Publication archive

Publication archive

Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation. Edited by Atad-Ettedgui, Eli; Lemke, Dietrich. Proceedings of the SPIE, Volume 7018, pp. 70181Y-70181Y-15 (2008)

The James Webb Space Telescope (JWST) mission is a collaborative project between the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA) and the Canadian Space Agency (CSA) and is considered as the successor to the Hubble Space Telescope (HST). The European contribution consists in providing the Ariane 5 launcher and two out of the four instruments: a combined mid-infrared camera/spectrograph (MIRI) and a near infrared spectrograph (NIRSpec). This article will address the mechanical aspects of NIRSpec by providing an overview of the design drivers and the related solutions for the structure, the thermal design and the mechanisms so as to achieve the required stringent optical performances. The industrial set-up and the project development status will also be presented.

Published: 24 July 2008
Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation. Edited by Atad-Ettedgui, Eli; Lemke, Dietrich. Proceedings of the SPIE, Volume 7018, pp. 701821-701821-12 (2008)

The Grating and Filter Wheel Mechanisms of the JWST NIRSpec instrument allow for reconfiguration of the spectrograph in space in a number of NIR sub-bands and spectral resolutions. Challenging requirements need to be met simultaneously including high launch loads, the large temperature shift to cryo-space, high position repeatability and minimum deformation of the mounted optics. The design concept of the NIRSpec wheel mechanisms is based on the ISOPHOT Filter Wheels but with significant enhancements to support much larger optics. A well-balanced set of design parameters was to be found and a considerable effort was spent to adjust the hardware within narrow tolerances.

Published: 24 July 2008
High Energy, Optical, and Infrared Detectors for Astronomy III. Edited by Dorn, David A.; Holland, Andrew D. Proceedings of the SPIE, Volume 7021, pp. 702127-702127-12 (2008)

We present interim results from the characterization test development for the Detector Subsystem of the Near-Infrared Spectrograph (NIRSpec). NIRSpec will be the primary near-infrared spectrograph on the James Webb Space Telescope (JWST). The Detector Subsystem consists of a Focal Plane Assembly containing two Teledyne HAWAII-2RG arrays, two Teledyne SIDECAR cryogenic application specific integrated circuits, and a warm Focal Plane Electronics box. The Detector Characterization Laboratory at NASA's Goddard Space Flight Center will perform the Detector Subsystem characterization tests. In this paper, we update the initial test results obtained with engineering grade components.

Published: 23 July 2008
In "High Energy, Optical, and Infrared Detectors for Astronomy III", edited by David A. Dorn, Andrew D. Holland, Proc. of SPIE Vol. 7021, 70210N, (2008), doi: 10.1117/12.789726

We present the development of a Focal Plane Module (FPM) for the Mid-Infrared Instrument on JWST. MIRI will include three FPMs, two for the spectrometer channels and one for the imager channel. The FPMs are designed to support the detectors at an operating temperature of 6.7 K with high temperature stability and precision alignment while being capable of surviving the launch environment. The flight units will be built and will undergo a rigorous test program in the first half of 2008. This paper includes a description of the full test program and will present the results.

Published: 23 July 2008

Aims: We report on the production of a large area, shallow, sky survey, from XMM-Newton slews. The great collecting area of the mirrors coupled with the high quantum efficiency of the EPIC detectors have made XMM-Newton the most sensitive X-ray observatory flown to date. We use data taken with the EPIC-pn camera during slewing manoeuvres to perform an X-ray survey of the sky.

Methods: Data from 218 slews have been subdivided into small images and source searched. This has been done in three distinct energy bands; a soft (0.2-2 keV) band, a hard (2-12 keV) band and a total XMM-Newton band (0.2-12 keV). Detected sources, have been quality controlled to remove artifacts and a catalogue has been drawn from the remaining sources.

Results: A "full" catalogue, containing 4710 detections and a "clean" catalogue containing 2692 sources have been produced, from 14% of the sky. In the hard X-ray band (2-12 keV) 257 sources are detected in the clean catalogue to a flux limit of 4×10-12 ergs s-1 cm-2. The flux limit for the soft (0.2-2 keV) band is 6×10-13 ergs s-1 cm-2 and for the total (0.2-12 keV) band is 1.2×10-12 ergs s-1 cm-2. The source positions are shown to have an uncertainty of 8" (1 sigma confidence).

Published: 01 March 2008
Phyllosilicates, a class of hydrous mineral first definitively identified on Mars by the OMEGA (Observatoire pour la Mineralogie, L'Eau, les Glaces et l'Activitié) instrument, preserve a record of the interaction of water with rocks on Mars. Global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy (Fe/Mg and Al smectite clays). This was interpreted to indicate that phyllosilicate formation occurred during the Noachian (the earliest geological era of Mars), and that the conditions necessary for phyllosilicate formation (moderate to high pH and high water activity) were specific to surface environments during the earliest era of Mars's history. Here we report results from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) of phyllosilicate-rich regions. We expand the diversity of phyllosilicate mineralogy with the identification of kaolinite, chlorite and illite or muscovite, and a new class of hydrated silicate (hydrated silica). We observe diverse Fe/Mg-OH phyllosilicates and find that smectites such as nontronite and saponite are the most common, but chlorites are also present in some locations. Stratigraphic relationships in the Nili Fossae region show olivine-rich materials overlying phyllosilicate-bearing units, indicating the cessation of aqueous alteration before emplacement of the olivine-bearing unit. Hundreds of detections of Fe/Mg phyllosilicate in rims, ejecta and central peaks of craters in the southern highland Noachian cratered terrain indicate excavation of altered crust from depth. We also find phyllosilicate in sedimentary deposits clearly laid by water. These results point to a rich diversity of Noachian environments conducive to habitability.
Published: 17 July 2008
We present an analysis of the deepest hard X-ray survey to date of about 2500 deg² performed by the IBIS instrument on board INTEGRAL in the 20-60 keV band, with a total exposure time of 4 Ms. We find 34 candidate sources, for which we try to find counterparts at other wavelengths. The ratio of Seyfert 1 to Seyfert 2 is significantly more than the ratio found in the optical. This effect may be explained in the framework of the receding-torus model, but could also be due to absorption columns large enough to affect the 20-60 keV band. None of the predicted Compton-thick objects with 1024 < NH < 1025 cm-2 is detected unambiguously; when taking lower limits on NH into account, the fraction of these objects is found to be lower than 24%. We do not see, but cannot exclude, a relationship between absorption and luminosity similar to what is seen in the 2-10 keV band. Our data suggests the possibility of a lack of objects with 1021 <= NH <= 1022 cm-2, which could be expected if absorption has two origins, for instance a torus-like structure and the host galaxy. We find that the Log N-Log S diagram of our sources is compatible with those obtained in other surveys in hard X-rays. Compared to models of the AGN population selected in the 2-10 keV band, the Log N-Log S diagram is generally in good agreement, but the NH distribution is significantly different, with significantly less unabsorbed sources (NH < 1022 cm-2) at a given flux limit compared to the models. In this survey, we resolve about 2.5% of the cosmic X-ray background in the 20-60 keV band. -- Remainder of abstract is truncated --
Published: 16 July 2008
  • Foreword
  • AO-7 Announcement
  • AO-6 Programme
  • Science Operations
  • Contacting ISOC
Published: 16 July 2008
In "Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter", edited by Jacobus M. Oschmann, Jr., Mattheus W. M. de Graauw, Howard A. MacEwen, Proc. of SPIE Vol. 7010, 70103K, (2008), doi: 10.1117/12.788672

We present how it is achieved to mount a double prism in the filter wheel of MIRIM - the imager of JWST's Mid Infrared Instrument. In order to cope with the extreme conditions of the prisms' surroundings, the low resolution double prism assembly (LRSDPA) design makes high demands on manufacturing accuracy. The design and the manufacturing of the mechanical parts are presented here, while 'Manufacturing and verification of ZnS and Ge prisms for the JWST MIRI imager' are described in a second paper. We also give insights on the astronomical possibilities of a sensitive MIR spectrometer. Low resolution prism spectroscopy in the wavelength range from 5-10 microns will allow to spectroscopically determine redshifts of objects close to/at the re-ionization phase of the universe.

Published: 13 July 2008
In "Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter", edited by Jacobus M. Oschmann, Jr., Mattheus W. M. de Graauw, Howard A. MacEwen, Proc. of SPIE Vol. 7010, 70100W, (2008), doi: 10.1117/12.789089

One of the main objectives of the instrument MIRI, the Mid-InfraRed Instrument, of the JWST is the direct detection and characterization of extrasolar giant planets. For that purpose, a coronagraphic device including three Four-Quadrant Phase Masks and a Lyot coronagraph working in mid-infrared, has been developed. We present here the results of the first test campaign of the coronagraphic system in the mid-infrared in the facility developed at the CEA. The performances are compared to the expected ones from the coronagraphic simulations. The accuracy of the centering procedures is also evaluated to validate the choice of the on-board centering algorithm.

Published: 13 July 2008
In "Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter", edited by Jacobus M. Oschmann, Jr., Mattheus W. M. de Graauw, Howard A. MacEwen. Proc. of SPIE Vol. 7010, 701039, (2008), doi: 10.1117/12.788750

The MTS, MIRI Telescope Simulator, is developed by INTA as the Spanish contribution of MIRI (Mid InfraRed Instrument) on board JWST (James Web Space Telescope). The MTS is considered as optical equipment which is part of Optical Ground Support Equipment for the AIV/Calibration phase of the instrument at Rutherford Appleton Laboratory, UK. It is an optical simulator of the JWST Telescope, which will provide a diffractionlimited test beam, including the obscuration and mask pattern, in all the MIRI FOV and in all defocusing range. The MTS will have to stand an environment similar to the flight conditions (35K) but using a smaller set-up, typically at lab scales. The MTS will be used to verify MIRI instrument-level tests, based on checking the implementation/realisation of the interfaces and performances, as well as the instrument properties not subject to interface control such as overall transmission of various modes of operation. This paper includes a functional description and a summary of the development status.

Published: 13 July 2008
Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter. Edited by Oschmann, J.M., Jr.; de Graauw, Mattheus W.M.; MacEwen, Howard A. Proceedings of the SPIE, Volume 7010, pp. 701035-701035-12 (2008)

The James Webb Space Telescope (JWST) mission is a collaborative project between the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA) and the Canadian Space Agency (CSA). JWST is considered the successor to the Hubble Space Telescope (HST) and although its design and science objectives are quite different, JWST is expected to yield equivalently astonishing breakthroughs in infrared space science. Due to be launched in 2013 from the French Guiana, the JWST observatory will be placed in an orbit around the anti- Sun Earth-Sun Lagrangian point, L2, by an Ariane 5 launcher provided by ESA. The payload on board the JWST observatory consists of four main scientific instruments: a near-infrared camera (NIRCam), a mid-infrared camera/spectrograph (MIRI), a near-infrared tunable filter (TFI) and a near-infrared spectrograph (NIRSpec). The instrument suite is completed by a Fine Guidance Sensor (FGS). NIRSpec is a multi-object spectrograph capable of measuring the spectra of about 100 objects simultaneously at low (R~100), medium (R~1000) and high (R~2700) resolutions over the wavelength range between 0.6 micron and 5.0 micron. It features also a classical fix-slits spectroscopy mode as well as a 3D-spectrography mode with spectral resolutions up to 2700. The availability of extensive and accurate calibration data of the NIRSpec instrument is a key element to ensure that the nominal performance of the instrument will be achieved and that high-quality processed data will be made available to the users. In this context, an on-ground calibration is planned at instrument level that will supplement the later in-flight calibration campaign.
-- the remainder of the abstract was truncated --

Published: 13 July 2008
Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter. Edited by Oschmann, Jacobus M., Jr.; de Graauw, Mattheus W.M.; MacEwen, Howard A. Proceedings of the SPIE, Volume 7010, pp. 70103D-70103D-10 (2008)

Microshutter arrays are one of the novel technologies developed for the James Webb Space Telescope (JWST). It will allow Near Infrared Spectrometer (NIRSpec) to acquire spectra of hundreds of objects simultaneously therefore increasing its efficiency tremendously. We have developed these programmable arrays that are based on Micro-Electro Mechanical Structures (MEMS) technology. The arrays are 2D addressable masks that can operate in cryogenic environment of JWST. Since the primary JWST science requires acquisition of spectra of extremely faint objects, it is important to provide very high contrast of the open to closed shutters. This high contrast is necessary to eliminate any possible contamination and confusion in the acquired spectra by unwanted objects. We have developed and built a test system for the microshutter array functional and optical characterization. This system is capable of measuring the contrast of the mciroshutter array both in visible and infrared light of the NIRSpec wavelength range while the arrays are in their working cryogenic environment. We have measured contrast ratio of several microshutter arrays and demonstrated that they satisfy and in many cases far exceed the NIRSpec contrast requirement value of 2000.

Published: 13 July 2008
In "Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter", edited by Jacobus M. Oschmann, Jr., Mattheus W. M. de Graauw, Howard A. MacEwen, Proc. of SPIE Vol. 7010, 70100T, (2008), doi: 10.1117/12.790101

MIRI is the mid-IR instrument for the James Webb Space Telescope and provides imaging, coronography and integral field spectroscopy over the 5-28 micron wavelength range. MIRI is the only instrument which is cooled to 7K by a dedicated cooler, much lower than the passively cooled 40K of the rest of JWST, which introduces unique challenges. The paper will describe the key features of the overall instrument design. The flight model design of the MIRI Optical System is completed, with hardware now in manufacture across Europe and the USA, while the MIRI Cooler System is at PDR level development. A brief description of how the different development stages of the optical and cooling systems are accommodated is provided, but the paper largely describes progress with the MIRI Optical System. We report the current status of the development and provide an overview of the results from the qualification and test programme.

Published: 13 July 2009
In "Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter", edited by Jacobus M. Oschmann, Jr., Mattheus W. M. de Graauw, Howard A. MacEwen, Proc. of SPIE Vol. 7010, 70103A, (2008), doi: 10.1117/12.789460

The Mid-Infrared Instrument (MIRI) is one of the three scientific instruments to fly on the James Webb Space Telescope (JWST), which is due for launch in 2013. MIRI contains two sub-instruments, an imager, which has low resolution spectroscopy and coronagraphic capabilities in addition to imaging, and a medium resolution IFU spectrometer. A verification model of MIRI was assembled in 2007 and a cold test campaign was conducted between November 2007 and February 2008. This model was the first scientifically representative model, allowing a first assessment to be made of the performance. This paper describes the test facility and testing done. It also reports on the first results from this test campaign.

Published: 13 July 2008
We present zonal and meridional wind measurements at three altitude levels within the cloud layers of Venus from cloud tracking using images taken with the VIRTIS instrument on board Venus Express. At low latitudes, zonal winds in the Southern hemisphere are nearly constant with latitude with westward velocities of 105 ms-1 at cloud-tops (altitude ~ 66 km) and 60-70 ms-1 at the cloud-base (altitude ~ 47 km). At high latitudes, zonal wind speeds decrease linearly with latitude with no detectable vertical wind shear (values lower than 15 ms-1), indicating the possibility of a vertically coherent vortex structure. Meridional winds at the cloud-tops are poleward with peak speed of 10 ms-1 at 55° S but below the cloud tops and averaged over the South hemisphere are found to be smaller than 5 ms-1. We also report the detection at subpolar latitudes of wind variability due to the solar tide.
Published: 11 July 2008
We report on the THEMIS and Double Star TC-1 observations at the geocentric distances of 3 < R < 8 RE during substorms on March 23, 2007. THEMIS crossed the inner boundary of the equatorial dusk-side plasma in the string-of-pearls configuration, allowing the dynamics of particle populations to be traced within time ranges from hours to 10 minutes. Observations show co-existence of the plasma sheet ion population (5 - 30 keV) with the ring current ion population (100 - 1000 keV) at 4 < R < 6 RE . The plasma sheet population was characterized by pronounced "nose"-like dispersion with the spectral density maximum at ~10 keV. The plasma sheet boundary, defined by a sharp decrease of the ~1 keV electron flux, moved inward to R = 4 and outward back to ~8 RE within about 1 hour. Local enhancements of the plasma sheet (1 - 5 keV) electron flux with the characteristic time scale of 2 - 10 min were detected at 5 < R < 6 RE during the substorm.
Published: 10 July 2008
The LYRA instrument onboard ESA PROBA2 satellite will provide 6-hourly solar irradiance at the Lyman-alpha (121.6 nm) and the Herzberg continuum (~200220 nm wavelength range). Because the nowcasting of the neutral and ionic state of the middle atmosphere requires the solar irradiance for the wide spectral area (120680 nm) we have developed the statistical tool for the reconstruction of the full spectrum from the LYRA measurements. The accuracy of the reconstructed irradiance has been evaluated with 1-D transient radiative-convective model with neutral and ion chemistry using the daily solar spectral irradiance measured with SUSIM and SOLSTICE instruments onboard UARS satellite. We compared the results of transient 1-yr long model simulations for 2000 driven by the observed and reconstructed solar irradiance and showed that the reconstruction of the full spectrum using linear regression equation based on the solar irradiance in two LYRA channels can be successfully used for nowcasting of the middle atmosphere. We have also defined some conditions when the proposed approach does not provide reasonable accuracy.
Published: 01 July 2008
We present a statistical study on reconnection occurrence at the dayside magnetopause performed using the Double Star TC1 plasma and magnetic field data. We examined the magnetopause crossings that occurred during the first year of the mission in the 0600-1800 LT interval and we identified plasma flows, at the magnetopause or in the boundary layer, with a different velocity with respect to the adjacent magnetosheath. We used the Walén relation to test which of these flows could be generated by magnetic reconnection. For some event we observed opposite-directed reconnection jets, which could be associated with the passage of the X-line near the satellite. We analyzed the occurrence of the reconnection jets and reconnection jet reversals in relation to the magnetosheath parameters, in particular the local Alfvèn Mach number, the plasma beta, and the magnetic shear angle. We also studied the positions and velocities of the reconnection jets and jet reversals in relation to the magnetosheath magnetic field clock angle. We found that the observations indicate the presence of a reconnection line hinged near the subsolar point and tilted according to the observed magnetosheath clock angle, consistently with the component merging model.
Published: 28 June 2008
Simultaneous observations of AKR emission using the four-spacecraft Cluster array were used to make the first direct measurements of the angular beaming patterns of individual bursts. By comparing the spacecraft locations and AKR burst locations, the angular beaming pattern was found to be narrowly confined to a plane containing the magnetic field vector at the source and tangent to a circle of constant latitude. Most rays paths are confined within 15° of this tangent plane, consistent with numerical simulations of AKR k-vector orientation at maximum growth rate. The emission is also strongly directed upward in the tangent plane, which we interpret as refraction of the rays as they leave the auroral cavity. The narrow beaming pattern implies that an observer located above the polar cap can detect AKR emission only from a small fraction of the auroral oval at a given location. This has important consequences for interpreting AKR visibility at a given location. It also helps re-interpret previously published Cluster VLBI studies of AKR source locations, which are now seen to be only a subset of all possible source locations. The observations are inconsistent with either filled or hollow cone beaming models.
Published: 25 June 2008
21-Jan-2021 16:00 UT

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