| Summary: | We highlight chemistry and trend measurements from the Atmospheric Chemistry Experiment (ACE) which is providing precise middle troposphere to the lower thermosphere measurements of the Earth's upper troposphere to lower mesosphere with the solar occultation technique. The primary instrument is a 0.02 cm-1 resolution Fourier transform spectrometer covering 750-4400 cm-1 simultaneously. ACE also known as SCISAT 1 is a Canadian lead mission launched into a 74 ° inclined orbit at 650 km altitude on August 12, 2003 by a U.S.-supplied Pegasus vehicle. Additional measurements are obtained with a UV-visible spectrometer and two imagers providing measurements at 0.525 and 1.02 microns. 2004 SOLAR FLARES The Sun produced some of the most powerful solar flares ever recorded between 18 October and 5 November 2003. ACE measurements of Arctic NOx vs. pressure from 0.07-2 hPa (~40-60 km) during February and March 2004 showed the dilution of NOx resulting from photochemical loss in the sunlit atmosphere, and the time series of measurements were used to estimate the descent rate from the upper stratospheric NOx time series [1]. Figure 1. ACE time series of NOx (NO+NO2) measurements [Rinsland et al. [1]] _____________________________________________________ Proc. ‘Envisat Symposium 2007’, Montreux, Switzerland
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