This work describes the hardware control system of the Prime Focus Corrector (PFC) and the Spectrograph, two of the
main parts of WEAVE, a multi-object fiber spectrograph for the WHT Telescope. The PFC and Spectrograph control
system hardware is based on the Allen Bradley’s Programmable Automation Controller and its modules. Mechanisms,
sensors and actuators of both systems are summarized and their functionality described, showing how they meet the
We present the preliminary design of the WEAVE next generation spectroscopy facility for the William Herschel
Telescope (WHT), principally targeting optical ground-based follow up of upcoming ground-based (LOFAR) and spacebased
(Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2 degree prime focus field of view
at the WHT, with a buffered pick and place positioner system hosting 1000 multi-object (MOS) fibres or up to 30
integral field units for each observation. The fibres are fed to a single spectrograph, with a pair of 8k(spectral) x 6k
(spatial) pixel cameras, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting
observations at R~5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with
limited coverage in each arm at R~20000.
The Laser Guide Star commissioned in 2007 at the WHT on La Palma is based on Rayleigh backscattering of a 515 nm
beam provided by a diode pumped Q-switched doubled frequency Yb:YAG laser launched from behind the WHT
secondary mirror. At the time the laser beam is focused at a distance of 15km above the telescope ground and its power
just under 20W. With such a pulsed laser, careful fine tuning of the range gate system is essential to isolate the most
focused part of the LGS and eliminate parts of the laser plume which would degrade the Shack-Hartmann spots and
consequently AO correction. This is achieved by an electro-optic shutter using Pockels cells, triggered by a delay
generator synchronised on the laser pulses, and by spatial filters. Images of 0.15" resolution in J and H bands, very close
to expected performance, have been routinely taken as soon as the third and fourth commissioning runs. Here we show
the performance of the range gate system as measured and improved over the successive commissioning runs, as well as
the off sky and on sky calibration procedures of the LGS AO system.
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.