MAORY RTC, a status update

The Multi Conjugate Adaptive Optics RelaY (MAORY) for the ESO Extremely Large Telescope (ELT) is an Adaptive Optics module offering Multi-Conjugate (MCAO) and Single-Conjugate (SCAO) compensation modes. In MCAO, it relies on the use of a constellation of Laser Guide Stars (LGS) and up to three Natural Guide Stars (NGS) for atmospheric turbulence sensing, and multiple deformable mirrors for correction, providing uniform, high Strehl and high sky coverage. MAORY will be installed at the Nasmyth focus of the E-ELT and will feed the MICADO first-light diffraction limited imager and a future second instrument. MAORY is being built by a Consortium composed by INAF in Italy, IPAG in France and the School of Physics at the National University of Ireland Galway. In this paper we report about the status of the design of the MAORY Real Time Computer, which is the component in charge of implementing the main AO control loops, as well as of auxiliary computations to keep the loops operating optimally, and of telemetry data collection for postprocessing, monitoring, testing and troubleshooting. We will start by discussing the evolution of requirements towards MAORY RTC, with an emphasis on the main driving ones. Then, we will describe how the analysis of requirements has led to the derivation of the main design parameters. Finally, we will illustrate possible RTC designs satisfying user requirements, while also complying with standards set forth by ESO.