. Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA)), Sagamihara, Kanagawa Japan, Orbit determination results for the Kaguya satellites are presented, with a special focus on the orbit determination performance of new gravity field models containing farside tracking data. The models are compared with pre-Kaguya models in terms of data fit and orbit overlap analysis, showing that the Kaguya models have a similar performance as the Lunar Prospector-based LP100K model, with an improved performance in cross-track direction. Orbit precision from overlaps is 50 m in a root-sum-square sense. Results for the Kaguya extended mission (that started from November 2008) are also discussed. During this phase, tracking data were fewer and for a large part the main satellite was in thruster-mode, making precise orbit determination especially difficult. The used orbit determination strategy is discussed, showing the possibility for regular levels of data fit, although overall orbit quality deteriorates. Altimetry data from the laser altimeter LALT have also been used in the orbit determination process, and it is shown that especially along-track and cross-track directions are improved., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA0064734041

第42回 月・惑星シンポジウム(2009年8月5-7日, 宇宙航空研究開発機構宇宙科学研究本部), The 42nd ISAS Lunar and Planetary Symposium (August 5-7, 2009. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)), Sagamihara, Kanagawa Japan, 形態: カラー図版あり, 形態: CD-ROM1枚, 著者人数: 11人, Physical characteristics: Original contains color illustrations, Note: One CD-ROM, 資料番号: AA0064739014

第42回 月・惑星シンポジウム(2009年8月5-7日, 宇宙航空研究開発機構宇宙科学研究本部), The 42nd ISAS Lunar and Planetary Symposium (August 5-7, 2009. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)), Sagamihara, Kanagawa Japan, Gravity and topography data obtained by KAGUYA (SELENE) are used to characterize the structure of South Pole-Aitken basin of the Moon. Previously proposed elliptic basin shape was confirmed by the revised topography and Moho depth (and crustal thickness) distribution by KAGUYA. Moho depth just outside the SPA basin is about 50-70 km, whereas Moho at the central region of SPA is as shallow as 30 km., 形態: カラー図版あり, 形態: CD-ROM1枚, Physical characteristics: Original contains color illustrations, Note: One CD-ROM, 資料番号: AA0064739015

第42回 月・惑星シンポジウム(2009年8月5-7日, 宇宙航空研究開発機構宇宙科学研究本部), The 42nd ISAS Lunar and Planetary Symposium (August 5-7, 2009. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)), Sagamihara, Kanagawa Japan, A new spherical harmonic solution of the lunar gravity field to degree and order 100, called SGM100h, has been developed using historical tracking data and 14.2 months of SELENE tracking data. The latter includes all usable 4-way Doppler data collected which allowed direct observations of the farside gravity field for the first time. The new model successfully reveals farside features in free-air gravity anomalies which are characterized by ring-shaped structures for large impact basins and negative spots for large craters. SGM100h produces a correlation with SELENE-derived topography as high as about 0.9, through degree 70. Comparison between SGM100h and LP100K (one of the pre-SELENE models) shows that the large gravity errors which existed in LP100K are drastically reduced and the asymmetric error distribution between the nearside and the farside almost disappears. The gravity anomaly errors predicted from the error covariance, through degree and order 100, are 26 mGal and 35 mGal for the nearside and the farside, respectively. Owing to the 4-way Doppler measurements the gravity coefficients below degree and order 70 are now determined by real observations with contribution factors larger than 80 percent., 形態: カラー図版あり, 形態: CD-ROM1枚, Physical characteristics: Original contains color illustrations, Note: One CD-ROM, 資料番号: AA0064739018

第42回 月・惑星シンポジウム(2009年8月5-7日, 宇宙航空研究開発機構宇宙科学研究本部), The 42nd ISAS Lunar and Planetary Symposium (August 5-7, 2009. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)), Sagamihara, Kanagawa Japan, At present, a multi-satellite mission to Mars called MELOS (i.e. Mars Exploration with Lander-Orbiter Synergy) is under study. An instrument called iVLBI (i.e. Inverse Very Long Baseline Interferometry) has been proposed as one of the instruments in this project. This instrument will allow us to carry out precise measurements on Mars' rotation (e.g. precession, nutation, polar motion, and length-of-day variation) through a radio link between the satellites and station(s) on the Earth. Researchers and technicians mainly in National Astronomical Observatory of Japan (NAOJ) and Institute of Space and Astronautical Science (ISAS) are discussing this instrument, especially, its observation system and scientific effort. The aim of this presentation is to introduce the latter. We will show how we expand our knowledge of the surface environment, the internal structure, and their evolution on Mars by observing its rotational variation through iVLBI on MELOS as mentioned above., 形態: CD-ROM1枚, Note: One CD-ROM, 資料番号: AA0064739005

Symposium on Flight Mechanics and Astrodynamics 2008 (July 28-29, 2008. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)), Sagamihara, Kanagawa Japan, Results are presented for the orbit determination of the three satellites of Kaguya.Doppler data fit for the main satellite is typically at a level of 0.5 mm/s, and that for the subsatellites is typically less than 0.5 mm/s. Orbit accuracy for the main satellite from altimeter crossovers gives a total orbit accuracy of 50 m. For the subsatellites Rstar and Vstar, accuracy is restricted due to sparse data coverage, but the inclusion of high-precision differential VLBI data can improve the consistency of the orbits greatly, to a level of ten meter in a three-dimensional sense., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA0064733048

著者人数：18名, 資料番号: SA1000852000

第9回宇宙科学シンポジウム(2009年1月6日-7日, 宇宙航空研究開発機構宇宙科学研究本部), 形態: カラー図版あり, 著者人数: 17名, 資料番号: AA0064293113

資料番号: SA1000851000

著者人数：30名, 資料番号: SA1000850000

The 41st ISAS Lunar and Planetary Symposium (August 6-8, 2008. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)), This paper describes processing strategies for, and results of modeling the global lunar gravity field from tracking data of Kaguya and previous lunar missions., Physical characteristics: Original contains color illustrations, Number of authors: 14, 資料番号: AA0064291017

International audience; The Gravity Recovery and Interior Laboratory (GRAIL) mission has sampled lunar gravity with unprecedented accuracy and resolution. The lunar GM, the product of the gravitational constant G and the mass M, is very well determined. However, uncertainties in the mass and mean density, 3345.56 ± 0.40 kg/m 3 , are limited by the accuracy of G. Values of the spherical harmonic degree-2 gravity coefficients J 2 and C 22 , as well as the Love number k 2 describing lunar degree-2 elastic response to tidal forces, come from two independent analyses of the 3 month GRAIL Primary Mission data at the Jet Propulsion Laboratory and the Goddard Space Flight Center. The two k 2 determinations, with uncertainties of~1%, differ by 1%; the average value is 0.02416 ± 0.00022 at a 1 month period with reference radius R = 1738 km. Lunar laser ranging (LLR) data analysis determines (C À A)/B and (B À A)/C, where A < B < C are the principal moments of inertia; the flattening of the fluid outer core; the dissipation at its solid boundaries; and the monthly tidal dissipation Q = 37.5 ± 4. The moment of inertia computation combines the GRAIL-determined J 2 and C 22 with LLR-derived (C À A)/B and (B À A)/C. The normalized mean moment of inertia of the solid Moon is I s /MR 2 = 0.392728 ± 0.000012. Matching the density, moment, and Love number, calculated models have a fluid outer core with radius of 200-380 km, a solid inner core with radius of 0-280 km and mass fraction of 0-1%, and a deep mantle zone of low seismic shear velocity. The mass fraction of the combined inner and outer core is ≤1.5%.

第13回宇宙科学シンポジウム (2013年1月8日-9日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県, 13th Space Science Symposium (January 8-9, 2013. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)Sagamihara Campus), Sagamihara, Kanagawa Japan, 資料番号: SA6000063250, レポート番号: P4-046

第45回月・惑星シンポジウム (2012年8月1日-3日. 宇宙航空研究開発機構宇宙科学研究所), 相模原市, 神奈川県, 45th ISAS Lunar and Planetary Symposium (August 1-3, 2012. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan, 形態: カラー図版あり, 形態: CD-ROM1枚, 資料番号: SA6000014018

44th ISAS Lunar and Planetary Symposium (August 1-3, 2011. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan, 形態: カラー図版あり, 形態: CD-ROM1枚, 著者人数: 14人, Physical characteristics: Original contains color illustrations, Note: One CD-ROM, Number of authors: 14, 資料番号: AA0065390007

44th ISAS Lunar and Planetary Symposium (August 1-3, 2011. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan, The South Pole-Aitken basin (SPA) is the largest (2500km in diameter), deepest and presumably oldest impact basin in the solar system. SPA was characterized by an ellipse with axes 2400 by 2050 km, but more precise topography and gravity data are necessary to discuss the structure of SPA on the lunar farside. We use topography and gravity data obtained by KAGUYA(SELENE). The direction of an ellipse denoting the depression is similar to the previous result. The region with the thinnest crust is offset southward from the center of SPA. We analyzed interior structure of small basins in and around SPA. We interpret that a positive gravity anomaly corresponds to a Moho uplift. A distinct Moho uplift beneath Schrodinger corresponds to the presence of olivine at the central peak rings., 形態: カラー図版あり, 形態: CD-ROM1枚, Physical characteristics: Original contains color illustrations, Note: One CD-ROM, 資料番号: AA0065390010

著者人数：38名, Accepted: 2009-11-30, 資料番号: SA1001003000