共查询到20条相似文献,搜索用时 531 毫秒
1.
Ray DuVarney Charlie Bleau Garry Motter Richard Dekany Mitchell Troy Gary Brack 《Experimental Astronomy》2001,11(3):237-249
SciMeasure, in collaboration with Emory University and the Jet Propulsion Laboratory, has developed a very versatile CCD controller for use in adaptive optics, optical interferometry, and other applications requiring high-speed readout rates and/or low read noise. The overall architecture of this controller system will be discussed and its performance using both EEV CCD39 and MIT/LL CCID-19 detectors will be presented. This controller is used in the adaptive optics system, developed by JPL, for the 200′′ Hale telescope at Palomar Mountain. Early diffraction-limited science results, recently achieved by the AO system, are presented. We gratefully acknowledge the financial support of NASA through SBIR contracts NAS8–97195 and NAS8–98081. 相似文献
2.
Vanscheidt R. Bleul H. Manthey E. Jütte M. Pohlen M. Schmidtobreick L. Altmann M. Dieball A. Geffert M. Sanner J. Notni P. Schmoll J. 《Earth, Moon, and Planets》1998,81(3):223-231
Extensive widefield CCD direct imaging of C/1995 O1 (Hale-Bopp) at UBVRI was carried out at Hoher List Observatory with the
1.06 m telescope (field of view 20′ × 20′) and at Potsdam Observatory with the 0.70 m telescope (field of view 8′ × 8′). The
corresponding spatial resolution is 850–1000 km pix-1and 525–590 km pix-1, respectively. The data covers 25 nights from February 20 to April 21, 1997.
In order to quantify the various features in the apparent inner coma we introduce a new tomographic method that minimizes
the morphological bias caused by image processing. The tomographic analysis leads to quantitative maps refering to the position
and intensity of the dust ejections for each image frame. Variability and periodicity within the inner coma can be thoroughly
deduced due to various sets of consecutive nights in the observation period mentioned above. The results are compared with
applications of adaptive Laplace filtering.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
A. Chalabaev E. Le Coarer P. Rabou Y. Magnard P. Petmezakis D. Le Mignant 《Experimental Astronomy》2002,14(3):147-181
The GraF instrument using a Fabry-Perot interferometer cross-dispersed with a grating was one of the first integral-field
and long-slit spectrographs built for and used with an adaptive optics system. We describe its concept, design, optimal observational
procedures and the measured performances. The instrument was used in 1997–2001 at the ESO3.6 m telescope equipped with ADONIS
adaptive optics and SHARPII+camera. The operating spectral range was 1.2–2.5 μm. We used the spectral resolution from 500
to 10 000 combined with the angular resolution of 0.1″–0.2″. The quality of GraF data is illustrated by the integral field
spectroscopy of the complex0.9″ × 0.9″ central region of η Car in the1.7 μm spectral range at the limit of spectral and angular
resolutions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
H. S. Sawant R. Ramesh J. R. Cecatto C. Faria F. C. R. Fernandes R. R. Rosa M. C. Andrade S. Stephany L. B. T. Cividanes C. A. I. Miranda L. C. L. Botti J. W. S. V. Boas J. H. Saito C. E. Moron N. D. Mascarenhas K. R. Subramanian M. S. Sundararajan E. Ebenezer M. R. Sankararaman 《Solar physics》2007,242(1-2):213-220
An East – West, one-dimensional radio interferometer array consisting of five parabolic dish antennas has been set up at Cachoeira
Paulista (longitude 45°0′20″ W, latitude 22°41′19″ S) for observations of the Sun and some of the strong sidereal sources
by the Instituto Nacional de Pesquisas Espaciais (INPE), Brazil. This is Phase-I of the proposed Brazilian Decimetric Array
and can be operated at any frequency in the range 1.2 – 1.7 GHz. The instrument has been in operation since November 2004
onwards at 1.6 GHz. The angular and temporal resolutions at this frequency are ∼3′ and 100 ms, respectively. Details of the
array, analog/digital receiver system, and a preliminary East – West one-dimensional solar image at the 1.6 GHz are presented
in this paper. 相似文献
5.
D. B. Jess M. Mathioudakis D. J. Christian F. P. Keenan R. S. I. Ryans P. J. Crockett 《Solar physics》2010,261(2):363-373
The Rapid Oscillations in the Solar Atmosphere (ROSA) instrument is a synchronized, six-camera high-cadence solar imaging
instrument developed by Queen’s University Belfast. The system is available on the Dunn Solar Telescope at the National Solar
Observatory in Sunspot, New Mexico, USA, as a common-user instrument. Consisting of six 1k × 1k Peltier-cooled frame-transfer
CCD cameras with very low noise (0.02 – 15 e s−1 pixel−1), each ROSA camera is capable of full-chip readout speeds in excess of 30 Hz, or 200 Hz when the CCD is windowed. Combining
multiple cameras and fast readout rates, ROSA will accumulate approximately 12 TB of data per 8 hours observing. Following
successful commissioning during August 2008, ROSA will allow for multi-wavelength studies of the solar atmosphere at a high
temporal resolution. 相似文献
6.
In this empirical study, we compare high-resolution observations obtained with the 65-cm vacuum reflector at Big Bear Solar
Observatory (BBSO) in 2005 and with the Dunn Solar Telescope (DST) at the National Solar Observatory/Sacramento Peak (NSO/SP)
in 2006. We measure the correction of the high-order adaptive optics (AO) systems across the field of view (FOV) using the
spectral ratio technique, which is commonly employed in speckle masking imaging, and differential image motion measurements.
The AO correction is typically much larger (10′′ to 25′′) than the isoplanatic angle and can be described by a radially symmetric function with a central core and extended wings.
The full-width at half-maximum (FWHM) of the core represents a measure of the AO correction. The average FWHM values for BBSO
and NSO/SP are 23.5′′ and 18.2′′, respectively. The extended wings of the function show that the AO systems still contribute to an improved speckle reconstruction
at the periphery of the 80′′×80′′ FOV. The major differences in the level of AO correction between BBSO and NSO/SP can be explained by different contributions
of ground-layer- and free-atmosphere-dominated seeing, as well as different FOVs of the wavefront sensors. In addition, we
find an anisotropic spectral ratio in sunspot penumbrae caused by the quasi-one-dimensional nature of penumbral filaments,
which introduces a significant error in the estimation of the Fourier amplitudes during the image restoration process. 相似文献
7.
Douglas P. Looze Markus Kasper Stefan Hippler Orhan Beker Robert Weiss 《Experimental Astronomy》2003,15(2):67-88
This paper develops a compensation algorithm based on Linear–Quadratic–Gaussian (LQG) control system design whose parameters
are determined (in part) by a model of the atmosphere. The model for the atmosphere is based on the open-loop statistics of
the atmosphere as observed by the wavefront sensor, and is identified from these using an auto-regressive, moving average
(ARMA) model. The (LQG) control design is compared with an existing compensation algorithm for a simulation developed at ESO
that represents the operation of MACAO adaptive optics system on the 8.2 m telescopes at Paranal, Chile.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
The Reuven Ramaty High-Energy Solar Spectroscopic Imager RHESSI telescope produces hard X-ray images by Fourier imaging techniques
that are capable of determining the sizes and shapes of sources with spatial scales in the range ∼ 2′′–180′′. Applying the
method of Unpixelized Forward Fitting to RHESSI modulation profiles from simple flares, we have identified the presence of
`halo' sources whose size scale (∼ 40′′) greatly exceeds the `core' sizes (≤ 6′′–14′′). Although such `core-halo' structures
have been observed at radio wavelengths using a similar technique, the radio and hard X-ray phenomena may be different. These
observations raise questions about the nature of these `halos'. Among the possibilities are that they are albedo sources,
thin-target loops, or unidentified diffuse structures.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022484822851 相似文献
9.
Hard X-ray lightcurves, spectrograms, images, and spectra of three medium-sized flares observed by the Reuven Ramaty High-Energy
Solar Spectroscopic Imager (RHESSI) are presented. Imaging spectroscopy of the 20 February 2002, 11:06 UT flare at 10′′ spatial
resolution, comparable to the best previous hard X-ray imaging from Yohkoh, shows two footpoints with an ∼ 8 s delay of peak emission between footpoints. Subsequent imaging at le4′′ shows three sources consistent with two separate loops and simultaneous brightening in connected footpoints. Imaging for
the simple two footpoint flare of 2 June 2002 also shows simultaneous footpoint brightening. The more complex 17 March 2002
flare shows at least four different sources during the main peak of the event, and it is difficult to clearly demonstrate
simultaneous brightening of connected footpoints. Non-thermal power laws are observed down to ∼ 12–13 keV without flattening
in all these events, indicating the energy content in energetic electrons may be significantly greater than previously estimated
from assumed 25 keV low energy cutoff. Simultaneously brightening footpoints show similar spectra, at least in the three flares
investigated. Double-power-law spectra with a relatively sharp break are often observed.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022469902940 相似文献
10.
H.U. Kufl 《Astronomische Nachrichten》2010,331(5):549-554
Near‐Infrared high spectral and spatial resolution spectroscopy offers new and innovative observing opportunities for astronomy. The “traditional” benefits of IR‐astronomy – strongly reduced extinction and availability of adaptive optics – more than offset for many applications the compared to CCD‐based astronomy strongly reduced sensitivity. Especially in high resolution spectroscopy interferences by telluric lines can be minimized. Moreover for abundance studies many important atomic lines can be accessed in the NIR. A novel spectral feature available for quantitative spectroscopy are the molecular rotational‐vibrational transitions which allow for fundamentally new studies of condensed objects and atmospheres. This is also an important complement to radio‐astronomy, especially with ALMA, where molecules are generally only observed in the vibrational ground state. Rot‐vib transitions also allow high precision abundance measurements – including isotopic ratios – fundamental to understand the thermo‐nuclear processes in stars beyond the main sequence. Quantitative modeling of atmospheres has progressed such that the unambiguous interpretation of IR‐spectra is now well established. In combination with adaptive optics spectro‐astrometry is even more powerful and with VLT‐CRIRES a spatial resolution of better than one milli‐arcsecond has been demonstrated. Some highlights and recent results will be presented: our solar system, extrasolar planets, star‐ and planet formation, stellar evolution and the formation of galactic bulges (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
I. Roxburgh 《Astrophysics and Space Science》2003,285(2):363-366
The Eddington mission was given full approval by the European Space Agency on the 23rd May 2002, with launch scheduled for 2007/8. Its
science objectives are stellar evolution and asteroseismology, and planet finding. In its current design it consists of 4
× 60 cm folded Schmidt telescopes, each with 6o × 6o field of view and its own CCD array camera. Eddington will spend 2 years primarily devoted to asteroseismology with 1–3 months on different target fields monitoring up to 50,000
stars per field, and 3 years continuously on a single field monitoring upwards of 100,000 stars for planet searching. The
asteroseismic goal is to be able to detect oscillations frequencies of stars with a precision 0.1–0.3 μHz, to probe their
interior structure and the study the physical processes that govern their evolution.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
The system gain of two CCD systems in regular use at the Vainu Bappu Observatory, Kavalur, is determined at a few gain settings.
The procedure used for the determination of system gain and base-level noise is described in detail. The Photometrics CCD
system at the 1-m reflector uses a Thomson-CSF TH 7882 CDA chip coated for increased ultraviolet sensitivity. The gain is
programme-selected through the parameter ‘cgain’ varying between 0 and 4095 in steps of 1. The inverse system gain for this
system varies almost linearly from 27.7 electrons DN-1 at cgain = 0 to 1.5 electrons DN-1 at cgain = 500. The readout noise is ≲ 11 electrons at cgain = 66. The Astromed CCD system at 2.3-m Vainu Bappu Telescope
uses a GEC P8603 chip which is also coated for enhanced ultraviolet sensitivity. The amplifier gain is selected in discrete
steps using switches in the controller. The inverse system gain is 4.15 electrons DN-1 at the gain setting of 9.2, and the readout noise ∼ 8 electrons. 相似文献
13.
Ultra-violet image sensors and UV optics have been developed for a variety of space borne UV astronomy missions. Technology progress has to be made to improve the performance of future UV space missions. Throughput is the most important technology driver for the future. Required developments for different UV detector types – detectors are one of the most problematic and critical parts of a space born mission – and for optical components of the instruments are given in these guidelines. For near future missions we need high throughput optics with UV sensors of large formats, which show simultaneously high quantum efficiency and low noise performance. 相似文献
14.
We report observations of 24 stars in the fields of the three Seyfert galaxies MCG +08-23-067, Mrk 817, and Mrk 290. The observations
were made with a CCD array photometer in the BVRcIc bands. The V magnitudes of the observed stars ranged from 13.5 and 17.2.
For stars of approximate magnitude 15, the typical photometric errors are 0.010, 0.011, 0.008 and 0.011 magnitude in the BVRI
bands, respectively. The BVRI magnitudes of all these stars were not known previously. In the field of the galaxy Mrk 290
a star has been found that probably has a periodic brightness variation with P=1.518 days and the mean value V=14.80 and which
may belong to the class of “spotted” stars. 14′x14′ charts are supplied for identifying the stars. These results can be used
for differential photometry of active galactic nuclei in the BVRI bands.
__________
Translated from Astrofizika, Vol. 51, No. 1, pp. 41–50 (February 2008). 相似文献
15.
Josep M. Trigo-Rodriguez José M. Madiedo Peter S. Gural Alberto J. Castro-Tirado Jordi Llorca Juan Fabregat Standa Vítek Pep Pujols 《Earth, Moon, and Planets》2008,102(1-4):231-240
By using high-resolution, low-scan-rate, all-sky CCD cameras, the SPanish Meteor Network (SPMN) is currently monitoring meteor
and fireball activity on a year round basis. Here are presented just a sampling of the accurate trajectory, radiant and orbital
data obtained for meteors imaged simultaneously from two SPMN stations during the continuous 2006–2007 coverage of meteor
and fireball monitoring. Typical astrometric uncertainty is 1–2 arc min, while velocity determination errors are of the order
of 0.1–0.5 km/s, which is dependent on the distance of each event to the station and its particular viewing geometry. The
cameras have demonstrated excellent performance for detecting meteor outbursts. The recent development of automatic detection
software is also providing real-time information on the global meteor activity. Finally, some examples of the all-sky CCD
cameras applications for detecting unexpected meteor activity are given. 相似文献
16.
17.
J. Y. Hu 《Astrophysics and Space Science》1994,217(1-2):53-54
A high spatial resolution near infrared imaging system is being developed at Beijing Observatory. It is a joint-project with Institute of Optics and Electronics, CSA, and National Astronomical Observatory, Japan. The system contains a 512 × 512 PtSi CSD near infrared camera and a 21-element adaptive optics system and will be operated at Coudé focus of the 2.16 meter telescope at Xinglong Station, Beijing Observatory. The infrared camera will be fixed at Cassegrain focus with focus reducers too. 相似文献
18.
《天文和天体物理学研究(英文版)》2016,(12)
A first generation sodium Laser Guide Star Adaptive Optics System(LGS-AOS) was developed and integrated into the Lijiang 1.8 m telescope in 2013. The LGS-AOS has three sub-systems:(1) a 20 W long pulsed sodium laser,(2) a 300-millimeter-diameter laser launch telescope, and(3) a 37-element compact adaptive optics system. On 2014 January 25, we obtained high resolution images of an mV8.18 star,HIP 43963, during the first light of the LGS-AOS. In this paper, the sodium laser, the laser launch telescope,the compact adaptive optics system and the first light results will be presented. 相似文献
19.
We designed a prime focus CCD photometer, Argos, optimized for high speed time-series measurements of blue variables (Nather
& Mukadam 2004) for the 2.1 m telescope at McDonald Observatory. Lack of any intervening optics between the primary mirror
and the CCD makes the instrument highly efficient. We measure an improvement in sensitivity by a factor of nine over the 3-channel
PMT photometers used on the same telescope and for the same exposure time. The CCD frame transfer operation triggered by GPS
synchronized pulses serves as an electronic shutter for the photometer. This minimizes the dead time between exposures, but
more importantly, allows a precise control of the start and duration of the exposure. We expect the uncertainty in our timing
to be less than 100μs.
Hubble Fellow 相似文献
20.
S. García-Burillo F. Combes J. Graciá-Carpio A. Usero M. Guélin 《Astrophysics and Space Science》2008,313(1-3):261-265
High-resolution CO maps are an essential tool to search for observational evidence of AGN fueling in galaxy nuclei. While
their capabilities will be surpassed by ALMA, current mm-interferometers can already provide relevant information on scales
which are critical for the process of angular momentum transfer in fueling the AGN. In this context we present the latest
results issued from the NUclei of GAlaxies (NUGA) project, a high-resolution (0.5′′–1′′) CO survey of low luminosity AGNs conducted with the IRAM Plateau de Bure interferometer (PdBI). The use of more specific
molecular tracers of dense gas can probe the feedback influence of activity on the chemistry and energy balance in the interstellar
medium of nearby galaxies, a prerequisite to understanding how feedback operate at higher redshift galaxies. We discuss the
results obtained in an ongoing study devoted to probe the feedback of activity from nearby Seyferts to high-redshift QSO. 相似文献