Twilight tropospheric and stratospheric photodissociation rates derived from balloon borne radiation measurements

Abstract

Abstract.A new ligthweight multichannel moderate bandwidth filter instrument designed to be flown on balloons, is described. The instrument measures the radiation field within the short UV (center wavelength at 312 nm) and long UV (center wavelength at 340 nm). The angular and spectral characteristics of the instrument are discussed and the calibration procedure outlined. Measurements made during a stratospheric balloon flight at twilight conditions from GapTallard, France, are presented and compared with state-ofthe-art radiative transfer model simulations. The model simulations and the measurements agree within ±10% (±20%) for solar zenith angles smaller than 93 • (90 • ) for the 340 (312) nm channel. Based on the model simulations of the measured radiation, actinic flux spectra are reconstructed. These are used to calculate various photodissociation rates.

Stratosphere Conditions Inactivate Bacterial Endospores from a Mars Spacecraft Assembly Facility

“…In comparison, the stratosphere UV model developed for this study generated similar levels for UVC and UVB at 20–50 km ASL: 0.00550–5.20 and 4.16–17.1 W/m 2 , respectively. Our model was consistent within the range of measured values by Kylling et al (2003), who flew a UV radiometer to 30.5 km ASL in the stratosphere over France (∼44.5°N), recording measurements at 312 and 340 nm across a solar zenith range of 76–94° in flight.…”

“…The next-generation E-MIST payload system will also aim to incorporate a dosimeter for measuring ionizing radiation levels in the stratosphere. Until a reflight opportunity for the E-MIST payload, independent radiation measurements from the stratosphere can be used for evaluating the fidelity of the UV model developed herein ( e.g., Kylling et al, 2003; Mertens et al, 2016). Our forecast suggested that stratosphere UVB/UVC levels (averaged between 20 and 50 km ASL) would be similar to martian conditions calculated by Schuerger et al .…”

“…Relative humidity levels can drop below 1%, and temperatures in the lower stratosphere regularly reach −100°C. Stratospheric radiation is substantially higher (Kylling et al, 2003; Adams et al, 2007; Dachev, 2013) than doses at other frequently visited Mars analog environments, including the McMurdo Dry Valleys of Antarctica (Wynn-Williams and Edwards, 2000) and the Atacama Desert (McKay et al, 2003). Laboratory environmental chamber experiments have been employed in the past to simulate martian conditions (Schuerger et al, 2003; Diaz and Schulze-Makuch, 2006; Tauscher et al, 2006; de la Vega et al, 2007; Moores et al, 2007; Osman et al, 2008; Fendrihan et al, 2009; Smith et al, 2009; Gómez et al, 2010; Peeters et al, 2010; Johnson et al, 2011; Kerney and Schuerger, 2011), but artificial illumination sources do not realistically represent the dynamic nature of sunlight.…”

An overview of the HIBISCUS campaign

“…The new NILUCUBE has had improved input optics which deviates less than 5% from the ideal cosine response for zenith angles smaller than 85 • . By combining the measurements from all heads, the actinic flux may be derived as shown by Kylling et al (2003).…”

“…A new version of the NILUCUBE instrument of the Norwegian Institute for Air Research (NILU) described by Kylling et al (2003) was developed for HIBISCUS. The new sensor has six channels in each of its six heads.…”