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Balancing Act

Friday, March 9, 2018

March 9, 2018 - Exciting progress took place in February at subcontractor Asturfeito in Spain, where personnel assigned to the Telescope Mount Assembly (TMA) engaged in balancing and metrology activities.

Although LSST’s telescope will eventually be controlled by computers, current balancing activities require a manual approach in which the telescope, while floating on oil, is moved by winches. Measurements of the force on the telescope are taken to ensure the telescope is balanced whenever it’s off-zenith. This video, taken during the balancing of the elevation structure, illustrates the process.

The LSST Camera and glass mirrors won’t be integrated with the TMA until it arrives on Cerro Pachón and undergoes extensive testing there, so steel surrogates (painted yellow) are being used to simulate the mass of those components in the factory. According to LSST TMA Technical Manager Shawn Callahan, “With the surrogates installed, and the telescope balanced, you could theoretically move the entire structure with your hand.”

The Asturfeito team is also using a laser tracker, mounted on the Primary/Tertiary Mirror (M1M3) surrogate, to carefully measure the locations of the critical optical interfaces, ensuring all the surfaces are exactly where they need to be for successful integration of the Camera and mirrors.

This month, subcontractors from all over Europe are meeting at Asturfeito to install the support equipment necessary to move the telescope under computer control, which is currently scheduled to take place at the end of March. 

Read more about the construction of the TMA here.


Financial support for Rubin Observatory comes from the National Science Foundation (NSF) through Cooperative Agreement No. 1258333, the Department of Energy (DOE) Office of Science under Contract No. DE-AC02-76SF00515, and private funding raised by the LSST Corporation. The NSF-funded Rubin Observatory Project Office for construction was established as an operating center under management of the Association of Universities for Research in Astronomy (AURA).  The DOE-funded effort to build the Rubin Observatory LSST Camera (LSSTCam) is managed by the SLAC National Accelerator Laboratory (SLAC).
The National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 to promote the progress of science. NSF supports basic research and people to create knowledge that transforms the future.
NSF and DOE will continue to support Rubin Observatory in its Operations phase. They will also provide support for scientific research with LSST data.   

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