SAFIREA MEASUREMENTS DURING THE APEGAIA CAMPAIGN

SAFIRE−A MEASUREMENTS DURING THE APE−GAIA CAMPAIGN

Giovanni Bianchini(1), Bruno Carli(1), Ugo Cortesi, Alessandro Gignoli(1), Luca Palchetti(1), Enzo Pascale(1), Bianca Maria Dinelli(2), Peter Ade(3), Peter Hamilton(3), Clare Lee(3).

(1)Istituto di Ricerca sulle Onde Elettromagnetiche "Nello Carrara" (CNR−IROE)

Via Panciatichi 64, 50127 Firenze, Italy

gb@r.it

(2)Istituto di Spettroscopia Molecolare (CNR−ISM)

Bologna, Italy

(3)Queen Mary and Westfield College

London, UK

INTRODUCTION

In this paper results of measurements obtained by the SAFIRE−A instrument(Spectroscopy of the Atmosphere using Far InfraRed Emission−Airborne)during the APE−GAIA(Airborne Polar Experiment Geophysica Aircraft In Antarctica, Ushuaia, Argentina, 15th September 15th October 1999) campaign are presented.

SAFIRE−A is a far infrared Fourier transform(FT)spectrometer operating onboard the M55Geophysica stratospheric aircraft.In the five scientific flights which the aircraft performed over the Antarctic Peninsula,during the APE−GAIA campaign,the instrument provided limb sounding observations of atmospheric emission spectra over two frequency intervals:[22−23.5cm−1],and[123−125cm−1]where spectral features respectively of O3,ClO,N2O, HNO3 and HCl, H2O are displayed.

Volume mixing ratio(VMR)vertical profiles of the observed species are retrieved from spectra obtained with the limb−scanning technique.Concentration of observed species along the flight track has been studied as a function of altitude and latitude aiming at the investigation of the chemistry and dynamics across the boundary of the southern polar vortex.

The results also provide an assessment of instrument performances in view of its use in the planned M55−Geophsyica activities for ENVISAT validation.In the next section,we will briefly describe experimental apparatus and review instrumental performances as derived from the analysis of APE−GAIA data.In the last section we will present some examples of the results obtained during the campaign concerning VMR vertical distribution and geographic variability of two of the measured molecular species, ozone and ClO.

THE SAFIRE−A INSTRUMENT: NEW PERFORMANCES ASSESSMENT

SAFIRE−A is a particular implementation of the Martin−Puplett[1]polarising FT spectrometer specially designed for airborne operation[2].Optical path folding and a misalignment−compensating[3]optical scheme have permitted to enclose the whole instrument,including optics,control and data storage electronics and cryogenic detectors in a compact package suitable for integration on the M55platform.The principal instrumental characteristics are resumed in table 1.

Table 1. SAFIRE−A instrumental specifications

Parameter Value

Instrument type Polarising FT spectrometer

Dimensions1800 x 880 x 650 mm

Weight387 kg

Interferogram acquisition time12, 24, 48, 96 s

Number of detection channels2

Operating spectral range10−250 cm−1