M1M3 Monolith

In the Rubin Observatory optical design, the 8.4 m primary (M1) and 5.0 m tertiary (M3) mirrors form a continuous surface. Because the two mirrors curve differently, a slight cusp is formed where they meet, as seen in the picture below. This design makes it possible to fabricate both the primary and tertiary mirrors from a single monolithic substrate, the M1M3 monolith.

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Usually the redshift of a galaxy is measured spectroscopically. The spectrum of the galaxy is observed: Emission or absorption lines are identified and their wavelengths are measured. These measured wavelengths are then compared with the rest wavelengths to determine the redshift. Photometric redshifts (also known as "color redshifts" or "photo-z") utilize broad-band photometry to measure the redshifts of galaxies rather than spectroscopy.

Once a simulated survey is planned, designed and executed, it is useful to evaluate whether that particular survey met the LSST project science goals. Quantifying how well a simulated survey achieves a science objective or whether one simulation is "better than" another is a complex and open-ended problem.

The LSST Project developed the Operations Simulator to verify that the LSST Science Requirements could be met with the telescope design. It was used to demonstrated the capability of the LSST to deliver a 27,000 square degree survey probing the time domain and with 20,000 square degrees for the Wide-Fast-Deep survey, while effectively surveying for NEOs over the same area.  Currently, the Operations Simulation Team is investigating how to optimally observe the sky to obtain a single 10-year dataset that can be used to accomplish multiple science goals. 

Software

The LSST Operations Simulator a software tool created primarily with an open-source simulation package--SimPy.  SimPy is an object-oriented, process-based, discrete-event simulation package based on standard Python and released under the GNU GPL.