No abstract

No abstract

The Ionospheric Connection Explorer, or ICON, is a new NASA Explorer mission that will explore the boundary between Earth and space to understand the physical connection between our world and our space environment. This connection is made in the ionosphere, which has long been known to exhibit variability associated with the sun and solar wind. However, it has been recognized in the 21st century that equally significant changes in ionospheric conditions are apparently associated with energy and momentum The Ionospheric Connection Explorer (ICON) mission Edited by Doug Rowland and Thomas J. Immel B T.J. Immel

Measurements by the University of California Berkeley Infrared Spatial Interferometer at 11.15 km have yielded strong evidence for multiple dust shells and/or signiÐcant asymmetric dust emission around NML Cyg. New observations reported also include multiple 8È13 km spectra taken from 1994È1995 and N-band (10.2 km) photometry from 1980È1992. These and past measurements are analyzed and Ðtted to a model of the dust distribution around NML Cyg. No spherically symmetric single dust shell model is found consistent with both near-and mid-infrared observations. However, a circularly symmetric maximum entropy reconstruction of the 11 km brightness distribution suggests a double-shell model for the dust distribution. Such a model, consisting of a geometrically thin shell of intermediate optical depthplus an outer shell is consistent not only with the 11 km visibility data but (q 11 km D 1.9) (q 11 km D 0.33), also with near-infrared speckle measurements, the broadband spectrum, and the 9.7 km silicate feature. The outer shell, or large-scale structure, is revealed only by long-baseline interferometry at 11 km, being too cold (D400 K) to contribute in the near-infrared and having no unambiguous spectral signature in the mid-infrared. The optical constants of Ossenkopf, Henning, & Mathis proved superior to the Draine & Lee (1984) constants in Ðtting the detailed shape of the silicate feature and broadband spectrum for this object. Recent observations of maser emission around NML Cyg by Richards, Yates, & Cohen H 2 O (1996) are consistent with the location of the two dust shells and provide further evidence for the twoshell model.

No abstract

No abstract

No abstract

A detailed description is given of the Infrared Spatial Interferometer (ISI), developed at the Space Sciences Laboratory of the University of California at Berkeley, which is a high spatial resolution interferometer for mid-infrared wavelengths. The instrumentation, its capabilities and performance, data analysis, science program, and future plans are all discussed. The systemÏs use of heterodyne detection, analogous to that of a modern radio interferometer, is also compared with the homodyne or direct methods more commonly encountered in the visible and infrared. The ISI has been operating productively on Mount Wilson for the past 10 years measuring materials immediately surrounding stars and their changes as well as some stellar diameters. The new spectral capabilities described here, a recent increase in baseline length, and the upcoming expansion to a closure-phase imaging array provide important additional types of measurements.