The York University Red Line Photometer was launched on the ISIS-II spacecraft on April 1, 1971. Its operations for more than a decade were ended not by any physical fault, but by a policy decision to terminate support for ISIS operations. Since ISIS-II was the last of a series of four satellites this effectively concluded Canada's scientific satellite program. The satellite was then 'given' to the Japanese, who continued to operate it to obtain topside sounder data. They did not have the resources needed to operate the other instruments, so no Red Line Photometer data were obtained after that time. It is nevertheless of considerable interest to track the behavior of the optical elements, which had a decade of operation in space. This paper presents 10 years of calibration of the Red Line Photometer, no degradation of any optical elements can be identified.