Infrared telescopes are often required to work in a complex thermal environment. A long time of daytime heating will cause the temperature of the telescope dome and the surrounding facilities different from the ambient air during the night. Different levels of temperature controlling and the accuracy of forecasting will lead to the temperature departures between the components in the system. Furthermore, the contaminated particles settled on the optical elements will change the optical characteristics of the optical elements. All of these factors will degrade the stray light performances of infrared telescopes. In this paper, taking Cassegrain as a typical example and using the optical analysis software, i.e., ASAP, the three-dimensional simulation models of the infrared telescope and the dome has been built up. On this basis, the stray light performances and the variation of the systems have been simulated and analyzed for the different cases of the different coating for the dome, the change of the temperature of primary and ambient, as well as the existence of the mirror contamination. The effective emissivity has been introduced and the stray light performance of the systems has been evaluated. The results indicate that the contaminated particles settled on the optical elements will degrade the system performances significantly, whereas the influences of other factors are relatively small. Therefore, it is of great importance to focus on the contaminated particles settled on the optical elements to adopt proper methods to improve the stray light performances of infrared telescope systems.

Date Published: 13 October 2010
PDF: 6 pages
Proc. SPIE 7654, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes, 76540V (13 October 2010); doi: 10.1117/12.866848

Published in SPIE Proceedings Vol. 7654:
5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes
Wenhan Jiang; Myung K. Cho; Fan Wu, Editor(s)