It is well known that luminance from photo-chemical reactions of hydroxyl ions in the upper atmosphere (~85 km
altitude) produces a significant amount of night time radiation in the short wave infra-red (SWIR) band with
wavelength between 0.9 and 1.7 μm. By examining images in an urban and a rural setting, we investigate the
correlation between the appearances of passive dark of night images in the SWIR with NIR- visible. The
experimental setup consists of two sensors, a NIR-visible CCD and an InGaAs array sensitive in the SWIR, both colocated
on an AZ-EL mount, and both co-boresighted so that different viewing angles of the sky and terrestrial
scenes are possible. By making corrections for focal length and pixel size, the visible and SWIR data can be
compared. After taking several nights of data in the urban environment of Albuquerque, NM, the entire system was
then re-located to a rural location on the island of Kauai in a rural setting with very low ambient light. It is shown
that under most conditions the SWIR sensor produces significantly better imagery using the airglow illumination
source.
It is well known that luminance from photo-chemical reactions of hydroxyl ions in the upper atmosphere (~85 km
altitude) produces a significant amount of night time radiation in the short wave infra-red (SWIR) band between
0.9 and 1.7 μm wave length. This has been demonstrated as an effective illumination source for night time imaging
applications. It addition it has been shown that observation of the spatial and temporal variations of the
illumination can be used to characterize atmospheric tidal wave actions in the sky glow region. These spatiotemporal
variations manifest themselves as traveling wave patterns whose period and velocity are related to the
wind velocity at 85 km as well as the turbulence induced by atmospheric vertical instabilities. Ground to space
observation systems especially those employing adaptive optics are adversely affected by high altitude turbulence
and winds. In this paper we propose the use of sky glow observations to predict and characterize image system
degradation due to upper atmosphere turbulence.
It is well known that luminance from photo-chemical reactions of hydroxyl ions in the upper atmosphere (~85 km
altitude) produces a significant amount of night time radiation in the short wave infra-red (SWIR) band of wave
length 0.9 to 1.7 μm. Numerous studies of these phenomena have demonstrated that the irradiance shows significant
temporal and spatial variations in the night sky. Changes in weather patterns, seasons, sun angle, moonlight, etc
have the propensity to alter the SWIR air glow irradiance pattern. By performing multiple SWIR measurements a
mosaic representation of the celestial hemisphere was constructed and used to investigate these variations over time
and space. The experimental setup consisted of two sensors, an InGaAs SWIR detector and a visible astronomical
camera, co-located and bore sighted on an AZ-EL gimbal. This gimbal was programmed to view most of the sky
using forty five discrete azimuth and elevation locations. The dwell time at each location was 30 seconds with a
total cycle time of less than 30 minutes. The visible astronomical camera collected image data simultaneous with
the SWIR camera in order to distinguish SWIR patterns from clouds. Data was reduced through batch processing
producing polar representations of the sky irradiance as a function of azimuth, elevation, and time. These spatiotemporal
variations in the irradiance, both short and long term, can be used to validate and calibrate physical models
of atmospheric chemistry and turbulence. In this paper we describe our experimental setup and present some results
of our measurements made over several months in a rural marine environment on the Islands of Kauai and Maui
Hawaii.
Between the wavelengths of the visible and the Short Wave Infrared (SWIR), the glow of the sky from chemical
radiance and absorption changes dramatically. Thus too, the structure and appearance of clouds change. By directly
and simultaneously examining clouds in an urban and a rural setting, we investigate the correlation between the
appearance of clouds present in the SWIR, NIR, and visible. The experimental setup consists of two sensors, one a
NIR to SWIR sensitive InGaAs array, and the other a visible CCD, both co-located on an AZ-EL mount, and both
co-boresighted so that different viewing angles of the sky are possible. The SWIR sensor is sensitive from 0.9 μm to
1.7 μm. The CCD sensor collects cloud images in the visible region. By making corrections for focal length and
pixel size, the visible and SWIR data can be compared. After taking several nights of data in the urban environment
of Albuquerque, NM, the entire system was then re-located to a rural location in southern New Mexico.
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