排序方式: 共有54条查询结果,搜索用时 15 毫秒
31.
White Oran R. Fox Peter A. Meisner Randy Rast Mark P. Yasukawa Eric Koon Darryl Rice Crystal Lin Haosheng Kuhn Jeff Coulter Roy 《Space Science Reviews》2000,94(1-2):75-82
Two Precision Solar Photometric Telescopes (PSPT) designed and built at the U.S. National Solar Observatory (NSO) are in operation in Rome and Hawaii. A third PSPT is now in operation the NSO at Sunspot, NM. The PSPT system records full disk solar images at three wavelengths: K line at 393.3 nm and two continua at 409 nm and 607 nm throughout the observing day. We currently study properties of limb darkening, sunspots, and network in these images with particular emphasis on data taken in July and September 1998. During this period, the number of observations per month was high enough to show directional properties of the radiation field surrounding sunspots. We show examples of our PSPT images and describe our study of bright rings around sunspots. 相似文献
32.
Jin Ho Kang Jeffrey A. Hinkley Keith L. Gordon Sheila A. Thibeault Robert G. Bryant Juan M. Fernandez W. Keats Wilkie Héctor E. Diaz Morales Donovan E. Mcgruder Ray S. Peterson Charlotte J. Brandenburg Evin L. Hill Nina R. Arcot 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(9):2727-2735
Deployable space structures are being built from thin-walled fiber-reinforced polymer composite materials due to their high specific strength, high specific stiffness, and designed bistability. However, the inherent viscoelastic behavior of the resin matrix can cause dimensional instability when the composite is stored under strain. The extended time of stowage between assembly and deployment in space can result in performance degradation and in the worst case, mission failure. In this study, the viscoelastic properties of candidate commercial polymers consisting of difunctional and tetrafunctional epoxies and thermoplastic and thermosetting polyimides were evaluated for deployable boom structures of solar sails. Stress relaxation master curves of the candidate polymers were used to predict the relaxation that would occur in 1 year at room temperature under relatively low strains of about 0.1%. A bismaleimide (BMI) showed less stress relaxation (about 20%) than the baseline novolac epoxy (about 50%). Carbon fiber composites fabricated with the BMI resin showed a 44% improvement in resistance to relaxation compared to the baseline epoxy composite. 相似文献
33.
Peter G. Roma Steven R. Hursh Robert D. Hienz Henry H. Emurian Eric D. Gasior Zabecca S. Brinson Joseph V. Brady 《Acta Astronautica》2011,68(9-10):1581-1588
Logistical constraints during long-duration space expeditions will limit the ability of Earth-based mission control personnel to manage their astronaut crews and will thus increase the prevalence of autonomous operations. Despite this inevitability, little research exists regarding crew performance and psychosocial adaptation under such autonomous conditions. To this end, a newly-initiated study on crew management systems was conducted to assess crew performance effectiveness under rigid schedule-based management of crew activities by Mission Control versus more flexible, autonomous management of activities by the crews themselves. Nine volunteers formed three long-term crews and were extensively trained in a simulated planetary geological exploration task over the course of several months. Each crew then embarked on two separate 3–4 h missions in a counterbalanced sequence: Scheduled, in which the crews were directed by Mission Control according to a strict topographic and temporal region-searching sequence, and Autonomous, in which the well-trained crews received equivalent baseline support from Mission Control but were free to explore the planetary surface as they saw fit. Under the autonomous missions, performance in all three crews improved (more high-valued geologic samples were retrieved), subjective self-reports of negative emotional states decreased, unstructured debriefing logs contained fewer references to negative emotions and greater use of socially-referent language, and salivary cortisol output across the missions was attenuated. The present study provides evidence that crew autonomy may improve performance and help sustain if not enhance psychosocial adaptation and biobehavioral health. These controlled experimental data contribute to an emerging empirical database on crew autonomy which the international astronautics community may build upon for future research and ultimately draw upon when designing and managing missions. 相似文献
34.
Eric Quémerais Rosine Lallement Bill R. Sandel John T. Clarke 《Space Science Reviews》2009,143(1-4):151-162
We present an analysis of Voyager UVS data obtained between 1993 and mid-2007. These data are used to study the interplanetary background and the hydrogen number density in the outer heliosphere. Two types of observations are studied, first the heliospheric scans performed until 2003 and then the fixed line of sight observations, close to the upwind direction, which are still performed at the end of 2007. We make comparisons with models including multiple scattering and hydrogen distributions derived from self-consistent modeling of the interface region. It is found that there is a remaining discrepancy between models and data. The origin of this difference is unknown but it may be linked to a possible tilting of the heliospheric interface due to the presence of an interstellar magnetic field. We should also estimate alternate sources of emission which are not backscattering of solar photons like collisional excitation of hydrogen in the heliosheath and emission after charge transfer or recombination of proton and electron in HII regions. Line profiles from HST/STIS are also presented. 相似文献
35.
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
36.
A direct fusion drive for rocket propulsion 总被引:1,自引:0,他引:1
Yosef S. Razin Gary Pajer Mary Breton Eric Ham Joseph Mueller Michael Paluszek Alan H. Glasser Samuel A. Cohen 《Acta Astronautica》2014
The Direct Fusion Drive (DFD), a compact, anuetronic fusion engine, will enable more challenging exploration missions in the solar system. The engine proposed here uses a deuterium–helium-3 reaction to produce fusion energy by employing a novel field-reversed configuration (FRC) for magnetic confinement. The FRC has a simple linear solenoid coil geometry yet generates higher plasma pressure, hence higher fusion power density, for a given magnetic field strength than other magnetic-confinement plasma devices. Waste heat generated from the plasma?s Bremsstrahlung and synchrotron radiation is recycled to maintain the fusion temperature. The charged reaction products, augmented by additional propellant, are exhausted through a magnetic nozzle. A 1 MW DFD is presented in the context of a mission to deploy the James Webb Space Telescope (6200 kg) from GPS orbit to a Sun–Earth L2 halo orbit in 37 days using just 353 kg of propellant and about half a kilogram of 3He. The engine is designed to produce 40 N of thrust with an exhaust velocity of 56.5 km/s and has a specific power of 0.18 kW/kg. 相似文献
37.
Andrew W. Stephan Eric J. Korpela Martin M. Sirk Scott L. England Thomas J. Immel 《Space Science Reviews》2017,212(1-2):645-654
The NASA Ionospheric Connection Explorer Extreme Ultraviolet spectrograph, ICON EUV, will measure altitude profiles of the daytime extreme-ultraviolet (EUV) OII emission near 83.4 and 61.7 nm that are used to determine density profiles and state parameters of the ionosphere. This paper describes the algorithm concept and approach to inverting these measured OII emission profiles to derive the associated \(\mathrm{O}^{+}\) density profile from 150–450 km as a proxy for the electron content in the F-region of the ionosphere. The algorithm incorporates a bias evaluation and feedback step, developed at the U.S. Naval Research Laboratory using data from the Special Sensor Ultraviolet Limb Imager (SSULI) and the Remote Atmospheric and Ionospheric Detection System (RAIDS) missions, that is able to effectively mitigate the effects of systematic instrument calibration errors and inaccuracies in the original photon source within the forward model. Results are presented from end-to-end simulations that convolved simulated airglow profiles with the expected instrument measurement response to produce profiles that were inverted with the algorithm to return data products for comparison to truth. Simulations of measurements over a representative ICON orbit show the algorithm is able to reproduce hmF2 values to better than 5 km accuracy, and NmF2 to better than 12% accuracy over a 12-second integration, and demonstrate that the ICON EUV instrument and daytime ionosphere algorithm can meet the ICON science objectives which require 20 km vertical resolution in hmF2 and 18% precision in NmF2. 相似文献
38.
Panning Mark P. Lognonné Philippe Bruce Banerdt W. Garcia Raphaël Golombek Matthew Kedar Sharon Knapmeyer-Endrun Brigitte Mocquet Antoine Teanby Nick A. Tromp Jeroen Weber Renee Beucler Eric Blanchette-Guertin Jean-Francois Bozdağ Ebru Drilleau Mélanie Gudkova Tamara Hempel Stefanie Khan Amir Lekić Vedran Murdoch Naomi Plesa Ana-Catalina Rivoldini Atillio Schmerr Nicholas Ruan Youyi Verhoeven Olivier Gao Chao Christensen Ulrich Clinton John Dehant Veronique Giardini Domenico Mimoun David Thomas Pike W. Smrekar Sue Wieczorek Mark Knapmeyer Martin Wookey James 《Space Science Reviews》2017,211(1-4):611-650
Space Science Reviews - The InSight lander will deliver geophysical instruments to Mars in 2018, including seismometers installed directly on the surface (Seismic Experiment for Interior Structure,... 相似文献
39.
S. E. Harris S. B. Mende V. Angelopoulos W. Rachelson E. Donovan B. Jackel M. Greffen C. T. Russell D. R. Pierce D. J. Dearborn K. Rowe M. Connors 《Space Science Reviews》2008,141(1-4):213-233
The comprehensive THEMIS approach to solving the substorm problem calls for monitoring the nightside auroral oval with low-cost, robust white-light imagers and magnetometers that can deliver high time resolution data (0.33 and 2 Hz, respectively). A network of 20 Ground-Based Observatories (GBOs) are deployed across Canada and Alaska to support the collection of data from these instruments. Here we describe the system design of the observatory, with emphasis on how the design meets the environmental and data-collection requirements. We also review the design of the All Sky Imager (ASI), discuss how it was built to survive Arctic deployments, and summarize the optical characterizations performed to qualify the design to meet THEMIS mission requirements. 相似文献
40.
Baliukin Igor Bertaux Jean-Loup Bzowski Maciej Izmodenov Vladislav Lallement Rosine Provornikova Elena Quémerais Eric 《Space Science Reviews》2022,218(6):1-33
Space Science Reviews - The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) is a robotic arm-mounted instrument onboard NASA’s Perseverance... 相似文献