THE INSTRUMENT

The MAORY main structure is   based on a latticework tower made of standard structural steel truss-beam shaped pipes, welded/bolted with different section properties.  The truss is connected to the Nasmyth platform through 10 legs that merge into 3 points. The overall design has been constrained to be able to fit with the three legs concept, in order to null the distortion induced by the Nasmyth displacements out of a rigid body motion.

 

General overview of the MAORY instrument (thermal cover in transparency) installed on the Nasmyth platform with MICADO

A general overview of the MAORY global architecture is illustrated in Figure 3.   The main hardware subsystems indicated in the figure are complemented by the electronics at system and sub-systems level, instrument control software and real time computer.

 

 

WAVEFRONT SENSOR MODULES

The MCAO mode in MAORY is based on the use of two wave-front sensor (WFS) modules:  an LGS WFS module with 6 beacons (upgradable for 8) arranged in a 45” asterism,  an NGS WFS module with 3 low order sensors and 3 reference sensors patrolling a technical field of 160 arcses.

The LGS WFS module is a device dedicated to measurement of the wavefront aberrations due to atmospheric turbulence and other effects.  In the following figure  we show an overall view of the full LGS WFS assembly.

Overview of the LGS WFS module

 

 

The LGS WFS module contains 6 wavefront sensor units to measure wavefront distortion on the laser guide stars. It is attached below the MAORY main structure  in a gravity invariant configuration.  The light of wavelength shorter than about 600 nm is propagated from the Dichroic beam-splitter through the LGS Path Optics and then to the LGS Wavefront Sensor module. The light enters each probe, where it is collected by a WFS camera

The Low Order and Reference (LOR) Module implements the Natural Guide Star wavefront sensing functionalities needed by MAORY in the MCAO mode.

 

Detail of the hardware implemented within the LOR WFS module.

 

The LOR WFS Module is downstream of the Post Focal Relay Optics (PFRO), and the LOR WFS benefits from the MCAO correction, of course in a way that depends on the off-axis distance of the NGS. It consists of 3 identical LOR WFS units to sense the aberrations in the direction of 3 NGSs chosen in a technical field having an outer radius of 80 arcsec.  Each LOR WFS Unit is equipped with a Low-Order WFS and a Reference WFS sharing the light from the same NGS. The Low-Order (LO) WFS configuration is a Shack-Hartmann sensor with 2×2 sub-apertures operating in the H band. The Reference WFS act as “truth” sensor to de-trend LGS wavefront estimates and measure pseudo-static aberrations of the telescope and of the post focal relay optics.