Improved ozone trend measuring capabilities of TOMS instruments

Three TOMS (Total Ozone Mapping Spectrometers) of a new design series are scheduled to be launched successively over the next several years. Changes have been made in the area of instrument calibration which should significantly improve the precision of TOMS ozone measurements over their predecessors. In the BUV method for determining ozone overburden, the precision of retrieved ozone amounts is directly related to knowledge of changes in diffuser: reflectance. A three solar diffuser system employed on a previous TOMS proved capable of detecting a 0.25% (2 sigma) ozone error over the three year mission. In addition to multiple diffusers, the new TOMS have on board a system for monitoring diffuser reflectance which alone should maintain instrument calibration with. a precision at least double that of earlier TOMS. Improvements in prelaunch calibration techniques should result in closer inter-instrument agreement, an important consideration when measuring trends with multiple instruments. Unfortunately, the agreement between instruments is not likely to be better than about 1% ozone.