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131.
A. R. Foster R. K. Smith N. S. Brickhouse T. R. Kallman M. C. Witthoeft 《Space Science Reviews》2010,157(1-4):135-154
Successfully modeling X-ray emission from astrophysical plasmas requires a wide range of atomic data to be rapidly accessible by modeling codes, enabling calculation of synthetic spectra for fitting with observations. Over many years the astrophysical databases have roughly kept pace with the advances in detector and spectrometer technology. We outline here the basic atomic processes contributing to the emission from different types of plasmas and briefly touch on the difference between the methods used to calculate this data. We then discuss in more detail the different issues addressed by atomic databases in regards to what data to store and how to make it accessible. Finally, the question of the effect of uncertainties in atomic data is explored, as a reminder to observers that atomic data is not known to infinite precision, and should not be treated as such. 相似文献
132.
The James Webb Space Telescope 总被引:4,自引:0,他引:4
Jonathan P. Gardner John C. Mather Mark Clampin Rene Doyon Matthew A. Greenhouse Heidi B. Hammel John B. Hutchings Peter Jakobsen Simon J. Lilly Knox S. Long Jonathan I. Lunine Mark J. Mccaughrean Matt Mountain John Nella George H. Rieke Marcia J. Rieke Hans-Walter Rix Eric P. Smith George Sonneborn Massimo Stiavelli H. S. Stockman Rogier A. Windhorst Gillian S. Wright 《Space Science Reviews》2006,123(4):485-606
The James Webb Space Telescope (JWST) is a large (6.6 m), cold (<50 K), infrared (IR)-optimized space observatory that will be launched early in the next decade into orbit around the second Earth–Sun Lagrange point. The observatory will have four instruments: a near-IR camera, a near-IR multiobject spectrograph, and a tunable filter imager will cover the wavelength range, 0.6 < ; < 5.0 μ m, while the mid-IR instrument will do both imaging and spectroscopy from 5.0 < ; < 29 μ m.The JWST science goals are divided into four themes. The key objective of The End of the Dark Ages: First Light and Reionization theme is to identify the first luminous sources to form and to determine the ionization history of the early universe. The key objective of The Assembly of Galaxies theme is to determine how galaxies and the dark matter, gas, stars, metals, morphological structures, and active nuclei within them evolved from the epoch of reionization to the present day. The key objective of The Birth of Stars and Protoplanetary Systems theme is to unravel the birth and early evolution of stars, from infall on to dust-enshrouded protostars to the genesis of planetary systems. The key objective of the Planetary Systems and the Origins of Life theme is to determine the physical and chemical properties of planetary systems including our own, and investigate the potential for the origins of life in those systems. Within these themes and objectives, we have derived representative astronomical observations.To enable these observations, JWST consists of a telescope, an instrument package, a spacecraft, and a sunshield. The telescope consists of 18 beryllium segments, some of which are deployed. The segments will be brought into optical alignment on-orbit through a process of periodic wavefront sensing and control. The instrument package contains the four science instruments and a fine guidance sensor. The spacecraft provides pointing, orbit maintenance, and communications. The sunshield provides passive thermal control. The JWST operations plan is based on that used for previous space observatories, and the majority of JWST observing time will be allocated to the international astronomical community through annual peer-reviewed proposal opportunities. 相似文献
133.
The Dawn Gravity Investigation at Vesta and Ceres 总被引:2,自引:0,他引:2
A. S. Konopliv S. W. Asmar B. G. Bills N. Mastrodemos R. S. Park C. A. Raymond D. E. Smith M. T. Zuber 《Space Science Reviews》2011,163(1-4):461-486
The objective of the Dawn gravity investigation is to use high precision X-band Doppler tracking and landmark tracking from optical images to measure the gravity fields of Vesta and Ceres to a half-wavelength surface resolution better than 90-km and 300-km, respectively. Depending on the Doppler tracking assumptions, the gravity field will be determined to somewhere between harmonic degrees 15 and 25 for Vesta and about degree 10 for Ceres. The gravity fields together with shape models determined from Dawn??s framing camera constrain models of the interior from the core to the crust. The gravity field is determined jointly with the spin pole location. The second degree harmonics together with assumptions on obliquity or hydrostatic equilibrium may determine the moments of inertia. 相似文献
134.
The Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) on RBSP 总被引:2,自引:0,他引:2
C. A. Kletzing W. S. Kurth M. Acuna R. J. MacDowall R. B. Torbert T. Averkamp D. Bodet S. R. Bounds M. Chutter J. Connerney D. Crawford J. S. Dolan R. Dvorsky G. B. Hospodarsky J. Howard V. Jordanova R. A. Johnson D. L. Kirchner B. Mokrzycki G. Needell J. Odom D. Mark R. Pfaff Jr. J. R. Phillips C. W. Piker S. L. Remington D. Rowland O. Santolik R. Schnurr D. Sheppard C. W. Smith R. M. Thorne J. Tyler 《Space Science Reviews》2013,179(1-4):127-181
The Electric and Magnetic Field Instrument and Integrated Science (EMFISIS) investigation on the NASA Radiation Belt Storm Probes (now named the Van Allen Probes) mission provides key wave and very low frequency magnetic field measurements to understand radiation belt acceleration, loss, and transport. The key science objectives and the contribution that EMFISIS makes to providing measurements as well as theory and modeling are described. The key components of the instruments suite, both electronics and sensors, including key functional parameters, calibration, and performance, demonstrate that EMFISIS provides the needed measurements for the science of the RBSP mission. The EMFISIS operational modes and data products, along with online availability and data tools provide the radiation belt science community with one the most complete sets of data ever collected. 相似文献
135.
Allen J.J. Kinney R.D. Sarsfield J. Daily M.R. Ellis J.R. Smith J.H. Montague S. Howe R.T. Boser B.E. Horowitz R. Pisano A.P. Lemkin M.A. Clark W.A. Juneau T. 《Aerospace and Electronic Systems Magazine, IEEE》1998,13(11):36-40
Electronic sensing circuitry and micro-electro-mechanical sense elements can be integrated to produce inertial instruments for applications unheard of a few years ago. This paper describes the Sandia M3EMS fabrication process, inertial instruments that have been fabricated, and the results of initial characterization tests of micro-machined accelerometers 相似文献
136.
B. Smith T. HydeL. Matthews J. ReayM. Cook J. Schmoke 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(9):1510-1513
In semiconductor manufacturing, contamination due to particulates significantly decreases the yield and quality of device fabrication, therefore increasing the cost of production. Dust particle clouds can be found in almost all plasma processing environments including both plasma etching devices and in plasma deposition processes. Dust particles suspended within such plasmas will acquire an electric charge from collisions with electrons and ions in the plasma. If the ratio of inter-particle potential energy to the average kinetic energy is sufficient, the particles will form either a “liquid” structure with short-range ordering or a crystalline structure with long-range ordering. Many experiments have been conducted over the past decade on such colloidal plasmas to discover the character of the systems formed, but more work is needed to fully understand these structures. The preponderance of previous experiments used monodisperse spheres to form complex plasma systems. However, most plasma processing environments contain more arbitrary distributions of particle size. In order to examine in more detail the effects of a size distribution, experiments were carried out in a GEC rf reference cell modified for use as a dusty plasma system. Using two monodisperse particle sizes, experiments were conducted to determine the manner in which phase transitions and other thermodynamic properties depended upon the overall dust grain size distribution. Plasma crystals were formed from different mixtures of 8.89 and 6.50 μm monodisperse particles in argon plasma. With the use of various optical techniques, the pair correlation function was determined at different pressures and powers and then compared to measurements obtained for monodisperse spheres. 相似文献
137.
With robust polar satellite missions demonstrated and/or operational in the USA, Europe, Japan, China, Russia, India, and Brazil, and with other nations also likely to develop such capability, this paper examines the prospects for as well as the potential challenges to closer and perhaps more formal international polar satellite cooperation. In suggesting that now is the time to explore the development of a coordinated polar observing system, the present paper identifies potential contributors, assesses the relevance of existing space-based Earth observation international coordination mechanisms, and considers three potential models for a future system. 相似文献
138.
N. Murphy E. J. Smith B. T. Tsurutani A. Balogh D. J. Southwood 《Space Science Reviews》1995,72(1-2):447-452
Data collected by the magnetometer onboard the Ulysses spacecraft are surveyed for the occurrence of waves generated during the pick-up of interstellar hydrogen. Thirty one wave events were found during a 640 day study period, between March 21, 1992 and December 20, 1993 (after the Ulysses encounter with Jupiter). It is found that observation of the waves does not depend on the magnitude of the background magnetic field, but is a strong function of the angle between the magnetic field and the solar wind flow direction, with small angles being favored. 相似文献
139.
Moving Emitter Classification 总被引:1,自引:0,他引:1
One of the problems that plague emitter location systems is the presence of data from emitters that are in motion. If this motion is not detected, erroneous location estimates and filled data files result. An algorithm to classify an emitter as moving or stationary is presented along with extensive illustrations and results based upon simulated data. 相似文献
140.
The design and development of a system for inferring the position of terrestrial satellite uplink stations using existing domestic satellites with minimal disruption to normal satellite operation are described. Two methods are presented by which a quantity measured at a terrestrial receiving site is mapped into a curve of possible uplink locations on the Earth's surface. One method involves measuring differential time delays of a single uplink signal observed through two adjacent spacecraft. The other uses a short baseline interferometer composed of the two cross-polarized and spatially separated antenna feeds aboard an affected satellite. A unique location is obtained by using an appropriate combination of the two methods. A system for measurement of the required differential delays and phases and experimental work performed to demonstrate the feasibility of the location methods are described 相似文献