Embedding solid-state ceramic actuators in a bending style deformable mirror presents unique athermalization
challenges when operated at cryogenic temperatures. Approaches to athermally embed actuators in a substrate are
presented in this study. Each approach is rated according to established design criteria: unmatched displacement, range,
compliance ratio, bondline stress, design, and manufacturability. We show the results of our design that allows a large
thermal range of operation for the actuators.
A novel tip-tilt mechanism has been designed which is capable of aligning a small 1-inch optic with one arc second resolution. This mechanism performs this function without the aid of a piezoelectric device or other electronic technology. The optic is bonded to a three bipod mount in series with a spring-loaded flexure. Three manually adjustable differential screws drive the flexure. The bipod/flexure arrangement allows highly accurate and stable adjustment. This paper will give an overview of the design, and present laboratory data and analysis quantifying the adjustment resolution of the mechanism. Material and surface coating selection is also presented.
A proposed baseline design for the Space Infrared Telescope Facility includes a Tertiary Mirror Assembly (TMA)
which selectively redirects the telescope's converging science beam to each of several instruments. The TMA's mirror
rotates on an axis coincident with the beam's axis,'and is held steady during observation by a kinematic mount. A
bearing has been designed whose compliance causes minimal interference with the precision of the kinematic mount, and
which is well suited to the particular requirements of a cryogenic sateffite such as SIRTF. The bearing suspends its rotor
by taking advantage of the repulsion between a superconductor and a magnet. It potentially eliminates problems
associated with mechanical bearings that arise in similar applications, such as lubricant loss or failure, bearing wear, and
sensitivity to particulates, and does so without imposing the thermal load of a bearing heater or active magnetic bearing.
The bearing shows promise of offering an alternative to ball bearings in cryogenic applications where some compliance
is acceptable or advantageous.
This paper describes the design and testing of an indexing system for optical-beam steering. The cryogenic beam-steering mechanism is a 360-degree rotation device capable of discrete, high-precision alignment positions. It uses low-precision components for its rough alignment and kinematic design to meet its stringent repeatability and stability requirements (of about 5 arcsec). The principal advantages of this design include a decoupling of the low-precision, large angular motion from the high-precision alignment, and a power-off alignment position that potentially extends the life or hold time of cryogenic systems. An alternate design, which takes advantage of these attributes while reducing overall motion, is also presented. Preliminary test results show the kinematic mount capable of sub-arc second repeatability.