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Paper: On the Path to Binocular Pointing with LBT
Volume: 411, Astronomical Data Analysis Software and Systems XVIII
Page: 403
Authors: De La Peña, M.D.
Abstract: The Large Binocular Telescope (LBT) consists of two 8.4m mirrors on a common mount. Due to the binocular nature of the telescope, there are unique requirements imposed on the Telescope Control System (TCS), and in particular, on the Pointing Control Subsystem (PCS). The PCS must arbitrate the pointing requests from the two sides of the telescope which can perform, within specified requirements, both in an independent and in an interferometric mode. The PCS must position the mount and rotator in use, as well as contribute information to the subsystems handling the optical alignment and guiding/wavefront sensing in order for the telescope to point, track, and guide in a manner akin to a single telescope. This paper presents the design of the PCS, as it stands today in support of a single-sided telescope, servicing multiple focal stations. The PCS utilizes proprietary pointing kernel software developed by Patrick Wallace and David Terrett of Rutherford Appleton Laboratories. This software promotes the concept of the virtual telescope which associates a position on the sky (the target), a position in the telescope focal plane (the pointing origin), and the positions of the mount axes. Also described are the interfaces between the PCS and other components or subsystems of the TCS which allow for efficient sequencing of commands while compartmentalizing areas of responsibility or functionality. Finally, the anticipated design of the PCS which accommodates binocular pointing is described. Based upon the experience gained during monocular pointing, there are still unanticipated challenges ahead, particularly when one side of the telescope is performing an active exposure, and the other side of the telescope has made a request which requires the mount or an optical element to move.
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