Abstract

The Space Infrared Telescope Facility (SIRTF), planned for an early 21^st century launch, is the fourth of NASA's Great Observatories. It contains a 1-meter class Ritchey-Chretien telescope, all of whose components will be cryogenically cooled to superfluid helium temperatures. Achievement of diffraction-limited performance at wavelengths as short as 3 μm will likely require realignment of the secondary mirror following launch. Efficient use of SIRTF's limited cryogenic lifetime (5 years, with a sensitivity of 1 month/mW) requires a means for tilting the secondary mirror to rapidly relocate the telescope's line of sight and to map small regions of the sky. Furthermore, at the longest SIRTF wavelengths (200-1200 μm) the emission from the cooled telescope will be significant, thereby requiring the use of periodic tilt oscillations of the secondary mirror to modulate the signal.

© 1991 Optical Society of America