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1.
The Airborne Laser Ranging System is a proposed multibeam short pulse laser ranging system on board an aircraft. It simultaneously measures the distances between the aircraft and six laser retroreflectors (targets) deployed on the Earth's surface. Depending on the host aircraft and terrain characteristics, the system can interrogate hundreds of targets distributed over an area as large as 6×104 sq. kilometers in a matter of hours. Potentially, a total of 1.3 million individual range measurements can be made in a six hour flight. The precision of these range measurements is approximately ±1 cm. These measurements are then used in a procedure which is basically an extension of trilateration techniques to derive the intersite vector between the laser ground targets. By repeating the estimation of the intersite vector, strain and strain rate errors can be estimated. These quantities are essential for crustal dynamic studies which include determination and monitoring of regional strain in the vicinity of active fault zones, land subsidence, and edifice building preceding volcanic eruptions. 相似文献
2.
In January of 1981 the Transportable Laser Ranging System (TLRS) developed for NASA by The University of Texas was used to
conduct a four-day test of the relative lateration technique. The test evolved making repeated measurements of six lines over
the Los Angeles basin varying in distance from 26 to 84 kilometers. Although the raw times-of-flight to the various targets
changed typically by 5 parts in 106, their line ratios varied nearly an order of magnitude less. The test suggests that the TLRS or other pulsed laser ranging
systems might be able to economically combine Lageos ranging and long baseline horizontal work to survey large areas for accumulating
crustal strain. 相似文献
3.
The round-trip travel time measurements made by spacecraft laser altimeters are primarily used to construct topographic maps
of the target body. The accuracy of the calculated bounce point locations of the laser pulses depends on the quality of the
spacecraft trajectory reconstruction. The trajectory constraints from Doppler and range radio tracking data can be supplemented
by altimetric “crossovers”, to greatly improve the reconstruction of the spacecraft trajectory. Crossovers have been used
successfully in the past (e.g., Mars Orbiter Laser Altimeter on Mars Global Surveyor), but only with single-beam altimeters.
The same algorithms can be used with a multi-beam laser altimeter, but we present a method using the unique cross-track topographic
information present in the multi-beam data. Those crossovers are especially adapted to shallow (small angle) intersections,
as the overlapping area is large, reducing the inherent ambiguities of single-beam data in that situation. We call those “swath
crossovers”. They prove particularly useful in the case of polar-orbiting spacecraft over slowly rotating bodies, because
all the non-polar crossovers have small intersection angles. To demonstrate this method, we perform a simplified simulation
based on the Lunar Reconnaissance Orbiter (LRO) and its five-beam Lunar Orbiter Laser Altimeter. We show that swath crossovers
over one lunar month can independently, from geometry alone, recover the imposed orbital perturbations with great accuracy
(5 m horizontal, < 1 m vertical, about one order of magnitude smaller than the imposed perturbations). We also present new
types of constraints that can be derived from the swath crossovers, and designed to be used in a precision orbit determination
setup. In future work, we will use such multi-beam altimetric constraints with data from LRO. 相似文献
4.
Accurate geocentric three dimensional positioning is of great importance for various geodetic and oceanographic applications.
While relative positioning accuracy of a few centimeters has become a reality using Very Long Baseline Interferometry (VLBI), the uncertainty in the offset of the adopted coordinate system origin from the geocenter is still believed to be of the
order of one meter. Satellite Laser Ranging (SLR) is capable of determining this offset to better than10 cm, though, because of the limited number of satellites, this requires a long arc of data. The Global Positioning System (GPS) measurements provide a powerful alternative for an accurate determination of this origin offset in relatively short period
of time. Two strategies are discussed, the first utilizes the precise relative positions predetermined byVLBI, where as the second establishes a reference frame by holding only one of the tracking sites longitude fixed. Covariance
analysis studies indicate that geocentric positioning to an accuracy of a few centimeters can be achieved with just one day
of preciseGPS pseudorange and carrier phase data. 相似文献
5.
The consistency of the Chang’E-1 and SELENE reference frames as realized by the footprint positions of laser altimetry measurements
of the lunar surface during both missions was analyzed using a global 12-parameter model for small (with respect to unity)
deformations and rigid body motions. The rigid body motion and deformation parameters between the two reference frames estimated
from nearly-colocated without tie measurements are found to be consistent, i.e., nearly zero for the estimates of the translations,
rotations and shear parameters. However, the estimated three strain parameters, which are similar in magnitude and sign, reveal
a prominent scale difference, between the Chang’E-1 and SELENE reference frames, of about 0.9 × 10−5. The scale difference can be attributed to calibration of the data sets using the known coordinates of the lunar laser ranging
stations all located on the near side of the Moon. 相似文献
6.
A simulation study of multi-beam altimetry for lunar reconnaissance orbiter and other planetary missions 总被引：4，自引：4，他引：0
The combined use of altimetry, Earth-based Doppler and Earth-based range measurements in the lunar reconnaissance orbiter
(LRO) mission (Chin et al. in Space Sci Rev 129:391–419, 2007) has been examined in a simulation study. It is found that in
the initial phases of the mission orbit and altimeter geolocation accuracies should be better than 10 m in the radial component
and 60 m overall. It is demonstrated that LRO’s precise 1-way laser range measurement from Earth-based stations (Smith et
al. in Proceedings of the 15th International Laser Ranging Workshop, Canberra, Australia, October 15–20, 2006) will be useful
for gravity recovery. The advantages of multiple laser beams are demonstrated for altimeter calibration, orbit determination
and gravity recovery in general planetary settings as well as for LRO. 相似文献
7.
Precise orbit determination of the Sentinel-3A altimetry satellite using ambiguity-fixed GPS carrier phase observations 总被引：1，自引：0，他引：1
The Sentinel-3 mission takes routine measurements of sea surface heights and depends crucially on accurate and precise knowledge of the spacecraft. Orbit determination with a targeted uncertainty of less than 2 cm in radial direction is supported through an onboard Global Positioning System (GPS) receiver, a Doppler Orbitography and Radiopositioning Integrated by Satellite instrument, and a complementary laser retroreflector for satellite laser ranging. Within this study, the potential of ambiguity fixing for GPS-only precise orbit determination (POD) of the Sentinel-3 spacecraft is assessed. A refined strategy for carrier phase generation out of low-level measurements is employed to cope with half-cycle ambiguities in the tracking of the Sentinel-3 GPS receiver that have so far inhibited ambiguity-fixed POD solutions. Rather than explicitly fixing double-difference phase ambiguities with respect to a network of terrestrial reference stations, a single-receiver ambiguity resolution concept is employed that builds on dedicated GPS orbit, clock, and wide-lane bias products provided by the CNES/CLS (Centre National d’Études Spatiales/Collecte Localisation Satellites) analysis center of the International GNSS Service. Compared to float ambiguity solutions, a notably improved precision can be inferred from laser ranging residuals. These decrease from roughly 9 mm down to 5 mm standard deviation for high-grade stations on average over low and high elevations. Furthermore, the ambiguity-fixed orbits offer a substantially improved cross-track accuracy and help to identify lateral offsets in the GPS antenna or center-of-mass (CoM) location. With respect to altimetry, the improved orbit precision also benefits the global consistency of sea surface measurements. However, modeling of the absolute height continues to rely on proper dynamical models for the spacecraft motion as well as ground calibrations for the relative position of the altimeter reference point and the CoM. 相似文献
8.
Additional results are presented concerning a study that consider improvements over present Earth Rotation Parameter (ERP) determination methods by directly combining observations from various space geodetic systems in one adjustment. Earlier
results are extended, showing that in addition to slight improvements in accuracy substantial (a factor of three or more)
improvements in precision and significant reductions in correlations between various parameters can be obtained (by combining
Lunar Laser Ranging (LLR), Satellite Laser Ranging (SLR) to Lageos, and Very Long Baseline Interferometry (VLBI) data in one adjustment) as compared to results from individual systems. Smaller improvements are also seen over the weighted
means of the individual system results. Although data transmission would not be significantly reduced, negligible additional
computer time would be required if (standardized) normal equations were available from individual solutions. Suggestions for
future work and implications for the new International Earth Rotation Service (IERS) are also presented. 相似文献
9.
Christophe Vigny 《Journal of Geodesy》1996,70(5):300-306
In june 1990, NASA's Crustal Dynamics Project (CDP) has established a geodetic footprint for the Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI) systems located near Fort Davis, Texas using GPS measurements. The purpose of such a footprint is to assess both the tectonic and physical stability of the main observing monuments. Included in the survey were four new monuments forming a 20 to 30 km quadrilateral, as well as four existing monuments near the McDonald Laser Ranging System (MLRS), the Harvard Radio Astronomy (HRA) 85' antenna, and the new 85' antenna of the Very Long Baseline Array (VLBA).This network was partly reoccupied by the University of Texas Austin in may 1992. Three additional sites not observed in 1990 were occupied, two of them being old monuments in the observatory area (Harvard-RM4 and VLBA-SLR), and a new monument 80 km away across the closest active fault near Valentine, Texas.Thanks to existing ties between nearby monuments in the observatory area, the comparison between the two epochs was made possible. Significant motion of more than 1 cm of any of the implied sites over a two year period can be ruled out. Despite this quite reassuring results, smaller displacements cannot be detected mainly because of the poor quality of the 1990 data. Therefore it is strongly advised that a third occupation of the footprint sites takes place in the close future. Such a survey, occuring five years after the first one and three years after the second one, should definitely answer the questions on the Fort Davis area stability at the millimeter per year level. 相似文献
10.
11.
阿根廷圣胡安激光测距系统的SLR数据质量分析 总被引：2，自引：1，他引：1
利用自行研制的激光定轨软件CASMORD分析阿根廷圣胡安激光测距系统的SLR数据质量.结果表明,阿根廷圣胡安激光测距系统性能良好,具有较小的系统偏差(距离偏差和时间偏差),系统偏差稳定,随时间的变化较小,有效观测圈数和数据观测量处于全球台站前列;经系统偏差修正后,该系统达到了亚厘米级观测水平,具有较高的观测精度,可以为卫星的精密定轨提供在我国本土无法观测的轨道弧段的资料,为我国科学研究和国家的特殊需要提供必须的宝贵资料. 相似文献
12.
Since its launch in 2002, the Gravity Recovery and Climate Experiment (GRACE) mission has been providing measurements of the
time-varying Earth gravity field. The GRACE mission architecture includes two satellites in near-circular, near-polar orbits
separated in the along-track direction by approximately 220 km (e.g. collinear). A microwave ranging instrument measures changes
in the distance between the spacecraft, while accelerometers on each spacecraft are used to measure changes in distance due
to non-gravitational forces. The fact that the satellites are in near-polar orbits coupled with the fact that the inter-satellite
range measurements are directed in the along-track direction, contributes to longitudinal striping in the estimated gravity
fields. This paper examines four candidate mission architectures for a future gravity recovery satellite mission to assess
their potential in measuring the gravity field more accurately than GRACE. All satellites were assumed to have an improved
measurement system, with an inter-satellite laser ranging instrument and a drag-free system for removal of non-gravitational
accelerations. Four formations were studied: a two-satellite collinear pair similar to GRACE; a four-satellite architecture
with two collinear pairs; a two-satellite cartwheel formation; and a four-satellite cartwheel formation. A cartwheel formation
consists of satellites performing in-plane, relative elliptical motion about their geometric center, so that inter-satellite
measurements are, at times, directed radially (e.g. parallel to the direction towards the center of the Earth) rather than
along-track. Radial measurements, unlike along-track measurements, have equal sensitivity to mass distribution in all directions
along the Earth’s surface and can lead to higher spatial resolution in the derived gravity field. The ability of each architecture
to recover the gravity field was evaluated using numerical simulations performed with JPL’s GIPSY-OASIS software package.
Thirty days of data were used to estimate gravity fields complete to degree and order 60. Evaluations were done for 250 and
400 km nominal orbit altitudes. The sensitivity of the recovered gravity field to under-sampled effects was assessed using
simulated errors in atmospheric/ocean dealiasing (AOD) models. Results showed the gravity field errors associated with the
four-satellite cartwheel formation were approximately one order of magnitude lower than the collinear satellite pair when
only measurement system errors were included. When short-period AOD model errors were introduced, the gravity field errors
for each formation were approximately the same. The cartwheel formations eliminated most of the longitudinal striping seen
in the gravity field errors. A covariance analysis showed the error spectrum of the cartwheel formations to be lower and more
isotropic than that of the collinear formations. 相似文献
13.
Orbit determination of the Lunar Reconnaissance Orbiter 总被引：3，自引：1，他引：2
We present the results on precision orbit determination from the radio science investigation of the Lunar Reconnaissance Orbiter
(LRO) spacecraft. We describe the data, modeling and methods used to achieve position knowledge several times better than
the required 50–100 m (in total position), over the period from 13 July 2009 to 31 January 2011. In addition to the near-continuous
radiometric tracking data, we include altimetric data from the Lunar Orbiter Laser Altimeter (LOLA) in the form of crossover
measurements, and show that they strongly improve the accuracy of the orbit reconstruction (total position overlap differences
decrease from ~70 m to ~23 m). To refine the spacecraft trajectory further, we develop a lunar gravity field by combining
the newly acquired LRO data with the historical data. The reprocessing of the spacecraft trajectory with that model shows
significantly increased accuracy (~20 m with only the radiometric data, and ~14 m with the addition of the altimetric crossovers).
LOLA topographic maps and calibration data from the Lunar Reconnaissance Orbiter Camera were used to supplement the results
of the overlap analysis and demonstrate the trajectory accuracy. 相似文献
14.
15.
激光在天空对地观测中的应用 总被引：1，自引：0，他引：1
1960年7月世界上第一台激光器问世后，激光测距迅速兴起，不管是地面激光测距，还是激光测卫和激光测月，都为大地测量学的发展作出了重大贡献；特别是激光测卫测月成果，为我们深化对地球动态效应的认识，揭示地球的奥秘，提供了许多重要的科学数据，本文综析了值得注视的下列新近发展。.在IGEX-98国际大联测中，求定GLONASS卫星的激光轨道与微波轨道之差；.评定PRN05/06号GPS卫星星历的精度；.检核Topex/Poseidon海洋测高卫星用GPS定轨的测量误差，.用机载激光测深系统测量海水的浓度；.用EOS-ALT星载激光测距/测高系统测量地球动态参数。 相似文献
16.
LIU Jiyu CHEN Xiaoming 《地球空间信息科学学报》2000,3(1):50-56
l lntroductionIn the winter Of l989 Wuhan Technical Universi-ty of Surveying and Mapping COntracted withTrimble Navigation Ltd. to purchase fOur TrimbIe4000SST receivers. They were required tO suit theaeriaI phWetric work without intreducing avelocity limitation. In February, l993 twO of thereceivers were uPgraded to provide two eventrnarker plugfords and one pulse Per second(lPPS) output axkets. The uPgradd receivers canincormrate external event markers, e. g. the shutter.oPening … 相似文献
17.
GIOVE-B is one of two test satellites for the future European Global Navigation Satellite System Galileo. The Cooperative Network for GIOVE Observation (CONGO) is a global tracking network of GIOVE-capable receivers established by Deutsches Zentrum für Luft- und Raumfahrt (DLR) and Bundesamt für Kartographie und Geodäsie (BKG). This network provides the basis for the precise orbit determination of the GIOVE-B satellite for the time period 29 June till 27 October 2009 with a modified version of the Bernese GPS Software. Different arc lengths and sets of orbit parameters were tested. These tests showed that the full set of nine radiation pressure parameters resulted in a better performance than the reduced set of five parameters. An internal precision of about one to two decimeters could be demonstrated for the central day of 5-day solutions. The orbit predictions have a precision of about 1 m for a prediction period of 24 h. External validations with Satellite Laser Ranging (SLR) show residuals on the level of 12 cm. The accuracy of the final orbits is expected to be on the few decimeter level. 相似文献
18.
Single-epoch relative GPS positioning has many advantages, especially for monitoring dynamic targets. In this technique, errors occurring in previous epochs cannot affect the position accuracy at the current epoch, but careful processing is required, and resolving carrier phase ambiguities is essential. Statistical ambiguity resolution functions have been used to determine the best values of these ambiguities. The function inputs include as a minimum the known base station position, the approximate roving antenna “seed” position, and the dual-frequency carrier phase measurements from both receivers. We investigate different solutions to find the ambiguity function inputs that achieve the highest ambiguity resolution success rate. First, we address the rover seed position. A regionally filtered undifferenced pseudorange coordinate solution proves better than a double-differenced one. Multipath errors approximately repeat themselves every sidereal day in the case of static or quasi-static antennas; applying a sidereal filter to the pseudorange-derived positions mitigates their effects. Second, we address the relative carrier phase measurements, which for medium to long baselines are significantly affected by ionospheric propagation errors imperfectly removed during differencing. In addition to the International GNSS Service ionospheric model, we generate a local pseudorange-based ionospheric correction. Applying this correction improves the quality of the phase measurements, leading to more successful ambiguity resolution. Temporally smoothing the correction by means of a Kalman filter further improves the phase measurements. For baselines in the range 60–120 km, the mean absolute deviation of single-epoch coordinates improves to 10–20 cm, from 30–50 cm in the default case. 相似文献
19.
结合机载、星载激光雷达对GLAS(地球科学激光测高系统)光斑范围内的森林地上生物量进行估测,并利用MODIS植被产品以及MERIS土地覆盖产品进行了云南省森林地上生物量的连续制图。机载LiDAR扫描的260个训练样本用于构建星载GLAS的森林地上生物量估测模型,模型的决定系数(R2)为0.52,均方根误差(RMSE)为31Mg/ha。研究结果显示,云南省总森林地上生物量为12.72亿t,平均森林地上生物量为94Mg/ha。估测的森林地上生物量空间分布情况与实际情况相符,森林地上生物量总量与基于森林资源清查数据的估测结果相符,表明了利用机载LiDAR与星载ICESatGLAS结合进行大区域森林地上生物量估测的可靠性。 相似文献
20.
It has been widely known that the use of two-frequency Satellite Laser Ranging (SLR) system is limited by stringent precision
requirements of the range measurements and the proper atmospheric model. Owing to the stringent requirements, this SLR system
is impractical for the current requirement of SLR measurements within the framework of global geodetic observing system (GGOS).
If in the future this stringent requirement could be met, this SLR system would be an attractive tool to reduce atmospheric
propagation effects of SLR and would be of great benefit for the next generation of GGOS design. To anticipate possible future
developments of the two-frequency SLR systems, we have developed a new atmospheric correction formula for the two-frequency
SLR measurements. The new formula eliminates the total atmospheric density effect including its gradient and provides two
terms to calculate the curvature effect and the water vapor distribution effect. While the curvature effect can be calculated
by an accurate model, the required information about the water vapor distribution along the propagation path can be calculated
using previous developments of optical delay modeling or alternatively using results from microwave measurements. Theoretical
simulations using the two-frequency systems of the Graz and TIGO-Concepción stations shows that the new formula completely
reduces all propagation effects at any elevation angle above 3° with an accuracy better than 1 mm. However, the required precision
for the difference of the two-frequency SLR measurements, i.e. better than 45 μm for a single epoch, exceeds the capability
of the current state of the art SLR systems. 相似文献