Constellation of cubesats: 3-star in the humsat/geoid mission

The 3-STAR program is the new cubesat educational project at the Politecnico di Torino. It has been thought in response to the GEOID call for proposals issued by the Education Office of the European Space Agency. The GEOID (GENSO Experimental Orbital Initial Demonstration) initiative wants to settle an orbiting constellation of cubesats to be operated by the GENSO (Global Educational Network for Satellite Operations) ground-stations network. GEOID is expected to be the communication backbone of the initial version of the HUMSAT system. The main goal of HUMSAT is to use the constellation of satellites and the GENSO ground stations, to provide support for humanitarian initiatives, especially in developing areas or areas without infrastructure. The 3-STAR will be one of the nine cubesats in the GEOID constellation. It will be a 3U cubesat derived from the e-st@r cubesat experience. In addition, it will carry two payloads: the HumSat payload, consisting of a simple but extremely reliable communication module compatible with the elements of the HUMSAT system, and the P-GRESSION (Payload for GNSS remote sensing and signal detection) payload. The P-GRESSION payload aims at performing measurements by means of radio-occultation technique and scattering theory, using GNSS signals. In this paper the 3-STAR project is described together with a preliminary assessment on the performances of the GEOID/HUMSAT constellation. The main requirements of the GEOID/HUMSAT project have been used to drive an optimization process aimed at determining the best configurations of a swarm-like constellation of cubesats. The mission scenario is made of the nine GEOID cubesats, a number of GENSO ground nodes and several sensors distributed on the Earth surface. The results of the analysis demonstrate that the aspects related to the cubesat-system design cannot be decoupled from the design of the constellation, not even in a preliminary phase. Further, it is demonstrated that the performances of a swarm-like constellation are comparable to those of a well-distributed on

Constellation of cubesats: 3-star in the humsat/geoid mission

The 3-STAR program is the new cubesat educational project at the Politecnico di Torino. It has been thought in response to the GEOID call for proposals issued by the Education Office of the European Space Agency. The GEOID (GENSO Experimental Orbital Initial Demonstration) initiative wants to settle an orbiting constellation of cubesats to be operated by the GENSO (Global Educational Network for Satellite Operations) ground-stations network. GEOID is expected to be the communication backbone of the initial version of the HUMSAT system. The main goal of HUMSAT is to use the constellation of satellites and the GENSO ground stations, to provide support for humanitarian initiatives, especially in developing areas or areas without infrastructure. The 3-STAR will be one of the nine cubesats in the GEOID constellation. It will be a 3U cubesat derived from the e-st@r cubesat experience. In addition, it will carry two payloads: the HumSat payload, consisting of a simple but extremely reliable communication module compatible with the elements of the HUMSAT system, and the P-GRESSION (Payload for GNSS remote sensing and signal detection) payload. The P-GRESSION payload aims at performing measurements by means of radio-occultation technique and scattering theory, using GNSS signals. In this paper the 3-STAR project is described together with a preliminary assessment on the performances of the GEOID/HUMSAT constellation. The main requirements of the GEOID/HUMSAT project have been used to drive an optimization process aimed at determining the best configurations of a swarm-like constellation of cubesats. The mission scenario is made of the nine GEOID cubesats, a number of GENSO ground nodes and several sensors distributed on the Earth surface. The results of the analysis demonstrate that the aspects related to the cubesat-system design cannot be decoupled from the design of the constellation, not even in a preliminary phase. Further, it is demonstrated that the performances of a swarm-like constellation are comparable to those of a well-distributed on

Fresco Paintings: Development of an Aging Model from 1064 nm Excited Raman Spectra

In this study, we proposed a preliminary kinetic model applied to the carbonation process of fresh lime with the intention to realize a diagnostic tool for aged fresco paintings. The model can be useful, in particular, in the fields of conservation and restoration of ancient lime wall paintings. The dating procedure was achieved through the analysis of 1064 nm excited Raman spectra collected on artificially aged lime samples in addition to ancient samples taken from literature and covering a period of two thousand years. The kinetic model was developed monitoring the concentration of emitting defective centers related to the intensity of 780 cm−1 calcium hydroxide band as a function of the time and depth. This preliminary model shows how Raman spectroscopy, especially NIR micro-Raman, is advantageous for diagnostics and conservation in the cultural heritage field

Optimizing the Mechanoluminescent Properties of CaZnOS:Tb via Microwave-Assisted Synthesis: A Comparative Study with Conventional Thermal Methods

Recent developments in lighting and display technologies have led to an increased focus on materials and phosphors with high efficiency, chemical stability, and eco-friendliness. Mechanoluminescence (ML) is a promising technology for new lighting devices, specifically in pressure sensors and displays. CaZnOS has been identified as an efficient ML material, with potential applications as a stress sensor. This study focuses on optimizing the mechanoluminescent properties of CaZnOS:Tb through microwave-assisted synthesis. We successfully synthesized CaZnOS doped with Tb3+ using this method and compared it with samples obtained through conventional solid-state methods. We analyzed the material's characteristics using various techniques to investigate their structural, morphological, and optical properties. We then studied the material's mechanoluminescent properties through single impacts with varying energies. Our results show that materials synthesized through microwave methods exhibit similar optical and, primarily, mechanoluminescent properties, making them suitable for use in photonics applications. The comparison of the microwave and conventional solid-state synthesis methods highlights the potential of microwave-assisted methods to optimize the properties of mechanoluminescent materials for practical applications

Photoluminescent and paramagnetic centers in gamma irradiated porous silica

The photolummescence and electron spin resonance properties of gamma irradiated (up to 500 kGy) porous silica are reported. By exciting at 5.6 eV a photoluminescence contribution can be detected before irradiation, peaked at about 4.1 eV. Gamma irradiation causes the generation of the E' centers (about 1 x 10(14) defects cm(-3)) of paramagnetic hole centers and modifies the photoluminescence properties of the sample: the emission amplitude decreases and three contributions can be singled out at about 3.3, 3.8 and 4.4 eV. (c) 2005 Elsevier B.V. All rights reserved

Low temperature time resolved photoluminescence of the 3.1 and 4.2 eV emission bands in Ge-doped silica

Time resolved photoluminescence (PL) has been performed on Ge-doped silica preform in the temperature range 10 to 295 K. Under pulsed KrF laser (5 eV) the well known c~ and [3 emissions have been recorded at different delays from excitation. An accurate analysis of the time resolved spectra taken at different temperatures has shown the composite property of the two PL structures. At room temperature cx components (c~ ], ~2) are peaked at 4.09 and 4.26 eV with a decay time of about 10 ns. The peak energies of [3j and 132 components are calculated at 3.03 and 3.21 eV with lifetimes of 111 and 94 ~s, respectively. As temperature is decreased, a l and o~ 2 display the normal behaviour increasing in intensity down to 125 K; on the contrary, in the same temperature range, 13 n and [32 undergo a quenching of their intensities. Taking into account their mutual spectral characteristics, ~ has been correlated to [31 and c~ 2 to [32. The two sets of emission bands are tentatively attributed to a single center stabilized in different environments of the glassy matrix

Mesoporous silica photoluminescence properties in samples with different pore size

Ultraviolet excited photoluminescence of porous silica under vacuum conditions is investigated in samples with different pore diameters. By exciting in the 180–300 nm range, a manifold luminescence activity in the 300–600 nm is found. The reconstructed three-dimensional photoluminescence excitation pattern shows how the distribution of the emissions changes by varying the pore size of the samples. Two different centers are singled out and their relative concentration is suggested to be a function of the pore size of the samples

Photoconductive properties of HgGa2S4

Mercury thiogallate, HgGa2S4 is a defect chalcopyrite semiconductor with the space group S-4(2) which offers a combination of attractive properties for applications. In order to obtain information about the electron states in the energy gap, photoconductivity measurements are performed in the 80-300 K range. Photoconductivity spectra show two peaks related to intrinsic and extrinsic excitation at about 4 10 and 500 nm, respectively; these maxima show a temperature dependence similar to the linear coefficient of the energy gap. Thermally stimulated currents have been studied by exciting the samples with intrinsic light at different temperatures. For all excitation temperatures a single TSC peaks were obtained. The analysis of TSC curves allowed one to estimate the kinetics of the trap emptying, trap energy distribution and thermal activation energy. A model for the level distribution in the semiconductor energy gap is suggested which in good agreement with the results of a previous photoluminescence study. (C) 2003 Elsevier Ltd. All rights reserved