Pointing control for the SPIDER balloon-borne telescope
Abstract
We present the technology and control methods developed for the pointing system of the SPIDER experiment. SPIDER is a balloon-borne polarimeter designed to detect the imprint of primordial gravitational waves in the polarization of the Cosmic Microwave Background radiation. We describe the two main components of the telescope's azimuth drive: the reaction wheel and the motorized pivot. A 13 kHz PI control loop runs on a digital signal processor, with feedback from fibre optic rate gyroscopes. This system can control azimuthal speed with < 0.02 deg/s RMS error. To control elevation, SPIDER uses stepper-motor-driven linear actuators to rotate the cryostat, which houses the optical instruments, relative to the outer frame. With the velocity in each axis controlled in this way, higher-level control loops on the onboard flight computers can implement the pointing and scanning observation modes required for the experiment. We have accomplished the non-trivial task of scanning a 5000 lb payload sinusoidally in azimuth at a peak acceleration of 0.8 deg/s, and a peak speed of 6 deg/s. We can do so while reliably achieving sub-arcminute pointing control accuracy.
Keywords
Cite
@article{arxiv.1407.1880,
title = {Pointing control for the SPIDER balloon-borne telescope},
author = {Jamil A. Shariff and Peter A. R. Ade and Mandana Amiri and Steven J. Benton and Jamie J. Bock and J. Richard Bond and Sean A. Bryan and H. Cynthia Chiang and Carlo R. Contaldi and Brendan P. Crill and Olivier P. Doré and Marzieh Farhang and Jeffrey P. Filippini and Laura M. Fissel and Aurelien A. Fraisse and Anne E. Gambrel and Natalie N. Gandilo and Sunil R. Golwala and Jon E. Gudmundsson and Mark Halpern and Matthew Hasselfield and Gene C. Hilton and Warren A. Holmes and Viktor V. Hristov and Kent D. Irwin and William C. Jones and Zigmund D. Kermish and Chao-Lin Kuo and Carolyn J. MacTavish and Peter V. Mason and Krikor G. Megerian and Lorenzo Moncelsi and Tracy A. Morford and Johanna M. Nagy and C. Barth Netterfield and Roger O'Brient and Alexandra S. Rahlin and Carl D. Reintsema and John E. Ruhl and Marcus C. Runyan and Juan D. Soler and Amy Trangsrud and Carole E. Tucker and Rebecca S. Tucker and Anthony D. Turner and Alexis C. Weber and Donald V. Wiebe and Edward Y. Young},
journal= {arXiv preprint arXiv:1407.1880},
year = {2015}
}
Comments
20 pages, 12 figures, Presented at SPIE Ground-based and Airborne Telescopes V, June 23, 2014. To be published in Proceedings of SPIE Volume 9145