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1.
The application of chaos theory has become popular to understand the nature of various features of solar activity because most of them are far from regular. The usual approach, however, that is based on finding low-dimensional structures of the underlying processes seems to be successful only in a few exceptional cases, such as in rather coherent phenomena as coronal pulsations. It is important to note that most phenomena in solar radio emission are more complex. We present two kinds of techniques from nonlinear dynamics which can be useful to analyse such phenomena:
- Fragmentation processes observed in solar spike events are studied by means of symbolic dynamics methods. Different measures of complexity calculated from such observations reveal that there is some order in this fragmentation.
- Bursts are a typical transient phenomenon. To study energization processes causing impulsive microwave bursts, the wavelet analysis is applied. It exhibits structural differences of the pre- and post-impulsive phase in cases where the power spectra of both are not distinct.
2.
Pascal Willis Hervé Fagard Pascale Ferrage Frank G. Lemoine Carey E. Noll Ron Noomen Michiel Otten John C. Ries Markus Rothacher Laurent Soudarin Gilles Tavernier Jean-Jacques Valette 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
DORIS is one of the four space-geodetic techniques participating in the Global Geodetic Observing System (GGOS), particularly to maintain and disseminate the Terrestrial Reference Frame as determined by International Earth rotation and Reference frame Service (IERS). A few years ago, under the umbrella of the International Association of Geodesy, a DORIS International Service (IDS) was created in order to foster international cooperation and to provide new scientific products. This paper addresses the organizational aspects of the IDS and presents some recent DORIS scientific results. It is for the first time that, in preparation of the ITRF2008, seven Analysis Centers (AC’s) contributed to derive long-term time series of DORIS stations positions. These solutions were then combined into a homogeneous time series IDS-2 for which a precision of less than 10 mm was obtained. Orbit comparisons between the various AC’s showed an excellent agreement in the radial component, both for the SPOT satellites (e.g. 0.5–2.1 cm RMS for SPOT-2) and Envisat (0.9–2.1 cm RMS), using different software packages, models, corrections and analysis strategies. There is now a wide international participation within IDS that should lead to future improvements in DORIS analysis strategies and DORIS-derived geodetic products. 相似文献
3.
Michiel Otten Claudia Flohrer Tim Springer John Dow 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
This paper gives an overview of the DORIS related activities at the Navigation Support Office of the European Space Operations Centre. The DORIS activities were started in 2002 because of the launch of the Envisat satellite where ESOC is responsible for the validation of the Envisat Precise Orbits and a brief overview of the key Envisat activities at ESOC is given. Typical orbit comparison RMS values between the CNES POE (GDR-C) and the ESOC POD solution is 6.5, 18.8 and 23.1 mm in radial-, along- and cross-track direction. In the framework of the generation of the ITRF2008 ESOC participated in the reprocessing of all three space geodetic techniques; DORIS, SLR, and GPS. Here the main results of our DORIS reprocessing, in the framework of the International DORIS Service (IDS), are given. The WRMS of the weekly ESOC solution (esawd03) for the 2004–2009 period compared to the IDS-1 combined solution is of the order of 12 mm. Based on the long time series of homogeneously processed data a closer look is taken at the estimated solar radiation pressure parameters of the different satellites used in this DORIS analysis. The main aim being the stabilization of the Z-component of the geocentre estimates. We conclude that the ESOC participation to the IDS ITRF2008 contribution has been beneficial for both ESOC and the IDS. ESOC has profited significantly from the very open and direct communications and comparisons that took place within the IDS during the reprocessing campaign. 相似文献
4.
The Imaging Spectrometer Data Analysis System (ISDAS) is being developed by the Canada Centre for Remote Sensing and MacDonald Dettwiler and Associates on Sun Microsystems SPARC workstations using the Application Visualization System (AVS) software package to meet the requirements for efficient processing and analysis of hyperspectral data acquired with airborne as well as future spaceborne sensors. Various visualization tools have been developed for rapid exploratory analysis together with preprocessing and information extraction tools for numerical analysis. Linkages to a spectral database and a conventional image analysis system were established to support the analysis. ISDAS is being used for multidisciplinary applications development in areas such as agriculture, environment, and exploration geology using physically based analysis approaches to retrieve information from hyperspectral data. This continuing effort, in collaboration with industry will lead to streamlined procedures that are important to take hyperspectral satellite remote sensing towards an operational mode. 相似文献
5.
Benjamin S. Schwarz Adrian R.L. Tatnall Hugh G. Lewis 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
Coastal salinity is characterised by large and variable salinity contrasts on relatively small scales. Measurements of salinity at a resolution compatible with these coastal regions on a regular basis would provide a rich source of information that could be used for a number of applications that have a fundamental bearing on the world’s lifestyle. Doppler radiometry offers an approach to capture such measurements, as it reduces the number of required antennas needed to form an image, compared with an Interferometer type instrument. 相似文献
6.
Sounding rocket experiment of bare electrodynamic tether system 总被引:1,自引:0,他引:1
Hironori A. Fujii Takeo Watanabe Hirohisa Kojima Koh-Ichiro Oyama Tairo Kusagaya Yoshiki Yamagiwa Hirotaka Ohtsu Mengu Cho Susumu Sasaki Koji Tanaka John Williams Binyamin Rubin Charles Les Johnson George Khazanov Juan R. Sanmartin Jean-Pierre Lebreton Erick J. van der Heide Michiel Kruijff Fabio De Pascal Pavel M. Trivailo 《Acta Astronautica》2009,64(2-3):313-324
An overview of a sounding rocket, S-520-25th, project on space tether technology experiment is presented. The project is prepared by an international research group consisting of Japanese, European, American, and Australian researchers. The sounding rocket will be assembled by the ISAS/JAXA and will be launched in the summer of 2009. The sounding rocket mission includes two engineering experiments and two scientific experiments. These experiments consist of the deployment of bare electrodynamic tape tether in space, a quick ignition test of hollow cathode system in space, the demonstration of bare electrodynamic tether system in space, and the test of the OML (orbital-motion-limit) current collection theory. 相似文献
7.
A philosophy for the improvement of the extraction of controlled dc power from a polyphase ac supply line is presented. Extension of this philosophy for the interface of synchronous polyphase networks is briefly indicated. The needed kilovolt-ampere capacity of the supply line is reduced to nearly two thirds of the capacity needed for conventional controlled ac/dc converter systems. The new system requires only a small fraction of the physical weight of conventional converters. The improvements are derived from the interposition of a modulated high-power frequency carrier between the linked systems for the purpose of reconciliation of their conflicting characteristics. The harmonic content of the ac-phase currents is greatly reduced. The system operates with internal frequencies near 10 kHz; efficiencies in the upper nineties have been attained with this type of converter. 相似文献
8.
This paper highlights the design, qualification and mission performance of the tether deployer system on the second Young Engineers’ Satellite (YES2), that featured a tethered momentum transfer. The deployer is designed with a broad range of near-term tether applications in mind. The system contains the tether, including features to enhance safety and wound up in controlled manner onto a spool core, optical deployment sensors, a “barberpole” friction brake controlled by a stepper motor and a triple tether cutter system. To initiate the deployment a spring-based ejection system was developed, and to apply accurate momentum transfer a timer and release system is present on the subsatellite side. A small, 6 kg re-entry capsule was developed as subsatellite. On September 25th, 2007, YES2 deployed a 32 km tether in orbit and gathered a wealth of data. Confidence is gained from the mission results for use of the deployer in future missions. 相似文献
9.
Jan Jurčák Manuel Collados Jorrit Leenaarts Michiel van Noort Rolf Schlichenmaier 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(4):1389-1395
The European Solar Telescope (EST) is a project of a new-generation solar telescope. It has a large aperture of 4?m, which is necessary for achieving high spatial and temporal resolution. The high polarimetric sensitivity of the EST will allow to measure the magnetic field in the solar atmosphere with unprecedented precision. Here, we summarise the recent advancements in the realisation of the EST project regarding the hardware development and the refinement of the science requirements. 相似文献
10.
With the aid of numerical experiments we examined the dynamical stability of fictitious terrestrial planets in 1:1 mean motion resonance with Jovian-like planets of extrasolar planetary systems. In our stability study of the so-called "Trojan" planets in the habitable zone, we used the restricted three-body problem with different mass ratios of the primary bodies. The application of the three-body problem showed that even massive Trojan planets can be stable in the 1:1 mean motion resonance. From the 117 extrasolar planetary systems only 11 systems were found with one giant planet in the habitable zone. Out of this sample set we chose four planetary systems--HD17051, HD27442, HD28185, and HD108874--for further investigation. To study the orbital behavior of the stable zone in the different systems, we used direct numerical computations (Lie Integration Method) that allowed us to determine the escape times and the maximum eccentricity of the fictitious "Trojan planets." 相似文献