E. Arijs

Stratospheric positive ion composition measurements, ion abundances and related trace gas detection

Abstract Positive ion spectra obtained from measurements with a balloon-borne mass spectrometer during three balloon flights are critically investigated and compared with other data. Ion abundances for proton hydrates [H+(H2O)n ions] at different stratospheric temperatures are compared, as well as the abundances of non proton hydrates H+Xitl(H2O)m, X being most likely CH3CN. The detection of trace gases from ion composition measurements is discussed and an upper limit for the number densities of minor constituents such as NH3 and CH3OH is estimated at 35 km. Although sodium compounds cannot be responsible for the major positive ions, a closer investigation of high resolution daytime spectra suggests a small contribution of sodium in daytime ion chemistry.

Negative ion composition and sulfuric acid vapour in the upper stratosphere

Abstract The nature of negative ions in the altitude region 42–45 km has been investigated by means of a balloon borne mass spectrometer. Apart from the NO3− and HSO4− clusters, ions with different cores, which can be identified as CO3−, HCO3−, Cl− and ClO3− were observed. The spectra have been used to estimate the sulfuric acid number density at 45.2 and 42.3 km altitude.

Stratospheric ion chemistry: Present understanding and outstanding problems

Our present knowledge on stratospheric ion chemistry is reviewed. Available experimental data as well as modelling efforts are discussed and the needs for further research are pointed out.

Osiris - The optical, spectroscopic and infrared remote imaging system for the Rosetta orbiter

The scientific objectives, design, and implementation of the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) for the International Rosetta Mission are described. The instrument comprises two camera systems with a common electronics box. A narrow angle camera will provide high resolution images of the structure and morphology of the nucleus of a comet. A wide angle camera with high straylight rejection and dynamic range will be used to investigate the innermost coma and the emission process at the surface of the comet. An infrared imaging system, which dramatically enhances the scientific return has been included in the narrow angle camera at little extra cost.

Stratospheric positive ion composition measurements and acetonitrile detection: a consistent picture?

Abstract An overview is given of the positive ion composition measurements performed with balloon-borne ion mass spectrometers in the Earths atmosphere between 20 and 45 km. In particular, attention is paid to the derivation of the acetonitrile volume mixing ratio profile. The results are compared with model calculations, data obtained with airplane-borne instruments, and ground-level samplings. The consistency of the present picture is verified. The comparison with results of recent laboratory experiments show that electric field-induced collisional dissociation occurs in balloon-borne ion mass spectrometers. Probably, this is one of the major causes for the observed discrepancies between the data of airplane- and balloon-borne instruments.

Gas phase reactions of CF3O− and CF3O−H2O with nitric, formic, and acetic acid

Abstract The reactions of CF 3 O − , CF 3 O − H 2 O and CF 3 O − HF with HNO 3 , HCOOH, and CH 3 COOH have been studied at room temperature in a flowing afterglow instrument. Apart from the reaction of CF 3 O − HF with CH 3 COOH, all reactions proceed at the collision rate. Bare CF 3 O − ions react with the three acids mainly by fluoride transfer. An unambiguous identification of the reaction mechanisms of CF 3 O − H 2 O and CF 3 O − HF with the three neutral reactants is difficult to assess. The possibility to perform in situ measurements of HNO 3 , HCOOH, and CH 3 COOH concentrations in the atmosphere by chemical ionization mass spectrometry (CIMS), using a CF 3 O − ion source will be discussed.

Liquid helium cryopump and reliable opening device for a balloon‐borne mass spectrometer

The design, technical characteristics, and test and flight results of a liquid helium cryopump and an opening device operating on board a balloon-borne mass spectrometer combining a cryopump and a quadrupole mass filter are reported. The gas inlet of this mass spectrometer is opened through a simple and reliable remote-controlled system, which is also described.

Stratospheric chemical ionization mass spectrometry: nitric acid detection by different ion molecule reaction schemes

Abstract Detailed height profiles of stratospheric nitric acid mixing ratios have been derived with a baloon borne chemical ionization mass spectrometer by applying several ion molecule reaction schemes, each associated to a specific and selective ion source. These ions (CO 3 − , Cl n − , CF 3 O − , and CF 3 O − H 2 O) give rise to specific product ions (mainly CO 3 − HNO 3 , NO 3 − HCl, NO 3 − HF, and CF 3 O − HNO 3 ) upon reaction with ambient nitric acid molecules. This paper reports on the instrumental details as well as on the results obtained during two balloon flights with the instrument. Within the accuracy of the measurements, the nitric acid height profiles obtained with the three different ion sources are in good agreement with one another as well as with literature data.

Reactions of nitric acid with di- and trichloride ions, di- and tri-iodide ions and with CO−4 in the gas phase

Abstract The ion/molecule reactions of HNO 3 with Cl − n and I n − ( n = 2,3) have been studied at room temperature by means of a flow tube coupled to a quadrupole mass spectrometer. The reaction rates for Cl − n + HNO 3 for n = 2 and 3 have been determined relative to the known reaction rate for n = 1. Nitric acid reacts with Cl − 3 , resulting mainly in the product ion NO − 3 · HCl. The product ion(s) of the slower two body reactions of Cl − 2 could not be determined unambiguously, but from thermodynamical considerations NO − 3 · HCl seems to be the most probable candidate. For the study of I − n + HNO 3 , the known reaction CO − 3 + HNO 3 was used as a reference. No reaction has been observed for HNO 3 with I − n ions ( n = 2,3). Additionally, rate constants have been determined for the reactions of nitric acid with CO − 4 , (NO 3 OH) − , (NO 3 HO 2 ) − and NO − 3 · HCl.

Tomography of the Earth's atmosphere by the spaceborne occultation radiometer ORA: Spatial inversion algorithm

The occultation radiometer ORA was designed to perform measurements of O 3 , NO 2 , H 2 O, number density, and aerosol extinction altitude profiles in the Earths atmosphere through the occultation method viewing the full solar disk. The experiment was mounted on the EURECA satellite and measured the relative transmission of light during about 7000 orbital sunsets and sunrises from August 11, 1992, to May 13, 1993. The spatial inversion algorithm developed to retrieve the total extinction altitude profiles from these data is described here. It is shown that the signal measured by an instrument having a large field of view can be successfully processed to give a much better altitude resolution than the one related to the angular size of the Sun. The main difficulties concern the inclusion of all refractive effects, the application of a new inversion scheme and its associated mapping strategy to refine the aerosol layer detection. The algorithm applies to fully nonlinear occultation experiments requiring global and nonheuristic inversion schemes.