2007 IEEE Aerospace Conference最新文献

{"title":"Applications of MIMO Technique for Aerospace Remote Sensing","authors":"Wenqin Wang","doi":"10.1109/AERO.2007.353075","DOIUrl":"https://doi.org/10.1109/AERO.2007.353075","url":null,"abstract":"Inspired by recent advances in multiple-input multiple-output (MIMO) radar, this paper introduces the MIMO synthetic aperture radar (SAR) concept. This concept differs substantially from current SARs in which closely spaced antenna arrays are used. With closely spaced antenna elements, it is possible to coherent a beam toward a direction in space and to realize a coherent processing gain. However, these systems are prone to severe target fading, and hence they may suffer considerable performance degradation. The fundamental difference between MIMO SAR and other SAR is that the latter seek to maximize the coherent processing gain, while MIMO SAR capitalizes on the diversity of target scattering to improve radar performance. The superiority of MIMO SAR in many aspects over the conventional SAR, e.g., high resolution, good sensitivity, and countermining target fluctuations is investigated. It is shown that, the use of MIMO SAR leads to solutions that previously thought to be out of reach for remote sensing scientists and customers.","PeriodicalId":6295,"journal":{"name":"2007 IEEE Aerospace Conference","volume":"11 1","pages":"1-10"},"PeriodicalIF":0.0,"publicationDate":"2007-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79285408","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":"A Novel Leader-Follower Framework for Control of Helicopter Formation","authors":"M. Saffarian, F. Fahimi","doi":"10.1109/AERO.2007.352757","DOIUrl":"https://doi.org/10.1109/AERO.2007.352757","url":null,"abstract":"A framework for formation control of a group of autonomous helicopters is presented. We introduced two control schemes named as I - alpha and I - I, which are tailored to control the relative positions of a helicopter constrained by either one or two neighboring leaders, respectively. To stabilize the internal formation parameters of these schemes, a nonlinear model predictive controller is developed. The controller finds the future control commands by optimizing a cost function, which includes formation parameter errors among other parameters such as control forces. The gradient descent method is considered as a suitable optimizer candidate for our approach. The design steps of the I - I controller is presented in this work. By designing both the two l - alpha and I - I control schemes, any user-defined three dimensional grid pattern could be achieved by a group of autonomous helicopters.","PeriodicalId":6295,"journal":{"name":"2007 IEEE Aerospace Conference","volume":"11 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2007-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84256908","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 Quantifying Cost-Benefit of ISHM in Aerospace Systems","authors":"C. Hoyle, A. Mehr, I. Turner, W. Chen","doi":"10.1109/AERO.2007.352945","DOIUrl":"https://doi.org/10.1109/AERO.2007.352945","url":null,"abstract":"Integrated systems health management (ISHM) is a desired system engineering capability to detect, assess, and isolate faults in complex aerospace systems to improve safety and reliability. At the conceptual design level, system-level engineers must make decisions regarding the extent of vehicle fault coverage using on-board sensors and the data collection, processing, interpretation, display, and action capabilities for the various subsystems, all considered essential parts of ISHM. In this paper, we propose a Cost-Benefit Analysis approach to initiate the ISHM design process. The key to this analysis is the formulation of an objective function that explicitly quantifies the cost-benefit factors involved with using ISHM technology in various subsystems. In the end, to determine the best ISHM system configuration, an objective is formulated, referred to as Profit, which is expressed as the product of system availability (A) and revenue per unit availability (R), minus the sum of cost of detection (CD) and cost of risk (CR). Cost of detection includes the cost of periodic inspection/maintenance and the cost of including ISHM; Cost of Risk quantifies risk in financial terms as a function of the consequential cost of a fault and the probabilities of occurrence and detection. Increasing the ISHM footprint will generally lower cost of risk while raising cost of detection, while Availability will increase or decrease based upon the balance of the reliability and detectability of the sensors added, versus their ability to reduce total maintenance time. The analysis is conducted at the system functional level, with ISHM allocated to functional blocks in the optimization analysis. The proposed method is demonstrated using a simplified aerospace system design problem resulting in a configuration of sensors which optimizes the cost-benefit of the ISHM system for the given input parameters. In this problem, profit was increased by 11%, inspection interval increased by a factor of 1.5, and cost of risk reduced by a factor of 2.4.","PeriodicalId":6295,"journal":{"name":"2007 IEEE Aerospace Conference","volume":"3 1","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2007-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79505785","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":"An Interferometric Wave Front Sensor for Measuring Post-Coronagraph Errors on Large Optical Telescopes","authors":"J. Wallace, B. Macintosh, M. Shao, R. Bartos, P. Dumont, B. Levine, S. Rao, R. Samuele, C. Shelton","doi":"10.1109/AERO.2007.353078","DOIUrl":"https://doi.org/10.1109/AERO.2007.353078","url":null,"abstract":"The Gemini Planet Imager (GPI) [B.Macintosh et al.], now in the early stages of development, is a ground-based extreme adaptive optics system with an advanced coronagraphic system and integral-field spectrometer. At commissioning in early 2011, it will be deployed on one of the twin eight meter Gemini Telescopes. This powerful instrument, which works at a science wavelength in the near-infrared, will enable the direct detection and characterization of self-luminous Jupiter-class planets from the ground. Semi-static and non-common path wave front errors that are not sensed by the active wave front sensor in the adaptive optics system will lead to a focal plane speckle pattern that will mask exo-planets. The GPI Instrument will incorporate an interferometric wave front sensor, designed and developed at JPL, which will measure these errors. This talk will emphasis this novel sensor and describes how it is used to measure the non-common path amplitude and phase errors in the system that would otherwise limit the achievable contrast. We will describe the system error budget as well as simulations that model the system performance. Finally, we will also discuss the status of our laboratory testbed that is designed to test the fundamental principles of post-coronagraph wave front sensing. This system promises a rich combination of interferometry and large optical systems in support of cutting edge science research.","PeriodicalId":6295,"journal":{"name":"2007 IEEE Aerospace Conference","volume":"1 1","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2007-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79517300","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":"Dynamics of a 3D Rotating Tethered Formation Flying Facing the Earth","authors":"M. Sabatini, G. Palmerini","doi":"10.1109/AERO.2007.352671","DOIUrl":"https://doi.org/10.1109/AERO.2007.352671","url":null,"abstract":"Several on-going studies indicate interest in large, light orbiting structures, shaped like fishnets or webs: along the ropes of the web small spacecraft can move to position and relocate, at will, pieces of hardware devoted to specific missions.12 The presence of hard links adds the advantage of a simpler control strategy to the typical benefits of formation flying. Unfortunately, there is no stable configuration for an orbiting two dimensional web made by light, flexible tethers: in fact it cannot support compression forces caused by the gravity gradient. The proposed solution is to make use of centrifugal forces to pull the net, with a reduced number of simple thrusters located at the tips of the tethers to initially acquire the required spin. A sequence of simulations has been carried out to investigate the dynamic behavior of such a system. The numerical model adopted overlaps simpler elements, each of them given by a tether connecting two extreme bodies which accommodate the spinning thrusters. The combination of these \"diameter-like\" elements provides the web, shaped according to the specific requirements. The net is initially considered as rotating in the orbital plane, which is demonstrated to be the only configuration leading to a stable motion. However, as the earth-facing orientation can be of greater interest for earth observation and telecommunication missions, we have searched for a possible solution to stabilize the web. The solution has been identified by several authors with connecting two additional masses along the orbital radius, in a spinning double-pyramid configuration. Numerical analysis of the proper three dimensional web properties, namely spin rate and boom-to-corner mass ratio, is performed in this paper, showing regions where the structure satisfies the requirements both of earth-pointing accuracy and of shape integrity. Two kinds of motion are analyzed separately: the first one follows the conditions for relative equilibrium of a spinning axisymmetrical rigid body, which requires a non zero angle between the nadir direction and the spin axis; a number of different configurations for the central web have been proposed, highlighting the possible advantages. Stability has been proved also in the second case, namely zero off-nadir angle configurations, even though limited to a simplified orbital environment including the sole gravity gradient action. Extensive plots of the stable regions, considered as a useful baseline for more detailed mission design, are reported.","PeriodicalId":6295,"journal":{"name":"2007 IEEE Aerospace Conference","volume":"96 1","pages":"1-12"},"PeriodicalIF":0.0,"publicationDate":"2007-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85264745","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":"Frequency Synthesis Approach to Determine Spacecraft Angular Position with Sub-nanoradian Accuracy","authors":"D. Bagri","doi":"10.1109/AERO.2007.353036","DOIUrl":"https://doi.org/10.1109/AERO.2007.353036","url":null,"abstract":"This paper describes a possible approach to measuring angular position of a spacecraft with reference to a nearby calibration source (quasar) with an accuracy of a few tenths of a nanoradian using a very long baseline interferometer that measures the interferometer phase with a modest accuracy. It employs (1) radio frequency (RF) phase delay to determine the spacecraft position with a high precision, and (2) multiple group delay measurements using either frequency tones or telemetry signals at different frequency spacing to resolve ambiguity of the fringe (cycle) containing the direction of the spacecraft.","PeriodicalId":6295,"journal":{"name":"2007 IEEE Aerospace Conference","volume":"6 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2007-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82392197","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":"Space-Based Voice over IP Networks","authors":"S. Nguyen, C. Okino, L. Clare, W. Walsh","doi":"10.1109/AERO.2007.352904","DOIUrl":"https://doi.org/10.1109/AERO.2007.352904","url":null,"abstract":"In human space exploration missions, there will be a need to provide voice communications services. In this work we focus on the performance of Voice over IP (VoIP) techniques applied to space networks, where long range latencies, simplex links, and significant bit error rates occur. Link layer and network layer overhead issues are examined. We posit that imposing additional speech processing latencies in the form of multiple frames per packet is tolerable in the space regime, and show resulting performance overhead improvements. Furthermore, we find that even with channel bit error rates of 10-5 and 10-4, the frame size does not severely degrade the original speech.","PeriodicalId":6295,"journal":{"name":"2007 IEEE Aerospace Conference","volume":"17 1","pages":"1-11"},"PeriodicalIF":0.0,"publicationDate":"2007-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82353158","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":"Flower Constellation of Orbiters for Martian Communication","authors":"M. Sanctis, T. Rossi, M. Lucente, M. Ruggieri, D. Mortari, D. Izzo","doi":"10.1109/AERO.2007.352713","DOIUrl":"https://doi.org/10.1109/AERO.2007.352713","url":null,"abstract":"Flower Constellations are a particular set of satellite constellations where every satellite covers the same repeating space track. When the Flower Constellations are visualized on an Earth centered Earth fixed reference frame, the relative orbits show flower-shaped figures centered on the Earth. This innovative type of constellation presents features useful to be used in several applications, such as telecommunications, navigation, Earth science and interferometric radar. Several missions are foreseen to explore Mars in the next years to collect data in order to enhance our knowledge of the red planet. This effort requires the development of a reliable orbital infrastructure to support telecommunications with orbiters, landers and rovers. In this paper, a novel telecommunication architecture is presented, based on the previously introduced Flower Constellations. We designed an optimized Flower Constellation for the coverage of sites/regions of interest of the Mars surface. We proved that our proposed constellation provides better performance with respect to a reference constellation called 4retro 111 in terms of access duration and average gap time.","PeriodicalId":6295,"journal":{"name":"2007 IEEE Aerospace Conference","volume":"101 1","pages":"1-11"},"PeriodicalIF":0.0,"publicationDate":"2007-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82396128","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":"Electro-Optic Imaging Fourier Transform Spectrometer","authors":"T. Chao","doi":"10.1109/AERO.2007.353011","DOIUrl":"https://doi.org/10.1109/AERO.2007.353011","url":null,"abstract":"JPL is developing an innovative compact, low mass, electro-optic imaging Fourier transform spectrometer (E-O IFTS) for hyperspectral imaging applications. The spectral region of this spectrometer will be 1-2.5 mum (1000 - 4000 cm-1) to allow high-resolution, high-speed hyperspectral imaging applications. The specific applications for NASA's missions will focus on the measurement of a large number of different atmospheric gases simultaneously in the same airmass. Due to the use of a combination of birefringent phase retarders and multiple achromatic phase switches to achieve phase delay, this spectrometer is capable of hyperspectral measurements similar to that of the conventional Fourier transform spectrometer but without any moving parts. In this paper, the principle of operations, system architecture and recent experimental progress were presented.","PeriodicalId":6295,"journal":{"name":"2007 IEEE Aerospace Conference","volume":"30 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2007-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81027741","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":"Trajectory Comparison for Civil Aircraft","authors":"O. Baud, Y. El-Bied, N. Honore, O. Taupin","doi":"10.1109/AERO.2007.353090","DOIUrl":"https://doi.org/10.1109/AERO.2007.353090","url":null,"abstract":"This paper investigates the algorithms needed to compare two tracker outputs running on the same air situation trajectories. Tracking system provides aircraft trajectories containing aircraft kinematics supplemented with additional data. Tracker accuracy performance as well as tracker data output integrity and continuity is essential for controllers and safety nets applications, which guarantee a high safety level. The comparison procedure described in this paper provides tracking performance, automatic detection of tracking anomalies and is performed by considering a tested tracker and a reference. The reference is given by another tracker or a set of trajectories given by a sensor simulator. Results based on live data and simulation scenarios are presented. This method is used for mutual validation between two different types of tracker, perform some regression testing between two releases of the same tracker or assess the tracking performances using a sensor simulator.","PeriodicalId":6295,"journal":{"name":"2007 IEEE Aerospace Conference","volume":"27 1","pages":"1-9"},"PeriodicalIF":0.0,"publicationDate":"2007-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82827901","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}