ALMA Memo #288

An Optical Pointing System for the ALMA Prototype Antennas

In this memorandum we present an outline of the design requirements for an optical pointing telescope for the ALMA prototype antennas. The proposed system will draw heavily upon the experience with the successful optical pointing system in use at the 12 Meter Telescope on Kitt Peak. The system will be composed of an optical refracting telescope, a commercial CCD camera, a PC-based frame grabber, a control PC, and a software control system. This system will be able to work in tandem with the telescope control system to acquire star positions, measure their intensities, and produce fits to stellar positions to sub-arcsecond accuracy. The information gathered by this optical pointing system will be used to assess the stability and accuracy of the ALMA antenna tracking system and the form and stability of the ALMA telescope pointing behavior. It will serve as a fundamental tool for the diagnostic tests to be conducted on the ALMA prototype antenna. The system I describe in the following parallels a collaborative effort to build an optical pointing and tracking system for the GBT (see GBT memo by Phil Jewell for further information).

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Last modified: February 25, 2000