681 research outputs found
Free-Flying 3D Space Robot Prototype Design and Zero-g Experiments on ESA Parabolic Flights
No full textCalibration of an imaging system for monitoring light pollution from small UAVs
No full textThe paper presents the calibration activity of the imaging system of an autonomous sensor suite designed for monitoring light pollution Which, thanks to its extremely compact design, can be carried by drones or small balloons. Drones and air balloons can in fact play an important role in completing light emission measurement from satellites, allowing an increased spatial and time resolution from convenient altitudes and positions. The proposed sensor suite is able to measure the luminous intensity of polluting sources and their spectral power density with a wavelength resolution which allows to identify the different lamp echnology used in street lighting. By operating over a limited area, the spatial resolution can be about tenths of meter and the time evolution of the luminosity can be measured over hours. The expected performance of imaging system has been verified through an extensive laboratory test activity allowing calibration with referenced light sources. The calibration of the multi-luminance meter allows measurements with a base uncertainty of about 5% of the reading. The multi-spectrometer has a FWHM equal to 10 nm and is able to measure the power density of the outdoor light source in the range between 400 nm and 700 nm
Uncertainty experimental evaluation of the Mercury surfacereconstruction for the SYMBIO-SIS stereo camera
No full textThe present paper analyzes in detail the
measurement uncertainty achievable in 3D
reconstruction of a planetary surface by means
of stereo or multiple images. The analysis is
performed for SIMBIO-SYS experiment onboard
BepiColombo ESA space mission. The main
uncertainty sources, that propagate to the
indirect measurement of 3D points of the
surface by means of the stereo camera (STC),
are evaluated. A simplified model is used to
experimentally evaluate the uncertainty sources
in laboratory and allows to define a procedure
employable during the future development
phases of the mission
Evaluation of Sources of Artificial Light at Night With an Autonomous Payload in a Sounding Balloon Flight
No full textThe presence of artificial light at night is not only limiting astronomical observations but has been linked to negative effects on human health and behavior of wildlife. New measurement systems are therefore needed to monitor artificial light emissions and their time evolution; Misurazione dell’ INquinamento LUminoso autonomous payload has been designed and tested at University of Padova to provide complete aerial observations of artificial light sources over extended areas, with the capability to be integrated either on stratospheric balloons or drones. The implemented architecture is based on commercial components and is controlled by a Raspberry PI single board computer with the capability of uninterrupted operation up to 5 h. The payload was successfully launched with a stratospheric sounding balloon on July 8, 2021 from Lajatico (Tuscany) and performed continuous analysis of emission sources up to the burst altitude of 34 km. The article will describe the calibration activity of the imaging unit which includes commercial cameras with dedicated filters used as luminance measuring device and raw spectrometer and present the elaboration of georeferenced images after reconstruction of the unit's inertial pointing along flight trajectory using combined GPS and IMU data integration.publishedVersio
Lutetia surface reconstruction and uncertainty analysis
No full textMultiple views of Lutetia taken from OSIRIS NAC payload can be used to perform a metric reconstruction of its shape. In this work a general photogrammetric processing pipeline is described and a detailed uncertainty analysis is performed according with the standard metrological procedures. The uncertainty associated with the following quantities are highlighted and evaluated: intrinsic and extrinsic parameters of the multi-view system; the selected image feature detector and descriptor, which contribute to uncertainties associated with the used feature positions in each image plane; the lighting of the scene, which causes a not negligible uncertainty contribution to 2D positions in the image plane. The Bundle Adjustment, at the core of the reconstruction process, allows the assignment of the covariance of each input parameter and the estimation of derived 3D points covariance. The output covariance matrices represent the spatial uncertainty (magnitude and direction) of each reconstructed point and can be used to derive bounds on the uncertainty of other products as dense surface models and other physical parameters. Presented model of Lutetia is derived using 14 NAC images at the closest approach, 8042 features are tracked between consecutive frames and a final point cloud of 2590 points is produced. From the adjusted camera parameters a dense model with (approximately) 1.5 million of points is derived using two views. The dense model has a resolution which is approximately 120 m/px and contains the surface topography up to 1 km scale
UNCERTAINTY ANALYSIS OF IMAGE FEATURES FOR VISIONAPPLICATIONS IN SPACE
No full textA detailed uncertainty analysis for the position of image features is described. Three main uncertainty sources are identified and evaluated: image noise, lighting direction and image resolution. Since the proposed method does not need to acquire multiple images of the same scene in the same shooting conditions, it is particularly suited for applications with a relative motion between the camera and the scene and/or between the lighting source and the scene. The described method is applied to the images acquired during the recent asteroid Lutetia fly-by using the Narrow Angle Camera of the OSIRIS instrument. OSIRIS is a payload of the Rosetta ESA space mission. The obtained numerical results, including histograms and standard uncertainties, are depicted and discussed
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