84 research outputs found
Automatic image analysis for space debris measurement
No full textThe space debris represents a danger for operative satellites and human missions. A large amount of debris is located in Low Earth Orbit and in Geostationary Orbit. The worldwide surveillance networks, mainly NORAD and RosKosmos, started monitoring debris since a long a time and testify the continuous growing
tendency in the number of objects. Since a few years Aerospace Systems Laboratory of University of Rome started optical space debris observation campaigns by dedicated observatories. The observation activity includes not only planning and taking images of selected portions of the sky, but also analysis of raw picture data to extract the relevant astrometry and/or light-curve information. During the optical campaigns a large amount of images is typically taken and one of the most time consuming activities in optical space objects observation is the data analysis, requiring dedicated and specialized man power. This is the reason why the development of automatic images processing algorithms and procedures to identify the presence of debris, to identify its nature and perform the astrometry computations would highly desirable. This paper deals with the development of automatic procedures and algorithms to detect objects with
relative motion with respect to stars in both sidereal tracking mode or terrestrial fixed one. In particular, the developed software is able to recognize the debris inside the picture, solve the star field within the picture and use both these information to achieve the angular measurements of the debris. Relevant efforts have been devoted to software development, such that human interaction is not required. The astrometry computations
algorithm works without predefined information about the image. In particular the knowledge of the pointing angles are not required, even if starting from a condition close to the actual one improved the convergence speed, and the picture can be solved starting from a “lost in space" condition. The main algorithm drivers and the tradeoffs in the software implementation are depicted and preliminary results and software performance in actual observation campaigns are discussed in the paper
Plastic CubeSat: An innovative and low-cost way to perform applied space research and hands-on education
No full textThis paper describes the design and the manufacturing of a Cubesat realized within the activities of Space Robotics Laboratory and V-Lab of the II Faculty of Engineering of Bologna University in collaboration with the Space System Laboratory of the University of Rome "La Sapienza". Despite its small size, this single unit (IU) Cubesat has a system for active attitude control, a redundant telecommunication system, a payload camera and an high efficiency power control system. The subsystems developed for this Cubesat have been also designed to be scaled up for larger satellites as 2U or 3U Cubesats. The additional volume can be used for more complex payloads. Thus the satellite can be used as low cost platform for companies, institutions or universities to test components in space. The attitude control subsystem is based on active magnetic system with magnetorquers for detumbling and momentum dumping and three reaction wheels for fine control. It has a total dimension of about 50x50x50 mm and completely realized by the Space Robotics Laboratory during the PhD activities of one of the authors. A microcontroller implements the control law autonomously or by commands from ground, . taking data from magnetometers integrated in the control system, by solar arrays; reaction wheels and magnetic coils The Cubesat structure has been realized in plastic material (ABS) through "rapid prototyping" technique, thanks to the facilities provided by the V-Lab. The "rapid prototyping" technique has several advantages including fast implementation and low cost. Moreover, concerning the construction of a small satellite, this technique is very useful thanks to the accuracy achievable in details, which sometimes are difficult and expensive to realize with the use of tools machine. The structure must be able to withstand with the launch loads. For this reason, several simulations using a FEM code and intensive vibration test campaign have been performed in the system development phase. The developed communication subsystem has small dimensions, low power consumption and low cost. The main components of the system are the radios, the antennas (one of them is manufactured inside the ABS structure), the amplifiers and the microcontroller. It has been implemented a communication protocol used mainly by radio amateurs, the AX.25 protocol. The communication system has the capability to transmit both telemetry and data from the payload, in this case a microcamera. Copyright ©2010 by the International Astronautical Federation. All rights reserved
Automated image analysis for space debris identification and astrometric measurements
No full textThe space debris is a challenging problem for the human activity in the space. Observation campaigns are conducted around the globe to detect and track uncontrolled space objects. One of the main problems in optical observation is obtaining useful information about the debris dynamical state by the images collected. For orbit determination, the most relevant information embedded in optical observation is the precise angular position, which can be evaluated by astrometry procedures, comparing the stars inside the image with star catalogs. This is typically a time consuming process, if done by a human operator, which makes this task impractical when dealing with large amounts of data, in the order of thousands images per night, generated by routinely conducted observations. An automated procedure is investigated in this paper that is capable to recognize the debris track inside a picture, calculate the celestial coordinates of the image's center and use these information to compute the debris angular position in the sky. This procedure has been implemented in a software code, that does not require human interaction and works without any supplemental information besides the image itself, detecting space objects and solving for their angular position without a priori information. The algorithm for object detection was developed inside the research team. For the star field computation, the software code astrometry.net was used and released under GPL v2 license. The complete procedure was validated by an extensive testing, using the images obtained in the observation campaign performed in a joint project between the Italian Space Agency (ASI) and the University of Bologna at the Broglio Space center, Kenya. © 2014 IAA. Published by Elsevier Ltd. All rights reserved
NARCISO: a microsatellite that takes pictures of itself
No full textIn the early nineties the Group of Astrodynamics of the University of Roma “La Sapienza” (GAUSS), established the UNISAT program at the School of Aerospace Engineering of Roma with the aim to design, manufacture and operate in orbit small educational satellites involving students, researchers and professors in a real space project. In the framework of this program four satellites have been launched in 2000, 2002, 2004 and 2006 from Baykonour Cosmodrome using DNEPR launch vehicle. Next satellite of UNISAT series, UNISAT-5, will have attitude stabilization system based on the well known gravity gradient effect by exploiting a new kind of deployable boom. The design of this deployable boom, based on harmonic steel tape coil spring, is inspired to the booms developed for the SIRDARIA deorbiting system boarded on UNISAT-4. The same concept has been adapted to the attitude control of UNISAT-5, by increasing the boom length up to three meters. The boom deployment is going to be tested on board REXUS rocket. This is a small ballistic rocket, launched from ESRANGE base on the framework of ESA REXUS/BEXUS program, used to perform small experiments under microgravity conditions. The design, realization and tests of the boom are depicted in the first part of the paper. The second part of this paper deals with design and realization of the tip-mass. It is a one kilogram, ten by ten centimeters, autonomous payload, capable to perform simple experiments such as taking pictures of the mother satellite, which will be transmitted to the mother satellite itself using a wireless connection and then downloaded to the ground station. The tip-mass, named NARCISO, is realized by rapid prototyping technique, in ABS plastic material. Exploiting this technique, a complete structure capable of hosting all subsystems required by a small satellite, from electronic board to antennas and solar cells, can be manufactured in a short time (about 23 hours) with reduced costs. Moreover, almost any shape and mechanical detail within 0.3 mm accuracy (the height of the single layer) can be obtained. The UNISAT-5 satellite and the NARCISO tip-mass will take pictures of each other. In this way, the UNISAT solar cells degradation can be photographed and the ABS degradation can be also monitored by remote visual inspection
Donor affected by hemosiderosis: is kidney transplantation possible? A case report
No full textMarginal donors (advanced age, comorbidities, and so on) provide an increasing contribution to the kidneys used to alleviate the relative organ shortage. We describe the evaluation process and clinical outcome of two kidneys with hemosiderosis used as a double graft. The donor was a 59-year-old hypertensive man, known to have a mechanical mitral valve, who died from a cerebral hemorrhage, with a normal serum creatinine (SCr) and kidneys with normal appearances at sonography. A protocol donor biopsy showed a Karpinsky score of 5 for both kidneys. A double graft was therefore scheduled. The recipient was a 59-year-old man, on dialysis because of chronic glomerulonephritis. HLA match was incompatibility 4/6; immunosuppression was based on steroids, cyclosporine, and mycophenolate mofetil with basiliximab as induction therapy. The grafts showed delayed function with dialysis treatments performed from postoperative day (POD) 1. On POD 2, a magnetic resonance imaging (MRI) study showed the typical appearance of siderosis. Pearl's staining performed on a protocol biopsy confirmed the presence of widespread iron deposits. On POD 5, a recipient renal biopsy showed a superimposed severe acute tubular necrosis. Renal function recovered slowly; SCr at discharge on POD 22 was still 4.2 mg/dL. Two months later, the SCr was 2.2 mg/dL. A second MRI performed at 3 years and 6 months after transplantation confirmed a progressive removal of iron overload while the patient had stable renal function (glomerular filtration rate) of 33 mL/min and SCr: 2.3 mg/dL. We concluded that donors with hemosiderosis should be treated as marginal donors and may be grafted based on a pretransplant biopsy
Cohesion policy reform and the evolving role of the council
No full textThe reform of Cohesion policy is a complex process within the complex polity of the European Union. Understanding how it takes place requires insight into the interplay between different institutions at EU, national and sub-national levels as well as formal and informal alliances and networks of countries, regions and interest groups. This chapter examines the way that institutions play a role in determining the financial allocations and regulations of Cohesion policy, and discusses the recalibration of inter-institutional relationships in the latest reform with important implications for the design of Cohesion policy
Testing an innovative boom for microsatellite attitude stabilization: An educational experiment on sounding rocket rexus-7
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