VLT Nasmyth Adapter-Rotator

Overview

The complete adapter-rotator units comprise two major subsystems: the opto-mechanical part and the control system. The Opto-Mechanical part consists of five main sub-components:

• The Large Structure
• The Sensor Arm
• The M4 Unit
• The Folded Nasmyth Focus Device
• The Maintenance and Integration Equipment

The figure shows the general sectional view of the Nasmyth Adapter-Rotator indicating the main elements.

The Large Structure

The Large Sctructure is composed of three main sub-components, the Support Structure, the Instrument Rotator and the Adapter plus some smaller assemblies (Safety Brake, Limit Switch systems, Cable Wrap, Hoses and Cables, and Nasmyth Connection Box).

The Support Structure is a welded structure which supports the Instrument Rotator and the Adapter. It is fixed on the motor housing. The Instrument Rotator consists of a large flange to which the scientific instrument is attached. The flange is mounted on a bearing which is driven by a Drive Unit to allow the instrument to be rotated around the telescope optical axis to follow the rotation of the telescope field.

The Adapter consists of the Adapter Structure, the Adapter Box and the Drive Unit. The Adapter Structure is fixed to the Support Structure and supports the Adapter Box. Like the Instrument Rotator, the Adapter Box is supported by a large bearing. The Drive Unit allows the Adapter Box to be rotated about the telescope optical axis. The Adapter Box, in turn, supports the Sensor Arm described below.
The Cable Wrap transports Cables And Hoses from the Adapter Structure to the Adapter Box and Sensor Arm.

The Safety Brake prevents motion of the Instrument Rotator when the Rotator Drive Unit is not powered.
The Limit Switch Systems control the limits of rotation of the Adapter. The Nasmyth Connection Box serves as a junction point between the fixed cables and hoses coming from the CEC with those from the Adapter-Rotator.

The Sensor Arm

The Sensor Arm comprises a Turntable, a Supporting Arm, the Supporting Arm Structure, a Focusing Device, a Reference System and an Optical System. The Supporting Arm assembly is attached to the Adapter Box by means of the Turntable which allows it to rotate about an axis at the edge of the telescope optical field. At the end of the Supporting Arm is a pick-up mirror which directs light from the telescope beam, through the Optical System, to two CCD sensors.

The Focusing Device allows the adjustment of the CCD sensor focus position.
The Reference System inserts an optical fibre into the beam for calibration purposes. The combined movements of the Sensor Arm and the Adapter Box allow the pick-up mirror to be placed anywhere in the telescope field.

The M4 Unit

The M4 Unit bends the optical beam coming from the telescope to the folded Nasmyth Focus and Coudé Focus. It is mounted on a linear bearing assembly which moves it into the optical path.

The Folded Nasmyth Focus Device

The Folded Nasmyth Focus Device (FNFD) is located at the folded Nasmyth focus and provides the necessary tools for Coudé Beam alignment and optical maintenance of the telescope.

The Maintenance and Integration Equipment

The component comprises a number of assemblies which are used for the assembly, alignment, handling maintenance and tests.