First ISCCP Regional Experiment (FIRE) Cirrus Phase II Spectral Radiance Experiment (SPECTRE) SIRIS High Resolution Emission Data

The SIRIS instrument has been previously flown for balloon-borne studies of stratospheric chemistry relevant to the ozone cycles. It is a modified version of a Bomem continuously scanning Fourier transform spectrometer, operating in emission mode. The following instrument parameters were applicable for the Coffeyville SPECTRE campaign.

The field-of-view, 0.5 degrees full width at half-maximum, was directed towards the zenith, except for a day when limb were recorded. The highest emission-mode spectral resolution recorded during SPECTRE was taken by SIRIS 0.06 cm-1, apodized. Scan times varied from one to a few minutes, depending onthe resolution.

The instrument was run at ambient temperature, withthe Si:Ga detectors at liquid helium (LHe) temperature. Data are limited by photon noise from the emission from the instrument and from the atmosphere itself. Therefore data were recorded with two different width bandpasses: 1) narrow bandpass cooled filters in channels 1-4, which reduces the background noise, yielding higher signal-to-noise; and 2) wide band in channel 5 for more complete spectral coverage.It was the goal of SPECTRE to acquire clear-sky radiance spectra under a variety of temperature and water vapor conditions.