Mohammad Salari
Volume 12, Issue 2 , September 2019, , Pages 43-53
Abstract
In this paper, design and simulation of a deployment and release mechanism of a communication satellite antenna are described. Because of the simplicity and reliability of the system, a torsion spring is used to excite the antenna. Dynamic simulation is performed by Adams Software and the appropriate ...
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In this paper, design and simulation of a deployment and release mechanism of a communication satellite antenna are described. Because of the simplicity and reliability of the system, a torsion spring is used to excite the antenna. Dynamic simulation is performed by Adams Software and the appropriate spring and damper are selected for the mechanism. Also, a thermal cutter mechanism is used for the release mechanism of the antenna that shows a good performance in the tests. Also, a finite element analysis is performed to ensure the structural strength of the mechanism by Nastran-Patran Software. According to the results of the tests and simulations performed on the system, one can say that this mechanism is a simple, functional and reliable mechanism and can be done well the assigned duties in accordance with the requirements of the employer and the ECSS standard.
Space systems design (spacecraft, satellites, space stations and their equipment)
Hamed Alisadeghi; Azade Khadivi; Ehsan Zabihian
Volume 15, Issue 2 , June 2022, , Pages 43-58
Abstract
The interaction of thruster plumes with satellite components can have undesirable effects, such as disturbance force/torque, thermal loading, and species deposition in the surfaces. The purpose of this paper is to use the Direct Simulation Monte Carlo (DSMC) method to analyze the 3D plume impingement ...
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The interaction of thruster plumes with satellite components can have undesirable effects, such as disturbance force/torque, thermal loading, and species deposition in the surfaces. The purpose of this paper is to use the Direct Simulation Monte Carlo (DSMC) method to analyze the 3D plume impingement flows and investigate its effects. Two impingement problems are computed. The impact of a jet of nitrogen on an inclined flat plate is considered. Good agreement is found between surface quantities calculated by DSMC and experimental data. The plume of a hydrazine control thruster firing in a model satellite configuration is simulated. Surface quantities and net impingement effects are calculated. The effects of partial displacement of the thruster locations on the results have also been investigated. The results show that a 20% displacement of the thruster location can change the disturbance force/torque by up to 15% of the initial values.
investigating space radiation
Gholamreza Raisali; Masume Soleimaninia; Amir Moslehi
Volume 16, Issue 2 , June 2023, , Pages 43-54
Abstract
In this paper, the sensitive volume and critical charge of a 65-nm CMOS SRAM as two important quantities in Single Event Upset (SEU) calculations have been determined. SEU is the most common event in space investigations. To this purpose, a memory cell which is consisted of NMOS and PMOS was simulated ...
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In this paper, the sensitive volume and critical charge of a 65-nm CMOS SRAM as two important quantities in Single Event Upset (SEU) calculations have been determined. SEU is the most common event in space investigations. To this purpose, a memory cell which is consisted of NMOS and PMOS was simulated using Silvaco TCAD tool. Then, the variations in output voltages were studied after striking incident particles with different values of Linear Energy Transfer (LET) at different regions of the transistors. The Qcritical was obtained by integrating the output current when the output voltages were inverted. To determine the sensitive volume, the minimum amount of LET in which the output logic state of the memory cell flips, was considered as a criteria of sensitivity. The results showed the value of 0.054 µm3 and 1.48 fC for sensitive volume and critical charge, respectively which are in good agreement with the references.
Mohammadvali Arbabmir; Masoud Ebrahimi Kachoei
Volume 12, Issue 3 , September 2019, , Pages 43-54
Abstract
In the last decades, the visual navigation system has been investigated by many researchers as an aided navigation system for Inertial Navigation System (INS) in the Unmanned Aerial Vehicles (UAV). In this research, for improving the INS errors a new approach based on feature tracking algorithm is used. ...
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In the last decades, the visual navigation system has been investigated by many researchers as an aided navigation system for Inertial Navigation System (INS) in the Unmanned Aerial Vehicles (UAV). In this research, for improving the INS errors a new approach based on feature tracking algorithm is used. In this approach, in order to estimate the feature points in the current image, the INS states, the feature points of the previous image and dynamic equations are used. Also, in this approach, for improving the estimation of terrain points, the outlier estimated feature points delete. Furthermore, in this article, for improving the altitude error, a barometer is used by the mentioned vision navigation system. The simulation results illustrate the desirable accuracy of the vision system and barometer observations in the update step of Extended Kalman Filter (EKF) and remarkable performance of integrated navigation system for calculating the UAV navigation parameters.
Space Ground Segment: receiving, transmitting, controlling and data processing
Afshin Eskandari; S. Hassan Sedighi
Volume 15, Issue 4 , December 2022, , Pages 45-56
Abstract
In this paper, Design, optimization, and implementation of a Transparent Pseudo-Noise satellite Ranging relay are presented. CCSDS and DSN standards were studied for requirements of on board hardware for LEO satellites and ground station. To optimize the performance of the relay, a ground station for ...
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In this paper, Design, optimization, and implementation of a Transparent Pseudo-Noise satellite Ranging relay are presented. CCSDS and DSN standards were studied for requirements of on board hardware for LEO satellites and ground station. To optimize the performance of the relay, a ground station for a two-way ranging system was modeled in MATLAB according to the DSN standard architecture. The effects of non-ideal hardware for the Implementation of an on-board relay were simulated. The simulation results confirmed that the designed transparent relay hardware satisfies the requirements of CCSDS and DSN ranging standards system and has no detrimental effect on it. Finally, the implemented relay was tested with a Transceiver similar to the ranging Transceiver was confirmed for operation.
GPS and navigation GPS)، GLONASS، GALILEO
Mojtaba Behzad Fallahpour; Hamid Dehghani; Ali Jabbar Rashidi; Abbas Sheikhi
Volume 12, Issue 4 , December 2019, , Pages 47-56
Abstract
Reflectors are a very important tools in counteracting the space borne or airborne SAR imaging systems. Because they can be used in the form of decoy and camouflage protection designs due to their high level RCS. The remarkable thing on this mission is that the SAR radar is capable of sending the wave ...
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Reflectors are a very important tools in counteracting the space borne or airborne SAR imaging systems. Because they can be used in the form of decoy and camouflage protection designs due to their high level RCS. The remarkable thing on this mission is that the SAR radar is capable of sending the wave to earth in any direction, with any incident angle and in any frequency band, and capturing sensitive areas. The design of such an all-directional, multi-band reflector, and wide angles reflector is very complicated because the reflex function depends on various parameters such as the dimensions, shape and material of the reflector, the frequency, the incident angle, and the polarization of the radiated wave. Existing refractors generally have a high RCS in a particular direction at a specific frequency and at a narrow viewing angle. In this paper, we will attempt to design a refractor of all directions, multiple bands and wide angles using shape structures.
Space subsystems design: (navigation, control, structure and…)
Mohammad Javad Poustini; Seyed Hossein Sadati; Yosof Abbasi; Seyyed Majid Hosseini
Volume 15, Issue 1 , March 2022, , Pages 51-62
Abstract
Trajectory optimization is a familiar method for most of re-entry and Re-usable vehicles. This is because of the ability to include almost all of the problem constraints without facing restrictions such as time & Calculation issues. Adding or removing constraints in trajectory optimization problem ...
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Trajectory optimization is a familiar method for most of re-entry and Re-usable vehicles. This is because of the ability to include almost all of the problem constraints without facing restrictions such as time & Calculation issues. Adding or removing constraints in trajectory optimization problem has significant effects on overall optimization performance which even can upgrade the method to an on-line process. Most of optimization Algorithms such as nonlinear-programming need an initial guess and are also sensitive to it. Hence in this research management of initial guess is done to remove some constraints from optimization problem and transfer them to initial phase. Accordingly an effort is conducted through using a classic guidance method to satisfy constraints of distance error and angle of impact command. The output of guidance initial guess is then fed to the optimization problem. 6Dof Simulation results show the increase of optimization performance via reduced number of iterations and Optimization time and increased solution accuracy.
R. Jamilnia; A. Naghash
Volume 1, Issue 2 , December 2008, , Pages 35-42
Abstract
In this paper, a new approach is proposed for solving the problem of optimal low thrust orbit transfer. In this approach, the problem of trajectory optimization of optimal orbit transfer is defined by modified equinoctial orbital elements. For solving this problem, direct collocation method, that is ...
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In this paper, a new approach is proposed for solving the problem of optimal low thrust orbit transfer. In this approach, the problem of trajectory optimization of optimal orbit transfer is defined by modified equinoctial orbital elements. For solving this problem, direct collocation method, that is an efficient numerical method for solving optimal control problems, is used. By using this method, the problem of trajectory optimization is fully discretized and converted to a nonlinear programming problem. This discrete problem with large numbers of variables and constraints is solved by a powerful nonlinear programming solver (IPOPT). Finally, optimal state and control variables are achieved for optimal orbit transfer with minimum fuel consumption.
S. H. Miri Roknabadi; S. M. Mirshams; A. A. Nikkhah
Volume 2, Issue 3 , December 2009, , Pages 35-42
Abstract
This paper presents an optimal attitude maneuver by means of Reaction Wheels to achieve desired attitude for a Satellite. At first, Dynamic Equations of motion for a satellite with three Reaction Wheels as its active actuators has been educed, and then State Equations of this system has been obtained. ...
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This paper presents an optimal attitude maneuver by means of Reaction Wheels to achieve desired attitude for a Satellite. At first, Dynamic Equations of motion for a satellite with three Reaction Wheels as its active actuators has been educed, and then State Equations of this system has been obtained. In derivation of equations, coupling of Reaction Wheel electrical equations with dynamic equations of satellite motion, and Reaction wheel saturation avoidance approaches are considered. Then an optimal attitude control with the LQR method has exerted for a distinct satellite by its Reaction Wheels. As a result of simulation has presented an optimal effort by calculated Gain matrix to achieve desired attitude for chosen Satellite. It shows that satellite becomes stable in desired attitude with a low energy and time consumption.
Hojat Taei; M. Mirshams; M. Ghobadi; M. A. Vahid D.; H. Haghi
Volume 8, Issue 4 , January 2016, , Pages 35-44
Abstract
This article describes the details of a Tri-axial Spacecraft Simulator Testbed (TSST) that has been developed as part of a research program on spacecraft multi-body rotational dynamics and control in Space Research Laboratory (SRL) at K. N. Toosi University of Technology. This dumbbell style simulator ...
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This article describes the details of a Tri-axial Spacecraft Simulator Testbed (TSST) that has been developed as part of a research program on spacecraft multi-body rotational dynamics and control in Space Research Laboratory (SRL) at K. N. Toosi University of Technology. This dumbbell style simulator includes a variety of components: spherical air-bearing, inertial measurement unit (IMU), rechargeable battery, reaction wheels (RW), on-board computer (OBC) and balancing masses. In this paper, an attitude control problem for the spacecraft simulator actuated by three reaction wheels is studied. Under the assumption of uniform gravity and frictionless air-bearing environment, reaction wheels generate control moments about the roll, pitch and yaw axes of the base body. The control objective is to perform attitude commands sent from users with the least power consumption and a high precision. To handle the non-linear model, a Linear Quadratic Ricatti (LQR) controller has been programmed and it efficaciously controlled the computer-modeled simulator for any given slewing maneuver. This control approach has been developed to facilitate the system to accomplish large-angle, three-axis slewing maneuvers using RWs as effective actuators.
Z. Hajebrahimi; L. Alidoust; M. Arabian; E. Alavi; M. Ebrahimi; M. Bahrami
Volume 6, Issue 4 , January 2014, , Pages 37-42
Abstract
Stress environment of space flights including hypergravity and microgravity effect cell functions and processes. We studied effect of hypergravity and flight stress on function, death, growth and cellular damage of five cell lines including human vascular endothelial cells, rat bone marrow stromal cells, ...
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Stress environment of space flights including hypergravity and microgravity effect cell functions and processes. We studied effect of hypergravity and flight stress on function, death, growth and cellular damage of five cell lines including human vascular endothelial cells, rat bone marrow stromal cells, mouse embryonic fibroblast cells, PC12 cells and pancreas islands in Biological payload of 3th sounding rocket by NO, LDH, MTT and insulin assay kits. Our results indicated that effect of hypergravity increase significantly cellular death and NO secretion but we found no changes in insulin secretion and pancreas function.
Farhad Fani Saberi; Amir Eslami Mehrjardi
Volume 5, Issue 4 , January 2013, , Pages 39-45
Abstract
In this paper we are going to design an attitude control system for a Stereo-Imaging Remote Sensing Satellite using of four pyramidal reaction wheels. In this method, in order to provide the power requirements of the satellite by the energy stored in the reaction wheels, a power management law will be ...
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In this paper we are going to design an attitude control system for a Stereo-Imaging Remote Sensing Satellite using of four pyramidal reaction wheels. In this method, in order to provide the power requirements of the satellite by the energy stored in the reaction wheels, a power management law will be designed and added to the attitude control law to charge and discharge the wheels according to the preset profiles. Therefore, attitude control and power management of the satellite will be carried out simultaneously. In this method, while the satellite is in the light and the batteries are charged, the speed of the wheels increase up to the limited speeds and while the power requirements of the subsystems are inadequate, Power will be returned to the subsystems by reducing the speed of the wheels. The design of this system has been conducted to consider the effects of saturation of the wheels to prevent attitude deviations of satellite while power management is done. Simulation results show the good performance of the designed attitude control and power management system of the satellite.
Atefe Ajami; Siyamak Naseri; Davood Hashemi; Mahboube Arabsorkhi
Volume 5, Issue 3 , October 2012, , Pages 41-48
Abstract
In this paper, in order to separate images in four spectral bands (from blue to near infrared) in multispectral cameras, four-color separation prism advantagesarereviewed. Then, while description of ray tracing of four-color separation prism, main design parameters and principlesarementioned.After that, ...
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In this paper, in order to separate images in four spectral bands (from blue to near infrared) in multispectral cameras, four-color separation prism advantagesarereviewed. Then, while description of ray tracing of four-color separation prism, main design parameters and principlesarementioned.After that, design of a four-color separation prism model that attached to detector (CCD) by using the Zemaxsoftwarearedescribed,also spot diagrams,ray tracingand aberration graphsare analyzed. Finally, while expression four-color separation prism characteristics that yield fromprogramming with Zemax software, including weight, length of the optical path and thickness of equivalent blade, itsspecifications in remote sensing satellite multispectral camerasareexplained
S. Ghasemloo; S. Noori
Volume 7, Issue 1 , April 2014, , Pages 41-48
Abstract
In this paper, an approximate axisymmetric method is developed which can reliably calculate fully viscous hypersonic flow over blunt-nosed bodies. In this method, a Maslen’s second-order pressure expression is used instead of the normal momentum equation. The combination of Maslen’s second-order ...
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In this paper, an approximate axisymmetric method is developed which can reliably calculate fully viscous hypersonic flow over blunt-nosed bodies. In this method, a Maslen’s second-order pressure expression is used instead of the normal momentum equation. The combination of Maslen’s second-order pressure expression and viscous shock layer equations is developed to accurately and efficiently compute hypersonic flow fields of perfect gas around blunt-body configurations. The results show that, this combination leads to more accurate solutions and less extensive computer run times in the preliminary design environment. Furthermore, the utility of Cebeci-Smith turbulence model is adequate for application to long slender bodies. The results of these computations are found to be in good agreement with available numerical and experimental data.
Mohammad Hossein Refan; Adel Dameshghi; Mehrnoosh Kamarzarrin
Volume 8, Issue 2 , July 2015, , Pages 41-56
Abstract
For precise locating, Differentials Global Positioning System requires prediction of differential corrections for the future times. The system is comprised of both fixed and mobile stations. If the satellites of the two stations are exactly the same, the sources of errors will be close to each other ...
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For precise locating, Differentials Global Positioning System requires prediction of differential corrections for the future times. The system is comprised of both fixed and mobile stations. If the satellites of the two stations are exactly the same, the sources of errors will be close to each other at the two stations; in this case, reference position components factors can be used as corrective factors for offsetting user station positioning error. In this paper, Genetic and Artificial Neural Network hybrid algorithms (Evolutionary Neural Network), Support Vector Machines, Autoregressive Moving Average and Recurrent Neural Network have been used for corrections. In order to test the algorithms, static sampling of the position data of an inexpensive receiver was used and the predicted reference position components error corrections were applied elsewhere. The tests performed as post-process showed that the positioning RMS error decreases up to 0.5 m. The evolutionary neural network prediction model is more accurate than other models and its RMS error is 0.12 m.
Zeynab Aghajani; Ehsan Zabihian; Mehran Mirshams
Volume 10, Issue 4 , March 2018, , Pages 41-54
Abstract
The significance and the wide use of geostationary communication satellites and the long hours of work in the process of their conceptual design was the main motivation to develop a software based on the statistical design to reduce the time spent on the conceptual design phase. This software is based ...
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The significance and the wide use of geostationary communication satellites and the long hours of work in the process of their conceptual design was the main motivation to develop a software based on the statistical design to reduce the time spent on the conceptual design phase. This software is based on the statistical and parametric design method. The statistical model used in this software includes a database of 147 satellites launched between 2010 and 2016. To increase the accuracy of the software, the combined parametric model has been used from selected design references. The software is based on MATLAB and to make it more user friendly, the graphical GUI was used. In this article, the design of the software is presented and there is focus on the design and verification method. The accuracy of this tool was amply verified through a flight prototype, indicating the average error of 16% in the obtained results.
Hamed Chenarani; Tahereh Binazadeh; Mohammad Hosein Shafiei
Volume 11, Issue 2 , September 2018, , Pages 41-46
Abstract
This paper considers the problem of asymptotic stabilizing of velocity and body rates of a spacecraft in the presence of uncertainties and external disturbances. One of the important methods in controller design for nonlinear systems; is designing based on the passivity concept. This concept which provides ...
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This paper considers the problem of asymptotic stabilizing of velocity and body rates of a spacecraft in the presence of uncertainties and external disturbances. One of the important methods in controller design for nonlinear systems; is designing based on the passivity concept. This concept which provides a useful tool for analysis of nonlinear systems has been also used for asymptotic stabilizing of nonlinear dynamical systems especially mechanical systems. The passivity-based control law is a static output feedback and has valuable features. Because of existence of uncertainties and external disturbances in the state-space of equations of physical systems; first the robust version of passivity-based control method, which is recently developed in literature, is given and the control law for nonlinear uncertain systems with affine structure is presented. Then, this approach is used in controller design for a spacecraft. Since, this paper considers only the stabilization of velocity and body rates, therefore the reduced-order model is extracted from the state-space equation of a spacecraft with six degree of freedom and then the robust control law is designed. Computer simulations show the efficiency of the proposed controller in robust asymptotic stabilizing of the velocity and body rate vectors of the spacecraft in the presence of uncertainties and external disturbances.
M. Sayanjali; J. Roshanian; A. Ghafari
Volume 2, Issue 1 , April 2009, , Pages 43-50
Abstract
In this paper, equation of motion of three axis attitude dynamic of flexible spacecraft is derived using combination of finite element method and Euler equation. Flexible appendafes are modeled by beam elements. Goal of control is target attitude of spacecraft from initial state to desired attitude and ...
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In this paper, equation of motion of three axis attitude dynamic of flexible spacecraft is derived using combination of finite element method and Euler equation. Flexible appendafes are modeled by beam elements. Goal of control is target attitude of spacecraft from initial state to desired attitude and suppression of vibration that induced in flexible appendages. So a combination of backstepping and sliding mode control method used for three-axis attitude maneuver of flexible spacecraft and for suppressing vibration of flexible appendage used from active vibration control method by PZT actuator. Control law for vibration control is based on LQG method
A. Movafeghi; E. Yahaghi; N. Mohammadzadeh
Volume 6, Issue 2 , July 2013, , Pages 43-48
Abstract
Cosmic rays in the atmosphere can cause leukemia and other diseases in the astronauts. Changing in microgravity weight make some unwanted effects on cells of the immune system and hematopoiesis. However, the activity of the body organisms is random in different people, but it can be simulate by special ...
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Cosmic rays in the atmosphere can cause leukemia and other diseases in the astronauts. Changing in microgravity weight make some unwanted effects on cells of the immune system and hematopoiesis. However, the activity of the body organisms is random in different people, but it can be simulate by special models. There are many different models of hematopoiesis that are simulated the effect of microgravity in the bone marrow. In this study, a self-developed code is used for investigation of absorbed dose effects on declining health of the tissue, blood and lymph, due to cosmic rays in space. The simulation was implemented for different kinds of input dose to body with different time duration. This phenomenon is surveyed for two cases: with considering to effect of production and reproduction of the cells and microgravity and without considering them. The results show effect of production and reproduction of the cell and microgravity can be improve or damage of normal cell about centesimal percent. Also, it can be initiate the anemia and the leukemia on the human at long time.
D. Bustan; N. Pariz; S. K. HosseiniSani
Volume 7, Issue 3 , October 2014, , Pages 43-49
Abstract
In this paper, a new approach for orbital position prediction of satellites, is introduced. As traditional methods are based on keplerian equations of motion, orbital disturbances are uasualy neglected for simplicity. This paper, suggests artificial intelligent time series peridiction methods for orbital ...
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In this paper, a new approach for orbital position prediction of satellites, is introduced. As traditional methods are based on keplerian equations of motion, orbital disturbances are uasualy neglected for simplicity. This paper, suggests artificial intelligent time series peridiction methods for orbital position prediction of satellites. The advantage of this method is based on usage of actual data, so all disturbances are taken into account. For this reason use of TLE as the most reachable actual data is considered. Compariosion of output of this method with actual data, proofs the accuracy of proposed method.
Emad Azadi; Seyed Ahmad Fazelzadeh; Mohammad Azadi
Volume 8, Issue 1 , April 2015, , Pages 43-51
Abstract
In this paper, vibration suppression and maneuver control of a smart flexible satellite moving in acircular orbit are studied. The satellite is considered as a rigid hub and two flexible appendages withpiezoelectric layersattached on them as actuators. The satellite is moving in a circular orbit and ...
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In this paper, vibration suppression and maneuver control of a smart flexible satellite moving in acircular orbit are studied. The satellite is considered as a rigid hub and two flexible appendages withpiezoelectric layersattached on them as actuators. The satellite is moving in a circular orbit and has pitch angle rotation maneuver. The heat radiation effects on the appendages are considered. When the satellite is rotating around the Earth, the appendages experience periodic heating and cooling in the sunlight and shadow region of the Earth with the variation of the thermal environment.These nonlinear transient heat equations depends on the satellite maneuver angle and the panels vibrations, too. The thermally induced vibrations of the appendages and the heat transfer equation are coupled and should be solved simultaneously.Aninverse dynamic controller is proposed to control the satellite maneuver and appendage vibrations. Finally, the whole system is simulated and the effects of the heat radiation and piezoelectric actuators on the response of the system are studied. Also, the effectiveness and the capability of the controller are analyzed.
erfan beygi; Amirhossain Adami
Volume 11, Issue 4 , December 2018, , Pages 43-50
Abstract
Basically, it takes alot of time to analyze structures with different parameters, depending on the type of structure and parameters. Also, by changing any parameter, all the analysis process must be repeated. Therefore analyze the effect of different parameters on the behavior of structures, many analyzes ...
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Basically, it takes alot of time to analyze structures with different parameters, depending on the type of structure and parameters. Also, by changing any parameter, all the analysis process must be repeated. Therefore analyze the effect of different parameters on the behavior of structures, many analyzes should be carried out that are time consuming. The results obtained are valid only for the same parameters, and are not valid by changing the parameters. In this research, a Nested dependence method has been developed that can be used to determine the behavior of the structure with proper accuracy with short time. In this method, first an interval is considered for different parameters of the structure. Then, by using the finite element analysis method and applying the loading and boundary conditions, the behavior of the structure. By repeating this process to extract the appropriate number of input data, a Nested dependence method can be used to estimate the structure behavior of different inputs.
Space systems design (spacecraft, satellites, space stations and their equipment)
Mostafa Zakeri; Mehran Nosratollahi; MohammadReza Sabeti; Hamid Reza Moghadas Najaf Abad; Hamid Maleki
Volume 14, Issue 1 , March 2021, , Pages 43-54
Abstract
This research presents a new and effective approach to managing change control in the design process of complex engineering products. This approach involves using design constraints to combine two DSM matrix structures and a systematic process for controlling changes. The system process involves using ...
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This research presents a new and effective approach to managing change control in the design process of complex engineering products. This approach involves using design constraints to combine two DSM matrix structures and a systematic process for controlling changes. The system process involves using a systemic code to evaluate changes, how to create a transfer model, and a management change assessment request. The process presented in this article, in addition to using similar activities in this field, has provided a systematic approach to using the knowledge of designers of a project to guide the control of changes to major engineering projects, including decision-making on controlling changes and how to identify the best The path to the change control process
H. Bazrafshan; Sh. Baradaran Shokouhi; B. Ghorbani Vagheii
Volume 3, Issue 1 , July 2010, , Pages 45-54
Abstract
In this paper, the complete block diagram of the imaging payload of a spin satellite capable of real time imaging is designed. Because of the satellite spin, the system needs to recognize the suitable camera angle in order to start imaging. The angle is the starting point of the observation of the part ...
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In this paper, the complete block diagram of the imaging payload of a spin satellite capable of real time imaging is designed. Because of the satellite spin, the system needs to recognize the suitable camera angle in order to start imaging. The angle is the starting point of the observation of the part of the earth to be imaged. In this paper, at first the suitable imaging method and detector for this kind of satellite are elected and then the angle and the time of the spin camera imaging and the necessary number of lines and pixels are calculated. If the system is also capable of real time imaging, the captured images should be transmitted to the earth station before the next imaging starts. The completion of the above scenario needs a complete and parallel relationship between the satellite image payload subsystem and other subsystems such as power, communication and specially satellite on-board computer. For imaging and transmission, image payload status information such as temperature, voltage and current should be sampled and transmitted to the on-board computer for processing. Also this information should be attached to the image frames and transmitted to the earth station. All this processing is summarized into time pulses with exact timing between subsystems. Because of resource limitation in a space mission, satellite systems design must have the minimum mass, power and cost. But these shouldn’t cause the efficiency and specially system processing speed to decline. Imaging payload with real time capability needs a high processing speed requiring high resource utilization. In this paper, an imaging system is designed with the mentioned characteristics based on FPGA high parallel processing speed but having low mass, volume and power.
M. Navabi; N. Nasiri
Volume 3, Issue 2 , January 2011, , Pages 45-52
Abstract
Since last decades utilizing satellites in low earth orbits have had increasing tendency. These satellites experience the earth magnetic field due to their low altitude to the earth. The Earth magnetic intensity can be used in order to control the attitude of spacecraft utilizing the interaction between ...
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Since last decades utilizing satellites in low earth orbits have had increasing tendency. These satellites experience the earth magnetic field due to their low altitude to the earth. The Earth magnetic intensity can be used in order to control the attitude of spacecraft utilizing the interaction between the earth magnetic field and magnetic dipoles which are generated in the body of satellite. First of all, for using this phenomenon the magnitude and direction of the Earth magnetic field have to be obtained. There are various ways in order to simulate the earth magnetic field, that the most accurate one is utilizing the harmonic coefficients and mathematical model of the earth magnetic field. In this study, the earth magnetic field is modeled based on the 10thgeneration of the IGRF coefficients and the results are verified with the most valid reference. Due the Earth magnetic field is used in order to attitude control of a spacecraft, it is necessary to transform the results into the spacecraft Body frame. This transformation can be obtained utilizing linear and nonlinear transformation. In the next step, based on the comparison of the results of the spacecraft attitude dynamics utilizing linear and nonlinear transformation the validity margin of linear transformation is studied.
