Extension of observation and data analysis capabilities (new experimental techniques and algorithms):

Campaign-based activities:

• Ukkel, spring-summer 2001, technological campaign, including FTIR and FT-UV measurements, O₃ soundings and Dobson/Brewer observations
• Ile de la Reunion (22°S, 55°E), late summer 2002, campaign of FTS observations in the tropics
• Arctic, winter 2002-2003, NDSC campaign of UV-Vis DOAS observations - support to ENVISAT validation.

Off-axis DOAS measurements at OHP and Ile de la Réunion:

• Tropospheric abundances of O₃, NO₂, BrO and H₂CO.

Vertical inversion algorithms:

• Distinct troposopheric and stratospheric abundances of target gases; information about their vertical distribution.