OPTICAL-SYSTEM OF THE INFRARED TELESCOPE IN-SPACE

A 15-cm Ritchey-Chretien telescope with diamond-turned metallic mirrors has been developed for use in the cryogenically cooled infrared space mission, Infrared Telescope in Space (IRTS). The IRTS is designed to register infrared emission from 1 mum to 1 mm with a relatively wide beam (8' to 30' depending on the wavelength). It will be operated at superfluid helium temperatures (approximately 1.8 K). We tested the performance of the telescope system both at room temperature (approximately 300 K) and at near-liquid-nitrogen temperature (approximately 100 K) to investigate the effects of the support stress and the temperature on the telescope. The results indicated that the Hartmann constant stays within the design goal (approximately 1') even in the worst case. The origin of aberrations is examined and possible improvements for future application are discussed.