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1.
One long-standing difficulty in estimating the large-scale ocean circulation is the inability to observe absolute current
velocities. Both conventional hydrographic measurements and altimetric measurements provide observations of currents relative
to an unknown velocity at a reference depth in the case of hydrographic data, and relative to mean currents calculated over
some averaging period in the case of altimetric data. Space gravity missions together with altimetric observations have the
potential to overcome this difficulty by providing absolute estimates of the velocity of surface oceanic currents. The absolute
surface velocity estimates will in turn provide the reference level velocities that are necessary to compute absolute velocities
at any depth level from hydrographic data.
Several studies have been carried out to quantify the improvements expected from ongoing and future space gravity missions.
The results of these studies in terms of volume flux estimates (transport of water masses) and heat flux estimates (transport
of heat by the ocean) are reviewed in this paper. The studies are based on ocean inverse modeling techniques that derive impact
estimates solely from the geoid error budgets of forthcoming space gravity missions. Despite some differences in the assumptions
made, the inverse modeling calculations all point to significant improvements in estimates of oceanic fluxes. These improvements,
measured in terms of reductions of uncertainties, are expected to be as large as a factor of 2.
New developments in autonomous ocean observing systems will complement the developments expected from space gravity missions.
The synergies of in situ and satellite observing systems are considered in the conclusion of this paper.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
随着火星探测技术的不断发展和探测任务的不断推进,载人火星探测在未来将会成为火星探测的重要手段。首先,回顾了无人火星探测任务的发展历程,对比分析了部分无人火星探测器进入、下降与着陆(EDL)过程的参数。然后,结合无人火星探测、载人月球探测和载人航天再入过程,梳理了载人火星探测的特点及需求,系统地总结了前苏联/俄罗斯和美国的载人火星探测研究进展以及技术储备。接着,归纳了载人火星探测的体系构成、集结方式和主要的技术挑战。最后,概括了载人火星EDL过程面临的难题,重点阐述了EDL的导航、制导与控制(GNC)关键技术。 相似文献
3.
《Aerospace and Electronic Systems Magazine, IEEE》2009,24(2):4-12
This presents the capabilities of two English Electric Aviation Canberra aircraft owned by High Altitude Mapping Missions, Inc. These aircraft are available for high altitude commercial, government, and scientific missions. The basic specifications of the Canberra are provided and compared to other high-performance jet aircraft falling into the same category. This describes the high altitude flight characteristics and mission capabilities of the Canberras. The aircraft are configured to conduct up to eight-hour flight operations with up to six hours at 50,000 feet altitude. Shorter missions can be conducted at higher altitudes. Potential missions include: IFSAR, magnetic field mapping, gravity field mapping, imaging (SAR, IR, & hyper-spectral), LIDAR, communications relay, dropsonde deployment, hybrid rocket launching, severe storm monitoring, and disaster monitoring. Canberra high altitude operations have minimal weather impact on missions, are free from flight constraints imposed by air traffic control, can do large area coverage, and long mission times. 相似文献
4.
This paper presents a review of geoid error characteristics of three satellite gravity missions in view of the general problem
of separating scientifically interesting signals from various noise sources. The problem is reviewed from the point of view
of two proposed applications of gravity missions, one is the observation of the mean oceanic circulation whereby an improved
geoid model is used as a reference surface against the long term mean sea level observed by altimetry. In this case we consider
the presence of mesoscale variability during assimilation of derived surface currents in inverse models. The other experiment
deals with temporal changes in the gravity field observed by GRACE in which case a proposed experiment is to monitor changes
in the geoid in order to detect geophysical interesting signals such as variations in the continental hydrology and non-steric
ocean processes. For this experiment we will address the problem of geophysical signal contamination and the way it potentially
affects monthly geoid solutions of GRACE.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
Geodetic Methods for Calibration of GRACE and GOCE 总被引:2,自引:0,他引:2
It is beyond doubt that calibration and validation are essential tools in the process of reaching the goals of gravity missions
like GRACE and GOCE and to obtain results of the highest possible quality. Both tools, although general and obvious instruments
for any mission, have specific features for gravity missions. Therefore, it is necessary to define exactly what is expected
(and what cannot be expected) from calibration and what from validation and how these tools should work in our case. The general
calibration and validation schemes for GRACE and GOCE are outlined. Calibration will be linked directly to the instrument
and the measurements whereas validation will be linked to data derived from the original measurements. Calibration includes
on-ground, internal, and external calibration as well as error assessment. The calibration phase results in corrected measurements
along with an a posteriori error model. Validation of e.g. calibrated measurements or geoid heights means checking against
independent data to assess whether there are no systematic errors left and/or whether the error model describes the true error
reasonably well. Geodetic methods for calibration typically refer to external calibration and error assessment, and will be
illustrated with an example.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
Starting from 1960s, a great number of missions and experiments have been performed for the study of the high-energy sky. This review gives a wide vision of the most important space missions and balloon experiments that have operated in the 10–600 keV band, a crucial window for the study of the most energetic and violent phenomena in the Universe. Thus it is important to take the stock of the achievements to better establish what we have still to do with future missions in order to progress in this field, to establish which are the technologies required to solve the still open issues and to extend our knowledge of the Universe. 相似文献
7.
火星进入减速器技术综述与展望 总被引:1,自引:1,他引:0
随着火星着陆探测任务的不断推进,火星采样返回、载人登陆火星和火星基地等任务要求能将更大、更重的探测器着陆到火星表面,这就需要在火星大气进入阶段进行高效减速。基于以往成功的火星着陆探测任务,首先系统地回顾了火星进入段气动减速技术的发展历史;然后,结合火星进入过程的特点阐述了火星进入段减速设计的必要性及其面临的挑战;接着,系统地总结了充气式气动减速器、可展开式气动减速器和超声速反推减速器的系统构成和研究进展;最后,对这3种减速器技术的未来发展方向和亟待解决的关键问题进行了比较全面的分析和展望。 相似文献
8.
9.
The nation is presently seeking smaller and faster space missions that cost less. Furthermore, there is pressure to spin off technologies into the commercial sector as well as spin in technologies to the space program. In this environment, ideas that were dismissed in the past have come to the forefront again. This paper discusses high performance photovoltaic devices, solar dynamic systems, new batteries and power management and distribution schemes. Spin offs of power technologies are impacting aeronautical, terrestrial and naval applications as well. It is believed that interactions with terrestrial commercial industries will lead to deeper understanding of how to reduce space costs as well as increasing quality and reliability 相似文献
10.
《中国航空学报》2023,36(5):125-144
Solar sail technology has been proposed and developed for space explorations with advantages of low launch cost, no-propellant consumption, and continuous thrust, which has great potentials in earth polar detection, interstellar explorations and etc. The development of solar sail has made significant progress in structural design, manufacturing, materials, orbit transfer, and stability control in the past few decades, which makes meaningful contributions to astronomy, physics, and aerospace science. Technological breakthroughs of Solar Radiation Pressure (SRP) propulsion and interstellar transfer have been achieved in current solar sail missions. However, there are still many challenges and problems need to be solved. This paper attempts to summarize the research schemes and potential applications of solar sailing in space missions from the viewpoint of key technologies, so as to provide an overall perspective for researchers in this field. Analyses of the key technologies of solar sailing system design are provided. Finally, challenges and prospective development of solar sailing are discussed. 相似文献
11.
Elfes A. Hall J. Kulczycki E. Clouse D. Morfopoulos A. Montgomery J. Cameron J. Ansar A. Machuzak R. 《Aerospace and Electronic Systems Magazine, IEEE》2008,23(7):16-24
The Huygens probe arrived at Saturn's moon, Titan, January 14,2005, unveiling a world that is radically different from any other in the solar system. The data obtained, complemented by continuing observations from the Cassini spacecraft, show methane lakes, river channels and drainage basins, sand dunes, cryovolcanos and sierras. This has led to an enormous scientific interest in a follow-up mission to Titan, using a robotic lighter-than-air vehicle (or aerobot). Aerobots have modest power requirements, can fly missions with extended durations, and have very long distance traverse capabilities. They can execute regional surveys, transport and deploy scientific instruments and in-situ laboratory facilities over vast distances, and also provide surface sampling at strategic science sites. This describes our progress in the development of the autonomy technologies that will be required for exploration of Titan. We provide an overview of the autonomy architecture and some of its key components. We also show results obtained from autonomous flight tests conducted in the Mojave Desert. 相似文献
12.
宇航空间中的微低重力环境使得所处其中的航天器和宇航员表现出与在地面重力环境下不同的受力状态和动态性能,因此需要在地面对这种微低重力环境进行模拟。综述了目前常用的几种微低重力模拟方法,其中悬吊法因为模拟时间长、模拟范围大、不引入附加惯量的优势被广泛采用。从微低重力模拟原理角度对现有的悬吊式微低重力模拟系统研究成果进行了分类和国内外研究现状的综述。根据微低重力模拟的需求归纳了悬吊式微低重力模拟系统的2条设计准则和3个关键技术,详细综述了这3个关键技术的研究现状。探讨了未来悬吊式微低重力模拟系统设计方面和3个关键技术方面的发展趋势。 相似文献
13.
V: SEA LEVEL: Benefits of GRACE and GOCE to sea level studies 总被引:1,自引:0,他引:1
The recently published Third Assessment Reports of the Intergovernmental Panel on Climate Change have underlined the scientific
interest in, and practical importance of past and potential future sea level changes. Space gravity missions will provide
major benefits to the understanding of the past, and, thereby, in the prediction of future, sea level changes in many ways.
The proposal for the GOCE mission described well the improvements to be expected from improved gravity field and geoid models
in oceanography (for example, in the measurement of the time-averaged, or ‘steady state’, ocean surface circulation and better
estimation of ocean transports), in geophysics (in the improvement of geodynamic models for vertical land movements), in geodesy
(in positioning of tide gauge data into the same reference frame as altimeter data, and in improvement of altimeter satellite
orbits), and possibly in glaciology (in improved knowledge of bedrock topography and ice sheet mass fluxes). GRACE will make
many important steps towards these ‘steady state’ aims. However, its main purpose is the provision of oceanographic (and hydrological
and meteorological) temporally-varying gravity information, and should in effect function as a global ‘bottom pressure recorder’,
providing further insight into the 3-D temporal variation of the ocean circulation, and of the global water budget in general.
This paper summaries several of these issues, pointing the way towards improved accuracy of prediction of future sea level
change.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
我国中继卫星系统在交会对接任务中的应用 总被引:1,自引:0,他引:1
我国中继卫星系统在交会对接任务中得到了成功应用,显著提升了测控通信覆盖率,充分体现了中继卫星系统在交会对接任务测控通信中发挥的重要作用.结合中继卫星系统特点,分析交会对接任务对中继卫星系统的任务需求;探讨了中继卫星捕获跟踪用户目标、对用户目标测定轨、着陆场直升机缝隙通信等关键技术;最后总结了中继卫星系统抗雨衰影响、多目标支持能力、应急支持能力等方面的经验做法,并提出了后续改进和完善的建议. 相似文献
15.
Space-Wise,Time-Wise,Torus and Rosborough Representations in Gravity Field Modelling 总被引:1,自引:0,他引:1
The decade of the geopotentials started July 2000 with the launch of the German high-low SST mission CHAMP. Together with the joint NASA-DLR low-low SST
mission GRACE and the ESA gradiometry mission GOCE an unprecedented wealth of geopotential data becomes available over the
next few years.
Due to the sheer number of unknown gravity field parameters (up to 100 000) and of observations (millions), especially the
latter two missions are highly demanding in terms of computational requirements. In this paper several modelling strategies
are presented that are based on a semi-analytical approach. In this approach the set of normal equations becomes block-diagonal
with maximum block-sizes smaller than the spherical harmonic degree of resolution. The block-diagonality leads to a rapid
and powerful gravity field analysis tool.
Beyond the more-or-less conventional space-wise and time-wise formulations, the torus approach and Rosborough's representation
are discussed. A trade-off between pros and cons of each of the modelling strategies will be given.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
17.
在研究国内外测控通信技术现状与发展动态的基础上,梳理出未来测控通信发展趋势:将走向综合化网络、高精度和航天器自主导航,发展光学测控通信技术,提升跟踪与数据中继能力,建设天基靶场,加强安全防护,以及设备高度综合化、数字化、软件化和低成本等;结合我国测控通信技术发展遇到的技术“瓶颈”与挑战,探讨了当前我国测控通信发展面临的主要任务:制定顶层规划,继续提升技术水平,满足新平台新任务测控需求,探索新概念与前沿技术等;最后,提出了我国测控通信重点发展方向及其关键技术的建议. 相似文献
18.
19.
Resolution Needed for an Adequate Determination of the Mean Ocean Circulation from Altimetry and an Improved Geoid 总被引:4,自引:0,他引:4
The sea surface topography observed by satellite altimetry is a combination of the geoid and of the ocean dynamic topography.
Satellite altimetry has thus the potential to supply quasi-global maps of mean sea surface heights from which the mean geostrophic
surface ocean currents can be derived, provided that the geoid is known with a sufficient absolute accuracy. At present, however,
given the limited accuracy of the best available geoid, altimetric mean sea surface topographies have been derived only up
to degree 15 or so, i.e. for wavelengths of approximately 2000 km and larger. CHAMP, GRACE, and the future GOCE missions are
dedicated to the improvement of the Earth's gravity field from space. Several studies have recently investigated the impact
of these improvements for oceanography, concluding to reductions of uncertainties on the oceanic flux estimates as large as
a factor of 2 in the regions of intense an narrow currents. The aim of this paper is to focus on what are the typical horizontal
scales of the mean dynamic topography of the ocean, and to compare their characteristics to the error estimates expected from
altimetry and these future geoids. It gives also an illustration of the oceanic features that will be resolved by the combination
of altimetry and the GRACE and GOCE geoids. It further reassesses the very demanding requirements in term of accuracy and
resolution agreed in the design of these new gravity missions for ocean science applications. The present study relies on
recent very high-resolution numerical Ocean General Circulation Model simulations.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
Tidal Models in a New Era of Satellite Gravimetry 总被引:3,自引:0,他引:3
The high precision gravity measurements to be made by recently launched (and recently approved) satellites place new demands
on models of Earth, atmospheric, and oceanic tides. The latter is the most problematic. The ocean tides induce variations
in the Earth's geoid by amounts that far exceed the new satellite sensitivities, and tidal models must be used to correct
for this. Two methods are used here to determine the standard errors in current ocean tide models. At long wavelengths these
errors exceed the sensitivity of the GRACE mission. Tidal errors will not prevent the new satellite missions from improving
our knowledge of the geopotential by orders of magnitude, but the errors may well contaminate GRACE estimates of temporal
variations in gravity. Solar tides are especially problematic because of their long alias periods. The satellite data may
be used to improve tidal models once a sufficiently long time series is obtained. Improvements in the long-wavelength components
of lunar tides are especially promising.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献