The VIR Spectrometer De Sanctis, M. C.; Coradini, A.; Ammannito, E. ...
Space science reviews,
12/2011, Letnik:
163, Številka:
1-4
Journal Article
Recenzirano
The Dawn spectrometer (VIR) is a hyperspectral spectrometer with imaging capability. The design fully accomplishes Dawn’s scientific and measurement objectives. Determination of the mineral ...composition of surface materials in their geologic context is a primary Dawn objective. The nature of the solid compounds of the asteroid (silicates, oxides, salts, organics and ices) can be identified by visual and infrared spectroscopy using high spatial resolution imaging to map the heterogeneity of asteroid surfaces and high spectral resolution spectroscopy to determine the composition unambiguously. The VIR Spectrometer—covering the range from the near UV (0.25 μm) to the near IR (5.0 μm) and having moderate to high spectral resolution and imaging capabilities—is the appropriate instrument for the determination of the asteroid global and local properties. VIR combines two data channels in one compact instrument. The visible channel covers 0.25–1.05 μm and the infrared channel covers 1–5.0 μm. VIR is inherited from the VIRTIS mapping spectrometer (Coradini et al. in Planet. Space Sci. 46:1291–1304,
1998
; Reininger et al. in Proc. SPIE 2819:66–77,
1996
) on board the ESA Rosetta mission. It will be operated for more than 2 years and spend more than 10 years in space.
In this work, the performance analysis and discussion of a space vector modulation technique used for a three-phase direct matrix converter feeding a three-phase induction motor is presented. For ...this, the induction motor models and the method of the space vector modulation technique are developed. Then, the overall electrical drive system is simulated using MatLab/Simulik software. Results obtained from simulation are the harmonic spectrum analysis of the motor current and the total harmonic distortion for unbalanced input voltages. These results show the good performance of the control system strategy.
The limited knowledge about the majority of the Mercury surface leaves many open questions regarding its geological evolution, the anomalously high metal/silicate ratio, the magnetic field generation ...and exosphere evolution. An integrated suite of instruments, Spectrometer and Imagers for MPO BepiColombo-Integrated Observatory SYStem (SIMBIO-SYS), which includes a stereo imaging system (STC), a high-resolution imager (HRIC) and a visible–near-infrared imaging spectrometer (VIHI), has been selected for the ESA BepiColombo mission to Mercury. SIMBIO-SYS will scan the hermean surface with the three channels and map the physical, morphological, tectonic and compositional properties of the entire planet. The availability of high-resolution images will unveil details of specific target at an unprecedented resolution. The main scientific objectives and performances along with technical characteristics of SIMBIO-SYS are described in this paper.
The STereo imaging Channel (STC) is a double wide-angle camera developed to be one of the channels of the SIMBIO-SYS instrument onboard of the ESA BepiColombo mission to Mercury. STC main goal is to ...map in 3D the whole Mercury surface. The geometric and radiometric responses of the STC Proto Flight model have been characterized on-ground during the calibration campaign. The derived responses will be used to calibrate the STC images that will be acquired in flight. The aim is to determine the functions linking the detected signal in digital number to the radiance of the target surface in physical units. The result of the radiometric calibration consists in the determination of well-defined quantities: (1) the dark current as a function of the integration time and of the detector temperature, settled and controlled to be stable at 268 K; (2) the read out noise, which is associated with the noise signal of the read-out electronic; and (3) the fixed pattern noise, which is generated by the different response of each pixel. Once these quantities are known, the photon response and the photo-response non-uniformity, which represents the variation of the photon responsivity of a pixel in an array, can be derived. The final result of the radiometric calibration is the relation between the radiance of an accurately known and uniform source, and the digital numbers measured by the detector.
BepiColombo, an European Space Agency (ESA) mission being conducted in cooperation with the Japan space agency, will explore Mercury with a set of eleven instruments onboard the spacecraft Mercury ...Planetary Orbiter (MPO). Among them, SIMBIO-SYS (Spectrometers and Imagers for MPO BepiColombo Integrated Observatory SYStem) is a complex instrument that will provide images and spectra in the 400–2000nm wavelength range of the entire surface of Mercury. Pre-flight calibration of the SYMBIO-SYS instrument is mandatory for reliable scientific interpretation of images and spectra returned from the planet Mercury. This paper presents the calibration device designed and implemented for the specific requirements of this instrument. It mainly consists of a thermal vacuum chamber simulating the space environment, an optical bench collecting calibration sources and optical elements that simulate the conditions of Mercury observations, mechanical interfaces used for positioning the three channels inside the vacuum chamber, thermal interfaces to explore the operating temperatures, computer interfaces that allow to communicate with both the instrument and the calibration elements and synchronize the calibrations sequences with the status of the calibration device. As the major goal is the characterization of the radiometric performances of the three channels of SIMBIO-SYS, radiometric performances of the test setup evaluated by simulations and measurements are emphasized.
●The on-ground device dedicated to the calibration of SIMBIO-SYS is described.●Radiometric performances of the setup is evaluated by simulations and measurements.●Their compliance with the objectives of the calibration are modeled and validated.
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