共查询到20条相似文献，搜索用时 15 毫秒
1.
ISLA will be an astronomical observatory, operating at the upper limit of our planet Earth atmosphere, offering space like
observing conditions in most aspects. ISLA can be maintained easily, modified easily if necessary, always kept at the state
of the art and operated for very extended periods without polluting the stratosphere. ISLA is ideally suited to become the
first world space observatory as the observing conditions are very much space-like – diffraction limited angular resolution,
very low ambient temperature, remote control – however ISLA is easily accessible, telescopes and instruments can be continuously
improved and ISLA's costs corresponds only to those of ground-based modern astronomical installations like the ESO-VLT-, KECK-
and GEMINI-observatories. The cost of observing and experimenting on ISLA will be orders of magnitudes lower than those of
building and operating any space telescope, allowing the astronomers of developing nations to participate in the ISLA observatory
within their limited financial possibilities as competent and full partners. ISLA's 4-m and 2-m telescopes will operate diffraction
limited from 0.3 μm in the optical, over the infrared, far-infrared to the sub-mm spectral range. ISLA's individual telescopes
will permit imaging with 20 milli-arcsec spatial resolution in the optical, 5 times better than the Hubble Space Telescope.
ISLA's telescopes can be combined to form an interferometer with a maximum baseline of 250 m with nearly complete coverage
of the u,v plane. Interferometric resolution will be of the order of 20 micro-arcsec for the optical. ISLA will thus offer
spatial resolution comparable or better than the intercontinental VLBI radio interferometers. ISLA's telescope efficiency
will be many orders of magnitude better than comparable ground-based telescopes. The light collecting power of ISLA's interferometric
telescopes will be orders of magnitudes greater than the future space interferometers under discussion. ISLA, being an aviation
project and not a space project, can be realised in the typical time scale for the development of aviation: about 5 years.
ISLA's cost for the whole observatory, including its movable ground station etc. will be of the order of a typical medium
size ESA space mission. ISLA's lifetime will be in excess of many decades, as it can easily be maintained, modernised, repaired
and improved. ISLA will become the origin of a new astronomical international organisation with worldwide participation. ISLA's
telescopes will be of the greatest importance to all astronomical fields, as it will permit to study much fainter, much more
distant objects with microscopic spatial resolution in wavelength regions inaccessible from ground. ISLA's many telescopes
permit easily simultaneous observations at many wavelengths for rapidly varying objects, from continuously monitoring the
surfaces of the planets in our solar system, surfaces of close-by stars, nuclei of galaxies to QSO's.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
M. Alice Gasparini Phil Marshall Tommaso Treu Eric Morganson Florian Dubath 《Monthly notices of the Royal Astronomical Society》2008,385(4):1959-1964
We use present theoretical estimates for the density of long cosmic strings to predict the number of strong gravitational lensing events in astronomical imaging surveys as a function of the angular resolution and survey area. We show that angular resolution is the single most important factor, and that interesting limits on the dimensionless string tension G μ/ c 2 can be obtained by existing and planned surveys. At the resolution of the Hubble Space Telescope ( HST ) (0.14 arcsec), it is sufficient to survey of the order of a few square degrees – well within reach of the current HST archive – to probe the regime G μ/ c 2 ∼ 10−7 . If lensing by cosmic strings is not detected, such a survey would improve the limit on the string tension by a factor of two over that available from the cosmic microwave background. Future high resolution imaging surveys, covering a few hundred square degrees or more, either from space in the optical or from large-format radio telescopes on the ground, would be able to further lower this limit to G μ/ c 2 ∼ 10−8 . These limits will not be improved significantly by increasing the solid angle of the survey. 相似文献
3.
《Chinese Astronomy and Astrophysics》2019,43(3):405-423
Due to the atmospheric turbulence, the static aberration, tracking and pointing errors of telescopes, the point spread functions (PSFs) in different fields of view are different. Meanwhile, there are different PSFs in the images obtained by different telescopes. The quality of co-adding image is limited by the image with the poorest quality, and finally the resolution and sensitivity of the quad-channel telescope will also be affected. Dividing the image into some regions with the same type of PSF, and deconvolving these regions can improve the quality of the co-adding image. According to this theory, an image restoration algorithm based on the PSF clustering is proposed. Firstly, this paper makes the PSF clustering analysis by using Self-Organizing Maps, and makes the image segmentation based on the result of the PSF clustering analysis, then using the clustered PSFs to make deconvolutions on the sub-images. Then, the restored sub-images after deconvolution are joined together. Finally, by through the image registration and co-adding, the image with a high signal to noise ratio can be obtained. The result shows that the signal to noise ratio of the astronomical images are improved with our method, and the detection capability on faint stars is also improved. 相似文献
4.
Dominic J. Benford Michael J. Amato John C. Mather S. Harvey Moseley Jr David T. Leisawitz 《Astrophysics and Space Science》2004,294(3-4):177-212
The Single Aperture Far-InfraRed (SAFIR) Observatory’s science goals are driven by the fact that the earliest stages of almost
all phenomena in the universe are shrouded in absorption by and emission from cool dust and gas that emits strongly in the
far-infrared (40μ–200μ) and submillimeter (200μ–1 mm). In the very early universe, the warm gas of newly collapsing, unenriched
galaxies will be revealed by molecular hydrogen emission lines at these long wavelengths. High redshift quasars are found
to have substantial reservoirs of cool gas and dust, indicative of substantial metal enrichment early in the history of the
universe. As a result, even early stages of galaxy formation will show powerful far-infrared emission. The combination of
strong dust emission and large redshift (1 < z < 7) of these galaxies means that they can only be studied in the far-infrared and submillimeter. For nearby galaxies, many
of the most active galaxies in the universe appear to be those whose gaseous disks are interacting in violent collisions.
The details of these galaxies, including the effect of the central black holes that probably exist in most of them, are obscured
to shorter wavelength optical and ultraviolet observatories by the large amounts of dust in their interstellar media. Within
our own galaxy, the earliest stages of star formation, when gas and dust clouds are collapsing and the beginnings of a central
star are taking shape, can only be observed in the far-infrared and submillimeter. The cold dust that ultimately forms the
planetary systems, as well as the cool “debris” dust clouds that indicate the likelihood of planetary sized bodies around
more developed stars, can only be observed at wavelengths longward of 20μ.
Over the past several years, there has been an increasing recognition of the critical importance of the far-infrared to submillimeter
spectral region to addressing fundamental astrophysical problems, ranging from cosmological questions to understanding how
our own Solar System came into being. The development of large, far-infrared telescopes in space has become more feasible
with the combination of developments for the James Webb Space Telescope (JWST) of enabling breakthroughs in detector technology.
We have developed a preliminary but comprehensive mission concept for SAFIR, as a 10 m-class far-infrared and submillimeter
observatory that would begin development later in this decade to meet the needs outlined above. Its operating temperature
(≤4 K) and instrument complement would be optimized to reach the natural sky confusion limit in the far-infrared with diffraction-limited
performance down to at least the atmospheric cutoff, λ {>rsim} 40 {μ}. This would provide a point source sensitivity improvement of several orders of magnitude over that of the Spitzer
Space Telescope (previously SIRTF) or the Herschel Space Observatory. Additionally, it would have an angular resolution 12
times finer than that of Spitzer and three times finer than Herschel. This sensitivity and angular resolution are necessary
to perform imaging and spectroscopic studies of individual galaxies in the early universe. We have considered many aspects
of the SAFIR mission, including the telescope technology (optical design, materials, and packaging), detector needs and technologies,
cooling method and required technology developments, attitude and pointing, power systems, launch vehicle, and mission operations.
The most challenging requirements for this mission are operating temperature and aperture size of the telescope, and the development
of detector arrays. SAFIR can take advantage of much of the technology under development for JWST, but with much less stringent
requirements on optical accuracy. 相似文献
5.
《Experimental Astronomy》2009,23(1):221-244
Millimetron is a Russian-led 12 m diameter submillimeter and far-infrared space observatory which is included in the Space
Plan of the Russian Federation for launch around 2017. With its large collecting area and state-of-the-art receivers, it will
enable unique science and allow at least one order of magnitude improvement with respect to the Herschel Space Observatory.
Millimetron will be operated in two basic observing modes: as a single-dish observatory, and as an element of a ground-space
very long baseline interferometry (VLBI) system. As single-dish, angular resolutions on the order of 3 to 12 arc sec will
be achieved and spectral resolutions of up to a million employing heterodyne techniques. As VLBI antenna, the chosen elliptical
orbit will provide extremely large VLBI baselines (beyond 300,000 km) resulting in micro-arc second angular resolution. 相似文献
6.
We develop a new procedure to improve the angular resolution of coded-mask telescopes by the Direct Demodulation Method (DDM). DDM has been applied to both real and simulated data of INTEGRAL/IBIS. The angular resolution of IBIS/ISGRI has been improved from about 13' to 2'. 相似文献
7.
地基望远镜在成像过程中,由于受大气湍流、望远镜静态像差、跟踪误差、指向误差及视场变化的影响,不同视场区域的PSF (Point Spread Function)具有差异;同时,不同望远镜获取的图像PSF也存在差异.将多个望远镜获取的星象直接叠加至相同的区域后,图像质量受像质最差的望远镜限制,最终观测分辨率和灵敏度均会受到影响.通过图像复原,可以提高图像质量,进而提高叠加效果.根据该思路提出了1种基于PSF分区的迭代图像复原方法:该方法首先通过SOM (Self-organizing Maps)对PSF进行聚类分析,利用同类别PSF的平均PSF进行反卷积,再将反卷积结果按PSF聚类结果分割为不同大小的子图,最后将子图进行拼接.图像复原在提高图像质量的同时,降低了PSF不一致性对图像叠加带来的影响.将几个望远镜在同一时刻获取的图像经反卷积处理之后利用图像配准算法进行矫正并叠加,可获得高信噪比图像.对实际望远镜获取的数据处理后的结果表明:图像在进行复原和叠加过程中,星象目标信噪比不断提升,提高了成像系统对暗星的探测能力. 相似文献
8.
9.
N. Schartel 《Astronomische Nachrichten》2012,333(3):209-212
The historical development of ground based astronomical telescopes leads us to expect that space‐based astronomical telescopes will need tobe operational for many decades. The exchange of scientific instruments in space will be a prerequisite for the long lasting scientific success of such missions. Operationally, the possibility to repair or replace key spacecraft components in space will be mandatory. We argue that these requirements can be fulfilled with robotic missions and see the development of the required engineering as the main challenge. Ground based operations, scientifically and technically, will require a low operational budget of the running costs. These can be achieved through enhanced autonomy of the spacecraft and mission independent concepts for the support of the software. This concept can be applied to areas where the mirror capabilities do not constrain the lifetime of the mission (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.
The performance of large telescopes is determined both by their angular resolution and by their collection area. It is, therefore, important to achieve as high an angular resolution as possible by site selection, by avoiding image deterioration by the telescope and its environment, and by real time image restoration by adaptive optics. We summarize the principles of adaptive optics, their predicted performance and the current programs underway to implement adaptive optics for astronomical purposes.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988. 相似文献
11.
James M. Cordes 《Experimental Astronomy》2009,26(1-3):79-94
The early days of radio astronomy showed incredibly diverse experimentation in ways to sample the electromagnetic spectrum at radio wavelengths. In addition to obtaining adequate sensitivity by building large collection areas, a primary goal also was to achieve sufficient angular resolution to localize radio sources for multi-wavelength identification. This led to many creative designs and the invention of aperture synthesis and VLBI. Some of the basic telescope types remain to the present day, now implemented across the entire radio spectrum from wavelengths of tens of meters to submillimeter wavelengths. In recent years, as always, there is still the drive for greater sensitivity but a primary goal is now to achieve very large fields of view to complement high resolution and frequency coverage, leading to a new phase of experimentation. This is the “back to the future” aspect of current research and development for next-generation radio telescopes. In this paper I summarize the scientific motivations for development of new technology and telescopes since about 1990 and going forward for the next decade and longer. Relevant elements include highly optimized telescope optics and feed antenna designs, innovative fabrication methods for large reflectors and dipole arrays, digital implementations, and hardware vs. software processing. The emphasis will be on meter and centimeter wavelength telescopes but I include a brief discussion of millimeter wavelengths to put the longer wavelength enterprises into perspective. I do not discuss submillimeter wavelengths because they are covered in other papers. 相似文献
12.
F. Patru N. Tarmoul D. Mourard O. Lardière 《Monthly notices of the Royal Astronomical Society》2009,395(4):2363-2372
In the future, optical stellar interferometers will provide true images thanks to larger number of telescopes and to advanced cophasing subsystems. These conditions are required to have sufficient resolution elements (resel) in the image and to provide direct images in the hypertelescope mode. It has already been shown that hypertelescopes provide snapshot images with a significant gain in sensitivity without inducing any loss of the useful field of view for direct imaging applications. This paper aims at studying the properties of the point spread functions of future large arrays using the hypertelescope mode. Numerical simulations have been performed and criteria have been defined to study the image properties. It is shown that the choice of the configuration of the array is a trade-off between the resolution, the halo level and the field of view. A regular pattern of the array of telescopes optimizes the image quality (low halo level and maximum encircled energy in the central peak), but decreases the useful field of view. Moreover, a non-redundant array is less sensitive to the space aliasing effect than a redundant array. 相似文献
13.
R. S. Stobie 《Astrophysics and Space Science》1995,230(1-2):9-15
Because of its geographical location and (astronomically) excellent climate South Africa can make an unique contribution to international astronomical research. An assessment of recent developments in telescope technology has shown that an advanced technology telescope of 4m-class can be constructed which will out-perform most existing 4m-class telescopes. Detailed consideration is given to the construction of such a telescope for optical/infrared astronomy, the new science that this will enable and the selection of a site of sufficiently good quality to justify the erection of such a telescope. If a telescope of this nature is sited in southern Africa it would provide the premier astronomical facility in Africa for decades to come. 相似文献
14.
T. J. Waskett B. Sibthorpe M. J. Griffin P. F. Chanial 《Monthly notices of the Royal Astronomical Society》2007,381(4):1583-1590
The forthcoming Herschel space mission will provide an unprecedented view of the far-infrared/submillimetre Universe, with the SPIRE instrument covering the 200–670 μm wavelength range. To obtain the best quality of astronomical data from such an expensive mission the observing modes must be optimized as far as possible. This paper presents the possible scanning strategies that can be utilized by the SPIRE photometer, within the limitations imposed by the Herschel spacecraft. Each strategy is investigated for effectiveness by performing simulated observations, using the SPIRE photometer simulator. By quantifying the data quality using a simple metric, we have been able to select the optimum scanning strategy for SPIRE when it begins taking science data within the next couple of years.
Additionally, this work has led to the development of a specific SPIRE mapmaking algorithm, based on the CMB code MADmap, to be provided as part of the SPIRE data pipeline processing suite. This will allow every SPIRE user to take full advantage of the optimized scan map strategy, which requires the use of maximum likelihood mapmakers such as MADmap. 相似文献
Additionally, this work has led to the development of a specific SPIRE mapmaking algorithm, based on the CMB code MADmap, to be provided as part of the SPIRE data pipeline processing suite. This will allow every SPIRE user to take full advantage of the optimized scan map strategy, which requires the use of maximum likelihood mapmakers such as MADmap. 相似文献
15.
Ji Hang-xin Hu Zhong-wen Zhu Yong-tian Xu Ming-ming Dai Song-xin Zhang Hua-tao Tang Zhen Wang Jin-feng 《Chinese Astronomy and Astrophysics》2019,43(4):493-518
Due to its wide wavelength coverage, multi-resolution mode, and high transmission efficiency, the wide field multi-object spectrograph becomes the most common-used universal instrument in extremely large telescopes. It's still a great challenge to build the wide field multi-object spectrograph for a 30 m class telescope because of its sharply increased volume and budget. With the rapid development of astronomy and astrophysics, the innovation of astronomical technology is fundamentally required. In this paper, the research progress of different kinds of wide-field multi-object spectrographs is illustrated and reviewed, the recent status of conceptual designs and the instrument features of the wide field multi-object spectrographs of the three 30 m class telescopes in the world, especially the current effort made by the Chinese team for the wide field multi-object spectrograph of the Thirty Meter Telescope (TMT) are introduced. 相似文献
16.
E. Jehin J. Manfroid D. Hutsemékers C. Arpigny J.-M. Zucconi 《Earth, Moon, and Planets》2009,105(2-4):167-180
Isotopic abundance ratios are excellently suited to probe the origin of solar system matter. We review the recent measurements of the isotopic ratios of the light elements (D/H, 12C/13C, 16O/18O, 14N/15N, 32S/34S) in cometary dust and gas and discuss briefly their implications. Special emphasis will be put on the determinations and progress performed in the field over the past years thanks to high resolution spectroscopy of cometary comae obtained with the ESO Very Large Telescope. Future perspectives from space missions and ground-based observations with new large and extremely large telescopes operating in the optical, infrared and submillimeter wavelengths will be presented. 相似文献
17.
D. Lemke 《Astronomische Nachrichten》2009,330(6):562-567
While astronomical telescopes developed rather slowly over the last four centuries, infrared telescopes made a fast career in only four decades from high mountains to aircraft, balloons and satellites. They cover the huge wavelength region from 1 to 350 μ m and have uncovered the cold and dust hidden universe. While until today all infrared space telescopes had diameters of <1 m, cooled infrared observatories with 3.5 to 6.5m mirrors will be sent into heliocentric orbits at L2 within the next few years (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
18.
K.J. Leech L. Metcalfe B. Altieri 《Monthly notices of the Royal Astronomical Society》2001,328(4):1125-1128
We present mid- and far-infrared photometry of the high-redshift dusty quasar BR 1202−0725. The quasar was detected in the near-infrared, at a flux level consistent with an average radio-quiet quasar at its redshift. Only upper limits for the emission were obtained in the far-infrared. These upper limits, when combined with data from ground-based telescopes, are the first direct evidence for a turnover in the far-infrared emission, and hence confirm that a blackbody dominates the spectral energy distribution at far-infrared wavelengths. This blackbody is most probably cool dust, constrained to have a temperature below 80 K, for a β of 1.5. 相似文献
19.
大气湍流理论的进展及其天文学意义(英) 总被引：2，自引：0，他引：2
传统的大气湍流理论始于大约30年前．湍流理论的发展使得天文学家对大气湍流对天文观测的影响有了很好的认识，尤其是它为天文台选址和天文高分辨率技术提供了基础．近年来新的天文观测已对传统的大气湍流理论提出了挑战，并可能给地面天文观测带来一场革命．在回顾了大气湍流理论的发展历史后对传统大气湍流理论的基本特性及其应用作了系统的综述，并介绍了新的天文观测事实以及为此而提出的新的大气湍流理论模型． 相似文献
20.
J. Lequeux 《Astrophysics and Space Science》1999,265(1-4):561-566
Very recent observations have shown that there are dusty galaxies at redshifts larger that 5. Their integrated contribution
to the far-IR/submillimeter sky background is known. These galaxies are very hard to detect in the visible and in the infrared,
but they will be within reach of the NGST, although it will be very difficult to recognize them without further studies. However
their far-infrared emission will be detectable by FIRST and more easily by the large submillimeter interferometer (ALMA) presently
under study. The ALMA, FIRST, SIRTF and the NGST will make an ideal set for investigating the formation and early evolution
of galaxies.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献