International Conference on Recent Advances in Space Technologies, 2003. RAST '03. Proceedings of最新文献

{"title":"Robust time-optimal control for flexible structures by augmented dynamics","authors":"H. Bang, Hyun Jae Lee, Y. Eun","doi":"10.1109/RAST.2003.1303963","DOIUrl":"https://doi.org/10.1109/RAST.2003.1303963","url":null,"abstract":"Robust optimal control problem for flexible structures using on-off type discrete actuators has been a subject of intensive research. Optimization by switching time parameterization can be used to minimize the mauver time subject to equality boundary constraints. Sensitivity of the switching times with respect to modal parameters could be a critical factor degrading the performance of the time optimal solutions. A new approach for the robustness enhancement of switching times with respect to modal parameter uncertainty is introduced. The so-called augmented dynamic model is added to account for the modal uncertainty. The proposed approach turns out to be similar to some previous methods, but provides some new results.","PeriodicalId":272869,"journal":{"name":"International Conference on Recent Advances in Space Technologies, 2003. RAST '03. Proceedings of","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128709642","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Asteroid and NEA detection models","authors":"R. Michelsen, H. Haack, A. Andersen, J. Jørgensen","doi":"10.1109/RAST.2003.1303915","DOIUrl":"https://doi.org/10.1109/RAST.2003.1303915","url":null,"abstract":"We determine the possible detection rate of asteroids with the Bering mission. In particular we examine the outcome of the Bering mission in relation to the populations of Near-Earth Asteroids and main belt asteroids. This is done by constructing synthetic populations of asteroids, based on the current best estimates of the asteroid size-distributions. From the detailed information obtained from the simulations, the scientific feasibility of Bering is demonstrated and the key technical requirement for the scientific instruments on Bering is determined.","PeriodicalId":272869,"journal":{"name":"International Conference on Recent Advances in Space Technologies, 2003. RAST '03. Proceedings of","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122277461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bering - the first deep space mission to map asteroidal diversity, origin and transportation","authors":"A. Andersen, R. Michelsen, H. Haack, J. Jørgensen","doi":"10.1109/RAST.2003.1303914","DOIUrl":"https://doi.org/10.1109/RAST.2003.1303914","url":null,"abstract":"Asteroids are remnants of the material from which the Solar System formed. Fragments of asteroids, in the form of meteorites, include samples of the first solid matter to form in our Solar System 4.5 Myrs ago. Spectroscopic studies of asteroids show that they, like the meteorites, range from very primitive objects to highly evolved small Earth-like planets that differentiated into core, mantle and crust. The asteroid belt displays systematic variations in abundance of asteroid types from the more evolved types in the inner belt to the more primitive objects in the outer reaches of the belt thus bridging the gap between the inner evolved apart of the Solar System and the outer primitive part of the Solar System. High-speed collisions between asteroids are gradually resulting in their break-up. The size distribution of kilometer-sized asteroids implies that the presently undetected population of sub-kilometer asteroids far outnumber the known larger objects. Sub-kilometer asteroids are expected to provide unique insight into the evolution of the asteroid belt and to the meteorite-asteroid connection. We propose a space mission to detect and characterize sub-kilometer asteroids between Jupiter and Venus. The mission is named Bering after the famous navigator and explorer Vitus Bering. A key feature of the mission is an advanced payload package, providing full on board autonomy of both object detection and tracking, which is required in order to study fast moving objects in deep space. The autonomy has the added advantage of reducing the cost of running the mission to a minimum, thus enabling science to focus on the main objectives.","PeriodicalId":272869,"journal":{"name":"International Conference on Recent Advances in Space Technologies, 2003. RAST '03. Proceedings of","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116975122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the relation between solar activity and seismicity","authors":"M. Gousheva, K. Georgieva, B. Kirov, D. Antanasov","doi":"10.1109/RAST.2003.1303913","DOIUrl":"https://doi.org/10.1109/RAST.2003.1303913","url":null,"abstract":"Much attention is recently paid to the role of extraterrestrial factors in terrestrial seismicity, and to the possibility to assess the seismic risk. Seven centuries of records of ancient earthquakes in the Mediterranean region show that the century-scale variations in the number of strong earthquakes closely follow the secular cycle of solar activity. Two well expressed maxima in the global yearly number of earthquakes are seen in the 11-year sunspot cycle - one coinciding with sunspot maximum, and the other on the descending phase of solar activity. A day to day study of the number of earthquakes worldwide reveals that the arrival to the Earth of high speed solar streams is related to significantly greater probability of earthquake occurrence. The possible mechanism includes deposition of solar wind energy into the polar ionosphere where it drives ionospheric convection and auroral electrojets, generating in turn atmospheric gravity waves that interact with neutral winds and deposit their momentum in the neutral atmosphere, increasing the transfer of air masses and disturbing of the pressure balance on tectonic plates. The main sources of high speed solar streams are the solar coronal mass ejections (CMEs) which have a maximum in the sunspot maximum, and the coronal holes with a maximum on the descending phase of solar activity. Both coronal holes and CMEs are monitored by satellite-borne and ground-based instruments, which makes it possible to predict periods of enhanced seismic risk. The geoeffectiveness of solar wind from a coronal hole only depends on the position of the hole relative to the Earth, and for the CMEs an additional factor is their speed. It has been recently found that a useful tool in identifying the population of geoeffective CMEs is the detection of long-wavelength (decameter-hectometer) type II solar radio bursts, as the CMEs associated with them are much faster and wider than average.","PeriodicalId":272869,"journal":{"name":"International Conference on Recent Advances in Space Technologies, 2003. RAST '03. Proceedings of","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116454342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New European concept of single staged rocket to launch nano-satellites in low earth orbit (LEO)","authors":"O. Božić, J. Longo, P. Giese","doi":"10.1109/RAST.2003.1303392","DOIUrl":"https://doi.org/10.1109/RAST.2003.1303392","url":null,"abstract":"The possibility to launch small payloads into LEO by means of an electromagnetic railgun is the motivation of the present study. Here it is assumed that an electromagnetic railgun with barrel length of 180 m is able to launch a 120 mm diameter projectile at a speed of 6 km/s. In order to the payload achieves orbital motion and to compensate the velocity losses due to gravity and aerodynamic drag, a rocket engine which supplies the required velocity difference is integrated into the projectile structure. The development of such propelled projectile requires key technologies that could also benefit other industrial sectors. The paper presents the main concept and design aspects to be considered for such propelled projectile with special emphasis on: flight mechanics, aero/thermodynamics, materials and propulsion characteristics. The aerodynamic form of the projectile is optimized to achieve minimum drag and lower heat loads. Launch angles and trajectory optimization analysis are carried out by means of 3 degree of freedom simulations (3DOF). Furthermore, three concurrent propulsions systems are here considered for the rocket engine: solid, liquid and hybrid propellants type. The result of analysis pointed that the most promising propulsion systems are: (I) hybrid engine based on hydrogen peroxide/wax propellants and (II) liquid engine based on hydrogen peroxide/hydrocarbon propellants. The structural mass is analyzed mostly on the basis of carbon fiber reinforced materials as well as classical aerospace metallic in small amount. Finally, the paper gives a critical mark for the technical feasibility of small rockets for such missions.","PeriodicalId":272869,"journal":{"name":"International Conference on Recent Advances in Space Technologies, 2003. RAST '03. Proceedings of","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115642674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Swarm - a constellation to study the dynamics of the Earth's magnetic field and its interactions with the Earth system","authors":"P. L. Thomsen, F. Hansen, N. Olsen, E. Christensen","doi":"10.1109/RAST.2003.1303906","DOIUrl":"https://doi.org/10.1109/RAST.2003.1303906","url":null,"abstract":"The objective of the swarm mission is to provide the best survey ever of the geomagnetic field and its temporal evolution, enabling a better look at the global dynamics of the fluid core. Magnetic fields play an important role in physical processes, throughout the Universe. The magnetic field measurement at or near the surface of the Earth is the superposition of contributions from a variety of sources, the fluid core, the magnetisation of rocks in the Earth's crust, electric currents induced in the Earth by the time variations of the field, and electric currents induced by the oceanic circulation. The scientific challenge is the sophisticated separation of these various sources and the accurate determination of the spatial and temporal structure of them all. The swarm concept consists of a constellation of four satellites in two different polar orbits between 400 and 550 Km altitude. Each satellite provides high-precision and high-resolution measurements of the vector magnetic field. In combination, they provide the necessary observations for the global high-precision survey of the geomagnetic field that is needed to model the various sources of the geomagnetic field. A few additional instruments like GPS receivers, an accelerometer, and an electric field instrument provide supplementary information for studying the interaction of the magnetic field with other physical quantities describing the Earth system.","PeriodicalId":272869,"journal":{"name":"International Conference on Recent Advances in Space Technologies, 2003. RAST '03. Proceedings of","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116862261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental evidences of pre-seismic effects in the Earth's ionosphere as a reason for neutral density and temperature measurements onboard microsatellites","authors":"L. Bankov, A. Vassileva","doi":"10.1109/RAST.2003.1303969","DOIUrl":"https://doi.org/10.1109/RAST.2003.1303969","url":null,"abstract":"Complexity of the seismic activity requires a wide number of control parameters to be used from ground-based and orbital observations to examine ionosphere-thermosphere-lithosphere coupling processes. At present, it is commonly accepted that some of the processes addressed to the ionospheric plasma response of the seismic activity include electromagnetic ULF/VLF emissions, ion density irregularities, ion drift velocity and ion composition changes, night time airglow emissions, stimulated high energy particle precipitation etc. In the present paper, experimental data from the Neutral Atmospheric Composition Spectrometer (NACS) onboard Dynamics Explorer-B (DE-B) satellite are used. In a selected case, we have observed increased neutral He concentration at 830 km altitude, preceding Guam earthquake at 0605UT on 4 January 1982 with M=6.1 magnitude of the main shock. At the maximum of the He enhancement, He density is of about 55% higher than the observed mean value over the same latitudes from the few lateral orbits before and after the earthquake. A possible explanation of such an enhancement of He is addressed to some increase of the exospheric temperature over the earthquake zone. The existence of strong geomagnetic field control to the ionospheric seismic effects could be a serious problem when we are interested of local effects over the earthquake epicentre. As an example, electromagnetic emissions associated with seismic activity often registered in a broad area around the epicentre could be observed at distant conjugate regions along the geomagnetic field line. Under the same reason, ionospheric plasma density or temperature perturbations due to Earth's seismic activity could be observed far from the earthquake epicentre. In this sense, we suggest in situ satellite measurements of the neutral composition and temperature near/and above the F-peak to be used as a new opportunity in search of additional sensitive key parameters to examine the seismic effects in the preparatory phase of a certain earthquake. It is obvious that combined ionospheric plasma and neutral gas measurements carried out onboard the satellite enlarge significantly investigation opportunities of the microsatellite platform.","PeriodicalId":272869,"journal":{"name":"International Conference on Recent Advances in Space Technologies, 2003. RAST '03. Proceedings of","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126858220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"State space method for reducing phase fluctuations for the radio waves travelling through the ionosphere at 26 MHz","authors":"A. Okatan","doi":"10.1109/RAST.2003.1303990","DOIUrl":"https://doi.org/10.1109/RAST.2003.1303990","url":null,"abstract":"In this work one of the most important problems in the radio astronomy has been attacked. In radio astronomy antenna arrays are used with very long baselines in order to obtain good angular resolutions. For the baseline of 3000 km the two element array gives an effect of a parabolic antenna as if it has 3000 km radius. The antennas see different parts of the Ionosphere because of the large distance between the antennas. These different regions seen by the two antennas have different random dynamic structures with a small correlation of these dynamic time varying structures. These different changes in two different regions of the Ionosphere cause different random phase changes of received waves by the antennas. The effects are large for the frequencies at 26 MHz regions. The observations are important at this frequency region for different reasons. Because of the random phase fluctuations of the received waves, random phase drifts of the local oscillators and the limited observation time, the correlation between the signals obtained from the receivers is below the detection level. Therefore, detection becomes even impossible. In this work, the differential ionospheric phase error is modeled as quasi-sinusoidal exponential phase because of the periodic structure of ionospheric irregularity blobs. The differential oscillator drift is modeled as a linear change with a random slope. Finally, the total differential phase error is expressed as a matrix equation with approximate parameters. Applying the recursive Kalman Filter algorithm to the matrix equation the true phase is estimated. With the new phase, the correlation function is reconstructed. This process improved the S/N ratio in great extends. The method has been applied to the radio star 3C144 and very good results have been obtained. Because of improvements in the processing speeds of the computers lately, the method seems to be valuable.","PeriodicalId":272869,"journal":{"name":"International Conference on Recent Advances in Space Technologies, 2003. RAST '03. Proceedings of","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122309147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Target detection accuracy improvement in synthetic aperture radar","authors":"S. Kargin, M. Kartal, S. Kurnaz","doi":"10.1109/RAST.2003.1304000","DOIUrl":"https://doi.org/10.1109/RAST.2003.1304000","url":null,"abstract":"This paper proposes a decision method to improve the target identification accuracy in a synthetic aperture radar processing algorithm. In the imaging algorithm, Fourier based processing algorithm is used to obtain the processed image from the measured 2D cartesian backscattered frequency domain data. In practical applications, the measured data is limited in frequency band and aspect angle interval and this leads to radar images with limited resolution. Besides, the noise in measured data affects the target identification accuracy. In this paper, a decision rule is proposed to improve the target identification accuracy by comparing the processed image with the images in the data bank. With the decision rule, one can assign a well known target distribution to the processed image. In this work, the effects of noise, frequency and aspect angle limitation in the decision accuracy are investigated and the results are presented.","PeriodicalId":272869,"journal":{"name":"International Conference on Recent Advances in Space Technologies, 2003. RAST '03. Proceedings of","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122393160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Researches on the influence of vibration on the stability of fuel-water in flying apparatus","authors":"R. A. Ashrafov","doi":"10.1109/RAST.2003.1303982","DOIUrl":"https://doi.org/10.1109/RAST.2003.1303982","url":null,"abstract":"During the researches on the influence of vibratkavition on the stability of fuel-water in flying apparatus it was defined that vibratkavition fuel system does not exist constantly, but in some working regimes of separate units (aggregates). However, vibration is the constantly acting factor functioning in the fuel system in connection with it, practical and scientific interest puts forward the researches of power of vibration influence of the system of fuel-water. The influence of vibration on the condition of the fuel occurs in complicated interferential mutual influence of waves spreading in the capacity of fuel. They are directed from the lower parts of the tank to the upper parts of phases of fuel-air. In this case initial waves in the process of spreading come into contact with the waves moving away from the upper parts of phases. At the result of it thermodynamically condition of fuel changes to some extent in the tank.","PeriodicalId":272869,"journal":{"name":"International Conference on Recent Advances in Space Technologies, 2003. RAST '03. Proceedings of","volume":"2 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114134356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}