scholarly journals A low-frequency blind survey of the low Earth orbit environment using non-coherent passive radar with the Murchison widefield array

2020 ◽  
Vol 37 ◽  
Author(s):  
S. Prabu ◽  
P. Hancock ◽  
X. Zhang ◽  
S. J. Tingay
Keyword(s):  
Large Scale ◽  
Imaging Techniques ◽  
Careful Consideration ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Blind Detection ◽  
Passive Radar ◽  
Interferometric Imaging ◽  
Murchison Widefield Array ◽  
The Impact

Abstract We have extended our previous work to use the Murchison widefield array (MWA) as a non-coherent passive radar system in the FM frequency band, using terrestrial FM transmitters to illuminate objects in low Earth orbit (LEO) and the MWA as the sensitive receiving element for the radar return. We have implemented a blind detection algorithm that searches for these reflected signals in difference images constructed using standard interferometric imaging techniques. From a large-scale survey using 20 h of archived MWA observations, we detect 74 unique objects over multiple passes, demonstrating the MWA to be a valuable addition to the global Space Domain Awareness network. We detected objects with ranges up to 977 km and as small as $0.03$ ${\rm m}^2$ radar cross section. We found that 30 objects were either non-operational satellites or upper-stage rocket body debris. Additionally, we also detected FM reflections from Geminid meteors and aircraft flying over the MWA. Most of the detections of objects in LEO were found to lie within the parameter space predicted by previous feasibility studies, verifying the performance of the MWA for this application. We have also used our survey to characterise these reflected signals from LEO objects as a source of radio frequency interference (RFI) that corrupts astronomical observations. This has allowed us to undertake an initial analysis of the impact of this RFI on the MWA and the future square kilometer array (SKA). As part of this analysis, we show that the standard MWA RFI flagging strategy misses most of this RFI and that this should be a careful consideration for the SKA.

Trust, efficacy and ethicacy when testing prisoners for COVID-19

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Steve Lambert ◽  
Dean Wilkinson
Keyword(s):  
Large Scale ◽  
Current System ◽  
Epidemiological Studies ◽  
Careful Consideration ◽  
Power Relationships ◽  
England And Wales ◽  
Content Type ◽  
Large Scale Testing ◽  
The Uk ◽  
The Impact

Purpose The outbreak of the severe acute respiratory syndrome coronavirus 2 virus and subsequent COVID-19 illness has had a major impact on all levels of society internationally. The extent of the impact of COVID-19 on prison staff and prisoners in England and Wales is unknown. Testing for COVID-19 both asymptomatic and symptomatic, as well as for antibodies, to date, has been minimal. The purpose of this paper is to explore the widespread testing of COVID-19 in prisons poses philosophical and ethical questions around trust, efficacy and ethicacy. Design/methodology/approach This paper is both descriptive, providing an overview of the widespread testing of COVID-19 in prisoners in England and Wales, and conceptual in that it discusses and argues the issues associated with large-scale testing. This paper provides a discussion, using comparative studies, of the issues associated with large-scale testing of prisoners across the prison estate in England and Wales (120 prisons). The issues identified in this paper are contextualised through the lens of COVID-19, but they are equally transferrable to epidemiological studies of any pandemic. Given the prevalence of COVID-19 globally and the lack of information about its spread in prisons, at the time of writing this paper, there is a programme of asymptomatic testing of prisoners. However, there remains a paucity of data on the spread of COVID-19 in prisons because of the progress with the ongoing testing programme. Findings The authors argue that the widespread testing of prisoners requires careful consideration of the details regarding who is included in testing, how consent is gained and how tests are administered. This paper outlines and argues the importance of considering the complex nuance of power relationships within the prison system, among prisoner officers, medical staff and prisoners and the detrimental consequences. Practical implications The widespread testing of COVID-19 presents ethical and practical challenges. Careful planning is required when considering the ethics of who should be included in COVID-19 testing, how consent will be gained, who and how tests will be administered and very practical challenges around the recording and assigning of COVID-19 test kits inside the prison. The current system for the general population requires scanning of barcodes and registration using a mobile number; these facilities are not permitted inside a prison. Originality/value This paper looks at the issues associated with mass testing of prisoners for COVID-19. According to the authors’ knowledge, there has not been any research that looks at the issues of testing either in the UK or internationally. The literature available details countries’ responses to the pandemic rather and scientific papers on the development of vaccines. Therefore, this paper is an original review of some of the practicalities that need to be addressed to ensure that testing can be as successful as possible.

Preliminary Study on De-Orbiting Large-Scale Debris Using a Charged Membrane in Low Earth Orbit

2021 ◽  
Vol 19 (2) ◽  
pp. 270-274
Author(s):  
Takanobu MURANAKA ◽  
Takuma NAGATA ◽  
Hiroki NAGAI ◽  
Kazuma UENO ◽  
Teppei OKUMURA ◽  
...  
Keyword(s):  
Large Scale ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Charged Membrane ◽  
Preliminary Study

scholarly journals Emerging imaging methods to study whole-brain function in rodent models

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marija Markicevic ◽  
Iurii Savvateev ◽  
Christina Grimm ◽  
Valerio Zerbi
Keyword(s):  
Large Scale ◽  
Functional Organization ◽  
Imaging Techniques ◽  
Brain Activity ◽  
Research Question ◽  
Careful Consideration ◽  
Mammalian Brain ◽  
High Temporal Resolution ◽  
Imaging Methods ◽  
Evoked Activity

AbstractIn the past decade, the idea that single populations of neurons support cognition and behavior has gradually given way to the realization that connectivity matters and that complex behavior results from interactions between remote yet anatomically connected areas that form specialized networks. In parallel, innovation in brain imaging techniques has led to the availability of a broad set of imaging tools to characterize the functional organization of complex networks. However, each of these tools poses significant technical challenges and faces limitations, which require careful consideration of their underlying anatomical, physiological, and physical specificity. In this review, we focus on emerging methods for measuring spontaneous or evoked activity in the brain. We discuss methods that can measure large-scale brain activity (directly or indirectly) with a relatively high temporal resolution, from milliseconds to seconds. We further focus on methods designed for studying the mammalian brain in preclinical models, specifically in mice and rats. This field has seen a great deal of innovation in recent years, facilitated by concomitant innovation in gene-editing techniques and the possibility of more invasive recordings. This review aims to give an overview of currently available preclinical imaging methods and an outlook on future developments. This information is suitable for educational purposes and for assisting scientists in choosing the appropriate method for their own research question.

scholarly journals Atmospheric drag effects on modelled low Earth orbit (LEO) satellites during the July 2000 Bastille Day event in contrast to an interval of geomagnetically quiet conditions

2021 ◽  
Vol 39 (3) ◽  
pp. 397-412
Author(s):  
Victor U. J. Nwankwo ◽  
William Denig ◽  
Sandip K. Chakrabarti ◽  
Muyiwa P. Ajakaiye ◽  
Johnson Fatokun ◽  
...  
Keyword(s):  
Geomagnetic Activity ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Satellite Orbits ◽  
Percentage Increase ◽  
Atmospheric Drag ◽  
Drag Effect ◽  
Satellite Drag ◽  
Ballistic Coefficient ◽  
The Impact

Abstract. In this work, we simulated the atmospheric drag effect on two model SmallSats (small satellites) in low Earth orbit (LEO) with different ballistic coefficients during 1-month intervals of solar–geomagnetic quiet and perturbed conditions. The goal of this effort was to quantify how solar–geomagnetic activity influences atmospheric drag and perturbs satellite orbits, with particular emphasis on the Bastille Day event. Atmospheric drag compromises satellite operations due to increased ephemeris errors, attitude positional uncertainties and premature satellite re-entry. During a 1-month interval of generally quiescent solar–geomagnetic activity (July 2006), the decay in altitude (h) was a modest 0.53 km (0.66 km) for the satellite with the smaller (larger) ballistic coefficient of 2.2×10-3 m2 kg−1 (3.03×10-3 m2 kg−1). The associated orbital decay rates (ODRs) during this quiet interval ranged from 13 to 23 m per day (from 16 to 29 m per day). For the disturbed interval of July 2000 the significantly increased altitude loss and range of ODRs were 2.77 km (3.09 km) and 65 to 120 m per day (78 to 142 m per day), respectively. Within the two periods, more detailed analyses over 12 d intervals of extremely quiet and disturbed conditions revealed respective orbital decays of 0.16 km (0.20 km) and 1.14 km (1.27 km) for the satellite with the smaller (larger) ballistic coefficient. In essence, the model results show that there was a 6- to 7-fold increase in the deleterious impacts of satellite drag between the quiet and disturbed periods. We also estimated the enhanced atmospheric drag effect on the satellites' parameters caused by the July 2000 Bastille Day event (in contrast to the interval of geomagnetically quiet conditions). The additional percentage increase, due to the Bastille Day event, to the monthly mean values of h and ODR are 34.69 % and 50.13 % for Sat-A and 36.45 % and 68.95 % for Sat-B. These simulations confirmed (i) the dependence of atmospheric drag force on a satellite's ballistic coefficient, and (ii) that increased solar–geomagnetic activity substantially raises the degrading effect of satellite drag. In addition, the results indicate that the impact of short-duration geomagnetic transients (such as the Bastille Day storm) can have a further deleterious effect on normal satellite operations. Thus, this work increases the visibility and contributes to the scientific knowledge surrounding the Bastille Day event and also motivates the introduction of new indices used to describe and estimate the atmospheric drag effect when comparing regimes of varying solar–geomagnetic activity. We suggest that a model of satellite drag, when combined with a high-fidelity atmospheric specification as was done here, can lead to improved satellite ephemeris estimates.

Gynecologic Risk Mitigation Considerations for Long-Duration Spaceflight

2020 ◽  
Vol 91 (7) ◽  
pp. 543-564
Author(s):  
Jon G. Steller ◽  
Rebecca S. Blue ◽  
Roshan Burns ◽  
Tina M. Bayuse ◽  
Erik L. Antonsen ◽  
...  
Keyword(s):  
Risk Mitigation ◽  
Low Earth Orbit ◽  
Space Environment ◽  
Earth Orbit ◽  
Mineral Density ◽  
Management Options ◽  
Health Maintenance ◽  
Medical Risk ◽  
Long Duration ◽  
The Impact

INTRODUCTION: As NASA and its international partners, as well as the commercial spaceflight industry, prepare for missions of increasing duration and venturing outside of low-Earth orbit, mitigation of medical risk is of high priority. Gynecologic considerations constitute one facet of medical risk for female astronauts. This manuscript will review the preflight, in-flight, and postflight clinical evaluation, management, and prevention considerations for reducing gynecologic and reproductive risks in female astronauts.METHODS: Relevant gynecological articles from databases including Ovid, Medline, Web of Science, various medical libraries, and NASA archives were evaluated for this review. In particular, articles addressing preventive measures or management of conditions in resource-limited environments were evaluated for applicability to future long-duration exploration spaceflight.RESULTS: Topics including abnormal uterine bleeding, anemia, bone mineral density, ovarian cysts, venous thromboembolism, contraception, fertility, and health maintenance were reviewed. Prevention and treatment strategies are discussed with a focus on management options that consider limitations of onboard medical capabilities.DISCUSSION: Long-duration exploration spaceflight will introduce new challenges for maintenance of gynecological and reproductive health. The impact of the space environment outside of low-Earth orbit on gynecological concerns remains unknown, with factors such as increased particle radiation exposure adding complexity and potential risk. While the most effective means of minimizing the impact of gynecologic or reproductive pathology for female astronauts is screening and prevention, gynecological concerns can arise unpredictably as they do on Earth. Careful consideration of gynecological risks and potential adverse events during spaceflight is a critical component to risk analysis and preventive medicine for future exploration missions.Steller JG, Blue RS, Burns R, Bayuse TM, Antonsen EL, Jain V, Blackwell MM, Jennings RT. Gynecologic risk mitigation considerations for long-duration spaceflight. Aerosp Med Hum Perform. 2020; 91(7):543–564.

scholarly journals The Impact of Innovation in the Satellite Industry on the Telecommunications Services Market

2020 ◽  
Vol 73 ◽  
Author(s):  
Krasimir Terziev ◽  
Dimitar Karastoyanov
Keyword(s):  
Low Earth Orbit ◽  
Earth Orbit ◽  
Orbit Satellite ◽  
Leo Satellites ◽  
Different Types ◽  
Telecommunications Services ◽  
Global Communications ◽  
The Impact

The article analyses the role of the satellites in global communications. Different types of orbits and different types of satellites are described. The commercial start of low and medium orbit satellites is considered. The integration of some Low Earth Orbit (LEO) projects with Teleports is commented. Some significant LEO/MEO (Medium Earth Orbit) projects are cited. The impact of the satellite industry and the Teleport systems on the technological ecosystem is discussed. LEO satellites for monitoring the earth's surface are presented. Keywords: LEO, Orbit, Satellite, Teleport.

scholarly journals Precise Relative Orbit Determination for Chinese TH-2 Satellite Formation Using Onboard GPS and BDS2 Observations

2021 ◽  
Vol 13 (21) ◽  
pp. 4487
Author(s):  
Bin Yi ◽  
Defeng Gu ◽  
Kai Shao ◽  
Bing Ju ◽  
Houzhe Zhang ◽  
...  
Keyword(s):  
Orbit Determination ◽  
Low Earth Orbit ◽  
Asia Pacific ◽  
Earth Orbit ◽  
Reference Orbit ◽  
Satellite Formation ◽  
Relative Orbit ◽  
Comparison Results ◽  
Geo Satellites ◽  
The Impact

TH-2 is China’s first short-range satellite formation system used to realize interferometric synthetic aperture radar (InSAR) technology. In order to achieve the mission goal of InSAR processing, the relative orbit must be determined with high accuracy. In this study, the precise relative orbit determination (PROD) for TH-2 based on global positioning system (GPS), second-generation BeiDou navagation satellite system (BDS2), and GPS + BDS2 observations was performed. First, the performance of onboard GPS and BDS2 measurements were assessed by analyzing the available data, code multipath errors and noise levels of carrier phase observations. The differences between the National University of Defense Technology (NDT) and the Xi’an Research Institute of Surveying and Mapping (CHS) baseline solutions exhibited an RMS of 1.48 mm outside maneuver periods. The GPS-based orbit was used as a reference orbit to evaluate the BDS2-based orbit and the GPS + BDS2-based orbit. It is the first time BDS2 has been applied to the PROD of low Earth orbit (LEO) satellite formation. The results showed that the root mean square (RMS) of difference between the PROD results using GPS and BDS2 measurements in 3D components was 2.89 mm in the Asia-Pacific region. We assigned different weights to geostationary Earth orbit (GEO) satellites to illustrate the impact of GEO satellites on PROD, and the accuracy of PROD was improved to 7.08 mm with the GEO weighting strategy. Finally, relative orbits were derived from the combined GPS and BDS2 data. When BDS2 was added on the basis of GPS, the average number of visible navigation satellites from TH-2A and TH-2B improved from 7.5 to 9.5. The RMS of the difference between the GPS + BDS2-based orbit and the GPS-based orbit was about 1.2 mm in 3D. The overlap comparison results showed that the combined orbit consistencies were below 1 mm in the radial (R), along-track (T), and cross-track (N) directions. Furthermore, when BDS2 co-worked with GPS, the average of the ambiguity dilution of precision (ADOP) reduced from 0.160 cycle to 0.153 cycle, which was about a 4.4% reduction. The experimental results indicate that millimeter-level PROD results for TH-2 satellite formation can be obtained by using onboard GPS and BDS2 observations, and multi-GNSS can further improve the accuracy and reliability of PROD.

scholarly journals The Impact of Social Capital on FDI in Georgia

2017 ◽  
Vol 9 (1) ◽  
pp. 17
Author(s):  
Natia Aghladze
Keyword(s):  
Social Capital ◽  
Social Change ◽  
Financial Development ◽  
Large Scale ◽  
National Level ◽  
Careful Consideration ◽  
Scale Level ◽  
The Impact

FDI brings capital, innovation exchanges and new employments and administration aptitude. In numerous nations, FDI inflow is lower than anticipated. In spite of the inclination for more extensive large scale level examinations of the particular social developments inside which financial exercises happen, a considerable measure of national-level investigations of the determinants of outside contributed firms have given careful consideration to the parts played by social capital and its unexpected incentive in influencing remote direct venture inflows. Drawing on the rationale of social capital and institutional hypothesis, this article looks to offer a correlative clarification of FDI by inspecting experimentally the national-level effects of social capital (trust and affiliated action) on FDI and the directing part of administrative quality in its connections. FDI is the essential part for an open and fruitful global monetary framework and a noteworthy instrument for improvement. In this condition, the paper looks at the advantages of FDI as a key segment for fruitful and feasible financial development and as a piece of a strategy to social change. The point is to feature the most vital channels through which FDI makes a huge and uncommon effect on the monetary advancement of the host nations.

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