Previous: Introduction. Next: First results: VMR maps of the observed species Up: Ext. Abst.

 

SAFIRE/A operation during the APE-GAIA campaign

SAFIRE-A (Spectroscopy of the Atmosphere using Far-InfraRed Emission / Airborne) [1] is a polarising far infrared Fourier transform (FT) spectrometer operating onboard the M55 Geophysica stratospheric aircraft. In the five scientific flights which the aircraft performed over the Antarctic Peninsula, during the APE-GAIA (Airborne Polar Experiment - Geophysica Aircraft In Antarctica) campaign, the instrument provided limb sounding observations of atmospheric emission spectra over two frequency intervals: [22-23.5 cm-1], and [123-125 cm-1] where spectral features respectively of O3, ClO, N2O, HNO3 and HCl, H2O are displayed. Some of the principal characteristics of the SAFIRE/A instrument are presented in table 1.


Table: SAFIRE/A spectrometer characteristics
Instrument type Polarising FTS
Dimensions 1800 x 880 x 650 mm
Weight 387 Kg
Observation technique limb-scanning
Acquisition time 12-24-48-96 s
Number of detection channels 2
Operating spectral range 10-250 cm-1
Spectral resolution 0.004 cm-1
Vertical resolution about 1.5 km
Spectral signal-to-noise ratio >500
Vertical field of view 0.57o


In figure 1 the flight tracks corresponding to each of the scientific flights performed during the APE-GAIA campaign are shown. The choice of the Ushuaia international airport as a base for the campaign permitted to explore the Antarctic polar vortex region, spanning a latitude range from 58 to about 68 degrees south.

Figure 1 : Flight tracks corresponding to the scientific flights performed by the SAFIRE/A instrument during the APE-GAIA Antarctic campaign.
click to enlarge picture

During each flight the SAFIRE/A instrument vertically sampled the atmosphere with limb sounding sequences of 10 emission spectra, corresponding to a vertical resolution of about 1.5 km. The acquisition time for a single spectrum was 30 s, each sequence taking about 5 minutes. This, considering the aircraft average ground speed of 700 km/h at stratospheric altitude, gave an horizontal resolution of about 60 km, corresponding to 0.5 degrees of latitude. The amount of valid data acquired by SAFIRE/A in each flight is given in table 2 as a percentage of the total recorded data.


Table: Valid data content of the scientific flights performed by SAFIRE/A during the APE-GAIA Antarctic campaign.
Scientific flight Data acquired Failure reason
19/9/1999 (test) 0% photolitographic BS, aircraft roll
21/9/1999 60% reference laser, roll
23/9/1999 90% roll
2/10/1999 30% roll
8/10/1999 100% -
12/10/1999 100% -


In figure 2 a typical limb scanning sequence of spectra acquired from the long wavelength detection channel (22-23.5 cm-1) of the instrument is shown. The simultaneous presence in the same spectral interval of both chemically active species, like ozone, HNO3 and ClO and tracers, like N2O permits to obtain a characterization of chemical and dynamical processes in the lower stratosphere through correlation between atmospheric components.

Figure 2: Limb-sounding sequence of atmospheric emission spectra acquired from SAFIRE/A in the detection channel 1 (22-23.5 cm-1). Spectral features due to O3, HNO3, N2O and ClO are visible inside the considered region.
click to enlarge picture

Previous: Introduction. Next: First results: VMR maps of the observed species Up: Ext. Abst.