FEASIBILITY STUDY OF TOWER DESIGN AND VIBRATION SUPPRESSION FOR AN ANTARCTIC INFRARED TELESCOPE

• Main Author: Furlanetto, Anderson Michael
• Other Authors: Kraemer, David, Moen, Cristopher, Smith, Roger M
• Format: Thesis
• Language: English
• Published: Johns Hopkins University 2022
• Subjects: telescope; Antarctica; feasibility; stability; Cryoscope; Dome C; tower; design; vibration; isolation; decouple; structural analysis; suppression; active control; passive control; weather; civil engineering; mechanical engineering; observatory; MASTAN2; MATLAB; ASCE; wind; vibration control; vibration analysis; seeing; DOT; flexures; bearings; air bearings; rolling bearings; friction mounts; friction isolators; friction; Antarctic; vibration absorber; The Antarctic; Antarc*; Ice Shelf
• Online Access: http://jhir.library.jhu.edu/handle/1774.2/68025

There is increasing interest to develop a dedicated near-infrared (NIR) observatory in Antarctica due to the advantages of a colder, darker sky in the NIR band and because the turbulent ground layer, responsible for seeing, is limited to the first 30 m above the ice shelf. A telescope mounted atop a 25 to 30 m tower will have enhanced performance by operating at the top of the boundary layer and unprecedented sensitivity due to the Antarctic climate. Cryoscope is one such telescope and will be mounted atop a 30 m tower at Dome C, Antarctica. This presents a challenge for image stability since vibration-induced image motion must be less than 0.1 arcsec while the tower is subjected to 10 m/s wind buffeting. Seven tower designs were assessed using structural analysis programs to determine each tower’s stability and natural frequency from wind loads determined using ASCE Standards 7-16 and wind data from Dome C. Power law analysis was conducted to evaluate the relationships between stability and mass if a tower was linearly scaled. Furthermore, in case the tower designs provide insufficient stability, vibration isolation mounts are explored to provide additional compensation, mainly damping mounts and friction mounts. In addition, we hold in reserve the possibility of active cancellation of forces on the telescope by applying torques with direct drive motors in response to forces measured by rotary flexures and encoders incorporated into the bearing mounts. The primary purpose of this work is to assess the feasibility and degree of difficulty of designing a 30 m tower for Antarctica with sufficient stability through passive and active mitigation methods while considering construction and transportation constraints.