ISIS-II Atomic Oxygen Red Line Photometer.

One of the new features of the ISIS-II spacecraft, fourth in the Alouette/ISIS series, is the inclusion of two optical instruments. The scanning auroral photometer is described by Anger et al. in a companion paper [Appl. Opt. 12, 1753 (1973)]. The red line photometer described here is similar in concept; it is designed to map the global distribution of the 01 6300-A emission with a spatial resolution of about 100 km, a measurement accuracy of 10%, and a detection threshold of 10 R. The objective is to delineate the various processes leading to the excitation of O((1)D) in the airglow and aurora by observing the global variation and by comparison with data from other instruments on board the same spacecraft. The device is now operating successfully in orbit, and detailed orbital performance characteristics will appear in a later publication.