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- ItemDesign and performance of a three-wavelength LED-based total scatter and backscatter integrating nephelometer(München : European Geopyhsical Union, 2011) Müller, T.; Laborde, M.; Kassell, G.; Wiedensohler, A.Integrating nephelometers are instruments that directly measure a value close to the light scattering coefficient of airborne particles. Different models of nephelometers have been used for decades for monitoring and research applications. Now, a series of nephelometers (Ecotech models M9003, Aurora 1000 and Aurora 3000) with newly designed light sources based on light emitting diodes are available. This article reports on the design of these integrating nephelometers and a comparison of the Aurora 3000 to another commercial instrument (TSI model 3563) that uses an incandescent lamp. Both instruments are three-wavelength, total and backscatter integrating nephelometers. We present a characterization of the new light source design of the Aurora 3000 and provide parameterizations for its angular sensitivity functions. These parameterizations facilitate to correct for measurement artefacts using Mie-theory. Furthermore, correction factors are provided as a function of the Ångström exponent. Comparison measurements against the TSI 3563 with laboratory generated white particles and ambient air are also shown and discussed. Both instruments agree well within the calibration uncertainties and detection limit for total scattering with differences less than 5 %. Differences for backscattering are higher by up to 11 %. Highest differences were found for the longest wavelengths, where the signal to noise ratio is lowest. Differences at the blue and green wavelengths are less than 4 % and 3 %, respectively, for both total and backscattering.
- ItemObservations of NO in the upper mesosphere and lower thermosphere during ECOMA 2010(München : European Geopyhsical Union, 2012) Hedin, J.; Rapp, M.; Khaplanov, M.; Stegman, J.; Witt, G.In December 2010 the last campaign of the German-Norwegian sounding rocket project ECOMA (Existence and Charge state Of Meteoric smoke particles in the middle Atmosphere) was conducted from Andøya Rocket Range in northern Norway (69° N, 16° E) in connection with the Geminid meteor shower. The main instrument on board the rocket payloads was the ECOMA detector for studying meteoric smoke particles (MSPs) by active photoionization and subsequent detection of the produced charges (particles and photoelectrons). In addition to photoionizing MSPs, the energy of the emitted photons from the ECOMA flash-lamp is high enough to also photoionize nitric oxide (NO). Thus, around the peak of the NO layer, at and above the main MSP layer, photoelectrons produced by the photoionization of NO are expected to contribute to, or even dominate above the main MSP-layer, the total measured photoelectron current. Among the other instruments on board was a set of two photometers to study the O2 (b1Σg+−X3Σg) Atmospheric band and NO2 continuum nightglow emissions. In the absence of auroral emissions, these two nightglow features can be used together to infer NO number densities. This will provide a way to quantify the contribution of NO photoelectrons to the photoelectron current measured by the ECOMA instrument and, above the MSP layer, a simultaneous measurement of NO with two different and independent techniques. This work is still on-going due to the uncertainties, especially in the effort to quantitatively infer NO densities from the ECOMA photoelectron current, and the lack of simultaneous measurements of temperature and density for the photometric study. In this paper we describe these two techniques to infer NO densities and discuss the uncertainties. The peak NO number density inferred from the two photometers on ascent was 3.9 × 108 cm−3 at an altitude of about 99 km, while the concentration inferred from the ECOMA photoelectron measurement at this altitude was a factor of 5 smaller.