Measurements of Absolute, SI Traceable Lunar Irradiance with the Airborne LUnar Spectral Irradiance (air LUSI) Instrument

The Moon is a very useful calibration target for Earth-observing sensors in orbit because its surface is radiometrically stable and it has a radiant flux comparable to Earth scenes. To predict the lunar irradiance given an illumination and viewing geometry, the United States Geological Survey (USGS) has developed the Robotic Lunar Observatory (ROLO) Model of exo-atmospheric lunar spectral irradiance. The USGS ROLO model represents the current most precise knowledge of lunar spectral irradiance and is used frequently as a relative calibration standard by space-borne Earth-observing sensors. However, its accuracy as an absolute reference may be limited to several percent and it is not SI-traceable. Advancing the model to be a more accurate absolute lunar reference requires new measurements. The objective of the airborne LUnar Spectral Irradiance (Air-LUSI) mission is to make highly accurate, SI-traceable measurements of lunar spectral irradiance in the VNIR spectral region from NASA’s high-altitude ER-2 aircraft, above 95% of the atmosphere. To that end, the Air-LUSI system uses a non-imaging telescope system that robotically tracks the Moon in flight, fiber-optic coupled to a stable spectrometer housed in an enclosure providing a robustly controlled environment. The spectrometer measures about 350 to 1050 nm at 3.8 nm resolution, with 0.8 nm sampling. The instrument is reproducibly stable to 0.3% and rigorously calibrated before and after campaigns and flights using a similar transfer standard spectrograph. An on-board LED source is used to monitor the instrument response during flight ascent and descent. Air-LUSI successfully conducted a Demonstration Flight Campaign on five consecutive nights from 12 to 17 November 2019, corresponding to lunar phase angles of about 10°, 21°, 34°, 46° and 59°. Each night, the Air-LUSI system observed the Moon from above 68,000 feet altitude for 30 to 40 minutes. To reach a target uncertainty for lunar irradiance of 0.5% (k=1), processing the raw data to exo-atmospheric lunar spectral irradiance required accounting for various known behaviors of the instrument, such as thermal and stray light corrections. Additional measures were taken to address variances idiosyncratic to the campaign and were factored into the measurement error budget. The resulting error budget currently stands at less than 1% over most of the VNIR range. This paper reviews the steps taken towards high accuracy results for Demonstration Flight Campaign, how they factored in the error budget, and how our uncertainty target can be met in future campaigns

Wavelength Dependent UV Inactivation and DNA Damage of Adenovirus as Measured by Cell Culture Infectivity and Long Range Quantitative PCR

Adenovirus is regarded as the most resistant pathogen to ultraviolet (UV) disinfection due to its demonstrated resistance to monochromatic, low-pressure (LP) UV irradiation at 254 nm. This resistance has resulted in high UV dose requirements for all viruses in regulations set by the United States Environmental Protection Agency. Polychromatic, medium-pressure (MP) UV irradiation has been shown to be much more effective than 254 nm, although the mechanisms of polychromatic UV inactivation are not completely understood. This research analyzes the wavelength-specific effects of UV light on adenovirus type 2 by analyzing in parallel the reduction in viral infectivity and damage to the viral genome. A tunable laser from the National Institute of Standards and Technology was used to isolate single UV wavelengths. Cell culture infectivity and PCR were employed to quantify the adenoviral inactivation rates using narrow bands of irradiation (<1 nm) at 10 nm intervals between 210 and 290 nm. The inactivation rate corresponding to adenoviral genome damage matched the inactivation rate of adenovirus infectivity at 253.7 nm, 270 nm, 280 nm, and 290 nm, suggesting that damage to the viral DNA was primarily responsible for loss of infectivity at those wavelengths. At 260 nm, more damage to the nucleic acid was observed than reduction in viral infectivity. At 240 nm and below, the reduction of viral infectivity was significantly greater than the reduction of DNA amplification, suggesting that UV damage to a viral component other than DNA contributed to the loss of infectivity at those wavelengths. Inactivation rates were used to develop a detailed spectral sensitivity or action spectrum of adenovirus 2. This research has significant implications for the water treatment industry with regard to polychromatic inactivation of viruses and the development of novel wavelength-specific UV disinfection technologies

War Narratives: Framing Our Understanding of the War on Terror

Unlike past American wars, the current war on terror has not been associated with a centrally proffered narrative providing some guidance and orientation for those administering government services under state-of-war conditions. War is as much a cultural endeavor as it is a military undertaking, and the absence of a clear sensemaking narrative was detected in this study of public administrators from three agencies with varying proximity to the conflict. Q-methodology was used to explore the way individuals processed the war narratives put forth by the Bush administration and reported in the media immediately following the September 11 attacks. Though no distinct state-of-war narratives were found among the public administrators in this study, there are clear indications that latent narratives reflecting local political and organizational task environments have emerged