1,721,042 research outputs found
Flight test of an autonomous payload for measuring sky brightness and ground light pollution using a stratospheric sounding balloon
No full textMeasurement of light pollution and sky brightness in a sounding balloon flight: data elaboration through inertial pointing reconstruction.
No full textThe MINLU (“Misurazione dell’ INquinamento LUminoso”) payload was successfully launched on July
7th 2021 with a sounding balloon from Tuscany, achieving continuous observation of sky brightness
magnitude in Earth atmosphere from ground to stratospheric altitude of 32 km. The operation was the
result of a joint effort by the Department of Industrial Engineering (DII) and the Center of Studies and
Activities for Space “G.Colombo” of University of Padova which realized the scientific gondola in
collaboration with the Space Systems Lab from University of Pisa, that provided its UniPiHAB04 flight
platform to carry the system to stratospheric altitude and safely back to ground.
MINLU autonomous payload has been designed and tested to provide complete and detailed aerial
observations of light pollution sources and sky brightness, with the capability to be integrated either on
stratospheric balloons or drones. The implemented architecture includes three cameras with dedicated
filters and two commercial Sky Quality Meter (SQM-LE) units, controlled by a Raspberry based Central
Data Management Unit performing sensor conditioning, data acquisition, compression and storage;
inertial position and attitude information are acquired by on board GPS and IMU units and
automatically linked to scientific data.
The work will present first results of trajectory and attitude reconstruction along with the elaboration
of SQM data during the astronomical night, highlighting the impact of pointing accuracy on the
calculation of sky brightness altitude dependant profiles. Since no active attitude control mechanism is
present in the payload, light emitting areas on ground may enter in the field of view of SQM, inducing
errors in the readings if attitude is not taken into consideration to eliminate such interference from the
acquired signal
Analysis of ganymede rotational state using JANUS telescope
No full textGanymede as well as Europa and Callisto are thought to present a complex internal structure comprising a sub-surface ocean. The thickness of its ice shell, the presence and depth of the liquid layer as well as the details about the interior structure have not been well constrained. Direct measurement of librational motion of Ganymede will be a useful tool for detecting an ocean and characterizing the interior parameters of this moon. JUICE high-resolution camera images will be used to track landmarks on the surface of this body and measure their longitudinal shift. Goal of this work is to define an error budget for such kind of measurements, investigate to which extent the libration can be detected and define both the algorithms and the observational strategies that could be used for this analysis
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Determination and Uncertainty Analysis of Mercury Libration Using BepiColombo HRIC Images
No full textBepiColombo is an upcoming joint ESA/JAXA mission to Mercury. In particular the High Spatial Resolution Camera (HRIC), part of the SIMBIO-SYS (Spectrometer and Imagers for MPO Bepicolombo Integrated Observatory - SYStem) instrument suite, will characterize in detail the surface of the planet. In this work the BepiColombo rotation experiment is analysed: goal of the experiment is to investigate Mercury's interior measuring its rotational state. In this experiment images of surface regions taken at different epochs are used to retrieve information on Mercury's rotation and libration parameters. This analysis requires the use of an accurate model of the rotation of Mercury, to correlate the position of observed landmarks with planet libration. Then model parameters can be derived from observations using a maximum likelihood estimator. Uncertainties on spacecraft position, spacecraft attitude, imaged landmark position and camera intrinsic parameters result in the overall uncertainty on the estimated parameters. Simulations of the experiment and uncertainty analysis show that, with a small number of landmarks/images, the total planet libration can be measured. This analysis provides also support for the better design of the experiment in order to attain its scientific goals
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Design and development of a high capacity pressure controlled modular gondola for long duration stratospheric balloon missions
No full textMaximization of LEO Nanosatellite's Transmission Capacity to Multiple Ground Stations: Orbit Selection and Requirements on Attitude Control
No full textThis paper presents the study of an optimized orbital configuration for a 3-axis stabilized 6U LEO nanosatellite that accommodates a polarized calibrator designed to transmit a calibrated signal to seven ground telescopes devoted to Cosmic Microwave Background (CMB) detection with an accepted maximum absolute pointing error of 4 arcmin; visibility windows and revisit time are maximized by orbit selection and active attitude control considering no possibility of orbital mobility. The solution approach is divided in two parts: in the first part, a dedicated sensitivity study is conducted to find the optimal orbital parameters that maximize the mean contact time between the spacecraft and the list of ground telescopes; in the second part the identified promising orbital configurations are propagated to evaluate the attitude change maneuvers needed during the passage above each telescope to guarantee continuous signal transmission. The results of the sensitivity study report the maximum values for the duration and frequency of the CubeSat-to-Ground station visibility periods. The required performance in terms of pointing accuracy and repointing velocity is later used to propose an attitude control loop for precision pointing and to define a commercial off the shelf Attitude Determination and Control System (ADCS) architecture
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