PHEBUS: A double ultraviolet spectrometer to observe Mercury's exosphere

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/50768

Title:	PHEBUS: A double ultraviolet spectrometer to observe Mercury's exosphere
Authors:	Chassefiere,E;Maria,JL;Goutail,JP;Quemerais,E;Leblanc,F;Okano,S;Yoshikawa,I;Korablev,O;Gnedykh,V;Naletto,G;Nicolosi,P;Pelizzo,MG;Correia,JJ;Gallet,S;Hourtoule,C;Mine,PO;Montaron,C;Rouanet,N;Rigal,JB;Muramaki,G;Yoshioka,K;Kozlov,O;Kottsov,V;Moisseev,P;Semena,N;Bertaux,JL;Capria,MT;Clarke,J;Cremonese,G;Delcourt,D;Doressoundiram,A;Erard,S;Gladstone,R;Grande,M;Hunten,D;Ip,W;Izmodenov,V;Jambon,A;Johnson,R;Kallio,E;Killen,R;Lallement,R;Luhmann,J;Mendillo,M;Milillo,A;Palme,H;Potter,A;Sasaki,S;Slater,D;Sprague,A;Stern,A;Yan,N
Contributors:	天文研究所
Date:	2010
Issue Date:	2012-03-27 18:09:49 (UTC+8)
Publisher:	國立中央大學
Abstract:	Probing of Hermean exosphere by ultraviolet spectroscopy (PHEBUS) is a double spectrometer for the Extreme Ultraviolet range (55-155nm) and the Far Ultraviolet range (145-315nm) devoted to the characterization of Mercury's exosphere composition and dynamics, and surface-exosphere connections. This French-led instrument is implemented in a cooperative scheme involving Japan (detectors), Russia (scanner) and Italy (ground calibration). PHEBUS will address the following main scientific objectives relative to Mercury's exosphere: determination of the composition and the vertical structure of the exosphere; characterization of the exospheric dynamics: day to night circulation, transport between active and inactive regions; study of surface release processes, identification and characterization of the sources of exospheric constituents'. detection and characterization of ionized species and their relation with the neutral atmosphere; space and time monitoring of exosphere/magnetosphere exchange and transport processes, study and quantification of escape, global scale source/sink balance and geochemical cycles synergistically with other experiments of BepiColombo (Mercury Sodium Atmospheric Spectral Imager (MSASI), Mercury Plasma Particle Experiment (MPPE) on Mercury Magnetospheric Orbiter (MMO); Mercury imaging X-ray spectrometer (MIXS), Search for exosphere refilling and emitted neutral abundance (SERENA) on Mercury Planetary Orbiter (MPO)). Two gratings and two detectors are used according to a specific, compact design. The spectrum detection is based on the photon counting method and is realized using micro-channel plate (MCP) detectors with Resistive Anode Encoder (RAE). Typical photocathodes are CsI or KBr for the extreme ultra-violet (EUV) range, CsTe for the far ultra-violet (FUV) range. Extra visible lines are monitored using a photo-multiplier (PM) that is also used in photon counting mode. In order to prevent sensitivity losses which are critical in UV ranges, a minimum of reflections is achieved inside the instrument using only an off-axis parabola and a set of holographic gratings. A one degree-of-freedom in scanning system allows to probe, at the highest possible signal-to-noise ratio, selected regions and altitude ranges of interest. Different modes of observation will be used sequentially (vertical scans, along-orbit scans, grazing observations at twilight, etc.). During the mission, the instrument will be regularly calibrated on well chosen stars, in such a way to quantitatively estimate the overall degradation of the sensitivity of the instrument. (C) 2008 Elsevier Ltd. All rights reserved.
Relation:	PLANETARY AND SPACE SCIENCE
Appears in Collections:	[Graduate Institute of Astronomy] journal & Dissertation

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