Introduction: Before lunar samples were returned to Earth, it was shown that linear polarization curves and albedo measurements of the moon and asteroids could be used to predict the regolith surface texture of these bodies [1]. The prediction that lunar mare regolith is texturally similar to finely pulverized lava basalts was confirmed by returned lunar samples [2].Our ultimate objective is to use Cassini Imaging Science Subsystem (ISS) Narrow Angle Camera (NAC) images of icy Saturnian satellites -acquired through broadband color and polarization filters -to measure the linear polarizations and corresponding albedos of icy terrains and to characterize implied surface textural properties. In this preliminary study, we demonstrate the sensitivity of ISS NAC polarization images for the analysis of icy satellite surfaces by testing if these images can detect Umov's law, a wellknown inverse relationship between the linear-polarization and albedo of regolith-covered surfaces [3]. Iapetus is our test satellite because its terrain provides a broad range of albedos over which we expect linear polarization to systematically vary. In particular, we will use Cassini Regio's stark contrast with Iapetus' remaining brighter surface to demonstrate Umov's law. Our hypothesis is that the linear polarization of all materials on Iapetus will vary inversely and monotonically with their corresponding albedo.Method: Each ISS NAC polarization observation is a three-image sequence obtained for 0, 60, and 90 degree orientations of the electric field vector, respectively. The polarization filters are used in combination with broadband color filters from a tandem filter wheel, so that changes in polarization with wavelength can be studied. Each image sequence is obtained at approximately constant phase angle. First, the images are radio-metrically calibrated so that pixel DN value represents radiance factors. Camera pointing information is updated using control points and limb locations on the satellite's surfaces. The separate images are spatially co-registered and combined using an algorithm that produces a linear polarization image and a corresponding total intensity (i.e. non-polarized) image [4].To produce albedo images, the total intensity image must be corrected for the gradient in shading
Hovering and swarming activity of male Tabanus calens L. were documented at distinctive sites above a woodland road clearing in Knox Co., TN (7 d), and above a slow-flowing river in Morris Co., NJ (6 d). Activity was restricted to the period near sunset. Mean activity typically began about 10 min before sunset and continued until about 10 min after sunset, with an average duration of 18.7 min (Tennessee) and 20.8 min (New Jersey). Swarming began earlier and thus lasted longer (55 min) on one cool New Jersey date. Onset and particularly cessation of activity tended to be statistically correlated with sunset time. Most males hovered at heights of 5-8 m in Tennessee, and they hovered in stable locations for a median of only 10 s (maximum 2 min 57 s) before darting away. Hovering in New Jersey was observed from 0.5-8.0 m above the water. The behavior of T. calens might be especially interesting to study in more detail, given its unusual eye morphology (lack of obvious dorsoventral facet size differences found in males of most other Tabanidae).
A canopy trap and aerial nets led to finding 8 species of Tabanidae. There was an abundance of calyptrate muscoid flies. Camel’s Hump is in the Green Mountains of western New England, USA. Discovering Diptera on Camel’s Hump involved sixteen visits over 40 years. Upwards of 23 other Diptera species are listed. Habitats on the east side and above 762 m (2500 ft) elevation on Camel’s Hump differ from the west slope but the boreal forest on both sides is influenced by cloud and fog precipitation on trees. The cliffs just above the 900 m level along the east side are often overlooked, are not seen from the summit and provide access to morning sun for insects. Recent visits explored the role of polarized skylight in relation to the canopy trap, the boreal forest environment and flies found there.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.