A New Methodology for the Assessment of Relative Pointing Accuracy and Active Alignment Requirements of the Large Synoptic Survey Telescope

Abstract

The Large Synoptic Survey Telescope (LSST) is a large (8.4 m) wide-field (3.5°) survey telescope, which will be located on the summit of Cerro Pachón in Chile. The telescope mount assembly (TMA) acquires and tracks fields in the sky by providing motions about the azimuth and elevation axes. Therefore, it provides pointing, tracking, and slewing system performance requirements to comply with its space survey mission. With this scenario in mind, this article presents a new measurement methodology for the dimensional assessment of some pointing performance requirements. Based on laser tracker technology, a new measurement methodology has been developed for the measurement of the azimuth and elevation axes positioning of the TMA for any motion within the pointing range of the LSST. In addition, the laser tracker is also employed for the measurement of the alignment between the secondary (M2) and primary/tertiary (M1M3) mirrors as a part of the active alignment system of the telescope.