Challenges in the limb retrieval of noctilucent cloud properties from Odin/OSIRIS

Limb-viewing satellite instruments have become a major tool for the observation of noctilucent clouds (NLC), providing distinct advantages in the study of these thin mesospheric layers. The geographical coverage and the continuity of the data provide exclusive information on global distribution, seasonal variation, and planetary wave patterns. In combination with spectroscopic measurements, this provides the possibility to infer global information about NLC particle sizes. However, retrieval procedures for satellite-borne NLC observations are complex. Major challenges are related to the limb geometry, the discrimination between cloud and background, and albedo effects. This paper, describes the analysis of NLC observations from the OSIRIS instrument onboard the Odin satellite. Retrieval challenges and solutions are discussed with special emphasis on the spectral analysis of NLC particle properties. We show that OSIRIS can provide comprehensive information about individual clouds. However, intercomparisons between different satellites or ground-based instruments are generally limited to studies on a climatological basis.