Intercomparison of Simultaneous Laboratory Gas Absorption Measurements With ACE-FTS and MAESTRO

ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer) and MAESTRO (Measurements of Aerosol Extinction in the Stratosphere through Retrievals of Occultations) are the two spectrometers on board Canada's Scisat-1 satellite, which was launched in August 2003 in order to study polar stratospheric ozone chemistry and dynamics. The ACE-FTS is a high resolution Michelson Interferometer operating in the 750 to 4100 cm-1 spectral range, while MAESTRO is a dual holographic grating spectrometer operating in the 280-1000 nm range. A period of instrument testing and characterization took place at the University or Toronto's Instrument Characterization Facility during February and March of 2003. During this time a series of tests was performed where the two instruments, sitting inside a thermally controlled vacuum chamber, were simultaneously exposed to sources of blackbody radiation. Gas cells containing various concentrations and pressures of ozone and nitrogen dioxide were placed in between the sources and the instruments, and the resulting absorption spectra was simultaneously measured with both spectrometers. Since both instruments are looking at the same gas cell at the same time, discrepancies between the gas concentrations retrieved from ACE-FTS and MAESTRO spectra give insight into the validity of parameters used for spectral fitting. Results from these measurements will be presented along with a description of the experimental apparatus.