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.

An extended-wavelength exoplanet spectral model based on MODTRAN ® 5

Abstract: We overview a recently developed planetary radiative transfer (RT) model, PLANETS (PLANETary Spectroscopy), which is based on the MODTRAN® 5 band model RT algorithms. The basic features and RT algorithms are described and an application of PLANETS to a variety of observed Neptune spectra, spanning a broad spectral region, ultraviolet through far infrared, is highlighted. We also apply PLANETS to analysis of the recently reported observation of the thermal infrared emission spectrum of the exoplanet HR 8799c. We attribute the observed spectral features to CH 4 transmission and emission lines, located to the blue and red of the 4.3 μm CO 2 band edge, respectively.

Aerosols and cirrus clouds over Hanoi, Vietnam: comparison between satellite products and results derived from ground-based lidar measurements

Abstract: In this paper, we present examples of aerosol and Cirrus cloud altitude profiles over Hanoi, Vietnam, measured with the ground LIDAR setup of the Institute of Physics. Comparisons are made to LIDAR data collected by the Calipso satellite of the NASA A-Train during its orbits over the Hanoi area. The height distributions for both surface aerosols and Cirrus clouds derived from ground and satellite observations are generally consistent, with distributions between 2km-3km, and 8km-15km respectively for aerosols and Cirrus clouds. Cirrus cloud locations inferred from an analysis of limb spectral radiances obtained by the SCIAMACHY satellite are also consistent with the LIDAR data.

Forward Modeling of Cloud Shadows And the Impact of Cloud Shadows On Remote Sensing Data Products

Abstract: This paper will discuss the use of the MODTRAN (MODerate spectral resolution TRANsmittance) code to simulate shadows on terrain created by broken cloud fields. Under partially cloudy conditions, there are two main cloud-induced effects: shadowing, which results in diminished and spectrally altered ground illumination, and illumination enhancement of sunlit areas due to the photons scattered from the clouds into these areas. The work presented here will focus on the effects of cloud shadows on the retrieval of reflectance signatures for target detection applications. The impact of cloud shadows is examined using forward simulations of fully and partly shadowed scenes based on the Rochester Institute of Technology Target Detection Self-Test reflectance scene. A blue roof spectral signature extracted from the scene was used as a target signature. The roof signature was randomly embedded back into the scene at subpixel levels. The scene radiance is then modeled for a low altitude sensor flying below uniform and broken cloud fields, as well as under clear sky conditions. Target detection is performed on these radiance scenes after atmospheric correction. Preliminary detection results show significant performance loss when scenes include a combination of cloud shadows and sunlit areas.

Supermassive black holes with high accretion rates in active galactic nuclei. XI. Accretion disk reverberation mapping of Mrk 142

Abstract: We performed an intensive accretion disk reverberation mapping campaign on the high accretion rate active galactic nucleus Mrk 142 in early 2019. Mrk 142 was monitored with the Neil Gehrels Swift Observatory for 4 months in X-rays and 6 UV/optical filters. Ground-based photometric monitoring was obtained from the Las Cumbres Observatory, Liverpool Telescope and Dan Zowada Memorial Observatory in ugriz filters and the Yunnan Astronomical Observatory in V. Mrk 142 was highly variable throughout, displaying correlated variability across all wavelengths. We measure significant time lags between the different wavelength light curves, finding that through the UV and optical the wavelength-dependent lags, $\tau(\lambda)$, generally follow the relation $\tau(\lambda) \propto \lambda^{4/3}$, as expected for the $T\propto R^{-3/4}$ profile of a steady-state optically-thick, geometrically-thin accretion disk, though can also be fit by $\tau(\lambda) \propto \lambda^{2}$, as expected for a slim disk. The exceptions are the u and U band, where an excess lag is observed, as has been observed in other AGN and attributed to continuum emission arising in the broad-line region. Furthermore, we perform a flux-flux analysis to separate the constant and variable components of the spectral energy distribution, finding that the flux-dependence of the variable component is consistent with the $f_ u\propto u^{1/3}$ spectrum expected for a geometrically-thin accretion disk. Moreover, the X-ray to UV lag is significantly offset from an extrapolation of the UV/optical trend, with the X-rays showing a poorer correlation with the UV than the UV does with the optical. The magnitude of the UV/optical lags is consistent with a highly super-Eddington accretion rate.

Passive synchronization of complex spatio-temporal switching networks with coupling delays

Abstract: This paper formulates a new model of complex spatio-temporal switching network with coupling delays. Not only the dynamics of each node and the topology of the network is switched between different mode at different time intervals. A set of sufficient conditions for synchronization of the spatiotemporal switching network with coupling delays are presented in the state to be passive. Finally, an illustrative example is included.