共查询到17条相似文献，搜索用时 125 毫秒
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“SZ-4”飞船高度计天线指向角反演方法 总被引：1，自引：0，他引：1
利用2003年2月7到8日“SZ-4”高度计的波形数据,经过波形数据预处理(波形为1 s的平均、去除热噪声和波形归一化)后,对海面回波波形后沿进行拟合,计算出了高度计天线的指向角,结果表明,“SZ-4”飞船高度计天线的指向角几乎全部在0.024°以内,天线指向在计算时间内比较稳定. 相似文献
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中国近岸海域高度计JASON-1测量数据的波形重构算法研究 总被引：3，自引：1，他引：2
卫星雷达高度计的测量数据目前已被广泛应用于各个领域,但高度计在近海的测量数据却一直不可用,一方面是因为高度计在近岸海域的回波波形测量受陆地回波的影响,另一方面是因为一些校正量对近海不准确,如大气湿对流层校正、海洋潮汐校正以及大气高频因数校正等。通过对高度计在近海测量的回波波形进行重构处理,可以缩短近海数据不可用的距离,提高数据的数量和质量。以我国海域及邻近海域(14°~45°N,105°~130°E)为研究区域,采用四种波形重构算法(海洋算法、重力中心偏离算法、冰层算法二和阈值算法)对JASON-1高度计1 a共31个周期的测量波形重新进行了计算,比较了轨道交叉点处升轨和降轨的海面高度异常值以及海面高度值与验潮站的实测水位,结果表明重力中心偏离法比其他三种算法更适合我国近海的测高波形重构:计算结果精度最高,有效数目最多。 相似文献
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单颗星下点高度计卫星可进行一维海面高度测量，但时空分辨率较低，对涡旋的探测能力不足。梳状高度计卫星编队可提升海面高度时空分辨率，增强对涡旋的识别探测能力。为定量分析高度计编队下的涡旋探测能力，本文在黑潮延伸体海域开展观测仿真实验，对海平面高度进行沿轨采样，经优化插值算法处理后得到逐天海面高度异常数据场并进行涡旋识别与统计分析。此外，本文还同步开展了单颗星下点高度计和成像高度计卫星涡旋探测仿真实验及对比分析。结果表明，梳状高度计卫星编队在涡旋数量、极性、半径及振幅等方面识别效果较好，与成像高度计探测结果相近。 相似文献
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本文基于Amarouche的二阶理论回波模型,导出了带有偏度系数的二阶理论回波模型;针对HY-2A卫星高度计波形特点,引入了奇异值分解滤波,并根据最大似然估计算法反演参数的不同得到6种重跟踪方案;利用其中的五参数方案处理该波形数据,获得海面散射点高度概率密度函数中偏度的合理取值为0.15;将结果分别与浮标、Jason-1和HY-2AIDR有效波高对比,分析6种方案反演有效波高的准确度,确定了MLE4_SVD(波形重跟踪之前进行滤波)对HY-2A高度计重跟踪更适合反演有效波高。 相似文献
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工作在Ku波段的Cryo Sat-2和Sentinel-3A合成孔径雷达高度计是当前最先进的高度计。由于雷达回波信号的实际时间跟踪点较预设的时间跟踪点总发生偏移,而且Ku波段波长短,进行海冰探测时易受雪层干扰,造成雷达信号主散射面由海冰表面上移至雪层内,这两个因素都影响着海冰干舷高度的反演精度。针对这些问题,本文首先确定了Cryo Sat-2与Sentinel-3A雷达高度计反演北极海冰干舷高度的最优波形重跟踪阈值组合,然后分析了这两个Ku波段雷达信号的雪层穿透系数,发现Ku波段高度计的主散射面受雪层的影响显著,会高估海冰干舷高度。基于此,文中提出了一种改进的积雪校正方法,并以机载Operation Ice Bridge(OIB)为验证数据,将本文提出的方法与通用积雪校正法和欧洲空间局(European Space Agency,ESA)海冰干舷高度产品进行了对比验证。实验结果表明,本文提出的方法能够有效估计Ku波段电磁波穿透海冰表面积雪深度的比例系数,显著校正了通用积雪校正方法存在的高估海冰干舷高度的问题,提高了海冰干舷高度的估算精度。 相似文献
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为弥补测高数据在近海区域因为编辑准则被剔除而导致近海测量数据质量不高的缺点,利用5参数模型的两种形式和Ice-2模型对Jason-2卫星在中国南海部分海域的海洋回波波形进行了波形重跟踪的研究,并选择20个海洋回波波形,依据最小二乘原理进行计算、分析、对比,发现5参数模型的指数形式的结果和Ice-2模型结果非常接近。研究结果表明,在开阔的海域,对Jason-2波形进行3种方法波形重跟踪时,可以优先考虑Ice-2模型。波形重跟踪技术能够提高卫星测高数据利用率,为科学研究提供可靠的数据保障。 相似文献
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对3颗高度计卫星TOPEX/POSEIDON(TP),Jason-1(J1),Jason-2(J2)自1992—2011年683个重复周期,共18.6年的数据进行分析,得到全球海洋潮汐调和常数,并重点分析了采用不同样本大小的卫星高度计数据对潮汐信息提取的准度和精度所带来的影响。研究结果表明,参与分析的卫星高度计数据观测样本数的增加可以降低其反演潮汐各分潮振幅时的误差。观测时间为18.6年的高度计数据调和分析所得的主要半日分潮与实测比较,其振幅差相比于利用10年数据的计算结果减小约0.5cm;但是由于忽略了卫星更替过程所带来的观测时间差来进行调和分析,将会对计算分析过程中产生的迟角误差造成影响,主要全日分潮的迟角误差增加约2°,而半日潮迟角误差的改变则比较小。本文进一步用理想化实验解释了造成这种迟角计算误差变化的原因,比较了轨道交叉点上,由卫星在升轨和降轨2个轨道上各自的观测数据计算得到的调和常数,发现随着参与分析的高度计观测样本数的增加,调和分析计算潮汐调和常数时的内符精度也会显著提高。利用18.6年数据比利用10年数据进行调和分析时,主要半日潮调和常数的精度提高了约7%。 相似文献
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Retracking of Jason-1 Data 总被引：1，自引：0，他引：1
We present the results of retracking 18 cycles (15 from the Jason-TOPEX collinear period) of Jason-1 data. We used the retracking method of Rodriguez which simultaneously solves for all relevant waveform parameters using a 26 Gaussian model of the altimeter point target response. We find significant differences from the Jason-1 Project retracking in the key parameters of range and significant wave height (SWH) in the second version of the Project SGDRs. The differences from the Jason-1 data have a strong dependence on off-nadir angle and some dependence on SWH. The dependence of range on SWH is what is called sea state bias. The retracking technique also estimates surface skewness. For Jason-1 with its very clean waveforms we make the first direct estimates of the skewness effect on altimeter data. We believe that the differences found here and thus in overall sea surface height are the result of the standard project processing using a single Gaussian approximation to the Point Target Response (PTR) and not solving simultaneously for off nadir angle. We believe that the relatively large sea state bias errors estimated empirically for Jason-1 during the cal/val phase result from sensitivity of quantities, particularly SWH, in project GDRs to off nadir angle. The TOPEX-Jason-1 bias can be determined only when a full retracking of Jason-1 is done for the collinear period. 相似文献
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We present the results of retracking 18 cycles (15 from the Jason-TOPEX collinear period) of Jason-1 data. We used the retracking method of Rodriguez which simultaneously solves for all relevant waveform parameters using a 26 Gaussian model of the altimeter point target response. We find significant differences from the Jason-1 Project retracking in the key parameters of range and significant wave height (SWH) in the second version of the Project SGDRs. The differences from the Jason-1 data have a strong dependence on off-nadir angle and some dependence on SWH. The dependence of range on SWH is what is called sea state bias. The retracking technique also estimates surface skewness. For Jason-1 with its very clean waveforms we make the first direct estimates of the skewness effect on altimeter data. We believe that the differences found here and thus in overall sea surface height are the result of the standard project processing using a single Gaussian approximation to the Point Target Response (PTR) and not solving simultaneously for off nadir angle. We believe that the relatively large sea state bias errors estimated empirically for Jason-1 during the cal/val phase result from sensitivity of quantities, particularly SWH, in project GDRs to off nadir angle. The TOPEX-Jason-1 bias can be determined only when a full retracking of Jason-1 is done for the collinear period. 相似文献
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1IntroductionSZ-4spaceborne,launched on30December2002,is the fourth unmanned spaceborne of China.Multimode microwave remote sensor is its primaryload,of which the altimeter mode is the most impor-tant one.During about five months,a large numberofSZ-4altim… 相似文献
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Retracking altimeter waveforms over inland water bodies is a challenging task as a wide range of waveform is encountered while the retracking algorithms are available only for a handful of echo shapes. One such waveform shape widely encountered in lakes and reservoirs is the multipeak echo. These echoes are produced when the interacting surface in the altimeter footprint is not homogeneous and a number of different types of surfaces contribute to the resulting waveform. The widely used conventional retrackers, namely the Brown, Beta-5, Ice-2, OCOG, and threshold, can retrack a number of different waveform shapes such as the Brown like waveforms, specular waveforms, and rectangular waveforms but may not perform well for multipeak waveforms. In this article, a technique has been demonstrated to identify the different subwaveforms within a multipeak waveform and identify the subwaveform corresponding to the target at nadir. The subwaveform that is reflected from the nadir surface is identified from apriory information about the surface topography of the area. The subwaveform is then retracked using the 50% threshold to find the correct retracked range and water height. This technique has been tested for nine cycles of SARAL SIGDR data on Ukai reservoir, Gujarat, India, and found to perform much better than the other retrackers, particularly for multipeak waveforms. 相似文献
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L. AMAROUCHE P. THIBAUT O. Z. ZANIFE J.-P. DUMONT P. VINCENT N. STEUNOU 《Marine Geodesy》2013,36(1-2):171-197
After two years of verification and validation activities of the Jason-1 altimeter data, it appears that all the mission specifications are completely fulfilled. Performances of all instruments embarked onboard the platform meet all the requirements of the mission. However, the star tracker system has shown some occasional abnormal behavior leading to mispointing angles out of the range of Jason-1 system specification which states that the altimeter antenna shall be pointed to the nadir direction with an accuracy below 0.2 degree (3 sigma). This article discusses the platform attitude angle and its consequences on the altimetric estimates. We propose improvements of the Jason-1 retracking process to better account for attitude effects. The first star tracker anomalies for the Jason-1 mission were detected in April 2002. The Poseidon-2 algorithms were specified assuming an antenna off-nadir angle smaller than 0.3 degree. For higher values, the current method to estimate the ocean parameters is known to be inaccurate. Thus, the algorithm has to be reviewed, and more specifically, the present altimeter echo model has to be modified to meet the desired instrument performance. Therefore, we derive a second order analytical model of the altimeter echo to take into account attitude angles up to 0.8 degree, and consequently, we adapt the retracking algorithm. This new model is tested on theoretical simulated data using a maximum likelihood estimation. Biases and noise performance characteristics are computed for the different estimated parameters. They are compared to the ones obtained with the current algorithm. This new method provides highly improved estimations for high attitude angles. It is statistically validated on real data by applying it on several cycles of Poseidon-2 raw measurements. The results are found to be consistent with those obtained from simulations. They also fully agree with the TOPEX estimates when flying along the same ground track. Finally, the estimates are also in agreement with the ones available in the current I/GDR (Intermediate Geophysical Data Record) products when mispointing lies in the mission specifications. 相似文献
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L. Amarouche P. Thibaut O. Z. Zanife J. -P. Dumont P. Vincent N. Steunou 《Marine Geodesy》2004,27(1):171-197
After two years of verification and validation activities of the Jason-1 altimeter data, it appears that all the mission specifications are completely fulfilled. Performances of all instruments embarked onboard the platform meet all the requirements of the mission. However, the star tracker system has shown some occasional abnormal behavior leading to mispointing angles out of the range of Jason-1 system specification which states that the altimeter antenna shall be pointed to the nadir direction with an accuracy below 0.2 degree (3 sigma). This article discusses the platform attitude angle and its consequences on the altimetric estimates. We propose improvements of the Jason-1 retracking process to better account for attitude effects.
The first star tracker anomalies for the Jason-1 mission were detected in April 2002. The Poseidon-2 algorithms were specified assuming an antenna off-nadir angle smaller than 0.3 degree. For higher values, the current method to estimate the ocean parameters is known to be inaccurate. Thus, the algorithm has to be reviewed, and more specifically, the present altimeter echo model has to be modified to meet the desired instrument performance.
Therefore, we derive a second order analytical model of the altimeter echo to take into account attitude angles up to 0.8 degree, and consequently, we adapt the retracking algorithm. This new model is tested on theoretical simulated data using a maximum likelihood estimation. Biases and noise performance characteristics are computed for the different estimated parameters. They are compared to the ones obtained with the current algorithm. This new method provides highly improved estimations for high attitude angles. It is statistically validated on real data by applying it on several cycles of Poseidon-2 raw measurements. The results are found to be consistent with those obtained from simulations. They also fully agree with the TOPEX estimates when flying along the same ground track. Finally, the estimates are also in agreement with the ones available in the current I/GDR (Intermediate Geophysical Data Record) products when mispointing lies in the mission specifications. 相似文献
The first star tracker anomalies for the Jason-1 mission were detected in April 2002. The Poseidon-2 algorithms were specified assuming an antenna off-nadir angle smaller than 0.3 degree. For higher values, the current method to estimate the ocean parameters is known to be inaccurate. Thus, the algorithm has to be reviewed, and more specifically, the present altimeter echo model has to be modified to meet the desired instrument performance.
Therefore, we derive a second order analytical model of the altimeter echo to take into account attitude angles up to 0.8 degree, and consequently, we adapt the retracking algorithm. This new model is tested on theoretical simulated data using a maximum likelihood estimation. Biases and noise performance characteristics are computed for the different estimated parameters. They are compared to the ones obtained with the current algorithm. This new method provides highly improved estimations for high attitude angles. It is statistically validated on real data by applying it on several cycles of Poseidon-2 raw measurements. The results are found to be consistent with those obtained from simulations. They also fully agree with the TOPEX estimates when flying along the same ground track. Finally, the estimates are also in agreement with the ones available in the current I/GDR (Intermediate Geophysical Data Record) products when mispointing lies in the mission specifications. 相似文献
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O. Z. Zanif P. Vincent L. Amarouche J. P. Dumont P. Thibaut S. Labroue 《Marine Geodesy》2003,26(3):201-238
TOPEX/Poseidon is a well known success, with the operational altimeter (TOPEX) and the experimental one (Poseidon-1), providing data of unprecedented quality. However, there are two major differences between the TOPEX and Poseidon-1 radar altimeters on board TOPEX/Poseidon. The first is related to the estimated range noise; the second is linked to the sea-state bias (SSB) model estimates. Since the recent launch of the Jason-1 radar altimeter (also called Poseidon-2), we have been cross-comparing these three systems to better characterize each of them. Analyzing standard user products, we have found that Jason-1 is behaving like Poseidon-1 and thus shows the same observed differences when compared with TOPEX. A comparative analysis of their features was performed, starting from the on-board acquisition of the ocean return and ending with the ground generation of the high level accuracy oceanographic product. The results lead us to believe that the sources for these differences lie in both the waveform tracking processing and the presence or abscence of a retracking procedure whether on-board or on ground. Because Poseidon-1 and Jason-1 waveforms are retracked while TOPEX waveforms are not in the products distributed to the users, we have applied the same ground retracking algorithm to the waveforms of the three radar altimeters to get consistent data sets. The analysis of the outputs has shown that: (a) the noise level for the three radar altimeters is definitively the same, and (b) the source of the relative SSB between Jason-1 and TOPEX lies in the different behavior of the on-board tracking softwares. 相似文献