PHEBUS spectrometer: characterization of optical subsystems prototype (original) (raw)
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PHEBUS UV spectrometer on board ESA-BepiColombo Mission: Instrument design & performance results
International Conference on Space Optics — ICSO 2018, 2019
BepiColombo, a cornerstone mission of European Space Agency (ESA) in cooperation with the Japan Aerospace Exploration Agency (JAXA), will explore Mercury the planet closest to the Sun. This first European mission toward Mercury will be launched in October 2018 from the Guiana Space Centre, on a journey lasting up to six and a half years. The data that will be brought back from the two orbiters will tell us about Mercury's surface, the atmospheric composition, and the magnetospheric dynamics; it will also contribute to understanding the history and formation of terrestrial planets. Probing of Hermean Exosphere by Ultraviolet Spectroscopy (PHEBUS) is a double spectrometer that will be flown on the Mercury Planetary Orbiter (MPO) one of the two BepiColombo orbiters. This French-led instrument was developed with the purpose of detecting emission lines from Mercury's exosphere to reveal its composition and distribution, in the wide UV range 55 nm-315 nm and by recording full spectra. In this paper, we present the instrument design by focusing on the optical subsystems and giving a technical feedback of the major challenges we had to face. We also introduce the calibration philosophy and the main performance results of the instrument.
PHEBUS: A double ultraviolet spectrometer to observe Mercury's exosphere
Planetary and Space Science, 2010
Probing of Hermean exosphere by ultraviolet spectroscopy (PHEBUS) is a double spectrometer for the Extreme Ultraviolet range (55-155 nm) and the Far Ultraviolet range (145-315 nm) 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 scanning system allows to probe, at the highest possible signal-tonoise ratio, selected regions and altitude ranges of interest. Different modes of observation will be used sequentially (vertical scans, alongorbit 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. r
International Conference on Space Optics — ICSO 2010, 2017
PHEBUS (Probing of Hermean Exosphere by Ultraviolet Spectroscopy) is a double spectrometer for the Extreme Ultraviolet range (55-155 nm) and the Far Ultraviolet range (145-315 nm) dedicated to the characterization of Mercury's exosphere composition and dynamics, and surface-exosphere connections. PHEBUS is part of the ESA BepiColombo cornerstone mission payload devoted to the study of Mercury. The BepiColombo mission consists of two spacecrafts: the Mercury Magnetospheric Orbiter (MMO) and the Mercury Planetary Orbiter (MPO) on which PHEBUS will be mounted. PHEBUS is a French-led instrument implemented in a cooperative scheme involving Japan (detectors), Russia (scanner) and Italy (ground calibration). Before launch, PHEBUS team want to perform a full absolute calibration on ground, in addition to calibrations which will be made in-flight, in order to know the instrument's response as precisely as possible. Instrument overview and calibration philosophy are introduced along with the first lights results observed by a first prototype.
Journal of Instrumentation, 2012
Probing of Hermean By Ultraviolet Spectroscopy (PHEBUS) is a double spectrometer that will fly onboard of the BepiColombo mission. It will investigate the composition and dynamic of Mercury's exosphere to better understand the coupled surface -exosphere -magnetosphere system of the planet. The radiometric calibration tests are ongoing and an approach based on the Mueller Matrix formalism has been adopted to determine the pure efficiency of the instrument. To our knowledge, this is the first time that a such complete method is applied to the calibration of space instrumentation.
PHEBUS on Bepi-Colombo: Post-launch Update and Instrument Performance
Space Science Reviews
The Bepi-Colombo mission was launched in October 2018, headed for Mercury. This mission is a collaboration between Europe and Japan. It is dedicated to the study of Mercury and its environment. It will be inserted into Mercury orbit in December 2025 after a 7-year long cruise. Probing of Hermean Exosphere By Ultraviolet Spectroscopy (PHEBUS) is an ultraviolet Spectrograph and is one of the 11 instruments on-board the Mercury Planetary Orbiter (MPO). It is dedicated to the study of the exosphere of Mercury, its composition, dynamics and variability and its interface with the surface of the planet and the solar wind. The PHEBUS instrument contains four distinct detectors covering the spectral range from 55 nm up to 315 nm and two additional narrow windows at 404 nm and 422 nm. It also has a one-degree of freedom mechanism that allows observations along a cone with an half angle of 80 •. This paper follows a detailed presentation of the PHEBUS instrument design that was presented by Chassefière et al. (2010). Here we present an update of the science objectives and measurement requirements following the results published by the MErcury Surface, Space
IEEE Transactions on Geoscience and Remote Sensing, 2000
Visible and infrared hyperspectral imager (VIHI) is 6 one of the three optical heads of the Spectrometers and Imagers 7 for MPO BepiColombo Integrated Observatory SYStem (SIM-8 BIO-SYS) experiment onboard European Space Agency's Bepi-9 Colombo cornerstone mission to Mercury. The other two optical Q1 10 heads of SIMBIO-SYS are a stereo camera and a high-resolution 11 image camera [1]. The experiment is designed to scan the Hermean 12 surface from a polar orbit with the three channels to map the 13 physical, morphological, tectonic, and compositional properties 14 of the planet. The main scientific objectives of SIMBIO-SYS are 15 the study of Mercury's surface geology and stratigraphy, the 16 surface composition, the regolith properties, the crustal differ-17 entiation, impact, and volcanic processes. The VIHI experiment 18 uses a high-performance optical layout (Schmidt telescope and 19 spectrometer in Littrow configuration) which allows investigat-20 ing the 400-2000-nm spectral range with 256 spectral channels 21 (6.25 nm/band sampling). The instrument has an instrument field 22 of view (FOV) of 250 µrad corresponding to a spatial scale of 23 about 100 m/pixel at periherm and 375 m at apoherm. The 24 instrument operates in pushbroom configuration, sampling the 25 surface of Mercury with an FOV of 64 × 0.25 mrad. The main 26 technical challenges of this experiment are focal-plane design 27 (cadmium-mercury-telluride thinned to improve the efficiency 28 at visible wavelengths), short dwell time (from about 40 ms at 29 equator to about 100 ms at poles), thermal control, mechanical 30 miniaturization, radiation hardening, high data rate, and com-31 pression. A description of the internal calibration unit concept and 32 functionalities is given. 33 ). L. Tommasi, I. Ficai Veltroni, and M. Cosi are with the Selex-Galileo
Expected Scientific Performance of the Three Spectrometers on the Extreme Ultraviolet Explorer
International Astronomical Union Colloquium, 1990
The expected in-orbit performance of the three spectrometers included on the Extreme Ultraviolet Explorer (EUVE) astronomical satellite is presented. Recent calibrations of the gratings, mirrors and detectors using monochromatic and continuum EUV light sources allow the calculation of the spectral resolution and throughput of the instrument. An effective area range of 0.2 to 2.8 cm2 is achieved over the wavelength range 70-600Å with a peak spectral resolution λ/Δλ (FWHM) of ~ 360 assuming a spacecraft pointing knowledge of 10 arc seconds (FWHM). For a 40,000 sec observation, the average 3σ sensitivity to a monochromatic line source is 3 × 103 photons cm-2 sec-1. Simulated observations of known classes of EUV sources such as hot white dwarfs and cataclysmic variables are also presented.
Planetary and Space Science, 2010
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.
Far Ultraviolet Spectroscopic Explorer optical system: lessons learned
Instrumentation for UV/EUV Astronomy and Solar Missions, 2000
The Far Ultraviolet Spectroscopic Explorer (FUSE) is a NASA astrophysics satellite designed to produce high resolution spectra in the far-ultraviolet (90.5-118.7 nm bandpass) with a high effective area (20-70 cm 2) and low background detector. It was launched on a three-year mission in June 1999 aboard a Boeing Delta II rocket. The satellite has been performing routine science observations since December 1999. FUSE contains four co-aligned, normal incidence, off-axis parabolic primary mirrors which illuminate separate Rowland circle spectrograph channels equipped with holographically ruled diffraction gratings and microchannel plate detectors. Fine error sensors (slit jaw cameras) operating in the visible on two of the channels are used for target acquisition and guiding. The FUSE mission was first proposed in the late 1980s, and experienced several major conceptual changes prior to fabrication, assembly, and testing, which lasted from 1996 through 1999. During the program, we realized both positive and negative aspects to our design and processes that may apply to other space missions using telescopes and spectrographs. The specific topics we address are requirements, design, component specification, integration, and verification. We also discuss on-orbit alignment and focus. These activities were complicated by unexpected levels of motion between the optical elements, and the logistical problems associated with limited ground contact passes in low Earth orbit. We have developed methods to characterize the motions and mitigate their resultant effects on the science data through a combination of observing techniques and modifications to the data reduction software.
yThe Mercury sodium atmospheric spectral imager for the MMO spacecraft of Bepi-Colombo
Planetary and Space Science, 2010
The Mercury Sodium Atmosphere Spectral Imager (MSASI) on the Mercury Magnetospheric Orbiter (MMO) of the JAXA/ESA Bepi-Colombo (BC) Mission will address a range of fundamental scientific questions pertaining to Mercury's exosphere. The measurements will provide new information on regolith-exosphere-magnetosphere coupling as well as new understanding of the dynamics governing the exosphere bounded by the planetary surface, the solar wind and interplanetary space. MSASI is a highdispersion visible spectrometer working in the spectral region near the sodium D 2 emission (589 nm), a major constituent of the Mercury exosphere. A single high-resolution Fabry-Perot etalon is used in combination with a narrow-band interference filter to achieve a compact and efficient instrument design. The etalon and filter are extremely stable with respect to long-term aging and temperature variations. Full-disk images of the planet are obtained by means of a single-axis scanning mirror in combination with the spin of the MMO spacecraft. This paper presents an overview of the MSASI and the design of the Fabry-Perot interferometer used as its spectral analyser. It is concluded that: (1) The MSASI optical design is practical and can be implemented without new or critical technology developments. (2) The thermally stable etalon design is based on concepts, designs and materials that have a good space heritage. (3) The MSASI instrument will achieve a high signal-to-noise ratio (SNR) (410) in the range of 2 K-10 M Rayleigh.