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1
Anderson, Jason Lionel. "Autonomous Satellite Operations For CubeSat Satellites." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/256.
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In the world of educational satellites, student teams manually conduct operations daily, sending commands and collecting downlinked data. Educational satellites typically travel in a Low Earth Orbit allowing line of sight communication for approximately thirty minutes each day. This is manageable for student teams as the required manpower is minimal. The international Global Educational Network for Satellite Operations (GENSO), however, promises satellite contact upwards of sixteen hours per day by connecting earth stations all over the world through the Internet. This dramatic increase in satellite communication time is unreasonable for student teams to conduct manual operations and alternatives must be explored. This thesis first introduces a framework for developing different Artificial Intelligences to conduct autonomous satellite operations for CubeSat satellites. Three different implementations are then compared using Cal Poly's CP6 CubeSat and the University of Tokyo's XI-IV CubeSat to determine which method is most effective.
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Appleby, Graham M. "Satellite laser ranging and the ETALON Geodetic satellites." Thesis, Aston University, 1996. http://publications.aston.ac.uk/13270/.
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The technique of Satellite Laser Ranging is today a mature, important tool with applications in many area of geodynamics, geodesy and satellite dynamics. A global network of some 40 stations regularly obtains range observations with sub-cm precision to more than twelve orbiting spacecraft. At such levels of precision it is important to minimise potential sources of range bias in the observations, and part of the thesis is a study of subtle effects caused by the extended nature of the arrays of retro-reflectors on the satellites. We develop models that give a precise correction of the range measurements to the centres of mass of the geodetic satellites Lageos and Etalon, appropriate to a variety of different ranging systems, and use the Etalon values, which were not determined during pre-launch tests, in an extended orbital analysis. We have fitted continuous 2.5 year orbits to range observations of the Etalons from the global network of stations, and analysed the results by mapping the range residuals from these orbits into equivalent corrections to orbital elements over short time intervals. From these residuals we have detected and studied large un-modelled along-track accelerations associated with periods during which the satellites are undergoing eclipse by the Earth's shadow. We also find that the eccentricity residuals are significantly different for the two satellites, with Etalon-2 undergoing a year-long eccentricity anomaly similar in character to that experienced at intervals by Lageos-1. The nodal residuals show that the satellites define a very stable reference frame for Earth rotation determination, with very little drift-off during the 2.5 year period. We show that an analysis of more than about eight years of tracking data would be required to derive a significant value for 2. The reference frame defined by the station coordinates derived from the analyses shows very good agreement with that of ITRF93.
3
Sharifi, Mohammad A. "Satellite gradiometry using a satellite pair." [S.l. : s.n.], 2004. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11406716.
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Score, Robert H. "An examination of XM satellite subscriber's perceptions of satellite radio compared to traditional AM/FM radio." Instructions for remote access. Click here to access this electronic resource. Access available to Kutztown University faculty, staff, and students only, 2002. http://www.kutztown.edu/library/services/remote_access.asp.
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Thesis (M.S.)--Kutztown University of Pennsylvania, 2002.<br>Source: Masters Abstracts International, Volume: 45-06, page: 2720. Typescript. Abstract precedes thesis as preliminary leaves 1-2. Includes bibliographical references (leaves 34-35).
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Morimoto, Todd A., Thomas E. Nowitzky, and Steven A. Grippando. "OPERATING A LIGHTWEIGHT, EXPENSIVE LOW EARTH ORBITING SATELLITE." International Foundation for Telemetering, 1994. http://hdl.handle.net/10150/608842.
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International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California<br>An increasing number of satellite users and manufacturers are looking to lightweight,
inexpensive satellites as substitutes to traditional large, expensive satellites with
multiple payloads. Neither the Department of Defense nor the commercial sector can
bear the financial or reputational consequences associated with massive program
failures. With the low cost and weight of these new satellites, users can achieve
mission success without great risk. One example of this new class of inexpensive
spacecraft is the RADCAL (RADar CALibration) satellite. Detachment 2, Space &
Missile Systems Center at Sunnyvale, CA operates the satellite. RADCAL is a
200-pound polar orbiting satellite with an average altitude of 450 miles. It is primarily
used by 77 worldwide radars to calibrate their systems to within five meter accuracy.
Also flying on board RADCAL is a communication payload for remote field users
with small radios. The RADCAL program has satisfied all mission requirements.
However, with the limited size and cost come certain challenges, both in the satellite
and on the ground. Pre-launch testing was not as comprehensive as with more
expensive programs; anomalies have arisen that require extensive workarounds. Data
management is not a straightforward task, and it is sometimes difficult and inexact to
track satellite performance. These challenges are presented with their solutions in the
following discussion; this paper addresses the functional, operational, and testing
aspects associated with the RADCAL satellite.
6
Zaheer, Muhammad. "Kinematic orbit determination of low Earth orbiting satellites, using satellite-to-satellite tracking data and comparison of results with different propagators." Thesis, KTH, Geodesi och geoinformatik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-142627.
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The GPS data from Challenging Mini-satellite Payload (CHAMP) is used for its orbit determination for the epoch day of January 1st 2002. The orbit of CHAMP is computed from the GPS data and ionospheric effects are removed by frequency combination. Further, the orbits of CHAMP for the same epoch day are computed using the satellite tool kit (STK) employing simplified general perturbations (SGP4) and a high precision orbit propagator (HPOP). Results from both techniques (GPS computed orbit and STK computed orbit) are compared. Furthermore, orbits computed using GPS data are also compared with jet propulsion laboratory’s published CHAMP spacecraft orbit and we have found that root mean square difference in ECEF position X component is below 0.01km other than some spikes at poles. The standard deviation of the difference in ECEF position X coordinate is 11.7m. The accuracy of our computed satellite positions (using GPS data) is about 12 metres for other than polar areas. However there are some occasional spikes, especially at poles, having maximum errors (about 0.055 km).
7
Xi, Xiaojin. "Analytical representation for ephemeris with short time-span : application to the longitude of Titan." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEO015/document.
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Les éphémérides issues d'intégrations numériques qui peuvent être facilement téléchargées des sites de l'IMCCE ou du JPL, ont une très bonne précision pour les observations récentes. En même temps, un autre type d'éphémérides, celles analytiques comme TASS, décrivent en détail le système dynamique par une représentation en combinaison de fréquences propres. Notre but est d'associer ces deux types d'éphémérides pour l'utiliser dans les études de la rotation des satellites naturelles. Cela signifie qu'il faut reconstruire des éphémérides à long terme et de haute précision montrant les caractéristiques du système comme les fréquences propres à partir des intégrations numériques. La principale difficulté est d'éviter l'intervalle de temps limité des éphémérides numériques. Dans notre travail, nous partons de la représentation des éléments d'orbite de Titan sur 10 000 ans issues de TASS comme exemple et comme standard. Nous expérimentons comment obtenir les fréquences propres sur 1000 ans d'éphémérides de TASS, et comment obtenir la représentation analytique de la longitude moyenne de Titan sur cet intervalle limité. A cause de cette durée de 1000 ans, au lieu de l'analyse en fréquence, nous utilisons la méthode des moindres carrées, en particulier pour les termes à longue période. L'efficacité et l’exactitude de l'ensemble de la méthode sont vérifiées en comparant les représentations de la longitude moyenne de Titan issue de TASS par la méthode des moindres carrées et par la représentation standard de TASS sur 10 000 ans. Finalement et c'est ce qui importe, nous obtenons une représentation du mouvement de Titan pour les 1000 ans d'éphémérides du JPL. Il existe une différence de 60 km dans l'amplitude du terme principal entre les représentations du JPL et de TASS. Cette différence est considérée comme issue du système. L'intervalle de temps limité des éphémérides influence les fréquences propres et induit des erreurs dans les termes à longues périodes comme contenant la longitude du nœud de Titan. Pour toutes les autres composantes ou presque, leurs amplitudes et phases sont similaires à celles de TASS. L'erreur de représentation est inférieure à 100 km sur 1000 ans et la déviation standard est de 26 km environ<br>The numerical integration ephemeris, which are convenient to download from online service of IMCCE, or Horizons of JPL have very good precision based on recent observations. Meanwhile, another kind, the analytical ephemeris like TASS, describes in detail the dynamical system by combination representation of proper frequencies. We plan to make a connection between those two different type ephemeris, that it ’s benefited us to study the rotation of natural satellites with its high precision ephemeris, those instantaneous positions, velocity, and those system characteristics like proper frequencies. The main difficulty is to avoid the shortcoming of the limited interval of observation ephemeris.In our work, we take the combination representation of Titan with 10,000 years TASS ephemeris as an example and standard. Then, we experiment to obtain both the analytical representation of the mean longitude of Titan and the proper frequencies involved in it with 1,000 years TASS ephemeris by analysis frequency. Due to limited timespan, we extend the method with a least square method, especially for the long period terms. We verify the effectiveness and exactness of the whole method in rebuilt the combination representation.Finally and most important, we get the combination representation of Titan with 1000 years JPL ephemeris. Between the solution of JPL and the representation of TASS, there exists a 60 km difference in the amplitude of the major component, that is considered as a system difference. The limited interval ephemeris makes the influence of the proper frequency, which brings the error into the long period term like the one from the node of Titan. For nearly all other components, those amplitudes and phases are similar with the relative terms of TASS. The error of our representation is less than 100 kilometres over 1,000 years and the standard deviation is about 26 kilometres
8
Wolf, Robert. "Satellite orbit and ephemeris determination using inter satellite links." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=961611820.
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Bezuidenhout, Quintus. "Satellite communications strategy selection for optimal LEO satellite communication." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71930.
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Thesis (MScEng)--Stellenbosch University, 2012.<br>ENGLISH ABSTRACT: A low earth orbit satellite system can be useful in numerous communication applications
where physical connections are not possible. Communication time available from any point on
earth to the satellite is less than one hour per day. This one hour is fragmented into smaller
time slots due to the satellite orbiting. This is not much time to transfer data and there is
even less time available to transfer data when there are other external factors affecting the
system. It is thus crucial to optimise the satellite communications link so that more data can
be transferred per orbit.
The goal of this thesis is to improve the performance of a low earth orbit satellite communication
channel by varying certain parameters of the system, such as the protocol used,
modulation scheme, packet size, transmission power etc. and then to observe how these
parameters influence the system. The protocols that were chosen to be implemented are
CSMA-CA, CSMA-CA with DSSS technology and Round-Robin Polling.
A simulator for each protocol was designed with the Opnet platform, so that specific parameters
could be changed and the results observed, in order to optimise the communications link
between the satellite and ground stations.
The results showed that there is no particular configuration of modulation scheme, packet
size, transmission power etc. presenting the best overall solution for LEO satellite communications.
It must be considered what the specific LEO satellite application would be used for and
the characteristics required by that specific application. A suitable configuration must subsequently
be chosen from the set of configurations available to satisfy most of the application
requirements.<br>AFRIKAANSE OPSOMMING: ’n Satelliet met ’n lae wentelbaan kan gebruik word in verskeie kommunikasie toepassings
waar fisiese verbindinge nie noodwendig moontlik is nie. Die kommunikasietyd van enige
punt van aarde af na die satelliet, is minder as een uur per dag. Hierdie tyd word nog verder
verklein omdat die satelliet besig is om, om die aarde te wentel. ’n Uur is glad nie baie tyd
om data oor te dra nie en in realiteit is daar nog minder tyd beskikbaar as daar eksterne
faktore op die sisteem inwerk. Dus is dit baie belangrik om die satelliet kommunikasiekanaal
te optimiseer sodat soveel moontlik data as moontlik oorgedra kan word per omwenteling.
Die doel van hierdie tesis is om die deurset van die kommunikasiekanaal van n lae wentelbaan
satelliet te optimiseer, deur verskeie parameters te verander soos, protokol wat gebruik word,
modulasie skema, pakkie grootte, transmissiekrag ens. en dan waar te neem hoe dit die
sisteem beïnvloed. Die protokolle wat geïmplementeer is, is CSMA-CA, CSMA-CA met DSSS
tegnologie en Round-Robin Polling.
’n Simulator vir elke protokol was ontwerp in die Opnet simulasie platform, sodat die spesifieke
parameters verander kon word om die resultate te bestudeer met die doel om die kommunikasiekanaal
tussen die satelliet en grond stasies optimaal te benut.
Die resultate het bewys dat daar geen spesifieke konfigurasie van modulasie skema, pakkie
grootte, transmissiekrag ens. is wat die algehele beste oplossing is nie. Die spesifieke applikasie
waarvoor die lae wentelbaan satelliet gaan gebruik word moet geanaliseer word sowel
as die spesifieke karakteristieke van daai applikasie. Daarvolgens moet n unieke konfigurasie
opgestel word wat meeste van die applikasie se behoeftes bevredig.
10
Sharifi, Mohammad A. "Satellite to satellite tracking in the space-wise approach." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-28337.
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Hayes, Christopher. "Analyzing the performance of new TCP extensions over satellite links." Ohio : Ohio University, 1997. http://www.ohiolink.edu/etd/view.cgi?ohiou1177439390.
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Hutzell, William T. "The variations in the geometric albedo of Titan." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/28054.
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Paffett, John. "VHF band interference measurement, analysis and avoidance." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/2105/.
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Albanes, Stalin F. "1.2 GHz and 2.4 GHz LEO satellite communications." Thesis, Queensland University of Technology, 1995. https://eprints.qut.edu.au/35994/1/35994_Albanes_1995.pdf.
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This report outlines the steps taken to design and develop a 1.2 GHz and 2.4 GHz
LEO satellite communication facility at the QUT satellite ground station to allow
experimentation and communication links with low earth orbiting (LEO) satellites.
The design, setup, construction, testing and installation of the antenna system
required by the QUT satellite ground station to operate in the 1.2 GHz and 2.4 GHz
frequency bands are described.
Existing ground station capabilities and limitations were studied and a complete
operational satellite station is suggested for the future to further perform telemetry,
tracking and command control. Upgrading the ground station to 1.2 and 2.4 GHz
will enable QUT to proceed with investigations and trials on other space related
projects.
15
Borgsmiller, Scott A. "Effects of atmospheric scintillation in K[a]-band satellite communications." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/14982.
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Chintalapati, Lakshmi Venkata Bharadwaj. "Integration of Mission Control System, On-board Computer Core and spacecraft Simulator for a Satellite Test Bench." Master's thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-212663.
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The satellite avionics platform has been developed in cooperation with Airbus and is called „Future Low-cost Platform“ (FLP). It is based on an Onboard Computer (OBC) with redundant processor boards based on SPARC V8 microchips of type Cobham Aeroflex UT699. At the University of Stuttgart a test bench with a real hardware OBC and a fully simulated satellite is available for testing real flight scenarios with the Onboard Software (OBSW) running on representative hardware. The test bench as later the real flying satellite "Flying Laptop" – is commanded from a real Ground Control Centre (GCC). The main challenges in the FLP project were
- Onboard computer design,
- Software design and
- Interfaces between platform and payloads
In the course of industrialization of this FLP platform technology for later use in satellite constellations, Airbus has started to set up an in-house test bench where all the technologies shall be developed. The initial plan is to get first core elements of the FLP OBSW ported to the new dual-core processor and the new Space Wire(SpW) routing network. The plan also has an inclusion of new Mission Control Software with which one can command the OBC. The new OBC has a dual core processor Cobham Gaisler GR712 and hence, all the payload and related functionality are to be implemented only in a second core which involves a lot of low-level task distribution. The consequent SpW router network application and dual-core platform/payload OBSW sharing are entirely new in the field of satellite engineering.
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Manzoni, Vieira Fábio. "Fusion de données AIS et radar pour la surveillance maritime." Thesis, Toulouse, ISAE, 2017. http://www.theses.fr/2017ESAE0034/document.
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Dans le domaine de la surveillance maritime, les systèmes coopératifs d’identification et de positionnements tels que l’AIS (Automatic Identification System) sont souvent couplés à des systèmes d’observation de navires non coopératifs comme les Radars à Synthèse d’Ouverture (RSO). Dans ce contexte, la fusion des données AIS et Radar peut améliorer la détection de certains navires et d’identifier éventuels scénarii de surveillance. Le premier chapitre introduit les systèmes et détaille la structure des données AIS et Radar ainsi que le traitement du signal utilisé. Le deuxième chapitre présente l’apport potentiel de l’utilisation conjointe des données brutes Radar et AIS pour la détection de navires à l’aide d’un test basé sur le rapport des vraisemblances maximales (test GLRT). Bien que les performances soient encourageantes, la mise en pratique du détecteur en temps-réel semble compliquée. Le troisième chapitre présente une alternative sous-optimale qui explore les données brutes Radar et une carte des positions de bateaux provenant de l’AIS. Contrairement au chapitre deux, en plus de la détection simultanée par l’AIS et radar, les cas où seul l’un des systèmes détecte un objet peuvent maintenant être distinguées. Le problème est formalisé par deux tests d’hypothèses binaires successifs. Le test proposé est moins sensible à la proximité et à la densité des navires qu’un détecteur radar classique. Le quatrième chapitre présente le simulateur développé pour tester les algorithmes sur différents scénarii de surveillance, à savoir un scénario de piraterie sur un navire civil, un transbordement illégal et une navigation dans un environnement dense<br>In the maritime surveillance domain, cooperative identification and positioning systems such as AIS (Automatic Identification System) are often coupled with non-cooperative systems for ship observation such as Synthetic Aperture Radar (SAR). In this context, the fusion of AIS and Radar data can improve the detection of certain vessels and possible identify some maritime surveillance scenarios. The first chapter introduces both AIS and Radar systems, details the data structure as well as the related signal processing. The second chapter presents the potential contribution of the joint use of raw Radar and AIS data for the detection of vessels using a generalized likelihood ratio test (GLRT). Although the performance is encouraging, in practice the implementation in real-time of the detector seems complicated. As alternative, the third chapter presents a suboptimal detection method that explores Radar raw data and a positioning map of vessels obtained from the AIS system. Differently from chapter two, in addition to the simultaneous detection by both AIS and radar, the cases where only one of the systems detects an object can now be distinguished. The problem is formalized by two successive binary hypotheses test. The results suggests that the proposed detector is less sensitive to the proximity and density of ships than a conventional radar detector. The fourth chapter presents the simulator developed to test the algorithms on different surveillance scenarios, namely a civilian ship piracy scenario, an illegal cargo transhipment and a scenario of navigation in a dense environment
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Gremont, Boris Christian. "Fade countermeasure modelling for Ka band digital satellite links." Thesis, Coventry University, 1997. http://curve.coventry.ac.uk/open/items/d85e8a85-635c-d024-3737-d1205f235596/1.
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This thesis investigates the modelling of fade countermeasures (FCMs) for the design of geostationary Ka band digital satellite communication systems. The analysis focuses on a typical low-power low-rate very small aperture terminal application using adaptive forward error correction as a way of counteracting the high level of detected dynamic atmospheric fading. The management and performance of such systems is conditioned greatly by the ability of practical controllers at detecting the actual level of total signal attenuation. At 20 or 30 GHz, rain attenuation and tropospheric scintillation are the two major propagation effects of interest. Part of the solution relies on the consideration and integration of their random and dynamic nature in the design process. The finite response time of practical countermeasure systems is a source of performance degradation which can be minimised by the implementation of predictive control strategies. This is the focal point of this thesis. A novel on-line short-term predictor matched to the Ka band fading process is proposed. While the rain attenuation component is efficiently predicted, tropospheric scintillation is the source of the estimation error. To take this into account, a statistical model, based on an extension of the global fading model for rain and scintillation, is then developed so that long term performance of predictive countermeasures can be drawn. Two possible ways to compensate for scintillation-induced prediction errors, namely the fixed and variable detection margin approaches, are proposed, analysed and then compared. This is achieved by calculating the FCM utilisation factor, as well as the throughput and bit error rate performance of a typical Ka band system in the presence of dynamic fading within the context of predictive fade countermeasure control operations. In the last part of this thesis, the inclusion of instantaneous frequency scaling in the design of efficient FCM control schemes is investigated. This is applicable to systems using fade detection at a base frequency. In particular, a new statistical model, accounting for the impact of the stochastic temporal variations of rain drop size distribution on rain attenuation, is presented. This thesis further confirms that countermeasure systems are technologically viable. The consideration of more specific design problems does not change the overall validity of this statement. In this thesis, it is shown that a predictive FCM technique, based on readily available punctured convolutional codes, with their relatively modest coding gain, is sufficient to provide high link availability and user data throughput on a low-power low-rate in-bound VSAT link.
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Paul, Jean R. "Communication platform for inter-satellite links in distributed satellite systems." Thesis, University of Surrey, 2011. http://epubs.surrey.ac.uk/770149/.
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A Distributed Satellite System (DSS) for space weather monitoring, in which satellites are able to exchange data via Inter-Satellite Links (lSL) and a master node communicates with ground is the target of this research. As design of satellite systems is dictated by economical and engineering factors, the use of readily available commercial wireless terrestrial network technologies for ISLs is an attractive prospect in distributed satellite systems. This work addresses the application of wireless terrestrial networking standards to DSS operating in Low Earth Orbits (LEO), which are affected by orbital dynamics. All communication factors such as range, antenna gain, velocity, etc. vary with time, and as a result adaptive on-board data processing and transmission techniques are necessary to provide system responsiveness to orbital effects. A novel analysis of the impact of satellite attitude on the antenna loss is carried out and the minimum beam width that ensures ISL is determined. A high performance System-On-Chip (SoC) computing platform capable of supporting the adaptive MAC method has been simulated, and then implemented on hardware. The SoC design features a IEEE802.11 wireless transceiver core developed to support ISL, which is controlled by a software application running on the LEON3 32-bit RISC processor. The SOC is implemented on an FPGA for dynamic reconfigurability purposes, and the wireless transceiver is designed with the aim of extending the communication range of traditional wireless networks to hundreds of kilometres. The range determination mechanism can be hard-coded or defined in software. The Space Wire protocol, which is becoming the de facto standard for on-board spacecraft networks, is not yet defined for wireless communications. A bridge is proposed allowing fault-tolerant intra-spacecraft Space Wire networks to communicate via inter-satellite links. An analysis of the hardware requirements is presented for medium date rate systems. This reveals that the IEEE802.11 transceiver, implemented as a hardware accelerator, has the capability to support the full range of data rate provided by SpaceWire links, and adds extra robustness to SpaceWire networks.
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Bhattarai, S. "Satellite clock time offset prediction in global navigation satellite systems." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1464288/.
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In an operational sense, satellite clock time offset prediction (SCTOP) is a fundamental requirement in global navigation satellite systems (GNSS) tech- nology. SCTOP uncertainty is a significant component of the uncertainty budget of the basic GNSS pseudorange measurements used in standard (i.e not high-precision), single-receiver applications. In real-time, this prediction uncertainty contributes directly to GNSS-based positioning, navigation and timing (PNT) uncertainty. In short, GNSS performance in intrinsically linked to satellite clock predictability. Now, satellite clock predictability is affected by two factors: (i) the clock itself (i.e. the oscillator, the frequency standard etc.) and (ii) the prediction algorithm. This research focuses on aspects of the latter. Using satellite clock data—spanning across several years, corresponding to multiple systems (GPS and GLONASS) and derived from real measurements— this thesis first presents the results of a detailed study into the characteristics of GNSS satellite clocks. This leads onto the development of strategies for modelling and estimating the time-offset of those clocks from system time better, with the final aim of predicting those offsets better. The satellite clock prediction scheme of the International GNSS Service (IGS) is analysed, and the results of this prediction scheme are used to evaluate the performance of new methods developed herein. The research presented in this thesis makes a contribution to knowledge in each of the areas of characterisation, modelling and prediction of GNSS satellite clocks. Regarding characterisation of GNSS satellite clocks, the space-borne clocks of GPS and GLONASS are studied. In terms of frequency stability—and thus predictability—it is generally the case that the GPS clocks out-perform GLONASS clocks at prediction lengths ranging from several minutes up to one day ahead. There are three features in the GPS clocks—linear frequency drift, periodic signals and and complex underlying noise processes—that are not observable in the GLONASS clocks. The standard clock model does not capture these features. This study shows that better prediction accuracy can be obtained by an extension to the standard clock model. The results of the characterisation and modelling study are combined in a Kalman filter framework, set up to output satellite clock predictions at a range of prediction intervals. In this part of the study, only GPS satellite clocks are considered. In most, but not all cases, the developed prediction method out- performs the IGS prediction scheme, by between 10% to 30%. The magnitude of the improvement is mainly dependent upon clock type.
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Gabor, Michael Joseph. "GPS carrier phase ambiguity resolution using satellite-satellite single differences /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Han, Shin-Chan. "Efficient global gravity field determination from satellite-to-satellite tracking." Columbus, Ohio : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1061995200.
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Thesis (Ph. D.)--Ohio State University, 2003.<br>Title from first page of PDF file. Document formatted into pages; contains xvii, 198 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Christopher Jekeli, Dept. of Geodetic Science and Surveying. Includes bibliographical references (p. 192-198).
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Alouini, Mohamed-Slim. "Impact of the atmosphere on K [subscript a]-Band satellite communication systems." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/15364.
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Jasim, Ahmad, Mustafa Mohammed, and Fadi Sabah. "Satellite Communication Channel." Thesis, Linnéuniversitetet, Institutionen för datavetenskap, fysik och matematik, DFM, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-21051.
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Heslop, Louise. "Satellite cell heterogeneity." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395478.
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Gårdebäck, Agnes, and Vincent Haugdahl. "MIST Student Satellite." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-168958.
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In this report, parts of the systems engineering of a spacecraft are presented. In 2014 the Royal Institute of Technology KTH initiated a new space technology and research platform, the KTH Space Centre. The first student project at KTH Space Centre was the MIST student satellite with the scope of the system design and construction of a real satellite due for launch in 2017. As part of the MIST project this bachelor thesis covers the mission analysis and parts of the system design. The system design is confined to the orbit lifetime and attitude perturbation analysis of the spacecraft and a complete analysis of the solar array illumination for the power system. The orbit lifetime was simulated in two different software, AGI’s Satellite Toolkit (STK), and NASA’s Debris Assessment Software (DAS). An approximate lifetime could be calculated from the two separate programs. The perturbation analysis was done by deriving parts of the governing equations of disturbance torques in the orbit. The analysis is confined to aerodynamic, magnetic dipole moment and gravity gradient torques. From these calculations the actuatio strength needed by the attitude control system was determined. The solar array configuration analysis was done by looking at the power generation and illumination of the solar panels in all of the possible flight attitudes. Following a computation of the power requirements a power budget was created and in conjunction with the complete configuration analysis of the solar array the optimal flight attitude was determined. The results of the system design analyses are compiled into a baseline design specification. The report is concluded with a discussion of the future work in the project and the lessons learned from the systems design process.
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Guo, Quan. "Galactic satellite galaxies." Thesis, Durham University, 2013. http://etheses.dur.ac.uk/7354/.
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In this thesis, we investigate the luminosity functions (LFs) and projected number density profiles of galactic satellites around isolated primaries of differing luminosity. To this end, we develop a new method to select isolated galactic satellite systems using the Sloan Digital Sky Survey (SDSS) spectroscopic and photometric galaxy samples. For specific luminosity primaries, we are able to stack as many as ~ 50,000 galaxy systems to obtain robust statisitcal results. Based on these samples, we derive accurate satellite luminosity functions extending almost 8 magnitudes fainter than their primaries and accurate projected number densities profiles of satellites down to 4 magnitudes fainter than their primaries. Then, we determine how the satellite luminosity functions and projected number density profiles vary with both the properties of their satellites and their primaries. In addition, we find that the normalized profiles can be well fitted by the NFW profiles in most cases. The dependence of the NFW concentration parameters on the luminosity of the satellites and their primaries are explored. Inspired by the similar independent study, we also explore the dependence of estimates of satellite luminosity functions on two different background subtraction methods. We then measure these quantities for model satellites placed into the Millennium and Millennium II dark matter simulations by the GALFORM semi-analytic galaxy formation model for different bins of primary galaxy magnitude. We compare our model predictions to the data that we previously measured. The generally successful comparison of the GALFORM model with the SDSS data performed here provides a non-trivial validation of the assumptions and framework of this kind of modelling.
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Blasdel, Arthur N. Jr. "Simulating Satellite Telemetry." International Foundation for Telemetering, 1989. http://hdl.handle.net/10150/614700.
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International Telemetering Conference Proceedings / October 30-November 02, 1989 / Town & Country Hotel & Convention Center, San Diego, California<br>Ford Aerospace Corporation has been investigating the use of intelligent systems to automate space mission support functions since the early 1980's. A product of this research is Paragon, a model-based development environment for intelligent systems. Paragon has been used to develop functional models of satellites that are robust in their abilities to represent satellite behavior. The models have been used to simulate both nominal and anomalous temporal behavior. This paper describes our simulation approach and how the telemetry output from the system can be used during training and rehearsals to provide a closed-loop, interactive response to a wide variety of scenarios.
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Sheriff, Ray E., A. Donner, and A. Vanelli-Coralli. "Satellite Communications [Editorial]." Master's thesis, Hindawi Publishing Corporation, 2007. http://hdl.handle.net/10454/3488.
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Yes<br>We are delighted to bring to you this special issue on satellite
communications, which we have prepared as part of the
spreading of excellence remit of the satellite communications
network of excellence (SatNEx). The SatNEx project,
which began in 2004, is funded for five years under the European
Union¿s Sixth Framework Programme (FP6) Information
Society Technologies (IST) Thematic Area. Led by the
German Aerospace Center, SatNEx brings together a network
of 24 partners, distributed throughout Europe, with membership
drawn from ten countries.
The philosophy underlying the SatNEx approach revolves
around the selection of focused actions under Joint
Programmes of Activities, which are carried out collectively
by the partners and include research, integration, and dissemination
activities. Training represents an important part
of the SatNEx remit and is supported through a number of
initiatives including the hosting of internship projects and an
annual summer school.
The call for papers resulted in a high number of submissions,
from which we have been able to select 12 excellent
papers dealing with the different aspects of satellite communications
and navigation.<br>European Union
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Ruiz-de-Azua, Ortega Joan Adrià. "Contribution to the development of autonomous satellite communications networks : the internet of satellites." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/671780.
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The space is experiencing a revolution due to the em ergence of satellite services to satisfy environmental, socio-econom ic, and geo-political demands. Earth Observation satellite systems have become dependable resources for climate monitoring,
modern agriculture, and other applications. The 5G incursion in the aerospace domain has promoted the satellites as promising platforms to achieve global coverage, and cope the limitations of ground facilities. These demands can be
summarized in two system requirements: (1) increase of data transfer capacity, and (2) decrease of end-to-end
com m unications latency. Distributed Satellite Systems have emerged as an effective solution of m ultiple satellites operating simultaneouslyto satisfycommon requirements. Federated Satellite Systems are serious candidates to exploit the potential of distributed architectures by establishing opportunistic collaborations among satellites to share unallocated resources. These collaborations, called federations, allows to conceive the space as a cloud in which satellites leverage from other resources to improve their performance. The successive investigations have been centered on developing novel federation technologies. However, multiple design aspects are still open fields of study, such as the development of communications capabilities to establish these federations. This dissertation contributes to fill this gap bydefining mechanisms to deploy a network infrastructure for this purpose. A networked environment in which satellites are able to establish sporadically, and opportunisticallyfederations has been discussed. This context is called the Internet of Satellites paradigm, and prometes the temporal deployment of inter-satellite networks, composed of heterogeneous satellites. This feature---with satellite motion--poses a challenge on the definition of end-to-end communications routes composed of intermediate satellites. Areview of current routing protocols from other satellite networks is conducted to identify the ideal protocol for these dynam ic networks. The outcome remarks the need to combine capabilities from different domains to achieve the desired performance. Among them, the capabilityto predict future inter-satellite links becomes crucial to mitigate the fragmentation of the network. With this prem ise in mind, this dissertation presents a predictive protocol that perform s the estimation of these inter-satellite contacts in a distributed manner. This new satellite capability may support the routing protocol by allowing the estimation of future routes as a sequence of satellite contacts over time. The research presented in this dissertation also tackles other questions that remained unanswered: How can satellites be aware of the available resources offered by other satellites? What are the necessary mechanisms to deploy a federation? A software stack with two protocols to deal with this technology gap has been developed. The Opportunistic Service Availability Dissem ination Protocol allows notifying the services that are available in a satellite, while the Federation Deploym ent Control Protocol form alizes the rules to establish and m anage a federation. The application of these protocols considerably enhancded the capabilityof the satellite system to download data, becom ing thus enablers of future satellite m issions. The achieved perform anee has motivated the developm ent of a dedicated system. 11 has been named Federated Satellite Systems Experiment payload, and includes a communications device to create inter-satellite links. This system has been verified in a stratospheric balloon campaign, and integrated in a CubeSat miss ion. This dissertation discusses the results of the campaign, which emphasize the benefits and viabilityof this implementation. We expect that the contributions of this dissertation mayencourage to keep investigating on this inter-satellite communications for satellite federations.<br>L'espai esta experimentant! una revolució degut a l'aparició de serveis per satèl·lit que satisfan les noves demandes ambientals, socials i geo-polítiques. Els sistemes de satèl·lits per observar la Terra han esdevingut recursos essencials per el control del clima, !'agricultura moderna, i altres aplicacions. L'entrada del 5G en el sector aeroespacial ha promogut els satèl·lits com plataformes per aconseguir una cobertura global. Aquestes necessitats poden ser classificades en dos requeriments de sistema: (1) L'augment de la capacitat per transferir dades, i (2) la reducció de la latència en les comunicacions d'extrem-a-extrem. Els sistemes distribuïts de satèl·lits han esdevingut una solució efectiva amb múltiples satèl·lits essent operats simultàniament per satisfer uns requeriments comuns. Els sistemes federats de satèl·lits són candidats prometedors per explotar el potencial de les arquitectures distribuïdes mitjançant col·laboracions oportunistiques entre satèl·lits per compartir recursos. Aquestes col·laboracions, anomenades federacions, permeten concebre l'espai com un entorn on els satèl·lits poden beneficiar-se dels recursos d'altres per millorar el seu funcionament. Les investigacions s'han central en desenvolupar noves tecnologies per aquestes federacions. No obstant, molts aspectes de disseny encara són punts oberts de recerca, com ara el desenvolupament de protocols de comunicació per establir aquestes federacions. Aquesta tesina contribueix definint mecanismes que permeten desplegar una infraestructura en xarxa per establir federacions. A més a més, es discuteix sobre aquest context interconnectat on els satèl·lits poden establir esporàdicament i oportunísticament les federacions. Aquest escenari s'ha anomenat la Internet dels Satèl·lits, i promou els desplegament temporal de xarxes entre satèl·lits heterogenis. Aquesta característica, amb el moviment dels satèl·lits, suposa un repte en la definició de rutes entre extrems formades per satèl·lits intermitjos. Una revisió de protocols d'enrutament actuals d'altres xarxes de satèl·lits s'ha realitzat per identificar el protocol ideal per aquest tipus de xarxa dinàmica. El resultat remarca la necessitat de combinar capacitats de diferents dom in is per aconseguir el funcionament desitjat. Entre aquestes, la capacitat de preveure futurs enllaços entre satèl·lits esdevé crucial per mitigar la fragmentació de la xarxa. Amb aquesta premissa, aquesta tesina presenta un protocol predictiu que estima aquests contactes entre satèl·lits de forma distribuïda. Aquesta nova capacitat pot complementar el protocol d'enrutament mitjançant l'estimació de futures rutes com seqüències of contactes de satèl·lits a través del temps. La recerca presentada en aquesta tesina també respon altres preguntes que no s'havien res post encara: Com els satèl·lits poden descobrir els recursos disponibles en la xarxa? Quins són els mecanismes necessaris per establir i mantenir una federació? Una pila de protocols per cobrir aquesta necessitat tecnològica ha sigut desenvolupat. El protocol de dispersió de la disponibilitat de serveis oportunístics permet notificar els serveis disponibles en un satèl·lit, mentre que el protocol desplegament i control de federacions s'encarrega d'establir i gestionar les federacions. L'aplicació d'aquests protocols considerablement van realçar la capacita! del sistema de satèl·lit per descarregar dades, esdevenint així potenciadors de futures missions. Aquests resultats han motivat el desenvolupament d'un sistema dedica!, que inclou un dispositiu de comunicacions per crear enllaços entre satèl·lit. Aquest sistema ha estat verifica! en una campanya de globus estratosfèrics, i ha sigut integral en una missió de CubeSats. Aquesta dissertació presenta els resultats de la campanya, els quals emfasitzen els profits i viabilitat d'aquesta implementació.
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Mendy, Paul B. Jr. "Multiple satellite trajectory optimization." Thesis, Monterey California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1255.
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Approved for public release, distribution is unlimited<br>problem, with engine thrust as the only possible perturbation. The optimal control problems are solved using the general purpose dynamic optimization software, DIDO. The dynamical model together with the fuel optimal control problem is validated by simulating several well known orbit transfers. By replicating the single satellite model, this thesis shows that a multi-satellite model which optimizes all vehicles concurrently can be easily built. The specific scenario under study involves the injection of multiple satellites from a common launch vehicle; however, the methods and model are applicable to spacecraft formation problems as well.<br>Major, United States Air Force
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Canuet, Lucien. "Fiabilisation des transmissions optiques satellite-sol." Thesis, Toulouse, ISAE, 2018. http://www.theses.fr/2018ESAE0005/document.
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Les longueurs d’onde optiques sont une alternative aux liens radio-fréquences pour lestransmissions satellite-sol du futur. Elles sont envisagées pour les futurs systèmes de télémesuresatellitaires (liens optiques descendants en provenance de satellites LEO) ou de communication(liens optiques bi-directionnels avec des satellites GEO). A sa traversée de l’atmosphère l’ondeoptique peut être profondément affectée par la turbulence atmosphérique. Elle subit desvariations spatiales et temporelles d’amplitude et de phase. Les variations d’amplitudesse traduisent par des variations de la puissance lumineuse collectée (scintillations). Lesperturbations de la phase affectent la distribution spatiale de la puissance au foyer du systèmede détection, qui n’est alors plus limitée par la diffraction. Des pertes peuvent en découler lorsdu couplage du flux incident à un détecteur optronique ou à une fibre optique monomode.Ces pertes se traduisent par des atténuations du signal reçu et donc par la perte d’informations.Pour s’en abstraire, les études de faisabilité les plus récentes mettent en avant l’utilisation desystèmes d’optique adaptative et de techniques numériques adaptées (codage/entrelacement).Pour limiter la complexité et le coût des systèmes de liens optiques, la définition des techniquesde compensation des atténuations peut être menée conjointement. C’est l’objectif principalde cette thèse. Il s’agit d’investiguer les complémentarités des techniques de compensationphysiques (optique adaptative) et numériques (entrelacement, codes correcteurs) pour disposerdes éléments permettant de définir les systèmes de correction les mieux adaptés<br>Optical wavelengths are an alternative to radio-frequency links for future satellite-to-groundtransmissions. They are envisioned in the framework of payload/telemetry data transfer (opticaldownlinks from LEO satellites) or communication (bi-directional optical links with GEOsatellites). However, as it propagates through the atmosphere, the optical wave can be deeplyaffected by atmospheric turbulence which induces randomspatial and temporal variations ofits amplitude and phase. Variations in amplitude translate into fluctuations of the collectedpower (scintillation). The phase distortions affect the spatial distribution of the power at thefocal plane of the telescope causing deleterious losses when the incident flux needs to becoupled to an optoelectronic detector or to a single-mode optical fiber. Such losses result indynamical attenuations of the received signal -called fading- and hence potentially to the lossof information. The most recent feasibility studies highlight the use of two types of fadingmitigation techniques: adaptive optics systems and digital techniques (coding and interleaving).To limit the complexity and cost of such systems, the optimization of these mitigationtechniques should be conducted jointly. The main objective of this thesis is therefore theinvestigation of the complementarity of physical (adaptive optics) and digital data reliabilitymechanisms (interleaving, correcting and erasure codes in a cross-layer approach)
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Grungxu, Lungile Leonard. "Aspect of a hardware-in-the-loop integrated test system." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53292.
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Thesis (MScEng)--University of Stellenbosch, 2003.<br>ENGLISH ABSTRACT: A multiprocessor hardware-in-the-Ioop operating system was developed for the Integrated
Test System (ITS) and is aimed at implementing the ITS as a space emulation vehicle. The
thesis contains a study of satellite orbits, Kepler elements, geomagnetic fields and
communication protocol between the processors.
The system structure consists of an orbit generator, a core-operating system and is presented
with a study of the satellite sensors. In implementing the orbit propagator, there was a need
to pay special attention to the Halving algorithm, the Newton Raphson method and the True
Solution. These algorithms were used to calculate the true anomaly angle as a function of
eccentric anomaly. The communications protocol was tested and all the errors, with their
solutions, have been discussed.
A concept of a geomagnetic field emulator has also been included in the hardware-in-theloop
operating system. The evaluation of those aspects of the system and the conclusion are
presented together with recommendations.<br>AFRIKAANSE OPSOMMING: 'n multiprosesseerder Hardeware in die lus bedryfstelsel is ontwikkel vir 'n Geintegreerde
Toets Stelsel (ITS) en poog om die ITS te implementeer as 'n ruimte emulasie stelsel. Die
tesis behels die studie van sateliet wentelbane, Kepler wentelbaan elemente, geomagnetiese
velde en kommunikasie protokolle tussen die prosesseerders.
Die stelsel struktuur betaal uit 'n wentelbaan propageerder, 'n kern bedryfstelsel en 'n studie
van satelliet instrumentasie. As 'n deel van die implementering van die wentelbaan
propageerder is die halveer algoritme, Newton-Raphson algoritme en die ware oplossing as
numeriese oplossings ondersoek. Die kommunikasie protokol is getoets en foute ondersoek
en word bespreek.
'n konsep vir 'n Geomagnetiese veld emulasie word die hardeware in die lus stelsel ingesluit.
Die stelsel word ge-ewalueer en die gevolgtrekkings en aanbevelings gemaak.
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SYED, ANEES. "COLLISON PREDICTION AND AVOIDANCE OF SATELLITES IN FORMATION." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100034591.
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Hoffmann, Peter, Christoph Jacobi, and Sebastian Gimeno-Garcia. "Using Python language for analysing measurements from SABER instrument on TIMED satellite." Universität Leipzig, 2009. https://ul.qucosa.de/id/qucosa%3A16367.
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The practical handling and analysis of satellite data is outlined using the programming language Python. The limb sounding technique of the SABER instrument on board of the TIMED satellite delivers vertical profiles of kinematic temperature from the stratosphere (∼30 km) up to the lower thermosphere (∼120 km). The procedure may be summarised as follow: In the first step the level 2 data for one month are extracted from the netCDF format and arranged into a new altitude-latitude grid for the ascending and descending orbits. The longitudinal structure is rearranged applying the decomposition into zonal harmonics. Various cross sections of the data give a good overview of the thermal structure and dynamics of the atmosphere up to 120 km. The monthly values of the zonal averaged temperature are compared to the available data from stratospheric reanalyses up to 60 km as well as the initialized background climatology of general circulation models for the middle atmosphere.<br>In diesem Artikel soll der praktische Umgang mit Satellitendaten und deren Auswertung unter Verwendung der Programmiersprache Python skizziert werden. Auf der Basis der Horizontsondierungen des SABER Instruments auf dem TIMED Satelliten werden vertikale Profile wie die kinetischen Temperatur von der Stratosphäre (∼30 km) bis zur unteren Thermosphäre (∼120 km) gewonnen. Die Arbeitsschritte bei der Analyse lassen sich wie folgt gliedern: Als erstes werden die Level 2 Produkte eines Monats aus dem netCDF Format extrahiert und an ein neues Höhen-Breiten Gitter für jeden auf- und absteigenden Orbit angepasst. Die Längenstruktur wird mit Hilfe einer Zerlegung in harmonische Funktionen regularisiert. Diverse Querschnitte der Daten geben ein guten Überblick über die thermischen Struktur und Dynamik der Atmosphäre bis 120 km. Die Monatswerte des Zonalmittels der Temperatur werden mit denen aus operationellen Reanalysedaten (∼60 km) sowie der Hintergrundklimatologie von Zirkulationsmodellen der mittleren Atmosphäre verglichen.
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Thongtan, Thayathip. "Simultaneous single epoch satellite clock modelling in global navigation satellite systems." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/16782/.
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In order to obtain high quality positions from navigation satellites, range errors have to be identified and either modelled or estimated. This thesis focuses on satellite clock errors, which are needed to be known because satellite clocks are not perfectly synchronised with navigation system time. A new approach, invented at UCL, for the simultaneous estimation, in a single epoch, of all satellite clock offsets within a Global Navigation Satellite System (GNSS) from range data collected at a large number of globally distributed ground stations is presented. The method was originally tested using only data from a limited number of GPS satellites and ground stations. In this work a total of 50 globally distributed stations and the whole GPS constellation are used in order to investigate more fully the capabilities of the method, in terms of both accuracy and reliability. A number of different estimation models have been tested. These include those with different weighting schemes, those with and without tropospheric bias parameters and those that include assumptions regarding prior knowledge of satellite orbits. In all cases conclusions have been drawn based on formal error propagation theory. Accuracy has been assessed largely through the sizes of the predicted satellite clock standard deviations and, in case of simultaneously estimating satellite positions, their error ellipsoids. Both internal and external reliability have been assessed as there are important contributions to integrity, something that is essential for many practical applications. It has been found that the accuracy and reliability of satellite clock offsets are functions of the number of known ground station clocks and distance from them, quality of orbits and quality of range measurement. Also the introduction of tropospheric zenith delay parameters into the model reduced both accuracy and reliability by amounts depending on satellite elevation angles.
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Kim, Jeongrae. "Simulation study of a low-low satellite-to-satellite tracking mission /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Morgan, Ryan S. "Volcanism on Io spectral modeling of volatile deposits near active hot spots /." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1663116511&sid=3&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Alibert, Nicolas. "Algorithmes itératifs de prédistorsion adaptés à la montée en débit des communications par satellite." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2019. http://www.theses.fr/2019IMTA0126/document.
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La thèse concerne les techniques de prédistorsion appliquées aux communications par satellite de type DVB-S2X dans la perspective de la montée en débit de ces systèmes. Pour atteindre cet objectif, de faibles facteurs de retombée (inférieurs à 5%) et desordres de modulation plus élevés sont préconisés, augmentant la vulnérabilitévis-à-vis des non-linéarités introduites lors du passage par le satellite. Dans la littérature, deux classes de méthodes se distinguent par leur performance de linéarisation. La première est constituée des architectures d’apprentissage direct (Direct Learning Architecture) et indirect(Indirect Learning Architecture) et la seconde regroupe les méthodes itératives basées sur le théorème du point fixe. Le principal défaut de la première classe est la nécessité de choisir une structure de prédistortion a priori tandis que pour la deuxième classe, les conditions d'application du théorème du point fixe sont difficiles à vérifier dans la majorité des cas et nécessitent l'addition d'un gain empirique. Nous avons donc proposé 1) un schéma de prédistorsion itérative basé sur le théorème du point fixe, appliqué sur le signal mais optimisé en minimisant une erreur quadratique entre les symboles de modulation et la sortie de l'échantillonneur, 2) un schéma de prédistorsion itérative incluant une adaptation automatique des paramètres et adapté à tout type de canal<br>The thesis focuses on predistortion techniques applied to DVB-S2X satellite communications in order to increasing the throughput of these systems. To achieve this objective, sharp roll-off factors (less than 5%) and higher modulation orders are recommended, increasing sensibility with regard to the non-linearities introduced during the passage by the satellite. In the literature, two classes of methods are distinguished by their linearization performance. The first consists of direct (Direct Learning Architecture) and indirect (Indirect Learning Architecture) learning architectures and the latter includes iterative methods based on the fixed point theorem. The main defect of the first class is the need to choose a predistortion structure a priori, while for the second class, the conditions for applying the fixed point theorem are difficult to verify in most cases and require the addition of an empirical gain. We therefore proposed 1) an iterative predistortion scheme based on the fixed point theorem, applied to the signal but optimized by minimizing a quadratic error between the modulation symbols and the sampler output, 2) an iterative predistortion scheme including an automatic adaptation of the parameters and suitable for all types of channels
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Chen, Minjia, and Johan Engberg. "Satellite communication simulator for Cubsats." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-219609.
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The Miniature Student Satellite (MIST) is a project at the Royal Institute of Technology in Stockholm, Sweden. The goal of the project is to launch a satellite designed and constructed by different student teams. The satellite carries seven scientific experiments that continuously collects experiment data as the satellite orbits the Earth. When the satellite is launched, the communication link between the satellite and the ground station is an essential part. This communication consists of a radio link between the on-board computer through a radio module and the ground station on Earth. Satellite communication is not a new field and there exist predefined communication standards and protocols. These standards and protocols are quite extensive and need to be tailored for the specific mission. Once a satellite is launched, it is out of reach for further development. This makes it crucial that the software running on the on-board computer are well tested and correctly integrated with the mission control system (MCS) that are used the send commands to control the satellite from Earth. Since satellite radio equipment is expensive, this bachelor thesis describes how to set up, implement and test an end-to-end communication chain between the satellite on-board computer and the MCS using a hardware simulator. The simulator both mimics the functionality of an on-board radio and replaces the ground station and radio link. Communication standards and protocols are studied and investigated, alongside with on-board pre-implemented subsystem libraries and an MCS named Elveit from Solenix. As the simulator also replaces the radio link, data transfer errors such as data loss, data corruption and, connection time windows can be simulated and tested. The simulator development results in a feasible end-to-end communication chain between the on-board computer and the MCS. This includes mimicking and acting as a radio module against the on-board computer, simulation of the radio link with the possibility to add transmission errors and, acting as a ground station against the MCS. To ensure that the simulator performs as the on-board radio module, the simulator performance is tested against the on-board computer. These results can be compared with on-board radio module performance to make sure that the behavior is similar.<br>Miniature Student Satellite (MIST) är ett projekt vid Kungliga Tekniska Högskolan i Stockholm, Sverige. Projektets mål är att skjuta upp en satellit som är designad och konstruerad av olika grupper av studenter. Satelliten bär sju vetenskapliga experiment som kontinuerligt samlar experimentdata medan satelliten ligger i omloppsbana runt jorden. När satelliten väl har skjutits upp är kommunikationslänken mellan satelliten och markstationen en viktig del. Denna kommunikation består av en radiolänk mellan ombord datorn via en radiomodul och markstationen på jorden. Satellitkommunikation är inte ett nytt fält och det finns både standarder och fördefinierade kommunikations protokoll. Dessa standarer och protokoll är dock väldigt omfattande, och behöver anpassas för att bättre passa projektet. När en satellit har skjutits upp är den utom räckhåll för vidare utveckling. Detta gör det avgörande att mjukvaran som körs på omborddatorn är väl testad och korrekt integrerad med det kontrollsystem som används för kommunicera med satelliten från jorden. Då radioutrustning är dyr, beskriver denna bacheloravhandling hur man konfigurerar, implementerar och testar en "end-to-end" kommunikationskedja mellan omborddatorn och den programvara som används för att kontrollera satelliten från marken. Detta görs med en simulator som både efterliknar funktionaliteten hos en inbyggd radio och ersätter markstationen och radiolänken. Kommunikationsstandarder och protokoll studeras och utredas, tillsammans med förinstallerade mjukvarubibliotek och ett kontrollsystem, Elveit från Solenix. Då simulatorn också ersätter radiolänken kan dataöverföringsfel som dataförlust, datakorruption och kommunikations tidsfönster simuleras och testas. Utvecklingen av simulatorn resulterar i en kommunikationskedja mellan omborddatorn och kontrollsystemet. Detta inkluderar efterliknanda och funktionen som en radiomodul mot omborddatorn, simulering av en radiolänk med möjlighet att lägga till överföringsfel och att fungera som en markstation mot kontrollsystemet. För att säkerställa att simulatorn fungerar som en inbyggd radiomodul testas simulatorns prestanda funktionalitet mot omborddatorn och kontrollsystemet. Dessa resultat kan senare jämföras med prestandan på radionmodulen för att säkerhetställa att beteendet är likartat.
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Glettler, James Bernard. "Parameterized analysis of optical inter-satellite links for high resolution satellite communication." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53314.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 151-154).<br>The use of antenna arrays to exploit spatial information in single and multi-user RF communication receivers is well established for reducing interference and enabling frequency reuse. Antenna arrays have been deployed in single satellite applications but arrays have not been exploited in multi-satellite constellations where increased array size enables high spatial selectivity between ground transmitters. One requirement for these array systems is sufficient fidelity in transporting the received RF signals at each antenna to the array processor. Optical inter-satellite link architectures for signal transport are investigated and parameterized models to compare the performance of each are synthesized. Both analog and digital modulation schemes for the link are considered. A two-channel receiver with both low and high interference is analyzed. It is shown that high resolution satellite array receivers are practical with low required optical power. The optimum selection of transport architecture is shown by selecting for lowest error probability or minimum required optical power. A satellite-to-satellite distance threshold is found for selecting the optimum inter-satellite link architecture for a given application.<br>by James Bernard Glettler.<br>S.M.
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Hamilton, M. J., R. Abbott, P. Eggan, D. Golber, S. Hsieh, L. Jordan, T. Le, et al. "ASW-II: Advanced Satellite Workstation for the UHF Follow-On Satellite Program." International Foundation for Telemetering, 1992. http://hdl.handle.net/10150/611921.
Full textAbstract:
International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, California<br>ASW-II (Advanced Satellite Workstation, Version II) has been developed and delivered as an operational prototype in support of the Ultra High Frequency (UHF) Follow-On satellite. It provides unified and coordinated real time reception and storage of satellite telemetry, display of both real time and stored telemetry, expert-system analysis of spacecraft status, and an information navigator system that stores and presents information about the spacecraft. The architecture is modular and reconfigurable, and it provides support for multiple analyst workstations. There are several unusual aspects of the design. The entire telemetry history of the satellite is regarded as a continuum by the user, with ASW-II automatically tracking and displaying contact periods. A "streams" mechanism organizes the telemetry in such a way that the user can interactively define new derived parameters and have them presented graphically. Both real time and archived data can be displayed simultaneously. The user has very flexible controls for all display interfaces using mouse and window technologies.
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Teste, Florian. "Forecasting agricultural commodity prices from satellite data satellite data using machine learning." Electronic Thesis or Diss., université Paris-Saclay, 2025. http://www.theses.fr/2025UPASM003.
Full textAbstract:
Cette thèse développe un cadre méthodologique innovant destiné à la prévision des prix et des rendements agricoles à l'échelle mondiale, en s'appuyant exclusivement sur l'analyse de données satellitaires et l'utilisation d'algorithmes d'apprentissage automatique avancés. Alors que les modèles prévisionnels conventionnels reposent sur une combinaison de données météorologiques, d'analyses économétriques et de rapports agricoles — sources souvent affectées par des délais et des imprécisions — notre approche propose une alternative robuste et en temps réel.Notre méthodologie s'articule autour de l'exploitation de trois paramètres biophysiques clés dérivés des observations satellitaires : la Production Primaire Brute (GPP), l'Indice de Surface Foliaire (LAI) et la Fraction de Radiation Photosynthétiquement Active Absorbée (FAPAR). Ces indicateurs permettent une évaluation précise des conditions environnementales locales et une prédiction fiable des variations de rendements et de prix, s'affranchissant ainsi des limitations inhérentes aux rapports traditionnels.L'originalité de notre approche réside dans l'application d'algorithmes d'apprentissage automatique sophistiqués, couplée à des techniques avancées de réduction de la dimensionnalité. Nous explorons notamment l'utilisation des Fonctions Orthogonales Empiriques, des Autoencodeurs classiques et des Autoencodeurs Variationnels pour extraire les caractéristiques essentielles des données satellitaires complexes. La validation approfondie de notre cadre prédictif, réalisée sur différentes cultures stratégiques (maïs et soja) et diverses zones géographiques (États-Unis, Afrique du Sud, Malawi), démontre sa polyvalence et son adaptabilité.Les résultats empiriques confirment la remarquable efficacité de notre approche exclusivement satellitaire. Les prévisions de rendement atteignent des niveaux de précision exceptionnels, avec des coefficients de détermination (( R² )) de 0,90 pour le maïs et 0,79 pour le soja. Les prédictions de prix démontrent également une performance significative, avec des ( R² ) de 0,48 et 0,46 respectivement pour le maïs et le soja, surpassant notablement les méthodes conventionnelles pour les prévisions précoces et médianes de la saison.Ce travail de recherche apporte une contribution majeure au domaine de la prévision agricole en proposant un outil analytique alliant évolutivité, réactivité et précision. Au-delà des avancées méthodologiques, notre approche offre un potentiel considérable pour améliorer la stabilité des marchés agricoles mondiaux en fournissant des indicateurs précoces et fiables sur les tendances de production et de prix. Ces informations stratégiques permettront aux acteurs du secteur d'optimiser leur prise de décision et de mieux anticiper les dynamiques du marché<br>This thesis presents a novel methodological framework for forecasting the prices and yields of agricultural products on a global scale by exclusively using satellite-derived data and advanced machine learning techniques. Traditional forecasting models often rely on weather data, econometric analyses, or agricultural production reports, which are frequently hindered by delays and inaccuracies due to the limited availability and reliability of regional data on crop production and demand.To overcome these barriers, we exploit mid-season satellite-derived biophysical parameter estimates—Gross Primary Production (GPP), Leaf Area Index (LAI), and Fraction of Absorbed Photosynthetically Active Radiation (FAPAR)—to estimate local environmental conditions and predict variations in yields and prices of agricultural products without depending on third-party reports.We examine the effectiveness of various machine learning algorithms and dimensionality reduction techniques, including Empirical Orthogonal Functions, Autoencoders, and Variational Autoencoders, to identify critical features from high-dimensional satellite images. Our forecasting framework is validated on different staple crops—maize and soy—and across diverse geographical regions, including the United States, South Africa, and Malawi. This demonstrates the generalizability and robustness of the model under varying climatic conditions and agricultural practices.The results show that our forecasting framework, based exclusively on satellite data, achieves high predictive accuracies, with coefficients of determination (( R² )) reaching up to 0.90 for maize yields and 0.79 for soybean yields. Price predictions also exhibit notable performance, with ( R² ) values of 0.48 for maize and 0.46 for soy, thereby surpassing traditional methods for early and mid-season forecasts.This work contributes to the advancement of agricultural forecasting by providing a scalable, timely, and precise tool that allows various stakeholders to make more informed decisions. The proposed forecasting tool could potentially improve the stability of global agricultural markets by providing better visibility into expected levels of production and price trends
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Zetocha, Paul. "COMMAND AND CONTROL OF A CLUSTER OF SATELLITES." International Foundation for Telemetering, 2003. http://hdl.handle.net/10150/605333.
Full textAbstract:
International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada<br>There is an increasing desire in many organizations, including NASA and the DoD, to use
constellations or fleets of autonomous spacecraft working together to accomplish complex mission
objectives. At the Air Force Research Laboratory’s (AFRL) Space Vehicles Directorate we are
investigating and developing architectures for commanding and controlling a cluster of cooperating
satellites. For many space missions, large monolithic satellites are required to meet mission
requirements. In many cases this results in costly satellites which are more complex, more
susceptible to failure, and which have performance characteristics that are less than optimal due to
realistic physical size limitations. Recently various organizations have begun to explore how
distributed clusters of cooperating satellites can replace their larger monolithic counterparts resulting
in an overall cost reduction, enhanced mission performance, and increased system fault tolerance.
Large clusters of satellites flying in formation are required to have some level of on-board autonomy
in order to: fly within specified tolerance levels; perform collision avoidance; address fault detection,
isolation, and resolution (FDIR); share knowledge; and plan and schedule activities. In addition,
from an operations standpoint, commanding and controlling a large cluster of satellites can be very
burdensome for ground operators. At AFRL we are addressing these issues by development of an
on-board Cluster Management system which will, in essence, provide the capability to treat a cluster
of satellites as a single virtual satellite. A systems level approach is being taken, therefore from a
ground perspective the ground control station must also be able to treat the cluster as a virtual
satellite. [1]
This paper will describe our Cluster Management system, which is the intelligent entity that is
responsible for making cluster level decisions and which enables the satellite cluster to function as a
virtual satellite. The cluster manager functionality can be broken down into the following five areas:
• Command and control
• Cluster data management
• Formation flying
• Fault management
• On-board Planning
This paper will contain a detailed description of the Cluster Manager architecture along with its
various modules.
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Salazar, Kardozo Alexandros. "A High-Level Framework for the Autonomous Refueling of Satellite Constellations." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14534.
Full textAbstract:
Satellite constellations are an increasingly attractive option for many commercial and military applications. They provide a robust and distributed method of accomplishing the goals of expensive monolithic satellites. Among the many challenges that satellite constellations engender (challenges in control, coordination, disposal, and other areas), refueling is of particular interest because of the many methods one can use to refuel a constellation and the lifetime implications on the satellites.
The present work presents a methodology for carrying out peer-to-peer refueling maneuvers within a constellation. Peer-to-peer (P2P) refueling can be of great value both in cases where a satellite unexpectedly consumes more fuel than it was alloted, and as part of a mixed refueling strategy that will include an outside tanker bringing fuel to the constellation. Without considering mixed-refueling, we formulate the peer-to-peer refueling problem as an assignment problem that seeks to guarantee that all satellites will have the fuel they need to be functional until the next refueling, while concurrently minimizing the cost in fuel that the refueling maneuvers entail. The assignment problem is then solved via auctions, which, by virtue of their distributed nature, can easily and effectively be implemented on a constellation without jeopardizing any robustness properties.
Taking as a given that the P2P assignment problem has been solved, and that it has produced some matching among fuel deficient and fuel sufficient satellites, we then seek to sequence those prescribed maneuvers in the most effective manner. The idea is that while a constellation can be expected to have some redundancy, enough satellites leaving their assigned orbital slots will eventually make it impossible for the constellation to function. To tackle this problem, we define a wide class of operability conditions, and present three algorithms that intelligently schedule the maneuvers. We then briefly show how combining the matching and scheduling problems yields a complete methodology for organizing P2P satellite refueling operations.
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Balli, Gulsum Basak. "Micro-satellite Camera Design." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1043769/index.pdf.
Full textAbstract:
The aim of this thesis has been summarized as the design of a micro-satellite camera
system and its focal plane simulations. The average micro-satellite orbit heights
ranges in between 600-850 km and obviously a multipayload satellite brings volume
and power restrictions for each payload. In this work, an orbit height of 600 km and
a volume of 20×<br>20×<br>30 cm is assumed, since minimizing the payload dimensions
increases the probability of the launch. The pixel size and the dimensions of an
imaging detector such as charge-coupled device (CCD) have been defined by the
useful image area with acceptable aberration limits on the focal plane. In order to
predict the minimum pixel size to be used at the focal plane modulation transfer
function (MTF), point spread function (PSF), image distortion and aberration
simulations have been carried out and detector parameters for the designed camera
have been presented.
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Bassett, Robert M. "Automated satellite image navigation." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23552.
Full textAbstract:
Approved for public release; distribution is unlimited<br>This study investigated the automated satellite image navigation method (Auto-Avian) developed and tested by Spaulding (1990) at the Naval Postgraduate School. The Auto-Avian method replaced the manual procedure of selecting Ground Control Points (GCPs) with an autocorrelation process that utilizes the World Vector Shoreline (WVS) provided by the Defense Mapping Agency (DMA) as a "string" of GCPs to rectify satellite images. The automatic cross-correlation of binary references (WVS) and search (image) windows eliminated the subjective error associated with the manual selection of GCPs and produced accuracies comparable to the manual method. This study expanded the scope of Spaulding's (1990) research. The worldwide application of the Auto-Avian method was demonstrated in three world regions (eastern North Pacific Ocean, eastern North Atlantic Ocean, and Persian Gulf). Using five case studies, the performance of the Auto-Avian method on "less than optimum" images (i.e., islands, coastlines affected by lateral distortion and/or cloud cover) was investigated. The result indicated that utilizing the Auto-Avian method on these "less than optimum images" could achieve navigational accuracies approaching those obtained by Spaulding (1990).
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Lashbrook, David L. "Computer based satellite design." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23582.
Full textAbstract:
Approved for public release; distribution is unlimited<br>A computer program to design geosynchronous spacecraft has been developed. The program consists of four separate but interrelated executable computer programs. The programs are compiled to run on an dos based personal computer. the source computer code is written in DoD mandated Ada programming language. The thesis presents the design techniques and design equations used in the program. Detailed analysis is performed in the following areas for both dual-spin and three axis stabilized spacecraft configuration: Mass propellant budget and mass summary; Battery cell and solar cell requirements for a payload power requirement; Passive thermal control requirements. Thesis includes a users manual Appendix A, and the source code for the computer programs in Appendix B.
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Finean, Robert J. "Satellite access in FPLMTS." Thesis, University of Surrey, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321039.
Full text
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Maluleke, Enock Vongani. "Satellite-based web server." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/53040.
Full textAbstract:
Thesis (MScEng)--Stellenbosch University, 2002.<br>ENGLISH ABSTRACT: There is a large variety of telemetry recervmg software currently available for the
reception of telemetry information from different satellites. Most of the software used in
receiving telemetry data is satellite specific. Hence, a user-friendly way is needed to
make telemetry data easily accessible. A satellite-based web server is aimed at providing
telemetry information to any standard web browser as a way of bringing space
technology awareness to the people. Two different satellite-based web server methods are
examined in this thesis. Based on the evaluation, the on-board File server with proxy
server was proposed for satellite-based web server development. This requires that the
File server be ported to the on-board computer of the satellite. The web proxy server is
placed on the ground segment with the necessary communication requirements to
communicate with the on-board File server. In the absence of satellite, the satellite-based
web server was successfully implemented on two computers, laying a good foundation
for implementation on the on-board computer of the satellite (OBe).<br>AFRIKAANSE OPSOMMING: Daar is 'n groot verskeidenheid telemetrie ontvangs sagteware huidiglik beskikbaar vir
die ontvangs van telemetrie informasie vanaf verskillende satelliete. Die meeste van die
sagteware wat gebruik word om telemetrie data te ontvang is satelliet spesifiek.
Gevolglik, 'n gebruikers vriendelike metode is nodig om telemetrie data maklik
beskikbaar te maak. 'n Satelliet-gebaseerde web-bediener word beoog om telemetrie
informasie te verskaf aan enige standaard web-blaaier as 'n metode om mense bewus te
maak van ruimte tegnologie. Twee verskillende satelliet gebaseerde web-bediener
metodes salondersoek word in hierdie tesis. Gebaseer op 'n evaluering, word die
aanboord leêr-bediener met instaanbediener voorgestel vir satelliet-gebaseerde webbediener
ontwikkeling. Hiervoor is dit nodig dat die leêr-bediener na die aanboord
rekenaar van die satelliet gepoort word. Die web instaanbediener word op die grond
segment geplaas met die nodige kommunikasie benodighede, om te kommunikeer met
die aanboord leêr-bediener. In die afwesigheid van die satelliet was die satellietgebaseerde
web-bediener met sukses geïmplementeer op twee rekenaars, met die gevolg
dat 'n goeie fondasie gelê is vir die implementering op die aanboord rekenaar van die
satelliet (OBC).