Ball Aerospace & Technologies Corp. developed a Resonant Scanning Mechanism (RSM) capable of combining a 250- Hz resonant scan about one axis with a two-hertz triangular scan about the orthogonal axis. The RSM enables a rapid, high-density scan over a significant field of regard (FOR) while minimizing size, weight, and power requirements. The azimuth scan axis is bearing mounted allowing for 30° of mechanical travel, while the resonant elevation axis is flexure and spring mounted with five degrees of mechanical travel. Pointing-knowledge error during quiescent static pointing at room temperature across the full range is better than 100 μrad RMS per axis. The compact design of the RSM, roughly the size of a soda can, makes it an ideal mechanism for use on low-altitude aircraft and unmanned aerial vehicles. Unique aspects of the opto-mechanical design include i) resonant springs which allow for a high-frequency scan axis with low power consumption; and ii) an independent lower-frequency scan axis allowing for a wide FOR. The pointing control system operates each axis independently and employs i) a position loop for the azimuth axis; and ii) a unique combination of parallel frequency and amplitude control loops for the elevation axis. All control and pointing algorithms are hosted on a 200-MHz microcontroller with 516 KB of RAM on a compact 3”×4” digital controller, also of Ball design.
Ball Aerospace and Technologies Corp. (BATC) is developing a Fine Steering Mirror (FSM) for the James
Webb Space Telescope (JWST). This high reliability FSM is designed to provide line-of-sight steering in two
orthogonal axes as part of the Aft Optical System (AOS) of a large telescope that operates at the L2 Lagrange point.
This paper presents the mechanical design of the mechanism which satisfies stringent requirements for operation in
vacuum and cryogenic environments. Also given is a status of the flight hardware development and early results of
cryogenic testing.
Ball Aerospace & Technologies Corp. (Ball Aerospace) has developed a Risley Beam Pointer (RBP) mechanism capable of high pointing accuracy and operational bandwidth. The prisms offer a wide field of regard (FOR) and can be manufactured and operated with diffraction-limited optical quality. The unit is capable of steering a 4-in. diameter beam over a 72° half angle cone with better than 100 μrad precision. Absolute accuracy of the beamsteering is in the range of 100 μrad to 1 mrad, depending on the thermal environment of the system. The system has demonstrated a control bandwidth of 23 Hz and better than 10 deg/sec of smooth target tracking anywhere within the FOR.
A high performance reactionless scan mirror mechanism was developed for space applications. This paper presents a number of key new developments in the area of mechanical design of large scanner mechanisms. The design incorporates a unique mechanical means of providing reactionless operation which also minimizes weight, mechanical resonance operation to minimize power, combined use of a single optical encoder to sense coarse and fine angular position, and a new kinematic mount of the mirror. Along with the mechanical description, current status of the project is given.
A pointing/roll mechanism for the Ultraviolet Coronagraph Spectrometer (UVCS) is presented along with a description of the mechanism control algorithm. The mechanism, operating in space, will angulary position the 2.1 m long, 0.7 m diameter UVCS instrument in pitch and yaw, within a 54 arc-minute half-angle cone, also allowing it to rotate +/- 179.75 degree(s). After considerable design effort, an optimum mechanical solution was achieved which meets all scientific requirements as well as weight, volume, and power budgets. Evolution of the mechanism is presented along with the design status.
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