The Nasmyth Adaptive Optics for Multi-purpose Instrumentation (NAOMI) on the William Herschel Telescope (WHT) has been developed recently into a common user AO (Adaptive Optics) instrument to accompany OASIS (Optically Adaptive System for Imaging Spectroscopy), a multi-slit spectrograph and INGRID (Isaac Newton Group Red Imaging Device) an Infrared detector. The most recent changes are the addition of an Atmospheric Dispersion Corrector (ADC) to be used for the optical wavelengths and a Dichroic Changer mechanism to select either a pass band or IR light for the Universal Science Ports (UPS).
Future developments on NOAMI are planned as it is due to house the GLAS WFS (Ground Layer Adaptive optics System Wave Front Sensor), a wave front sensor for the future Laser Guide Star (LGS) system to be installed on the WHT in 2006.
This paper describes the changes made with respect to the science ports and the changes to be made for the GLAS WFS; focusing on the GLAS WFS and the optical path and interface to the NAOMI adaptive optics system.
The GLAS (Ground-layer Laser Adaptive-optics System) project is to construct a common-user Rayleigh laser beacon that will work in conjunction with the existing NAOMI adaptive optics system, instruments (near IR imager INGRID, optical integral field spectrograph OASIS, coronagraph OSCA) and infrastructure at the 4.2-m William Herschel Telescope (WHT) on La Palma. The laser guide star system will increase sky coverage available to high-order adaptive optics from ~1% to approaching 100% and will be optimized for scientific exploitation of the OASIS integral-field spectrograph at optical wavelengths. Additionally GLAS will be used in on-sky experiments for the application of laser beacons to ELTs. This paper describes the full range of engineering of the project ranging through the laser launch system, wavefront sensors, computer control, mechanisms, diagnostics, CCD detectors and the safety system. GLAS is a fully funded project, with final design completed and all equipment ordered, including the laser. Integration has started on the WHT and first light is expected summer 2006.
NAOMI is the AO system of the 4.2-m William Herschel Telescope on La Palma. It delivers near-diffraction-limited images in the IR, and a significantly improved PSF at optical wavelengths. The science cameras currently comprise an IR imager (INGRID), an optical integral-field spectrograph (OASIS) and a coronagraph which may be placed in the light path to either instrument. 19 science programmes were observed during 2002-3. Observing overheads are small, with as much as 60% of the night spent integrating on science targets. In late 2004 this year, the WFS will be equipped with a low-noise L3 CCD, giving a gain of a factor of 2 in S:N for faint guide stars. A Rayleigh laser guide star is under development, with first light expected summer 2006, providing a unique facility: AO-corrected optical integral-field spectroscopy anywhere on the northern sky.
The Nasmyth Adaptive Optics Multipurpose Instrument (NAOMI) is the adaptive optics (AO) platform on the 4.2m William Herschel Telescope (WHT) at the Isaac Newton Group of Telescopes (ING). Until recently NAOMI has been concentrating on near infrared observations using the Isaac Newton Group Red Imaging Device (INGRID). Recent developments have added an extra optical port to NAOMI. The observer can now rapidly switch between infrared and optical instrumentation during AO observing, making the system more appealing for visiting instruments.
To allow for the operation of the common user optical spectrograph OASIS, a new optical path was created around the existing NAOMI optics. Various mechanisms were also added to the whole optical system. The OASIS beam was reshaped to f/20. The original optical/IR beam remains unchanged at f/16, and forms a new universal science port (USP). The existing Nasmyth Calibration Unit (NCU) has been replaced with a new design. This new NCU has multiple fibre-fed light sources that include continuum and arc lamps. The intensity of light can be individually adjusted via computer control. A new acquisition camera is mounted such that it can be used simultaneously with the spectral lamps. Software upgrades now allow faster deformable mirror calibration. A moveable mirror is used to select which science port will receive the light. Enhancements to the NAOMI AO system are discussed in this paper and suggestions for possible future upgrades.
This paper describes an engineering programme to retrofit an improved mechanism control system to the Isaac Newton Group Red Imaging Device (INGRID), the infrared camera at the William Herschel Telescope. INGRID is an operational instrument and engineering upgrades need to be considered carefully with a view to minimising risks to the instrument and ensuring that it is back in service on the due date.
A number of alternative mechanical arrangements were considered; different stepper motor candidates were assessed together with the electronics to drive them. Motor drive parameters were optimised to increase the speed of optical setup. Finally, different technologies were considered for improving the arrangements for sensing the position of the instrument's mechanism wheels. The paper reports on the results of this programme and lessons learned.