جستجوی مقالات مرتبط با کلیدواژه « remote sensing » در نشریات گروه « مکانیک »

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.

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.

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.