Space subsystems design: (navigation, control, structure and…)
Amir Reza Kosari; Alireza Ahmadi; Alireza Sharifi; Masoud Khoshsima
Volume 15, Issue 1 , March 2022, , Pages 21-39
Abstract
Very High Resolution Passive Scan Agile Earth Observation Satellites are able to maneuver around all their three body axes and scan the target area in different directions, simultaneously. The most stringent mid-level requirements which dominate their attitude determination and control subsystem performance ...
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Very High Resolution Passive Scan Agile Earth Observation Satellites are able to maneuver around all their three body axes and scan the target area in different directions, simultaneously. The most stringent mid-level requirements which dominate their attitude determination and control subsystem performance are applied in detumbling and fine pointing modes. These performance requirements are maneuverability, agility, accuracy and stability. In this research, first, we derive the analytical and statistical relationships between quantitative criteria of mid-level requirements and spatial resolution as a high-level mission requirement, next the design drivers of reaction wheels are extracted consequently. Then the size, mass and consuming power of an operational satellite and the reaction wheels torque authority and momentum capacity is guesstimated based on its imaging payload size and specifications.
Remote sensing
Kobra Yaghoubi; Alireza Safdarinezhad; Marzieh Jafari
Volume 14, Issue 3 , September 2021, , Pages 23-37
Abstract
Image fusion is known as a synergetic process for merging multispectral and panchromatic images contents. So far, various methods have been developed in which the usage of the frequency domain is one of them. The frequency-based image fusion techniques are performed using high and low pass filters. So, ...
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Image fusion is known as a synergetic process for merging multispectral and panchromatic images contents. So far, various methods have been developed in which the usage of the frequency domain is one of them. The frequency-based image fusion techniques are performed using high and low pass filters. So, the determination of the sizes of these filters would be a challenge. In this paper, a weighted index is proposed to determine the sizes and shapes of the low and high filters in fusion of the panchromatic and multispectral images. In the proposed method, the weights of the spectral and spatial indicators are independently estimated for each image. So, the effects of the differentiation of the image contents and different range of the indicators are properly adjusted to reach the optimum filtering. The comparison of the best results obtained from the proposed method with the other well-known fusion methods, in the used datasets, was indicated an average improvement of 58% in RMSEs.
Remote sensing
Mohammad Hassan Vahidnia; Hossein Aghamohammadi
Volume 13, Issue 4 , December 2020, , Pages 49-58
Abstract
Studying vegetation status is one of the most important environmental issues. Using contemporary and field methods in this regard will cost a lot of time and money. Remote sensing technology and satellite image processing is a solution that can facilitate such difficult processes. In this study, remote ...
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Studying vegetation status is one of the most important environmental issues. Using contemporary and field methods in this regard will cost a lot of time and money. Remote sensing technology and satellite image processing is a solution that can facilitate such difficult processes. In this study, remote sensing technology will be integrated with web geographic services to provide users with adequate analysis of the growth of the plants and their changes based on vegetation indices in the shortest possible time. Important technologies used for this purpose are ENVI IDL, Google Map API, JavaScript, and ASP.NET. The service was successfully implemented and was employed for Landsat satellite images. In order to evaluate the performance of the service at different points and with a different number of images, the timeliness of the NDVI vegetation index was prepared. The processing time evaluation also showed that by increasing the number of satellite images the processing time will increase linearly.
R. Sayahnia; M. F. Makhdoum; S. Faryadi
Volume 7, Issue 3 , October 2014, , Pages 69-73
Abstract
Land is a limited and vulnerable resource with many permanent and renewable benefits if it is used appropriately.By considering the limited lands and the need for updated data and information for land planning, necessity and importance of land use studies is clear. In fact remote sensing data with geographic ...
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Land is a limited and vulnerable resource with many permanent and renewable benefits if it is used appropriately.By considering the limited lands and the need for updated data and information for land planning, necessity and importance of land use studies is clear. In fact remote sensing data with geographic information systems are strong tools in change detection of land use pattern. They are much cost and time effective.In this study, satellite image has been used for extraction of update land use map of Tehran metropolitan. Three different methods (unsupervised classification, supervised classification and visual interpretation) have been utilized for preparation of land use map.
M. S. Mohammadi; M. Mortazavi; M. Malekan
Volume 6, Issue 4 , January 2014, , Pages 43-52
Abstract
According to mission requirements in many of space missions, an exact time should be assigned for launch date namely launch window. Among various parameters influencing launch window, in this article a couple of most mission related ones are being researched. First is some constraints on handling satellite ...
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According to mission requirements in many of space missions, an exact time should be assigned for launch date namely launch window. Among various parameters influencing launch window, in this article a couple of most mission related ones are being researched. First is some constraints on handling satellite power and the second is the imaging mission constraintsfor a remote sensing satellite. Then after this study on mission requirements a conceptual method for launch window estimation is presented and supported by a case study on sample micro-satellite IRSAT.
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
