Abstract: In this study, an uplink light-emitting diode (LED) beacon that can enable a CubeSat to locate a laser communication ground station was designed, constructed, and tested, and detection of the beacon from low Earth orbit (LEO) with a CMOS camera on the AeroCube-5 CubeSat was demonstrated. The LED beacon described is an alternative to the near-infrared laser beacons commonly used in laser communication systems, and has the potential to be cheaper, easier to point, and to require less regulatory coordination than a laser beacon, while performing the same function. An optical design is detailed, consisting of an array of 80 green LEDs with a center wavelength of 528 nm, producing 15.9 watts of free-space optical power, focused to a beamwidth of 8.12 degrees full-widthhalf-max (FWHM). A link budget is presented that shows the beacon is detectable by a CubeSat-mounted camera with a 7.9 mm diameter aperture and a silicon CMOS detector. A prototype beacon comprised of an LED array, focusing optics, thermal control, and tracking mechanisms was designed and constructed, and laboratory measurements of the beam profile and optical power of the prototype beacon using an optical power meter are presented herein. A field test is also described, in which the beacon was deployed at Wallace Astrophysical Observatory in the early morning of May 15, 2017 and imaged with a camera on AeroCube-5. The array is successfully identified in a sequence of five images taken by the CubeSat, demonstrating the viability of LED uplink beacons with CubeSat imagers.

Abstract: Artificial lighting at night (ALAN) produced by urban, industrial, and roadway lighting, as well as other sources, has dramatically increased in recent decades, especially in coastal environments that support dense human populations. Artificial “lightscapes” are characterized by distinct spatial, temporal, and spectral patterns that can alter natural patterns of light and dark with consequences across levels of biological organization. At the individual level, ALAN can elicit a suite of physiological and behavioral responses associated with light-mediated processes such as diel activity patterns and predator-prey interactions. ALAN has also been shown to modify community composition and trophic structure, with implications for ecosystem-level processes including primary productivity, nutrient cycling, and the energetic linkages between aquatic and terrestrial systems. Here, we review the state of the science relative to the impacts of ALAN on estuaries, which is an important step in assessing the long-term sustainability of coastal regions. We first consider how multiple properties of ALAN (e.g., intensity and spectral content) influence the interaction between physiology and behavior of individual estuarine biota (drawing from studies on invertebrates, fishes, and birds). Second, we link individual- to community- and ecosystem-level responses, with a focus on the impacts of ALAN on food webs and implications for estuarine ecosystem functions. Coastal aquatic communities and ecosystems have been identified as a key priority for ALAN research, and a cohesive research framework will be critical for understanding and mitigating ecological consequences.

Abstract: The Galician Atlantic Islands Maritime-Terrestrial National Park (PNMTIAG), with the exception of the island of Cortegada, still has night skies of acceptable quality. However, the PNMTIAG islands are under strong photic pressures, both internal and external, that hinder the preservation of the basic features of the natural night, and call for an immediate action of all concerned stakeholders