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${}^2$, and a peak speed of 6 deg/s. We can do so while reliably achieving sub-arcminute pointing control accuracy.

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

References in corpus (8)

• BOOMERANG: A Balloon-borne Millimeter Wave Telescope and Total Power Receiver for Mapping Anisotropy in the Cosmic Microwave Background
• SPIDER: a balloon-borne CMB polarimeter for large angular scales
• The balloon-borne large-aperture submillimeter telescope for polarimetry: BLAST-Pol
• Design and performance of the Spider instrument
• Attitude determination for balloon-borne experiments
• Antenna-coupled TES bolometer arrays for CMB polarimetry
• Modeling and characterization of the SPIDER half-wave plate
• Thermal architecture for the SPIDER flight cryostat

Cited by in corpus (5)

• SPIDER: CMB polarimetry from the edge of space
• The Thermal Design, Characterization, and Performance of the SPIDER Long-Duration Balloon Cryostat
• Attitude determination for balloon-borne experiments
• Robust diffraction-limited NIR-to-NUV wide-field imaging from stratospheric balloon-borne platforms -- SuperBIT science telescope commissioning flight & performance
• Design and pre-flight performance of SPIDER 280 GHz receivers