Richard J. Bennett

The Visible and Infrared Survey Telescope for Astronomy (VISTA): Design, technical overview, and performance

The VISTA project was made possible by funding from the UK Joint Infrastructure Fund (JIF) and PPARC (later STFC).

M1 and M2 mirrors manufacturing for VISTA telescope

Nowadays LZOS is carrying out work on the manufacturing of the M1 Mirror and M2 Mirror for the VISTA project (Visible and Infrared Survey Telescope for Astronomy) with the 4100 mm diameter primary hyperbolic mirror with asphericity about 800 μmi and the 1241 mm diameter secondary hyperbolic mirror with asphericity about 350 μm. The current status of the work carried out is presented in the manuscript.

Status of the KMOS multi-object near-infrared integral field spectrograph

KMOS is a multi-object near-infrared integral field spectrograph being built by a consortium of UK and German institutes. We report on the final integration and test phases of KMOS, and its performance verification, prior to commissioning on the ESO VLT later this year.

Design of the KMOS multi-object integral field spectrograph

KMOS is a near-infrared multi-object integral field spectrometer which has been selected as one of a suite of second-generation instruments to be constructed for the ESO VLT in Chile. The instrument will be built by a consortium of UK and German institutes working in partnership with ESO and is currently at the end of its preliminary design phase. We present the design status of KMOS and discuss the most novel technical aspects and the compliance with the technical specification.

UIST: an imaging spectrometer for the UK Infrared Telescope

An imaging spectrometer is being designed to take advantage of recent improvements in the image quality achieved at the UK Infrared Telescope. The realization of near-diffraction limited imaging at two microns brings with it the possibility of significant improvements in sensitivity to IR observations. UIST will provide a versatile facility for high spatial resolution imaging and spectroscopy in the 1-5 micrometers wavelength range. We will present the opto-mechanical design of this new instrument, highlighting the innovative features. These include provision of multiple pixel scales within the camera and polarimetry via a Wollaston prism. One of the most challenging areas of the design is the inclusion of a cryogenic integral field unit for area spectroscopy over a 5 inch field. The spectroscopic modes include cross- dispersed spectroscopy over the complete 1-2.5 micrometers wavelength ranges and moderate resolution long slit or area spectroscopy over the complete 1-5 micrometers range. A higher resolution mode will also the included. This will allow USTI to take advantage of the very low backgrounds to be found between OH sky lines. The instruments will incorporate a 1024 X 1024 Indium Antimonide array from SBRC. The development of the IR array controller for UIST will also be discussed.

Active mirror support using pneumatic actuators

The requirements for position, orientation and performance of the primary mirror active support system have been optimised through extensive FEA to minimise the wavefront slope error. The output of this optimisation has been a detailed performance specification which also takes into account telescope control and wind rejection requirements. The FE model has also been used to calculate the active force eigenmodes based on the static actuator patterns rather than approximations to the vibration modes. In addition significant development and prototyping has been undertaken in the actuator and definer design including control. Interesting aspects of this development include use of flexures in the mirror definers in order to meet the stiffness requirements and control of a pneumatic astatic system. This paper describes the process of requirement optimisation for mirror performance and also the development and design of the support system.

Wide-field camera for the United Kingdom Infrared Telescope

This paper describes an ambitious new wide field IR camera for the 3.8m UK IR Telescope (UKIRT), located on Mauna Kea, Hawaii. The camera, currently under design at the UK Astronomy Technology Center, will include 4 2048 by 2048 pixel focal plane array IR detectors operating over a wavelength range of 1-2.5 micrometers . The optics provide a 1 degree diameter corrected field of view and a pixel scale of 0.4 arcsec per pixel. A novel Schmnidt type optical design allows the large field to be imaged with excellent image quality. The optical design includes a cold stop to maximize rejection of background radiation and stray light. Precise microstepping will be used to improve sampling. Four parallel data acquisition and processing channels will be used to cope with the large data rates expected. It is envisaged that a substantial fraction of UKIRT time will be devoted to large area sky surveys once WFCAM is operational, resulting in a unique IR catalogue containing hundreds of millions of objects.

Gemini multiobject spectrograph: a flexure critical design

Each of the two Gemini telescopes will be instrumented with the Gemini Multi-Object Spectrograph (GMOS), a general purpose optical spectrograph mounted at one of the Cassegrain foci. Two GMOS are currently being designed and built by a team of scientists and engineers in Canada and in the UK. A stringent flexure specification is imposed on these instruments by the scientific requirement to measure velocity to high precision, 2 km/s at R equals 5,000 with 0.5 arcsec slits. This implies a basic stability specification of 3.125 micrometer/hour at the detector focal plane. The GMOS design has met this specification by using a combination of stiff structure (where flexure is minimized); Serrurier trusses (where the flexure is controlled); precision mechanisms (where mechanical hysteresis and error are minimized) and, finally, an open-loop active correction system at the detector focal plane (where the CCD is translated to counteract any residual flexure). Once the GMOS design was conceptualized and its component groups were identified, the design team divided the basic stability specification into allowable contribution from each group. The final division was weighted according to the degree of design difficulty, based on inputs from the engineers. An error budget was developed and maintained to ensure that GMOS would meet its overall flexure specification by controlling the contribution from each component. The error budget approach will be described and discussed in the paper. We will also look at examples from the GMOS design with reference to calculations, analyses, FEA and actual measurements from prototype components.

Active Optics at UKIRT

The 3.8 m United Kingdom Infrared Telescope (UKIRT) has recently installed active control of the primary mirror figure, taking advantage of aspects of the original mirror design, which permits the correction of low order aberrations. In this paper, we present results from a campaign of all-sky wavefront sensing carried out UKIRT. As a result of the campaign, a lookup table is being used to correct for attitude dependent astigmatism, while fixed corrections are applied to trefoil and spherical aberrations. Coma is removed by secondary mirror alignment. A continuous, model based, correction of focus for thermal and elastic effects is also applied. Accurate focus is now maintained throughout an observing night.

Performance of the K-band multi-object spectrograph (KMOS) on the ESO VLT

KMOS is a multi-object near-infrared integral field spectrograph built by a consortium of UK and German institutes for the ESO Paranal Observatory. We report on the on-sky performance verification of KMOS measured during three commissioning runs on the ESO VLT in 2012/13 and some of the early science results.