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排序方式: 共有384条查询结果,搜索用时 15 毫秒
311.
Francisco Azpilicueta Claudio Brunini 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The high-precision demands imposed by the ocean altimetry community of the late 1980 resulted in the TOPEX/Poseidon mission. This mission was the first to carry as its main instrument a dual-frequency sea-altimeter on board a satellite. This instrument together with other state-of-the-art technologies involved in the mission, led to sea-height determinations with precision better than 2 cm. As a by-product, the TOPEX/Poseidon mission provided vertical TEC determinations that since they became available, have demonstrated to be a powerful tool for ionospheric studies. 相似文献
312.
初始对准时, 通常是基于地球参考椭球, 用正常重力公式计算重力矢量,
而实际情况下地球内部质量分布不均匀,实际重力包含正常重力和重力扰动。重力扰动
包括参考椭球面切线方向的分量(垂线偏差)和法线方向分量(重力异常)。研究重力
扰动下的初始对准,导出了重力扰动下水平姿态误差角与垂线偏差大小等值。重力扰动
下初始对准的方法是利用EGM2008 地球重力场模型计算出对准点的重力扰动并从加速度
计中剔除掉。仿真分析表明,补偿重力扰动后可提高初始对准精度。 相似文献
313.
314.
Baichang Deng Jiang Huang Weifeng Liu Jie Xu Lingfeng Huang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
This study presents a statistical analysis of GPS L-band scintillation with data observed from July 2008 to March 2012 at the northern crest of equatorial anomaly stations in Guangzhou and Shenzhen of South China. The variations of the scintillation with local time, season, solar activity and duration of scintillation patches were investigated. The relationship between the scintillation and TEC depletion was also reported. Our results revealed that GPS scintillation occurred from 19:30 LT (pre-midnight) to 03:00 LT (post-midnight). During quiet solar activity years, the scintillation was only observed in pre-midnight hours of equinox months and patches durations were mostly less than 60 min. During high solar activity years, more scintillation occurred in the pre-midnight hours of equinox and winter months; and GPS scintillation started to occur in the post-midnight hours of summer and winter. The duration of scintillation patches extended to 180 min in high solar activity years. Solar activity had a larger effect to strong scintillations (S4 > 0.6) than to weak scintillations (0.6 ? S4 > 0.2). Strong scintillations were accompanied by TEC depletion especially in equinox months. We also discussed the relationship between TEC depletion and plasma bubble. 相似文献
315.
A.O. Alothman M.A. Alsubaie M.E. Ayhan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The ionosphere is a dispersive medium for radio waves with the refractive index which is a function of frequency and total electron content (TEC). TEC has a strong diurnal variation in addition to monthly, seasonal and solar cycle variations and small and large scale irregularities. Dual frequency GPS observations can be utilized to obtain TEC and investigate its spatial and temporal variations. We here studied short term TEC variations over the Kingdom of Saudi Arabia (KSA). A regional GPS network is formed consisting of 16 sites in and around KSA. GPS observations, acquired between 1st and 11th February 2009, were processed on a daily basis by using the Bernese v5.0 software and IGS final products. The geometry-free zero difference smoothed code observables were used to obtain two hour interval snapshots of TEC and their RMS errors at 0.5 × 0.5 degree grid nodes and regional ionosphere models in a spherical harmonics expansion to degree and order six. The equatorial ionized anomaly (EIA) is recovered in the south of 20°N from 08:00 to 12:00 UT. We found that day-by-day TEC variation is more stable than the night time variation. 相似文献
316.
Yuanming Liu Da-Ming Zhu Donald M. Strayer Ulf E. Israelsson 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
We report successful levitation of large water droplets and mice using a newly built variable gravity simulator. The simulator consists mainly of a superconducting magnet with a room temperature accessible experimental levitating space. The superconducting magnet generates a field and field gradient product that is large enough to levitate water and many other common liquids. The warm bore of the magnet has a diameter of 66 mm, large enough to levitate small mammals. We demonstrate that water drops up to 50 mm in diameter and young mice can be levitated in the system. The capability of levitating large water drops and biological systems offers new opportunities for conducting detailed and in-depth study of properties of fluids and biological systems in reduced gravity environments. 相似文献
317.
David M. Lucchesi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
LAGEOS II general relativity pericenter precession has been analysed in terms of the errors produced by the mismodelling of both the gravitational and non-gravitational perturbations acting on the satellite orbit. The accuracy in the pericenter determination may be considered as an upper-bound value for the estimate of the strength α of a possible new-long-range-interaction described by a Yukawa-like potential. In the present work we have focused on the constraints in α that can be obtained with the current best multi-satellites gravity field model EGM96 (α < 2.6 × 10−10) and also with the first promising models from the CHAMP (α < 1.8 × 10−10) and GRACE (α < 1.2 × 10−10) gravimetric missions. These results represent, potentially, an improvement of two or three orders-of-magnitude with respect to the best constraints obtained in the past with Earth–LAGEOS and Lunar–LAGEOS data (|α| < 10−5–10−8). The impact of the non-gravitational perturbations mismodelling in the final error budget has been determined together with the improvements obtainable in the constraint of the strength α with the proposed LARES satellite. 相似文献
318.
Bernhard Schläppi Kathrin Altwegg Timm Riesen Martin Rubin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
The Pioneer anomaly, an unexpected acceleration of the Pioneer 10 and 11 spacecraft of ∼8.5 × 10−10 ms−2 directed towards the inner Solar System, has been of great interest for the physics community during the past decade: considered explanations range from new physical concepts to conventional mechanism. It is shown that non-isotropic outgassing of the complete spacecraft structure is comparable in magnitude and direction to the effect and should be considered as a significant contribution to the anomalous acceleration. Although gas leaks from e.g. the propulsion system and propulsive mass loss mechanism have been discarded as possible explanations for the anomaly, the arguments used against such mechanisms do not apply to global outgassing from the spacecraft. 相似文献
319.
贯彻“军用飞机强度和刚度规范”既不能照搬规范条文,又必须维护规范的严肃性,目前更应强调从严肃性。从实践中提出制定型号规范的重要性。正确理解和贯彻规范中有关重量、重心位置的规定。 相似文献
320.
赤道异常峰区电离层的某些特点 总被引:1,自引:0,他引:1
由于赤道异常北峰覆盖我国整个南部地带,因此对峰区电离层特征的研究就成为掌握中国电离层特点的关键之一。本文试图对以下六个问题作些介绍和评述:1.逐日起伏和子夜前极大;2.峰位置的移动;3.赤道异常的经度效应;4.不均匀结构引起的强闪烁和快速法拉第衰落;5.顶部电离层的离化突起和中性赤道异常;6.粒子沉降的双峰分布. 相似文献