MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) is operating on ENVISAT since March 2002.
After two years of nearly continuous limb-scanning measurements (from July 2002 to March 2004) at the end of March 2004 the instrument was stopped due to problems with the mirror drive of the interferometer. Operations with reduced maximum path difference, corresponding to both a lower spectral resolution (0.0625 cm^-1 instead of 0.025 cm^-1 ) and a shorter measurement time (1.8 sec instead of 4.5 sec), were tested for one month in August/September 2004 and then definetely resumed on January 2005. In order to exploit the reduction in measurement time a change in the measurement scenario was also implemented for measurements from January 2005 on. The new scenario adopts a finer vertical limb scanning step in the region of the troposphere and lower stratosphere. 

From the first analysis of the new measurements it results that these measurements are characterised by both an improved vertical resolution and a smaller estimated standard deviation.

Vertical resolution for the ozone retrieval, as a function of altitude and orbital coordinate, for both the orbit #17540, acquired with the new operation mode (plot on the right), and the orbit #7090, acquired with the old operation mode (plot on the left) . The orbital coordinates are linked to latitude and are equal to 0° and 180° at the equator, to 90° at the North pole and to 270° at the South pole.

Retrieval errors for the ozone retrieval, as a function of altitude and orbital coordinate, for both the orbit #17540, acquired with the new operation mode (plot on the right), and the orbit #7090, acquired with the old operation mode (plot on the left).

In general we obtain for all species that in the new operation mode the retrieval errors are smaller than in the old operation mode and the vertical resolution is significantly improved (in troposphere and stratosphere vertical resolution is often smaller than the IFOV).
This result has been obtained despite the improved vertical and horizontal resolution. Indeed, the distribution of the coloured spots along the orbital coordinate shows that also the horizontal sampling has improved.