Spectral Sciences Incorporated

About: Spectral Sciences Incorporated is a company organization based out in Burlington, Massachusetts, United States. It is known for research contribution in the topics: Hyperspectral imaging & Radiance. The organization has 114 authors who have published 342 publications receiving 10875 citations.

SMALL CARBONACEOUS MOLECULES, ETHYLENE OXIDE (c-C2H4O) AND CYCLOPROPENYLIDENE (c-C3H2): SOURCES OF THE UNIDENTIFIED INFRARED BANDS?

Abstract: We suggest that small carbonaceous molecules (SCMs) may be the sources of the unidentified infrared bands (UIRs) and the underlying continuum. We show that the IR spectroscopy of ethylene oxide (EO, c-C2H4O) and cyclopropenylidene (CP, c-C3H2) closely correlates with the major UIR bands at 3.3, 6.2, 7.7, 8.6, and 11.2 μm, the often seen strong bands at 12.7 and 16.4 μm, as well as many minor features. The differences in band locations and shapes between laboratory EO absorption spectra and astrophysical UIR emission spectra are attributed to vibrational anharmonicity, Fermi resonance splitting of nearly degenerate vibration levels, and rotational envelope narrowing due to the low temperatures in space. The excitation mechanism is absorption of UV radiation, primarily Lyα, by SCMs. Photon trapping for this very optically thick transition enhances the absorption by several orders of magnitude. Our abundance analysis for NGC 7027 reveals that the SCM abundance, relative to H2, is ~3 × 10–9 which compares well to radio measurements of the CP abundance range of ~10–9-10–7. The origin of the UIR continuum is discussed in terms of emission from vibrationally and rotationally hot SCM UV photodissociation products and UV excitation of rotationally hot SCM species. Radio lines of CP have been seen in numerous astronomical objects, most displaying the UIR bands. EO is also seen, but in fewer objects, none displaying the UIR bands. We theorize that in UIR objects, EO is formed on, and primarily resides on, carbonaceous grains, precluding radio detection of rotational lines. We suggest laboratory experiments, astronomical observations, and theoretical investigations to further evaluate the SCM mechanism for the UIR bands and continuum.

Single-Shot Spectral Imager

Abstract: A single-shot spectral imager or imaging system which acquires multiplexed spatial and spectral data in a single snapshot with high optical collection efficiency and with the speed limited only by the readout time of the detector circuitry. The imager uses dispersive optics together with spatial light modulators to encode a mathematical transform onto the acquired spatial-spectral data. A multitude of encoded images is recorded simultaneously on a focal plane array and subsequently decoded to produce a spectral/spatial hypercube.

DMD-based adaptive spectral imagers for hyperspectral imagery and direct detection of spectral signatures

Abstract: Dispersive transform spectral imagers with both one- and two-dimensional spatial coverage have been demonstrated and characterized for applications in remote sensing, target classification and process monitoring. Programmable spatial light modulators make it possible to adjust spectral, temporal and spatial resolution in real time, as well as implement detection algorithms directly in the digitally controlled sensor hardware. Operating parameters can be optimized in real time, in order to capture changing background and target evolution. Preliminary results are presented for short wave, mid-wave, and long-wave infrared sensors that demonstrate the spatial and spectral versatility and rapid adaptability of this new sensor technology.

Kinetic and spectroscopic requirements for the inference of chemical heating rates and atomic hydrogen densities from OH Meinel band measurements

Abstract: We present the accuracy requirements for specific kinetic and spectroscopic parameters used in modeling populations of vibrationally excited hydroxyl. The requirements are based on simulations of the inference of chemical energy deposition rates and atomic hydrogen densities from satellite observations of the hydroxyl Meinel band emission rates. Improvement in the rate constants which describe the collisional removal of the high-lying υ states of OH and the reaction of highlying υ states with atomic oxygen is required in addition to improved specification of the nascent distribution of energy within OH upon reaction of atomic hydrogen and ozone. These improvements are necessary for the interpretation of Meinel band measurements to be made from a new spaceflight experiment in less than 3 years.

AGN STORM 2. I. First results: A Change in the Weather of Mrk 817

Abstract: We present the first results from the ongoing, intensive, multi-wavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this AGN was, in part, selected for its historically unobscured nature, we discovered that the X-ray spectrum is highly absorbed, and there are new blueshifted, broad and narrow UV absorption lines, which suggest that a dust-free, ionized obscurer located at the inner broad line region partially covers the central source. Despite the obscuration, we measure UV and optical continuum reverberation lags consistent with a centrally illuminated Shakura-Sunyaev thin accretion disk, and measure reverberation lags associated with the optical broad line region, as expected. However, in the first 55 days of the campaign, when the obscuration was becoming most extreme, we observe a de-coupling of the UV continuum and the UV broad emission line variability. The correlation recovers in the next 42 days of the campaign, as Mrk 817 enters a less obscured state. The short CIV and Ly alpha lags suggest that the accretion disk extends beyond the UV broad line region.