摘要 :
A Folded Astronomical Space Telescope (FAST) is a 2.4-m Hubble Space Telescope (HST) class of telescope that can be packaged in a 1.5-m diameter cylinder through use of a single ring of eight deployable segments. Because it has ...
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A Folded Astronomical Space Telescope (FAST) is a 2.4-m Hubble Space Telescope (HST) class of telescope that can be packaged in a 1.5-m diameter cylinder through use of a single ring of eight deployable segments. Because it has less mass and uses a much smaller booster to inject it into orbit, the cost is greatly reduced.
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摘要 :
The position of the giant elliptical galaxy M87 at the center of the Virgo Cluster means that the inferred column density of dark matter associated with both the cluster halo and the galaxy halo is quite large. This system is thus...
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The position of the giant elliptical galaxy M87 at the center of the Virgo Cluster means that the inferred column density of dark matter associated with both the cluster halo and the galaxy halo is quite large. This system is thus an important laboratory for studying massive dark objects in elliptical galaxies and galaxy clusters by gravitational microlensing, strongly complementing the studies of spiral galaxy halos performed in the Local Group. We have performed a microlensing survey of M87 with the WFPC2 instrument on the Hubble Space Telescope. Over a period of thirty days, with images taken once daily, we discover seven variable sources. Four are variable stars of some sort, two are consistent with classical novae, and one exhibits an excellent microlensing lightcurve, though with a very blue color implying the somewhat disfavored possibility of a horizontal branch source being lensed. Based on sensitivity calculations from artificial stars and from artificial lightcurves, we estimate the expected microlensing rate. We find that the detection of one event is consistent with a dark halo with a 20% contribution of microlensing objects for both M87 and the Virgo Cluster, similar to the value found from observations in the Local Group. Further work is required to test the hypothesized microlensing component to the cluster.
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摘要 :
None given. From overview and conclusion:Keck Telescope case study. Objectives-low cost, good sky coverage. Approach--natural guide star at 0.8um, correcting at 2.2um.Concl- Good performance is possible for Keck with natural g...
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None given. From overview and conclusion:Keck Telescope case study. Objectives-low cost, good sky coverage. Approach--natural guide star at 0.8um, correcting at 2.2um.Concl- Good performance is possible for Keck with natural guide star AO system (SR>0.2 to mag 17).AO-optimized CCD should b every effective. Optimizing td is very effective.Spatial Coadding is not effective except perhaps at extreme low light levels.
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摘要 :
The Infrared Technology Testbed Telescope (ITTT) is a demonstration telescope meeting the needs of the SIRTF mission. It is a Ritchey-Cretien form designed for diffraction limited performance at 6.5 um, at 5.5 K with an 85 cm. clear aperture.
摘要 :
While large aperture telescopes are highly desirable for their enormous light grasp, smaller telescopes are increasingly pressed into service as wide-field survey instruments to aid in the search for near earth objects, satellites...
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While large aperture telescopes are highly desirable for their enormous light grasp, smaller telescopes are increasingly pressed into service as wide-field survey instruments to aid in the search for near earth objects, satellites and space debris. Various optical designs are found throughout the technical literature but not all represent truly capable wide-field survey instruments and the search to find such designs is time consuming without any guarantees of its completeness. Here we present an overview of wide-field optical designs suitable for survey instruments in the 1/2 meter class aperture range. The size is small enough to be affordable for many less well funded research programs, yet large enough that when coupled with a modest CCD mosaic, the resulting system represents a capable survey instrument. Many optical designs exist with each having its own strengths and limitations.
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