VARIATIONAL APPROACH TO THE CALCULATION OF CHARGE EXCHANGE CROSS SECTIONS FOR ADIABATIC COLLISIONS

Variational approach to calculation of charge exchange cross sections for adiabatic collisio

A cryogenically cooled, multidetector spectrometer for infrared astronomy

A liquid helium-cooled, 24 detector grating spectrometer was developed and used for low resolution astronomical observations in the 5 to 14 micron spectral range. The instrument operated on the 91 cm Kuiper Airborne Observatory, the 3 m IRTF (Mauna Kea), the 3 m Shane telescope Observatory, the 3 m Shane telescope (Lick Observatory), and the 152 cm NASA and University of Arizona telescope. The detectors are discrete Si:Bi photoconductors with individual metal oxide semiconductor field effect transistor preamplifiers operating at 4 K. The system uses a liquid helium-cooled slit, order-sorter filter, collimator mirror, grating, and camera mirror arranged in a Czerny-Turner configuration with a cold stop added between the collimator mirror and the grating. The distances between components are chosen so that the collimator mirror images the secondary mirror of the telescope onto the cold stop, thus providing a very effective baffle. Scattered radiation is effectively reduced by using liquid helium-cooled, black baffles to divide the spectrometer into three separate compartments. The system noise-equivalent flux density, when used on the 152 cm telescope from 8 to 13 microns with a resolving power of 50, is 4.4 x 10 to the minus 17th power W/sq cm micron square root of Hz. The main applications are for measuring continuum radiation levels and solid state emission and absorption features in regions of star and planet formation

SIRTF - The Shuttle Infrared Telescope Facility

The Shuttle Infrared Telescope (SIRTF) is a 1-m class cryogenically cooled telescope to be operated from the shuttle as a facility for infrared astronomy. By exploiting the very low infrared background of space, SIRTF will achieve 100 to 1000 times the sensitivity currently attainable at infrared wavelengths between 2 and 200 microns. The scientific requirements of SIRTF, the current design concept, and the scientific capabilities of the systems are reviewed. We also review recent experimental results showing that mirrors made of glassy materials may be suitable for use in large cryogenic telescopes such as SIRTF

Measurement of the nighttime infrared luminosity of Spacelab 1 in the H- and K-bands

Infrared measurements of the Spacelab 1, Space Transportation System 9, were made from the Maui Optical Station tracking facility using a sensitive photometer n two infrared bands, the H-band centered at a wavelength of 1.6 microns and the K-band centered at 2.3 micrometers. The objective was to measure radiation from the vicinity of the Shuttle arising from interaction of Shuttle surfaces with atmospheric particles. It was necessary to include the Shuttle itself in the field of view of the photometer. The integrated brightness of the entire Shuttle at a distance of 400 km was found to be equivalent to that of a star of magnitude +6.6 or 1.6 microns; it was much fainter in the visible. Most of the emission at 1.6 microns appears to be attributable to the Shuttle glow phenomenon. It is hundreds of times brighter than the zodiacal background. The radiation at 2.3 microns can be accounted for primarily by diffusely scattered thermal radiation from Earth's surface

Interstellar grain mantles

Interstellar molecular grain mantles are an important component of the interstellar dust inside dense molecular clouds as evidenced by the detection of absorption bands at 2.97, 3.08, 4.61, 6.0 and 6.8 microns. Mantles may also be the precursors of more complex grain mantles in the diffuse interstellar medium. The molecular composition of these icy grain mantles were calculated employing gas phase as well as grain surface reactions. The calculated mixtures consist mainly of the molecules H2O, H2CO, N2, CO, O2, H2O2, NH2, and their deuterated counterparts in varying ratios. The exact compositions depend strongly on the physical conditions in the gas phase. The absorption spectra of H2O with other molecules was studied in the laboratory. Optical constants were determined for a few selected mixtures. Extinction and polarization cross sections across the 3 micron ice band were calculated. A comparison with the observations towards BN shows that the low frequency wing observed on this feature is due to absorption by a mixture of H2O and other molecules rather than scattering by large, pure H2O ice grains

A multicomponent model of the infrared emission from Comet Halley

A model based on a mixture of coated silicates and amorphous carbon grains produces a good spectral match to the available Halley data and is consistent with the compositional and morphological information derived from interplanetary dust particle studies and Halley flyby data. The dark appearance of comets may be due to carbonaceous coatings on the dominant (by mass) silicates. The lack of a 10 micrometer feature may be due to the presence of large silicate grains. The optical properties of pure materials apparently are not representative of cometary materials. The determination of the optical properties of additional silicates and carbonaceous materials would clearly be of use

The 2.5-5.0 micron spectra of Io: Evidence for H2S and H2O frozen in SO2

The techniques of low temperature spectroscopy are applied to identify the constituents of the ices covering the surface of Io, a satellite of Jupiter. Infrared spectra of Io in the 4000-2000 cm exp -1 region, including new observational data, are analyzed using laboratory studies of plausible surface ices

Some 5-13 micrometer airborne observations of Comet Wilson 1986l: Preliminary results

Comet Wilson was observed from the Kuiper Airborne Observatory approximately 23.6 and 25.7 Apr. 1987, UT (approx. 3 to 5 days after perihelion) using the NASA-Ames Faint Object Grating Spectrometer. Spectrophotometric data were observed with a 21 inch aperture between 5 and 13 micrometer and with a spectral resolution of 50 to 100. Spectra of the inner coma and nucleus reveal a fairly smooth continuum with little evidence of silicate emission. The 5 to 8 micrometer color temperature of the comet was 300 + or - 15 K, approx. 15 percent higher than the equilibrium blackbody temperature. All three spectra of the nucleus show a new emission feature at approx. 12.25 micrometer approx. two channels (.22 micrometer) wide. Visual and photographic observations made during the time of these observations showed a broad faint, possible two component tail. No outburst activity was observed

Infrared spectra of WC10 planetary nebulae nuclei

The 5.2 to 8.0 micron spectra are presented for two planetary nebulae nuclei Hen1044 (He2-113) and CPD-56 8032. The unidentified infrared (UIR) emission bands at 6.2 microns, 6.9 microns, 7.7 microns are present in the spectra of Hen1044 and in CPD-56 8032, and the 8.6 micron band is present in the long wavelength shoulder of the 7.7 micron band in the spectrum of CPD-56 8032. The 8 to 13 micron spectra of these two stars by Aitken et. al. clearly show the presence of the 8.6 micron band in He2-113 while weakly resolving this feature in the spectra of CPD-56 8032. In their spectra the 11.3 micron band is also clearly detected in both objects. The 6.2 micron and 7.7 micron bands are characteristic of the infrared active C-C stretching modes in polycyclic aromatic hydrocarbons (PAHs); the 3.3 micron, 8.6 micron, and 11.3 micron bands are respectively assigned to the in-plane stretching mode, the in-plane bending mode, and the out-of-plane bending mode of the aromatic CH bond. The weak 6.9 micron emission feature is attributed to the UIR spectrum by Bregman et. al. The IRAS LRS spectra of He2-113 (IRAS 14562-5406) and CPD-56 8032 (IRAS 17047-5650) are presented. Cohen et. al. identify the broad plateau from 11.3 to 13.0 microns in the spectrum of He2-113 with increased hydrogenation of PAHs. This broad plateau is not seen in the LRS spectrum of CPD-56 8032. Also, He2-113 has greater infrared excess emission in the 17-22 micron region than does CPD-56 8032

First results on a new PIAA coronagraph testbed at NASA Ames

Direct imaging of extrasolar planets, and Earth-like planets in particular, is an exciting but difficult problem requiring a telescope imaging system with 1010 contrast at separations of 100 mas and less. Furthermore, the current NASA science budget may only allow for a small 1-2 m space telescope for this task, which puts strong demands on the performance of the imaging instrument. Fortunately, an efficient coronagraph called the Phase Induced Amplitude Apodization (PIAA) coronagraph has been maturing and may enable Earth-like planet imaging for such small telescopes. In this paper, we report on the latest results from a new testbed at NASA Ames focused on testing the PIAA coronagraph. This laboratory facility was built in 2008 and is designed to be flexible, operated in a highly stabilized air environment, and to complement existing efforts at NASA JPL. For our wavefront control we are focusing on using small Micro-Electro- Mechanical-System deformable mirrors (MEMS DMs), which promises to reduce the size of the beam and overall instrument, a consideration that becomes very important for small telescopes. At time of this writing, we are operating a refractive PIAA system and have achieved contrasts of about 1.2×10-7 in a dark zone from 2.0 to 4.8 λ/D (with 6.6×10-8 in selected regions). In this paper, we present these results, describe our methods, present an analysis of current limiting factors, and solutions to overcome them