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| Cryogenic Thermal Testing of the Verification Model Mid-Infrared Instrument (MIRI) Optics Module |
| Presented at the "International Conference On Environmental Systems", July 2009, Savannah, GA, USA, Session: Thermal Testing (Part 1 of 2), ID: 2009-01-2410
The Mid-Infrared Instrument (MIRI) is one of four scientific instruments on the James Webb Space Telescope (JWST) observatory, scheduled for launch in 2014. It will provide unique capabilities to probe the deeply dust-enshrouded regions of the Universe, investigating the history of star formation both near and far.
The MIRI is the coldest instrument on the observatory. Its thermal design is driven by requirements to cool an Optics Module (OM) to below 15.5 K and detectors within this to below 6.7 K with a stability of \ml10 mK over 1000 seconds. The OM is accommodated within the JWST Integrated Science Instrument Module (ISIM) which is cooled passively to between 32 and 40 K. The instrument temperatures are achieved by a combination of thermal isolation of the OM and the ISIM supplemented with active cooling of the OM by a dedicated cryo-cooler.
A flight representative "verification model" underwent two cryogenic thermal test campaigns at the UK's STFC Rutherford Appleton Laboratory between December 2007 and September 2008. This paper begins by summarizing the thermal design of the MIRI OM and describing the design of the cryogenic test facility. It goes on to describe the two test campaigns and the correlation of the MIRI OM thermal model to the thermal balance test measurements, concluding with the predicted in-flight thermal performance of the instrument based on this testing. |
| Publication date: 31 Jul 2009 |
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| SPICA Telescope Assessment Study - Executive Summary (Thales Alenia Space) |
| Reference: SPI-TAS-RP-100358212M
In the frame of ESA Cosmic Vision assessment study, Thales propose a 3.5m diameter Ritchey-Chretien telescope in HB-Cesic ceramics. The evaluation of its performances demonstrate that the proposed design perfectly fulfils the mission
requirements.
The objective of this paper is to provide to the reader an overview of the telescope design and performances of the HB-Cesic SPICA Telescope. The development plan is also addressed. It has been established to minimize risks and schedule. The last point is a sensitivity analysis to pupil diameter reduction: an interesting way to further reduce development schedule. |
| Publication date: 31 Jul 2009 |
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| Saturn's rotation period from its atmospheric planetary-wave configuration |
| The rotation period of a gas giant's magnetic field (called the System III reference frame) is commonly used to infer its bulk rotation. Saturn's dipole magnetic field is not tilted relative to its rotation axis (unlike Jupiter, Uranus and Neptune), so the surrogate measure of its long-wavelength (kilometric) radiation is currently used to fix the System III rotation period. The period as measured now by the Cassini spacecraft is up to ~7 min longer than the value of 10 h 39 min 24 s measured 28 years ago by Voyager. Here we report a determination of Saturn's rotation period based on an analysis of potential vorticity. The resulting reference frame (which we call System IIIw) rotates with a period of 10 h 34 min 13 +/- 20 s. This shifted reference frame is consistent with a pattern of alternating jets on Saturn that is more symmetrical between eastward and westward flow. This suggests that Saturn's winds are much more like those of Jupiter than hitherto believed. |
| Publication date: 30 Jul 2009 |
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| Liquid water on Enceladus from observations of ammonia and 40Ar in the plume |
| Jets of water ice from surface fractures near the south pole of Saturn's icy moon Enceladus produce a plume of gas and particles. The source of the jets may be a liquid water region under the ice shell - as suggested most recently by the discovery of salts in E-ring particles derived from the plume - or warm ice that is heated, causing dissociation of clathrate hydrates. Here we report that ammonia is present in the plume, along with various organic compounds, deuterium and, very probably, 40Ar. The presence of ammonia provides strong evidence for the existence of at least some liquid water, given that temperatures in excess of 180 K have been measured near the fractures from which the jets emanate. We conclude, from the overall composition of the material, that the plume derives from both a liquid reservoir (or from ice that in recent geological time has been in contact with such a reservoir) as well as from degassing, volatile-charged ice. |
| Publication date: 23 Jul 2009 |
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| Statistical analysis of earthward flow bursts in the inner plasma sheet during substorms |
| In this article, we study the velocity distribution, density, duration, and energy transport of earthward flow bursts in the inner plasma sheet (IPS) during three substorm phases using the data of Cluster in 2001 and 2002. The mean peak velocity of earthward flow bursts in recovery phases (390 km/s) is smaller than those in growth and expansion phases (490 and 520 km/s). The super earthward flow bursts (V > 1000 km/s) appear more frequently in the expansion phase. The average ion density of earthward flow bursts in the recovery phase is 0.14 cm-3, much smaller than those in growth and expansion phases (0.28 and 0.21 cm-3), indicating that lobe reconnections most likely occur in the recovery phase. The average durations of earthward flow bursts in recovery phase are 48 s, smaller than those in growth and expansion phases (99 and 103 s), suggesting that the reconnections occurring in recovery phase are rather short-lived. The earthward flow bursts in the expansion phase have largest capability of the transport of energy, about 7 times that in the recovery phase. Thus the earthward flow bursts in the expansion phase can produce largest impact effects to the inner magnetosphere. |
| Publication date: 16 Jul 2009 |
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| Using population synthesis of massive stars to study the interstellar medium near OB associations |
Aims. We study the massive stars in OB associations and their surrounding interstellar medium environment, using a population synthesis code. Methods. We developed a new population synthesis code for groups of massive stars, where we model the emission of different forms of energy and matter from the stars of the association. In particular, the ejection of the two radioactive isotopes 26Al and 60Fe is followed, as well as the emission of hydrogen ionizing photons, and the kinetic energy of the stellar winds and supernova explosions. We investigate various alternative astrophysical inputs and the resulting output sensitivities, especially effects due to the inclusion of rotation in stellar models. As the aim of the code is the application to relatively small populations of massive stars, special care is taken to address their statistical properties. Our code incorporates both analytical statistical methods applicable to small populations, as well as extensive Monte Carlo simulations. |
| Publication date: 16 Jul 2009 |
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| European Mars Science and Exploration Conference (EMSEC) |
| Edited by Dr. Angelo Pio Rossi and Dr. Olivier Witasse.
This Special Issue of Planetary and Space Science contains 15 papers; the majority of which were presented at the European Mars Science and Exploration Conference (EMSEC) - Mars Express & ExoMars.
There are several geoscience-related contributions covering volcanic, hydrologic, stratigraphic and geomorphologic investigations.
The EMSEC conference was held 12-16 November 2007 at ESA ESTEC, Noordwijk, The Netherlands (see right-hand menu for conference programme).
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| Publication date: 15 Jul 2009 |
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| Design and development of MIRI, the mid-IR instrument for JWST |
| 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. |
| Publication date: 12 Jul 2009 |
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| Cross-Scale Assessment Study - Executive Summary (EADS Astrium) |
| Executive Summary of the mission study by EADS Astrium (Ref: CS.ASU.TN.ES).
Cross-Scale is a mission that both builds on the advances from previous spacecraft missions like Cluster and also pushes the frontiers of knowledge in terms of magnetospheric dynamics, energy processes and couplings across different spatial and temporal scales. This is done by simultaneously measuring a minimum of two plasma scales (electron and ion scales in year 1 and then ion and fluid scales afterwards) with 7 spacecraft in two nested tetrahedral constellations (with a common apex), over a 5 year period. This document provides a concise summary of the findings from the ESA contract awarded to the Astrium Ltd study team, for the "System Design of the Cross-Scale Mission". |
| Publication date: 03 Jul 2009 |
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| Cross-Scale Assessment Study - Executive Summary (Thales Alenia Space) |
| Executive Summary of the mission study by the consortium led by Thales Alenia Space, including Deimos and OHB (Ref: CS-TAS-TN-100350224F).
The Consortium led by Thales Alenia Space, including Deimos and OHB, has completed the Assessment Phase contract "System Design of the Cross-Scale Mission" awarded by ESA. The expertise of the Consortium has allowed analysing the requirements, trading options extensively and selecting a baseline design that has been defined in detail and justified by a comprehensive set of analyses. The robust solution not only fully complies with the requirements, but also implements high TRL and strong design-to-schedule dispositions that lead to safer programmatics, to the maximization of the mass production effect and to the mastery of costs. The technical, schedule and cost elements produced will enable ESA to assess the Cross-Scale Mission in the frame of its Cosmic Vision selection process. |
| Publication date: 03 Jul 2009 |
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| An intermediate-mass black hole of over 500 solar masses in the galaxy ESO 243-49 |
| Ultraluminous X-ray sources are extragalactic objects located outside the nucleus of the host galaxy with bolometric luminosities exceeding 1039 erg s-1. These extreme luminosities - if the emission is isotropic and below the theoretical (Eddington) limit, where the radiation pressure is balanced by the gravitational pressure - imply the presence of an accreting black hole with a mass of ~ 10²-105 solar masses. The existence of such intermediate-mass black holes is in dispute, and though many candidates have been proposed, none are widely accepted as definitive. Here we report the detection of a variable X-ray source with a maximum 0.2-10 keV luminosity of up to 1.1 x 1042 erg s-1 in the edge-on spiral galaxy ESO 243-49, with an implied conservative lower limit for the mass of the black hole of 500 solar masses. |
| Publication date: 02 Jul 2009 |
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| Plan management system for space science mission systems |
| The number and complexity of systems that control Space Science Missions continues to increase. As a result, it is desirable to improve the efficiency of these systems and, in particular, their performance and their productivity. In this paper, we set out a strategy to achieve this goal. In order to talk about improving the Performance and Productivity of a system we need to discuss the functional architecture of the system. In order to make progress, our strategy is to develop a generic methodology that decomposes the functional architecture of a Space Science Mission System and uses this decomposition to identify areas where improvements can be made. This paper concentrates on the decomposition of one specific component, namely the Plan Management System. The purpose of the Plan Management System is to produce an operation plan that contains the directives that will operate the various nodes, i.e. physical parts, of the system such as the ground stations, the spacecraft, the instruments, or even human beings (when these are following specific instructions). In order to be generic, the decomposition of the Plan Management System must make no assumptions about the purpose and implementation choices that must ultimately be made. In order to describe a functional architecture, it must also make no assumptions about the nature and purpose of the nodes that the system will operate or the nodes on which it will run. In particular, it makes no assumptions as to whether the execution of the Plan Management System components is manual or automated or whether the functions will be executed on the ground or in space.
-- Remainder of abstract is truncated -- |
| Publication date: 01 Jul 2009 |
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