The pointing accuracy of a telescope is a fundamental performance metric, and the prevalent method for correcting telescope pointing deviations involves selecting stars that are uniformly distributed across the sky, measuring the difference between the telescope's observed calibration position and the expected position from a star catalog, and then applying correction models to compensate for the deviations. However, the uniformity of traditional star selection algorithms can be suboptimal. To address this issue, this study proposes a star uniform selection algorithm based on maximizing Kozachenko-Leonenko entropy (MKLE). Specifically, the proposed algorithm employs KL entropy computed based on the k-nearest neighbor approach as a metric of uniformity, where a higher KL entropy indicates more uniform star selections. To adapt the algorithm to the cylindrical surface formed by the telescope's azimuth and elevation axes, a KD-tree search strategy is proposed. Furthermore, to enhance the uniformity of selected stars, a simulated annealing method is utilized to maximize the KL entropy and select the most uniformly distributed stars. The performance of this method was verified by calculating the KL entropy using MKLE, rectangular grid method (RGM), and first-order self-organizing selection method (SO). The results indicate that the MKLE algorithm outperforms the other methods in terms of uniformity of star selection.
In active optics technology, the force actuator is a key component of the active support system. However, the existing electromechanical force actuators have difficulty ensuring the linearity of output force and have a complex structure with poor accuracy. This article addresses this issue by designing a high-precision and highly linear force actuator. The force actuator converts the linear displacement of the stepper motor driving the screw nut into the pressure of the spring through a composite spring group and achieves the output tensile and compressive forces through the preload of the spring group. According to the test results, this force actuator has high linearity, with a maximum tensile and compressive force of up to 200 N and a repeatability accuracy within 0.1 N, achieving the design goal.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.