Ljubljana, Slovenia
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Klancar G.,SPACE SI | Klancar G.,University of Ljubljana | Blazic S.,SPACE SI | Blazic S.,University of Ljubljana | And 4 more authors.
Journal of Intelligent and Robotic Systems: Theory and Applications | Year: 2012

This paper deals with the image-based control of a satellite for remote sensing. Approach is demonstrated by simulation where the position of the satellite is obtained with the Simplified General Perturbations Version 3 model and its orientation by simulating its dynamic and kinematic models. For a known position and orientation of the satellite the images are obtained using the satellite's onboard camera, simulated by the Google Earth application. The orientation of the satellite is governed by reaction wheels, which produce the required moments to the satellite. The image-based control law using SIFT image features is applied to achieve an automatic reference-point observation on the Earth's surface. Main contributions of the paper are the following: use of the same sensor for Earth observation and attitude control, simplicity of the approach, no need for explicit calibration of camera parameters and good tracking accuracy. Demonstrated simulation results and performance analysis confirm the approach applicability. © 2011 Springer Science+Business Media B.V.

Blazic S.,SPACE SI | Blazic S.,University of Ljubljana | Matko D.,SPACE SI | Matko D.,University of Ljubljana | And 7 more authors.
Acta Astronautica | Year: 2013

In this paper a method for estimating the relative orbit is proposed. The method requires a minimum number of simple sensors. The design of observers for formation-flying control, which is formulated as a control problem of tracking the target satellite, is treated. If the equations of the relative motion of the target and the chaser satellites are rewritten in the Local Vertical/Local Horizontal (LVLH) coordinate system, a nonlinear control system of the sixth order is obtained. It is very well known that such a control problem can be solved by a (linear or nonlinear) state controller. The formation-flying models are reviewed and analysed with respect to their observability according to the measured quantities. Based on the results of the observability analysis two state observers enabling an estimation of all the states are proposed in the paper: a simple observer of the linearised system and a nonlinear observer. Since cheap, small satellites are targeted, the application of cheap sensors is studied. In addition, the possibility of measuring the three relative position coordinates of the chaser satellite with a camera and a compass is given with some simulation results demonstrating the suppression of the measurement noise, which is significant when using cheap, COTS sensors and cameras. © 2012 Elsevier Ltd.

Blazic S.,University of Ljubljana | Matko D.,SPACE SI | Bosnak M.,SPACE SI | Klancar G.,University of Ljubljana | Music G.,University of Ljubljana
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2014

The paper describes the experimental ADCS mode of the NEMO-HD satellite, built in the cooperation between SPACE-SI and Space Flight Laboratory, University of Toronto. In the experimental ADCS mode several imaging modes will be implemented such as fixed target observation, path tracking target observation, area sweep mode and spread area sweep mode. A Matlab-Simulink based simulator was designed, which accurately incorporates the astrodynamics and the kinematics of the satellite in real time. It also provides the images of the observed target by means of the Active-X connection to the Google Earth. The results of simulations demonstrate the applicability of the proposed imaging modes to be implemented on the NEMO-HD satellite, which is planned to be launched in 2015. © IFAC.

Marsetic A.,SPACE SI | Kokalj Z.,SPACE SI | Ostir K.,SPACE SI
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2011

Lossy compression is becoming increasingly used in remote sensing although its effect on the processing results has yet not been fully investigated. This paper presents the effects of JPEG 2000 lossy compression on the classification of very high-resolution WorlView-2 imagery. The k-nearest neighbor and support vector machine methods of the object based classification were used and compared. The results explore the impact of compression on the images, segmentation and resulting classification. The study proves that in general lossy compression does not adversely affect the classification of images; what is more, in some cases classification of compressed images gives better results than classification of the original image. Classification accuracy of support vector machines method indicates that compression ratios of up to 30:1 can be used without any loss of accuracy. The best result of the k-nearest neighbor method was obtained with the highest compression ratio (100:1), but the outcome cannot be trusted without reserve. In the study we found that the support vector machine method gives better classification results than the k-nearest neighbor and is also recommended for further research. In addition to the classification method, image segmentation, a basic step of object classification, plays an important role in the accuracy of the results.

Lifshits J.,University of Toronto | Stras L.,University of Toronto | Grocott S.,University of Toronto | Pranajaya F.,University of Toronto | And 9 more authors.
Proceedings of the International Astronautical Congress, IAC | Year: 2013

NEMO-HD is a high performance multispectral earth-observation microsatellite currently in development by the University of Toronto Institute for Aerospace Studies - Space Flight Laboratory (UTIAS - SFL) for the Slovenian Centre of Excellence for Space Sciences and Technologies (Space-SI). The NEMO-HD payload consists of two instruments: The primary instrument is capable of imaging in four spectral bands at a GSD of 2.8 m, and covers a swath width of 10 km. The secondary instrument produces images at a GSD of 40 m and a much wider field of view. In addition to still imaging, both primary and secondary instruments capture high definition video at 25 frames per second. The video is H.264 encoded and downlinked in real time. Commercial off-the-shelf electronic assemblies are used extensively throughout the payload to capture, store, and downlink the vast quantities of data generated, and to perform real-time video encoding. Their use has facilitated substantial reductions to development costs, and has allowed the demanding timelines of the NEMO-HD mission to be met. Furthermore, embracing of industry accepted protocols and open source software has drastically reduced the required software development efforts, and allowed the use of readily available tools for development, testing, and debugging. This paper discusses how the use of commercial off-the-shelf hardware and open source software has enabled the design and development of a high performance multi-spectral earth observation instrument. In addition, an overview of the NEMO-HD mission and spacecraft are also provided. ©2013 by the International Astronautical Federation. All rights reserved.

Matko D.,Space SI | Rodic T.,Space SI | Blazic S.,Space SI | Music G.,Space SI
Advances in the Astronautical Sciences | Year: 2013

In the paper close formation flying equations are reviewed with respect to different manoeuvres and taking into account the required fuel consumption. Three scenarios are designed including parallel flying with in-track displacement demonstrating high-resolution optical dual satellite imaging and radar interferometric constellation, circumvolution as well as encircling of the target demonstrating debris observation and parallel flying with the radial displacement demonstrating fractionated spacecraft and accurate pointing of the formation. The designed scenarios were applied to a set of formation flying experiments, performed by SPACE-SI and OHB Sweden in September 2011 with Prisma satellites Mango and Tango. The results of the experiment are presented and the formation flying model predicted and measured data are compared.

Imhof A.B.,Liquifer Systems Group LSG | Kotler J.M.,Leiden University | Pell S.J.,ARTi Aquabatics Research Team | Peljhan M.,SPACE SI
Proceedings of the International Astronautical Congress, IAC | Year: 2012

The arts offer alternative insights into reality - which is explored by science in general, and broadened by the activities conducted by the European Space Agency (ESA) and other space agencies. Similar to the way the members of ESA are ambassadors for spaceflight and science, artists and cultural professionals are ambassadors for human expression, experimentation, and exploration. In June 2011, the ESA Topical Team Arts & Science (ETTAS), held a three-day workshop at the European Astronaut Centre in Cologne, Germany. During this workshop, topics and ideas were discussed to develop cooperations between the arts, sciences and ESA to foster and expand the human and cultural aspects of space exploration, and at the same time offer a means of communication that aims to reach audiences beyond the scope of traditional space-related channels. The preliminary findings and consensus of the team was that establishing and sustaining a transdisciplinary professional community consisting of ESA representatives, scientists and artists would fuel knowledge transfer, and mutual inspiration. [Imhof 2012] Potential ways to provide a sustainable cooperation within and between the various groups were discussed and will be presented. A number of measures and mechanisms in order to initiate and conduct such an initiative and a more in- depth view regarding organizational measures, procedures and consequences, as well as a proposition on how to proceed are included in the preliminary findings. Overall, the involvement and cooperation between the Arts, Space Science Research and ESA will enhance in the citizens of the ESA member states the sense of public ownership of ESA results, and participation in ESA's research. Copyright © (2012) by the International Astronautical Federation.

Ostir K.,SPACE SI | Duric N.,SPACE SI | Marsetic A.,SPACE SI | Rodic T.,SPACE SI
Proceedings of the International Astronautical Congress, IAC | Year: 2012

Secondary school students are very open to technology and because they are also enthusiastic Internet users they are well aware of satellite data. Increasingly they also have a rather good knowledge about environmental issues and high awareness of associated problems. However, some of the topics seem to be beyond their reach in understanding and providing real actions. Our experience shows that with appropriate support students can overcome this and become involved in "proper" environmental problem solving. In 2011 the Centre of Excellence SPACE-SI has therefore started the project Slovenia from Space. In total 12 secondary schools decided to participate in the project with almost 20 projects. Each of the secondary schools was addressing a different problem, related to the field of remote sensing, meteorology, astrophysics, micro- and nanosatellite technologies and materials. The projects are ranging from observation of the aurora phenomena, maritime security, detection of invasive plant species, bora wind observation, and archaeological site identifications to geology analysis, urban area change detection⋯ In the paper we will present the Slovenia from Space project, describe the working procedures, discuss the advantages and also the difficulties we have encountered. The project will be compared with similar activities in developed (e.g. USA, Europe) and developing (e.g. Thailand) space nations. The experience we have is very positive, since the students have been highly motivated and had the opportunity to get practical and theoretical knowledge about things that are only slowly getting in the school curriculum.

Ostir K.,SPACE SI | Veljanovski T.,Slovenian Academy of science and Arts | Kanjir U.,Slovenian Academy of science and Arts | Pehani P.,SPACE SI
Proceedings of the International Astronautical Congress, IAC | Year: 2012

Cities in Africa and developing countries in general are having difficulties coping with the influx of people arriving every day. Informal settlements (slums) are growing, and governments are struggling to provide even the most fundamental services to their populations. One of the tools that can be used to study these environments is satellite imagery, especially very high-resolution (VHR) images coming from systems such as 1KONOS, Quickbird, GeoEye and similar. Detection of informal settlements from satellite imagery is a challenging task due to their microstructurc and irregular shapes of buildings. Higher spatial resolution is necessary to identify and extract individual buildings, especially in slum communities that are characterized by small, densely packed shanties and other structures. In the paper we are dealing with the Kibcra (Nairobi, Kenya) slum that is composed of varying housing sizes, where roofs can be a combination of many different materials, and mainly unpaved road and path network. Typically this produces a spectral response, which is difficult to interpret, and makes traditional classification almost impossible. We have applied object-based classification on GeoEye and QuickBird imagery over a tree year period (from 2006 to 2009) to help differentiate slum rooftops and unpaved roads from non-build land and therefore residential areas or grasslands. Object-based segmentation automatically delimits segments on the image into homogeneous elements, which correspond to the real urban geographical objects on the Earth's surface. In the stage of classification all these homogeneous elements are classified into most appropriate classes. In addition to determination of the detailed urban structure we were also interested in the expansion of slum areas with change detection, which was analysed by comparison of images taken in different time sequences. The results of object-based analysis with morphology attributes were further used to estimate the potential population density in the slum area. There is a big discrepancy between different estimations on Kibera census, ranging from 1 to 2 million people, while no field survey was ever performed to assess the population. Different parameters were tested to estimate the potential population density scenarios. The paper will discuss merits and drawbacks of object-based image analysis in dense non-formal settlements analysis with remote sensing data. Overall, the use of the object-based image analysis holds great promise for dense urban environments and could be utilized in studies of urban change structure and corresponding population estimation. Copyright © (2012) by the International Astronautical Federation.

Matko D.,Space SI | Rodic T.,Space SI | Klancar G.,Space SI | Music G.,Space SI | Blazic S.,Space SI
2011 IEEE International Conference on Robotics and Biomimetics, ROBIO 2011 | Year: 2011

The paper deals with the image-based control of a space surveillance robot. The position of the robot is obtained by the Simplified General Perturbations model and its orientation by simulating its dynamic and kinematic models. For known position and orientation of the robot the images are obtained using Google Earth. The orientation of the robot is governed by reaction wheels which produce the required moments to the robot. The image based control law using image extraction features is applied to achieve automatic reference point observation on the Earth surface. Simulated experimental results with realistic assumptions are provided to demonstrate the operation of the proposed approach. © 2011 IEEE.

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