摘要:

A comparison of opportunities for optical aperture synthesis from the ground and from the moon suggests that the lunar surface (at night) will be an excellent site for interferometry to faint limits in the intermediate wavelengths, 4–20 &mgr;m. At shorter wavelengths, ground‐based observations are competitive. In the 5–20 &mgr;m region, ground‐based will be competitive if the background photon limit can be reached. Baselines up to 3 km will be required. In the far infrared, ≳40 &mgr;m, the faintest IRAS sources could be measured, and many of the brighter sources imaged, with baselines up to 0.6 km. The temperature of the lunar environment limits the likely far infrared performance of a lunar based system. The cooler ambient temperatures in the polar regions do not offer substantial sensitivity gains.

ISSN:0094-243X    

DOI:10.1063/1.39314

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The principle advantages of the moon in terms of interferometry at submillimeter and far‐infrared wavelengths are the absence of an atmosphere, the availability of a stable platform, and the possibility of extremely long baselines. At the Smithsonian Astrophysical Observatory, efforts are currently underway to construct a terrestrial submillimeter‐wavelength interferometer on a high mountain site. However, even at an excellent site such as Mauna Kea, the number of nights with less than 1 mm of precipitable water is small, perhaps somewhere between 40 to 80 nights every year. On those occasions, opacities at submillimeter wavelengths down to 350 &mgr;m will be acceptable, while the far‐infrared wavelengths will remain essentially blocked. In addition, the atmospheric extinction introduces phase instability. It can be calculated that seeing of better than 0.1‘will be difficult to achieve from the surface of the earth. Hence a lunar observatory, by virtue of the absence of an atmosphere, will provide transparency, unprecedented phase stability, and thus the kind of angular resolution that would otherwise not be possible.

ISSN:0094-243X    

DOI:10.1063/1.39315

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

This paper describes a system concept for a Synthsis Array for Lunar Submillimeter Astronomy (SALSA). It includes a brief discussion of the science objectives and the advantages of placing such an array on the moon, the system concept, and a top‐level discussion of the various subsystems, including the technology drivers associated with each.

ISSN:0094-243X    

DOI:10.1063/1.39316

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

This paper discusses the use of very low frequency radio emission as a probe of astrophysical plasmas. The density distribution and the degree of turbulence of a plasma can be determined from its effect on background radio source. These same absorption phenomena can be used to determine magnetic field strengths within the plasma. Detection of unabsorbed synchrotron emission can provide information of the relativistic plsam component. Finally, time variable emission may prove useful in the detection of brown dwarfs and Jupiter‐like planets.

ISSN:0094-243X    

DOI:10.1063/1.39317

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A simple, inexpensive experiment is proposed for the early lunar mission to make high angular resolution observations in one of the last unexplored parts of the electromagnetic spectrum. An array of nineteen simple crossed‐dipole antennas will make images at frequencis below the Earth’s ionospheric cut‐off from about 100 kHz to 10 MHz. It would serve as a precursor to a major low‐frequency telescope which would eventually be built on the back of the Moon, away from terrestrial interference.

ISSN:0094-243X    

DOI:10.1063/1.39318

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A number of astrophysical observatory concepts were studied under the overall direction of the NASA Astrophysics Division in support of NASA’s 90‐day study of the Human Exploration Initiative. The four observatory concepts described here were investigated at JPL. In three of them, interferometric techniques would be used to acquire high resolution synthetic aperture images in several different parts of the electromagnetic spectrum: in the UV/Visible Near Infrared; the Submillimeter; and the Very Low Frequency (1 to 30 MHz region). The fourth is a Gravitational Wave Detector which uses laser optical interferometry to measure the strains induced by the passage of a gravitational wave. The observatory concepts reflect the constraints on lunar surface science deployment anticipated for the Human Exploration Initiative in the period 2002 through 2015.

ISSN:0094-243X    

DOI:10.1063/1.39319

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A self‐deployable optical synthesis array can operate on the Moon before a manned station becomes available, and be further expanded afterwards. The concept is derived from the ground‐based Optical Very Large Array, with ‘‘walking’’ telescopes and a dynamic system of laser metrology. The phasing of the lunar version can be achieved with a reference star, using a field slicer. A prototype compact telescope with laser system is under construction for the OVLA.

ISSN:0094-243X    

DOI:10.1063/1.39320

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

In quest of higher angular resolution and broader spectral coverage, solar physics was the first astronomical discipline to obtain observations from rockets, and later from satellites. Solar physicists have also been pioneers in the application of new imaging technologies. For example, the first high resolution astronomical x‐ray images obtained with grazing incidence optics were of the sun; more recently, the first high resolution astronomical soft x‐ray /EUV images obtained with normal incidence multilayer x‐ray imaging techniques have also been of the sun.

ISSN:0094-243X    

DOI:10.1063/1.39321

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The rationale for a lunar solar observatory is described and the requirements for various candidate instruments are developed. The unique characteristics of the lunar surface, its stability, low seismicity, and long unobstructed paths make it an ideal site for a large, high performance optical telescope. The capabilities of such an instrument is used, as an example (1) for the science that might be achieved from the lunar surface, (2) to identify the magnitude of the instrumentation, and (3) to indicate the technologies that must be developed if such an observatory is to become a reality.

ISSN:0094-243X    

DOI:10.1063/1.39322

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A dual‐channel reflecting coronagraph is proposed that would provide observations of L&agr; corona and chromosphere, upper transition‐region phenomena in CIV, and also helioseismology observations in the continuum around 166 nm. Each channel would use a 104×104‐UV‐sensitive CCD array. The combined velocity and magnetic field data would link events in the chromosphere, the transition region and the corona to an elongation of about 2.5R0. These data would be used to study both the global‐scale and also the fine‐scale properties of the corona in terms of the physical processes that deposit energy and momentum in the corona. Specific question to be investigated would be the origin and morphology of CME’s and other coronal transients, sources of coronal heating, and the source(s) and dynamics of the coronal wind in the inner coronal region.

ISSN:0094-243X    

DOI:10.1063/1.39323

出版商:AIP    

年代:1990

数据来源: AIP