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/s2, and a peak speed of 6 deg/s. We can do so while reliably achieving sub-arcminute pointing control accuracy.
Original language | English (US) |
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Title of host publication | Ground-Based and Airborne Telescopes V |
Editors | Helen J. Hall, Larry M. Stepp, Roberto Gilmozzi |
Publisher | SPIE |
ISBN (Electronic) | 9780819496133 |
DOIs | |
State | Published - 2014 |
Event | Ground-Based and Airborne Telescopes V - Montreal, Canada Duration: Jun 22 2014 → Jun 27 2014 |
Publication series
Name | Proceedings of SPIE - The International Society for Optical Engineering |
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Volume | 9145 |
ISSN (Print) | 0277-786X |
ISSN (Electronic) | 1996-756X |
Other
Other | Ground-Based and Airborne Telescopes V |
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Country/Territory | Canada |
City | Montreal |
Period | 6/22/14 → 6/27/14 |
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Computer Science Applications
- Applied Mathematics
- Electrical and Electronic Engineering
Keywords
- Spider
- actuation
- balloon-borne telescopes
- control systems
- cosmic microwave background