COALA - the future of global vertical ozone profile trend monitoring

• Main Authors: Heilimo, J., Korpela, S., Leppelmeier, G. W., Sihvola, E., Saari, H., Astola, H., van Eijk-Olij, C., Visser, H., Hoekstra, R., Lundell, J.
• Other Authors: Attema, E., Schwehm, G., Wilson, A.
• Format: Book Part
• Language: English
• Published: European Space Research and Technology Centre (ESTEC) 1998
• Subjects: /dk/atira/pure/sustainabledevelopmentgoals/climate_action; SDG 13 - Climate Action; Arctic; Antarctic; The Antarctic; Antarc*
• Online Access: https://cris.vtt.fi/en/publications/1e7f0eda-b1ef-4727-868a-15488684cfda; http://www.scopus.com/inward/record.url?scp=0032323634&partnerID=8YFLogxK

As is now well known, a severe decline in the ozone UV shield over the Earth has been particularly noted in the Antarctic in the spring, with a more gradual decrease notable at some times of the year generally over the Earth, and more recently similar 'holes' have been noted over Arctic regions of the globe. Finding the trends of atmospheric ozone evolution and behaviour has become increasingly important not only in the area 'greenhouse gases', but also in areas like climate modelling and weather prediction, as ozone itself is also a major absorber of sunlight. This paper presents a new ozone- monitoring instrument called COALA (Calibration for Ozone through Atmospheric Limb Acquisitions). COALA measures atmospheric ozone profiles by using limb occultation technique, similar to that of GOMOS. COALA, however, is considerably smaller than GOMOS, weighting only 20-25 kg, which allows us to fly several COALAs onboard mini satellites and, thus, resulting considerably lower costs per unit. This reduction in instrument size is achieved by neglecting trace gases other than ozone, concentrating on dark limb measurements, relaxing the measurement accuracy, and using modern state-of-the-art technologies in instrument design. While reduced instrument accuracy (for example, due to a smaller input aperture) definitely leads to a reduction in the accuracy of the ozone profile obtained from a single occultation, flying two instruments in coordinated orbits not only provides complete redundancy, but gives better coverage and gains back the global trend accuracy by doubling the number of occultations per day.